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mopar help again...360 heads on a 318

Discussion in 'The Hokey Ass Message Board' started by makgreens, Aug 30, 2010.

  1. makgreens
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    makgreens
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    been reading a ton on this and the more i read the more questions i have so i figured id ask here since theres so much knowledge here

    long story short i got some heads from a guy with the intentions on putting em on my 318

    both went to a machine shop about 5 years ago and look clean minus some surface rust but my biggest worry about all of this is one is a "J" head and the other a 974....im guessing if they both went to the shop they would have matching valves and i will be fine

    can i use them? seeing that i only paid 60 bucks for em i wont be at a total loss but if i can use em ill be happy
  2. moparmonkey
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    moparmonkey
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    "J" heads are usually 915's, they use the same size valves and ports as the later 974's, so they're basically the same head.

    On a 318 you will have to consider the compression ratio. 360 chambers are usually at least 5cc's bigger than the 318 heads chambers were, and I'd have to say more like 7-8cc's bigger in the real world. So you won't just be able to slap them on unless you don't mind running 7:1 compression.

    So if you're doing a rebuild, make sure you pick your pistons appropriately. Either that or you'll have to have the heads shaved down a bit, but to get what you need you'll also have to have some work done on the intake manifold to get it to fit once you've cut the heads.
  3. makgreens
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    heres some pics of the heads

    J head
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]

    the other head
    [​IMG]
    [​IMG]
    [​IMG]
  4. ChryslerRodder
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    ChryslerRodder Member

    Maybe I'm not seeing this right but it looks like there is a difference in the exhaust port size between the 2 heads, J head looks bigger.
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  5. makgreens
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    makgreens
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    well i just measured the intake and exhaust valves and they are the same on both

    and whats the best way to clean up the rust and store them while i buld the rest of the motor?
  6. R Pope
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    R Pope Member

    Hit the gasket surfaces with an orbital sander, coat them with oil, and store them inside until you use them.
    I've run 318's with those heads many times, the CR might be a tad low, but you'd never know it. A hirise 4bbl and a 340 cam and they think they are 340's! Well, not quite, but lots better than a stock-headed 318.
  7. makgreens
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    did ya bore out the block?
  8. pdq67
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    pdq67 Member

    May i point out that the sparkplug locations appear to be different if it matters to you?

    And i would cc both heads chambers and keep the smallest chambered head, ebay the other head and find a match to the one kept.

    I had a '55, 265" SB once that had two different heads on it and it just never ran smooth is why I bring this up.

    pdq67
  9. makgreens
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    i dont see it...from my experience the heads are almost all identical except the valves and a few other things but the main stuff like sparkplug holes are the same....i tihnk atleast
  10. 4406
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    4406 Member

    Measure the exhaust ports and combustion chambers. the heads are different but will work. I would get a matching set.
  11. makgreens
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    makgreens
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    intake and exhaust ports are the same and the combustion chambers are the same
    maybe they were machined to match?
  12. 50dodge4x4
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    50dodge4x4 Member

    I would clean them up and run them, unless your building a race engine (in which case I'd question the 318 block). On the street you will likely not notice any difference.
    I also agree on the stock 340 cam and the 4bbl intake, add a set of headers or real good dual exhaust and that 318 will run hard on the street. If you have to bore the 318, step up in a little higher compression pistons (9:1 for street use.) If the bore is straight and round, don't worry too much about the compression ratio. Spend your money on the bottom end for things like better rod bolts, good bearings and the high volume oil pump, and DO NOT put a Fram oil filter on your engine. Gene
  13. T Hudson
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    T Hudson Member

    I had this set up in a 74 van. 318 w/360 heads-340 cam-2 bbl from a 400. My old boss built it up and I bought it a few years later. That thing would scream :D
    It would put you back in your seat pulling out to pass someone and punching it.:eek:
  14. Rodhotz
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    Rodhotz Member

    You need to lay a straight edge on top of the valve stems, it looks like a few are lower than the rest. if you are using adjustable rockers it won't matter but if non adjustable problems. also from the close up it looks like they need to be resurfaced.
  15. moparmonkey
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    Spark plug locations on ALL of the LA engine (318/340/360) are the same, from 1967 all the way to '91. Thinking about it, I don't think they changed for the Magnum ('91 up) heads either (although the chambers, ports, and intake bolt angles did).

    Your "J" heads are 915's (last 3 digits of the casting # is used to identify them). 915's were '70-'71 heads, the 974's are the '75-'76 version. The casting is a little different, but the valves are the same size, and the factory spec for the chamber and port volumes are the same.

    That said, having them cc'd isn't a bad idea, these heads varied quite a bit in chamber size even within the same casting. Just getting another 915 or 974 casting # head won't necessarily mean the "new" head will have the same chamber volume as the one you already have either. Spec for these heads was 65 cc's, but it's common to seem them all the way up to 70 cc's. Most are around 67cc's in the real world. And I'd agree that it looks like they should be surfaced.

    As far as the compression ratio, 318's are NOTORIOUS for having taller decks than the factory spec'd, leaving the pistons down in the holes to begin with. Considering a 318 never left the factory with compression better than 9.2:1 (pre '70) and most (post '70) are 8.6:1, that means it's a good bet than on a post '70 318 you'd be lucky to have 8:1 with a 60-63cc chamber. Slap a 360 head with a 65 cc chamber (spec) or worse (most are more like 67-68cc's) and you're looking at some seriously crappy compression.

    318's are good engines, and can benefit from the larger 360 head ports, but only if you set the compression up right and match the larger ports to a better cam, intake and carb. Just slapping on 360 heads will kill your port velocity and your compression in one swoop. It'll still run just fine, but compared to what it could be if done right it'll be pretty flat.
  16. Dolmetsch
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    Dolmetsch Member

    This wont be popular but it is true. This swap is the most common mopar mistake made. And yes I have tried it and helped others with it too. The 318 works much better with the Swrl port heads from the later 318s . Like a 87 Fifth avenue 318 head etc. basically the first gen roller cam engine heads for a rule of thumb. How much better? A lot better. I remember and may still have it in the pile that Hot Rod mag did a 318 project several years ago with Arruza motors (sic?) Hot Rod gurus did the 360/340 head swap , a cam as well and an intake. Wound up gaining something like 16 HP when all was said and done. Arruza asked if he could have a go and took the 360 valves and popped them in the 318 swirl port heads and gained 55HP. And remember that was 55 hp more than with the 360 heads.
    I had already discovered that 318s worked better with the 318 heads so i wasnt surprised. Compression is part of it but not all. If you were my customer would tell you either build a 360 and use them or sell them to someone you dont like.
    Don
    Last edited: Sep 2, 2010
  17. fstfish66
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    fstfish66 Member

    this reply is the most correct,,318 heads. 360 heads are not hard to come by,,search any of the mopar boards and get a matching set,,if your not changing pistions, use a set of 318 heads,,the only benifit of the 360 heads and 318 pistons would be ,you would be able to run 87 octane crappy gas,,,,, moparts.com forA bodies only .com etc,,or craigs list,,
  18. coolbreeze1340
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    coolbreeze1340 Member

    I agree with the last two posts. 318 heads are cheap, 360 motors are cheap. Either sell your motor or the heads and get a good combo to start with. Your 318 will run very well for a street car with a little head work, stock 340 cam, intake, and EXHAUST! The manifolds suck and you need a good flowing exhaust to really wake the motor up! I ran a similar set-up in the car in my avatar!
  19. makgreens
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    the block im using is a from 69
    its complete and running but needs a good rebuild

    i have some doug thorley headers for it and an offy 4 barrel intake
    i plan on upping the compression and using KB pistons
    and a large 340 cam

    around here 360 engines arent cheap and are hard to come by...


    theres a magnum block and heads on CL here for 100 bucks BUT i dont want magnum stuff
  20. coolbreeze1340
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    coolbreeze1340 Member

    If you are rebuilding the block and rasing the compression, go with the 360 heads. Just make sure you get the right pistons for those chambers. I don't know what car you are sitting it in but the headers can be a bear! The headers in my car are custom built by a little old guy that is hard to deal with, but his headers will work in an early A mopar! Good luck with the build!
  21. The photos show a BIG difference in exhaust port sizes. Maybe the photo is showing the difference between 318 and 360 heads? If not, take another look..a lot different.
  22. coolbreeze1340
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    coolbreeze1340 Member

    Almost forgot, plan a little extra in the budget. Mopar performance parts are pricey and you don't find much used stuff at the swap meets!
  23. makgreens
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    :eek:
    shit

    couldnt i just machine em to match?
    eh well it was just 60 bucks so im not out a ton
    guess ill sell em on flea bay and put the money back into rebuilding the 318

    scratch that....i think ill just talk to a machine shop and machine the exhaust ports to match....
    Last edited: Aug 31, 2010
  24. BuiltFerComfort
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    BuiltFerComfort Member

    Low compression ratio, big valves... anyone but me thinking "blower"?
  25. Mark Karger
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    IF you decide to use the 360 heads, I definately would get the heads surfaced. Pitted gasket surfaces= failed head gaskets.
  26. slayer
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    slayer
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    The ports look the same. The later head has a much larger machined surface around the port, giving an optical illusion that its smaller.
  27. makgreens
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    there a hair off like enough i wouldnt care but not sure if itd really make a hurge difference in the performance
  28. fstfish66
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    fstfish66 Member

    ports on a 318 are closer to a 273 then a 340/360...if you are going to spend the money to up the compression,,get a matched set of heads and have the bowls CC,ED before you buy pistons,,,call hughes performance,,all they do is mopar,,and they will point you to the correctt piston choice for your project and budget,, hughes can tell you the bowl size with the head part number,,saving you the cost of CC,ING or any mopar head chart

    get a edelbrock performer intake there are 2 versions performer and performer 360...both are dual plane or a intake similar in a dual plane version,,,

    dont over cam it,,it will fall on its face,,,if your planning on power brakes,,make sure you tell them that when you select the cam,,to much over lap and the cam will not make enough vacuum to make power brakes work,,,yea sounds koool lumpy di lump,,,but no brakes,,,

    a stock 340 grind cam has been proven to be the best selection in a mild 318...with either selection of heads,,,the wrong choice of parts and it will run worse then an old worn out 318 just my 2 cents
  29. MikePA
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    MikePA Member

    The following was copied from the AllPar website when I was researching what to do with the 318 I had for my '63 Dodge Truck. A lot of good information. I ended up finding a set of "302" heads, installing a new cam, intake, carb, electronic ignition, headers, and matched the port openings. It's a lot of fun......good luck.The 318 is a good, solid and dependable engine. I will be the first to admit and try to sell that. Secondly, the 360 is an outrageously great engine because it has so much potential, greater than a Chevy 350 or Ford 302/5.0. The SBChevy guys have a little advantage because all the heads and intakes all bolt on without major changes other than combustion chamber and valve sizes. MOPARs have two sizes of runners and various valve sizes. What you have to do is make the determination of what you really want to do. A 318 can be built rather easily using stock components and be very reliable and strong, the 360 you can do the same thing with a lot more aftermarket options. About the only things that are different between the two other than the heads/intake, are motor mounts (right side, actually), harmonic balancer and torque converter (being external balance on the 360) and rear main being smaller on the 360 means oil pan will not interchange. The 318 does have the advantage of a steel crank stock, so power and rpm limitations are minimal.If you are on a 'budget', your best choice is to 'freshen' the 318 and only replace or machine items as necessary.There are some differences between the 318 and the 360, but many parts interchange. It is easier to get raised or decent compression pistons for a 360, not as easy for the 318. Another common thing is there is no replacement for displacement. 4 inch bore is always good as opposed to the 3.91 inch bore for the 318, but you can still get whatever valve you want into the head so that is not an issue either. There is no better source than either the MOPAR Engines or MOPAR Chassis 'Speed Secrets' books available through your nearest dealer. I always advocate that anyone who lacks experience and/or technical training and wishes to 'build-up' or 'modify' an engine, should talk to engine builders, ask lots of questions and read and learn. Read and talk to a reputable machine shop, talk to MOPAR people at car cruises and swap meets in your area and find out who they recommend in the way of a machine shop and go talk to them about a hi-po 318 build. First performance enhancementThe first performance enhancement you do on a stock 318 is to install the (factory) 340/360 H.P. cam (or equivalent). With stock heads, 2Bbl carb and even 2.76 gears this is already a 'fun-package'. Even with 4.11 gears (and street tires), the FIRST 5 feet that the car travels is the most critical. Over carburetion or a non-functioning accelerator pump will pretty much have the same effect, the car may indeed 'fall on its face'. You will benefit from a quicker advance curve in the distributor and enough initial lead to give about 36 degrees max. A dist with 13 inside will double to 26 degrees on the crank then you can set the 'static' to 10. HEADSThe 360 heads and Intake swap will fit on the 318, but the compression will be around 7.2:1, which is not very good for performance, which is not to say that the heads cannot be shaved .050 and intake be rematched to fit, adjustable rockers added to offset the rocker geometry, and away you go. The book says the 360 to 318 works well, but, take the 318 heads, shave .020 off the head, install 1.88 intakes vice 1.78, port the heads and you would have a better combination, especially on the bottom end response and will still rev as high as you want and float the valves before the power falls off (how can you beat that?). It can be done, but, if you have a 360, which is physically the same dimensions externally as the 318 and 273, why not go the least expensive route? Keep in mind that the 318 runs about 8.5:1 compression and will be about 8:1 or as low as 7.5:1 with the J heads of the 360. This is going to drop the compression pretty low, which is great for cheap gas, but bad for the performance side, thus most 318s are rated at the 185hp, which is a shame. If the engine is out and heads are off, do some measuring to determine what the compression is going to be. Some of the pistons can be as much as .080 below deck just to start with. I am not trying to squelch your combination, but, as many others have done with similar combinations, if it is a dog, don't be surprised. As stated, the piston sits between .025 and .080 down in the bore. The area of the chamber of a 318 stock head and a 360 J head is greater. Unless the block was 0 decked to the pistons, aftermarket pistons were limiting the distance below the deck, or the J heads are shaved, measure the compression or it will be lower than stock.Now, there is a solution to this problem. Last month's Hotrod mag had an excellent article similar to yours, but the heads were with smaller chambers. They shaved theirs .050 to raise the compression, whereas you may have to do the same. When removing that much metal from the heads, the cork gaskets front and rear of intake may be too thick, so be cautious during installation of the intake. Here is the thing about the 318 heads compared to the 360 heads. The intake valves are smaller on the 318, but the stock 360 valves put into a 318 head (1.88 vice 1.78) and then the bowl tuliped, vice opened up all the way, really makes the head flow in the chamber side. The pushrod pinch on the intake port is the same for the 318 and 360 head, so there is no gain there, but the height of the port is taller than the 318, and the port mismatch can have detrimental effects. Port matching can be done on most castings; some are close at the top of the gasket. Here is the hard thing to deal with on the 318 head of 1969: The exhaust valves will be sunk within a couple years because the seats are not hardened and need the leaded gas to survive. Figure you can get approximately 25,000 miles out of the heads before they are affected completely by sunk valves. Have the 360 heads shaved .020 or get new pistons is the best solution because the cost of the work on the 318 heads will be a couple hundred dollars and the porting time, if you do the porting yourself. Another solution is to hit the junkyards. I had several sets of 318 heads that were closed chamber that I have had in 73-74 Plymouth engines. Don't know the casting number but they do exist. Then put the 360 valves in the heads and port them. These heads already have the hardened exhaust seats. Intake valves are not affected. Did it on two sets of heads and have had wonderful results in the power increase world. I originally ordered stock 318 valves and ended up with stock 360 valves. Cut the seats, ported the heads, and really noticed the breathing and torque increase. It was fun! You can indeed 'shave' the (360) heads 20 or 30 to raise the CR but that should still keep it under 9.0 to 1 and allow the use of (cheaper) 87 octane. The power potential is already there, but everything has to work together; the timing, the intake and exhaust flow, the distributor curve, the plugs and wires, the cam specs, the carb itself, and even the type/grade of engine oil to make any 360 dependable, efficient and a pleasure to drive. The 340/360 intake is a larger runner than the 318/273 heads. This is like taking a 3/4 inch pipe and running it into a 1/2 inch pipe. They have to be port matched, or, if that cannot be done, find a 318 specific Streetmaster type dual plane intake. Smog is a concern for some of us, not for others, but there are some things that can be done without too much worry. For starters, we have to remember that the 34/360 have better breathing heads with larger ports AND larger combustion chambers. The amount of shaving to get them down to the 318 size, so as not to lose compression (takes it down to about 7:1 vice 8.5:1). An old favorite, and extremely helpful thing to do is have 1.88 valves from a stock 360 installed. There is a requirement to tulip the intake port to do this, but the small amount of work is well worth the effort and money. This also prevents having to change out the intake manifold to fit. If you do go with the stock 360 heads, you have to stick with a 360 intake, for the 340/360 heads and 318 intake do not match, and vice versa.Edelbrock makes a really nice aluminum head, with the smaller chamber size, if they are anything like the big block aluminum heads, would be fantastic, along with headers/dual exhaust and a 4 bbl and 600cfm carb (or police 4bbl), would add in the neighborhood of 100 hp/ftlb torque. Go out to the salvage yard and find a set of closed chamber heads. Anything past 1973 will have hardened exhaust seats for added durability. The closed chamber heads add compression and simplifies the need to shave so much off to raise compression. Get a set of 360 valves (1.88inch) and get the intake seats cut for them. Port the heads to gasket size and tulip the bowl to the valve size, but don't just bore the bowl out to the bigger valve. The less you shave the heads, the less likely you will need adjustable rockers. (big bucks to add).If you can't get a set of heads that are closed chamber, only shave the heads .020 so as not to throw the geometry for the rockers off any more than necessary. Get a set from the salvage yard and get them prepped and ready instead of waiting a week with your car down. Port match and bowl work is the best. Do not switch everything over to 340/360 heads and intake. It really kills your compression and stock ported heads run higher velocity for the 318, which you need.You suggested replace the stock 1.75 (or 1.78) /1.50 valves with the 1.88/1.60 360size. Other people recommend this as well. Now I know that the 318 heads are better that 360 for compression. My question is, would the 0.10’ increase in valve area make that much difference on a slightly modified 318 (4bbl, duals, & quick bolt-ons)? Wouldn’t it be easier & less expensive to increase the intake flow with a 252 (stk 360) or 260 (Crane) cam? Or 1.6 rockers?I—d imagine for competition you—d want larger valves, but for a daily driver, would the effort & machine shop fees be worthwhile? And what about increased fuel consumption? I—m thinking of installing late 80s #302 swirl port heads on a 318. (about 500cfm & duals, no headers) Has anyone done just this upgrade alone, that could verify performance gain & MPG difference?I did just this to my 74 Barracuda 318 when the wrong valves were sent to me and I was not in a position to wait for them to be replaced. The difference between 1.78 and 1.88 is 100 thousandths of an inch. That's one tenth of an inch. Mileage did not decrease, it actually increased because the added efficiency with the small runners breathed better, not worse. I was using the Crane .444 cam and it was superb. I could feel the difference from stock and it worked well. It was coupled to a Streetmaster dual plane and Hedman headers, ported heads, balanced stock rods and pistons, and Holley 650 double pumper, 2.71 rear 8 3/4 rear. Oh, exhaust valve change is not necessary.All the machine shop has to do is cut the valve seats, which I simply ground with the standard 45 degree stone cutter, then tuliped the cut to the edge of the seat diameter (i Marked the edge of the seat with the new valve, properly ground at 45 degreese, by doing a quick lap job on they dyed valve seat so I could tell how much material needed to be removed). Do not hog out the whole pocket because that just defeats the purpose of the tulip design. The charge enters the pocket, expands to the outward direction, as the valve is opened and then closed, the velocity in the runner remains packed and at a higher velocity, but the valve closing compacts a larger charge in the tulip area for higher charge to wait and enter for the next valve open motion. The idea of a higher lift cam will drop the vacuum and velocity of the charge and then you have no bottom end power. Going with the 360 heads, unless you are running high rpm and higher compression domed pistons, are pretty dead on the bottom end because of the size of the intake runners and drop of compression to low to mid 7:1. The bore is too small and the stroke is too short to get good bottom end draw on the 318. Magnum heads, although good, have poor pushrod geometry, so I don't like that idea too much. They work, but I fear bent pushrods because of the poor angles. 1.6 rockers, other than not being able to work stock on the early heads, and are around $450 with pushrods in the aftermarket. (extra cost). If you can go with a complete Magnum block to go with the heads, that would be the best thing. I could routinely wind this motor up to 7500 rpm without it dropping out, and one time slipped a gear on the highway to move quickly to avoid an accident and hit first doing 55(7500 rpm) and shifted at 75 before I really realized what had happened (panic mode to avoid the accident). I figure I hit 8400 rpm and not only did it not float or bend a valve, but was still picking up rpm and power before I could correct my mistake. A stock 1.78 definitely would not have been able to do that. It's your decision, just some good solid personal experience with this set-up. Need more info or help, just ask. Buy a set of 1.88, stock valves for a 360. I have personally found PAW to be an excellent mail order company. They have never steered me wrong and they have all the good stuff. You can find ads for them in all the car mags. At the machine shop, ask that the intake seats be ground to the size of the 1.88s, have the valves (new) redressed (just lightly ground to check them; little or no material is removed to verify factory tolerance and angle), and have the machine shop let you have the heads to do the seat position and port work yourself, then, when you have ported the heads as described, porting up to about 20 thousandths to the inner edge of the valve seat you have verified the valve will sit. Return the heads for assembly. If you have a friend, this goes a lot smoother, and can be accomplished in one day. Explain to the machinist what you want to do, and he will tell you how much it will cost. Valve grinds are usually around the $100-150 price range. Enlarging the seat may be slightly more. 45-degree angle, by the way, is the stock angle for about 95 percent of factory heads. For the three angle valve grind, there is a 60 degree angle cut on the inside edge of the 45 degree seat that is about 30 thousandths inch, and then a 70 degree angle cut into the chamber. This isn't necessary if you are porting and especially with this tulip design porting.One reason I never like doing the 360 heads on the 318 is because the chambers are so large that you have to shave the heads .060 to get the compression up, have to use the 360 intake so there are not any vacuum leaks, and there is usually a flat spot on the bottom end because the intake runners are too large for the size of the engine. A good port job works good for the 318 heads, headers work well, and a dual plane intake with a 600 cfm Holley, or Carter, work well. Really want to make it a little better, get the closed chamber 318 heads, get a set of 360 intake valves 1.88 vice 1.78 (one tenth of an inch is a lot for a small engine, but they work really well), and port the intake runner in a tulip fashion from the floor to the valve edge. The small runners keep good throttle response, the tulip design packs the charge really good and adds a good amount of torque on the mid to upper rpm range. Cam selection is really good in the .444 range. Not too big to kill the bottom end, not so small that it won't rev to 7000rpm, either, and you won't need a stall converter with an automatic. There is a cam that was for the 340 in about this size, very nice. Remember, this is a small bore/short stroke engine, so they rev well, but too much lift and too large a runner (as in the 360 heads) does not work unless you are running above the 4000 rpm range, which is not feasible on the street, only the strip. Factory 360 heads are indeed larger inside than 273-318's. However, they are not nearly like Ford's (351) cleveland. Around 1978, MOPAR first sold the 'LA' version of the 318-4Bbl. They simply bolted on a 360 intake/thermo-quad. Shortly after, a (so-called) H.P. version was 'unleashed' on the motoring public. This version used the (current) 360 heads with the 1.88/1.60 valves. In fact, this H.P. 318 was available through 1984. Hey, some of you must have owned one.By 1977, 318 heads were only 1.0 c.c. smaller than the 360's. From 1968 through at least 1984, all 'LA' heads, either 318, 340 or 360 were of the 'open' chamber design. The 318 chambers were in the 61-62 c.c. range to 1975 then they slightly increased to about 63 and then to 65 a couple of years later. The 360 heads at that time were mostly 65's.If you mill either the 318 or 360 heads by about .005'', the chamber volume will be reduced by 1.0 c.c. Therefore, a cut of .050'' will reduce the 'c.v.' by 10 c.c.'s. This will in turn raise the C.R. by 3/4's of a point, on average; depending on the piston diameter.Finally, as taken right out of the MOPAR (factory) Engines manual, edited by Larry Shepard; "In general, the 318 lends itself to the 340 type conversion better than the 273, because of the larger bore, more cubic inches and basic low level of performance in standard 2-Bbl. trim. - - - the first conversion to be made will be assumed as the installation of the 340 heads (or 360). To install the 340 cylinder head (360 or '72-'73 340 is recommended on the 318) - - - The 318 bore does not have to be notched. - - - With the 340 heads installed, the next most likely change is the cam. - - - A good compromise choice for an automatic is the 'standard' 340 cam (1968-1971), - - - Now that the heads and cam installation have been discussed, the next step is the intake system. - - - etc., etc." Next find a set of late model 318 heads I believe the are 302 castings, circa 86-91 pre-magnum, they flow better than the early 360 heads and have swirl port heart shaped combustion chambers. Have the valve unshrouded, the ports mildly cleaned up and clean out the bowl area under the valves, for an intake use Edelbrocks dual plane intake set up very good for building power out of small cubes like the 318, buy there complete kit, intake carb, cam and lifters package which can be purchased thru Jegs or Summit for a small amount of money.Volunteer, one small correction to your open/closed chamber dates. I had a 74 Barracuda 318 with closed chamber heads in that car and floating piston pins, vice pressed pistons. I had to replace the motor after freezing and cracking a head (thanks mom and dad), and I found a 74 Road Runner engine of the same configuration. Might have been a fluke, but after about 1973, closed chamber heads have the hardened seats and closed chambers on occasion. Those really help to keep the compression with the rest of the smog pistons in around 8.5 - 9.0, depending. There is additionally, when you can find them, a tarantula 2 bbl intake manifold that is good for about 8-10 hp over the stock 2 bbl H pattern. I have seen them on cars, but usually on pickups and vans. I assumed that all '68 - '74 318 heads (with the '675' casting) were of the 'open chamber' design because that's what all the manuals say.When I rebuilt the original 318 from my brother's '70 Satellite back in '86, I remember that the chambers were 'round' and it did indeed have 'floating' pins, (like all 340's). I guess nothing is 'etched in stone'. My '74 Challenger should have a 'blacked-out' rear-end panel according to Paul Herd's resto guide but it definitely has a 'charcoal-gray bum' and I proved it. Thanks.P.S. I remember seeing the infamous 'single-plane' 2 Bbl. intake on a '71 Challenger and it had a Rochester carb., p.n. 7041180. Seriously. Hey Brad, I think the 318 heads would wheeze on a 360. I was debating myself on using my chiged' out 302' 318 heads cause I opened them up ALOT. But I'm thinking of staying with 360 heads instead. The intake runners are a lot bigger. Another reason why, is that I was told that going 2.02 intakes on the 302's was a bad idea, mainly because they would be too big for the 318. But looking at them more, (they are closed chamber) I think that putting in 2.02 valves would "shroud" and lose the effect anyway.318 heads have 1.78/1.50 valves,<--that might be 1.74 intake///most 360 heads have 1.88/1.60 valves, if you go with that, you can have the intakes enlarged to 2.02 and have the same thing as a 340 X head. Then just have it gasket matched and polished in the exhaust runners.Dana was mentioning 73? 74? 360 heads that were closed chamber as well, but I don't think he ever mentioned a casting #? If he did I've forgotten already.The closed chamber heads I was talking about were 318 heads. Boosting the compression by using 318 heads is one way to do it, and the smaller runners would work by opening them through porting. Thought on the subject is that the ports for a 360 can only be opened as wide as the pinch between the pushrods anyway, so gasket match and open up the runners wherever you can.Other solution, as shown in the 400hp 318 is to use the 302 heads. Shrouding of the valve is not an issue if you simply port the chamber as well. I noted from the pictures that they never took the time to round the closed combustion chamber so, there was probably another 15hp easy out of the combination. I just hate it when they do that. I do not know the casting number to the 318 closed chamber head. They were rather common early in the 318 history, but the 73-74 castings had hardened seats in them for unleaded gas, already.Note, I thought the 302 casting was the 318/360 pre-magnum design and was on both 5.2 and 5.9 before the magnum engine redesign? Did I misread the description? Also, dropping the 383 in the engine bay is quite a tight squeeze and a lot of work. I would not contemplate doing it without a full shop and lots of room, myself. Were you talking about rounding on the valve side, or also rounding the v at the top of the heart? I thought that was the "swirl" in the swirl port design?As far as I know, that's the same description on the 302's I've read, they still bolt up the same and all, the only real differences other then the chamber are the air holes, and the over sized 11/16 pushrod holes. Which is a bummer because i've had to be extra careful cutting in that area.I heard that they were also a template for some sb aftermarket heads, MP?After more thought, if any 318 heads were chopped and tricked they might be real monsters on a 360. you'd have close to similar sized runner to stock, but with all the obstructions gone, like a happy medium.I think Brad's thinking about regular open chambered 318 heads, it still would knock the compression up though, they just need to be chig'd out, which btw, i have an extra set just sitting around.That's about right. The 302 head with the small heart shaped chamber is fine to make the swirl, but after taking .050 off the top, it kind of destroys the purpose, thus, after the cut, the valves are shrouded, especially with the added valve size (which doesn't shroud the valve with the smaller valve). To make these heads work more efficiently, the edges of the machining process needs to be rounded, which will also allow more advance to be run, especially when they noted that they were getting the best results with less advance. SB always do best with about 38 degrees advance, brought in by 2400rpm, vacuum advance all in around 3500. They were talking about the best advance curve of a lot less, which confirms they had too much sharp edge, fuel not distributed properly. I would bet the piston top would show that there are quench areas at the spark plug top and the whole bottom of the piston. Poor flame travel because of the sharp edges. Just to set the records straight, there was only one 273/318 casting, #2843675, from 1968 through 1974. It was of the open chamber design, 61-63 cc's, and the valves were 1.78" and 1.50". In 1975 and '76, the #3769973 casting was used but there were no other significant changes. The next version was from '77-'84? but they were still of the open chamber config. After that came the 'infamous' and soon to be legendary - 302's. Volunteer, not to doubt you or the books, but I have had two sets of closed chambered 318 heads with the 1.78 intakes. Both engines they came off of had floating pistons (beside the point) and may have been Plymouth (one a stock 74 Barracuda, the other a stock 74 Road Runner). I do not know what the casting number is or was, but they are out there. I wish I had more information to help than that, considering they are not in your books. I rather liked the heads, simply punched to 1.88 intakes and ported because they would give the dropped deck flat top pistons a nice mellow 8.8:1 or so compression. VALVE TRAIN:Why new pushrods? Are you getting adjustable rockers (would be a good idea with anything above stock camshafts) to go with them? Stocks are pretty durable in other words, cupped pushrods needed with the adjustable rockers. CAMCamshaft is the next best upgrade you can do for the 318. They really like the 340 hipo cam, which is still very mild, but is just enough to wake a 318 up. It has a lift in the .440 range, so any aftermarket camshaft between .430 and .455 work really well and mileage will not suffer, won't have to be high compression and doesn't require any high torque converter. Any more than that and you will kill the bottom end and the 318 will run like junk. This is an excellent cam for the 318. 318s get a little radical with a cam larger than .450 lift on 270+ duration, 360s get radical when you get up to .485 and 290+ duration, so a .450 lift and 270 degree duration in a 360 screams, idles pretty smooth and will get a little better mileage without any sacrifices. EXHAUST:Headers are a nice addition. If you don't want to go that route, split the exhaust and do dual exhaust, and that is another big help. IGNITION:As far as the ignition goes, stock MOPAR electronic ignition is one of the best factory designs out there, but an upgrade only gains with higher performance levels, not needed on the street, but it is your money. INTAKE / CARBNotching a half inch deep slot from front to back in the intake plenum has a two-fold effect. It balances the idle signal side to side, which at low speeds/idle/cruising speed below 2000rps. If there is a slight difference between the two halves of the engine, it corrects this. On the top end, it helps a small amount by giving the assistance (very minor) as an open plenum manifold signal. It is kind of the best of two worlds without sacrificing much from either. This adds balance for the carb without sacrificing bottom end. Don't go larger than 650 cfm on the carb, as in Holley, and usually recommend 600 cfm vacuum secondary. (dana44 added:) Keith_Indy, a couple things to add about the three engines and a little info on the Magnum 302 heads. The 340 and the 318 share the same crank and rods, but there are beefier 340 rods around...the last couple years they were the same when the 340 started dropping compression and power. The bore for the 340 is larger than the 360 (4.040 and 4.00 respectively). The bearings are shared with the 318 and the 340, including oil pan and rear main dimension. Basically two rods available. All are stronger and heavier than small block Chevy and taking a belt sander and/or die grinder, not bench grinder, to remove the casting off the beams and balancing the rods is all that is necessary for anything you can build for the street.The 340 and 360 share intakes and heads, being the larger ports and low performance 340 had the 1.88 valves.There is, aparently, a misconceptionion through an article between High Performance Mopar and the latest Mopar Muscle concerning the Magnum 302 casting and the Magnum block and heads. The Magnum heads with the swirl ports, closed chamber and rocker arms on bolt-on pivots, oiled through the pushrods, is different from the 5.2/5.9 Magnum engine and heads, and will work on the old 318/340/360 blocks with some minor mods. The lifters have to have an oil hole in them to push oil thru the pushrods to the rocker arms that match the heads. The 5.2/5.9 Magnum is a completely different animal, other than external dimensions and mounting points. The pinch area between the pushrods/ports is corrected by widening the lifter bore positioning and that is the geometry problem I was talking about concerning Magnum heads on an older engine. My mistake. On the other side of that, I still don't like to have to shave heads that much in order to raise compression because intake geometry gets tricky and not worth the real hassle of it, especially if it is done incorrectly. Deck height of the piston, if kept near zero or .010 is a better way to get the compression up. Maybe we can find a couple aftermarket pistons that can give us corrected deck height to list on here.One last thing for the 360, and that is the W2 heads. Stock they are better than anything from the competition, ported flow better than any big block engine, upwards of 310-320cfm. Thing is, they require a matching intake and rocker arm assembly, but if you have about $1600-1800 laying around, big numbers on the dyno. Good collection for reference. Thanks Keith_Indy for collecting it. Carburetor upgrade: by Daniel C. Stickney, 1996(Disclaimers and safety notice copyright © 1996 by Daniel C. Stickney)Proceed at your own risk. Some changes may shorten engine life or the integrity or durability of other components. The author makes no claim or guarantee that information contained in this article will be suitable for your situation. The author accepts no liability for any problems that you may encounter while working on your own car. Modifying your car may violate Federal, State and local emissions laws and regulations. Emissions equipment does make the world a better place (ask any Californian.) It isn't that much harder to set up an emissions legal system, especially with junkyard parts.All trademarks mentioned belong to their respective owners.Again, if the car is going be used on the street, check your local laws regarding tampering with emissions equipment.
  30. stealthcruiser
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