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Projects Which heads would be best for a performance 318 (318, 340 or 360?)

Discussion in 'The Hokey Ass Message Board' started by JCash56, Mar 3, 2019.

  1. JCash56
    Joined: Mar 3, 2019
    Posts: 7

    JCash56
    Member

    I have a 1970 Mopar 318 LA that the previous owner put in my '56 Dodge, I'm trying to make it a decent performance motor on a budget, well as much as you could make a 318 powerful of course. But my question is, I've already planned on buying a Holley 600 CFM 4bbl carb, beefier cam, and a MidRise intake manifold. With the bump up from a 2bbl to 4, I read up that to compensate for the change either any 340 heads, 360 heads (with 1.88 Valves to flow better with the 8.6 compression that the 318 has) or mid 80's 318 (302 casting) Heads would work. Between all 3, the 318 heads seem the most economical choice, and wouldn't have to buy new pistons (to compensate for the loss of compression), but I'm not too bothered over spending a couple more bucks if the other options would give better performance. I'm worried the 340 or 360 heads would lower compression too much and dog it down, but with any choice, portwork would be done. Any help would be useful, would love to hear your thoughts.
     
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  2. Oldioron
    Joined: Dec 12, 2018
    Posts: 511

    Oldioron
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    What heads do you have now?
     
  3. JCash56
    Joined: Mar 3, 2019
    Posts: 7

    JCash56
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    The ones I got now are the original 318 Heads, casting date is 12-20-1970, I can get the specifics tomorrow. From what I read the heads I got now wouldn't give barely any performance gains but granted I wouldn't know.
     
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  4. gene-koning
    Joined: Oct 28, 2016
    Posts: 1,122

    gene-koning
    Member

    I'm going to take a lot of heat with this, but:
    If you are not drag racing (or street racing) and don't intend on spinning your 318 more then 4500 rpm, the stock 318 heads will work fine if they are in good shape. The small port 318 heads will give a better throttle response then the big port 340/360 heads. If you want bigger valves, you can put them in your 318 heads.

    If you feel the need to get "better" heads, the late model Magnum heads are about the best improvement you can bolt on, but then you need to deal with the valve oiling difference between the Magnum heads and the LA heads with a LA block.

    The next option would be a set of 302 heads, if you can find a set that are not cracked.

    I did a lot of street racing back in the day, with the right combo of motor parts and chassis parts, those lowly 318s can run pretty hard with stock block, crank, rods pistons and heads. I put a 318 in a 70 Road Runner that could scare the crap out of you, right up to 4500 rpm. Gene
     
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  5. Oldioron
    Joined: Dec 12, 2018
    Posts: 511

    Oldioron
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  6. I agree 100% with Gene on this one


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  7. JCash56
    Joined: Mar 3, 2019
    Posts: 7

    JCash56
    Member

    Yeah, I wouldn't be planning on running it in the high RPM's just wanting to get a bit more oomph out of the block. If you think the original heads would work with the 4bbl carb then It'd help save some cash which is always good. I have a buddy with 302 heads that he might part with them for pretty cheap but I'll have to see about that. Thanks for the suggestion, might just roll with stock honestly, but I'll look into the magnum heads like you and Oldioron suggested
     
  8. squirrel
    Joined: Sep 23, 2004
    Posts: 41,958

    squirrel
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    See if you can find a 360.....the added cubes might be more noticeable than just putting better heads on a 318. I haven't looked for one lately, I don't know how hard they are to find these days.
     
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  9. mopacltd
    Joined: Nov 11, 2008
    Posts: 686

    mopacltd
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    915 small block heads are the best stock form performance heads. The 302 stock heads are very good street heads and can be worked to be pretty darn good head and are more available and because of that are more reasonably priced. How much performance are you looking for is the answer
     
  10. JCash56
    Joined: Mar 3, 2019
    Posts: 7

    JCash56
    Member

    If I do get new heads then I’d prolly just stick to either newer 318 ones or the 302’s like you and others have suggested. Not trying to make it super powerful or anything, just some performance gains since it’d cost more and I’m trying to budget. Would love to have a 360 and get some real power out of that, but I’m stuck with the 318 for now, which isn’t a bad thing


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  11. dwollam
    Joined: Oct 22, 2012
    Posts: 727

    dwollam
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    '67 318 heads have a smaller combustion chamber and work very well. Try to stay with an intake that has 318 sized ports but the factory put large port 360 4bbl intake manifolds on the 318 when they finally went to a 4bbl and they still worked great. 273 4 bbl intake is a good match too. All the 340 other goodies work on 318 such as double roller timing sets, 340 camshaft and windage tray. Those trays are cheap and worth 10-15 horses. Don't forget to get the special main cap bolts. Good flowing dual exhaust too of course. I don't like headers for the street on small block Mopars. Keep small block Mopars at 6000 rpm or less and they live forever. They build their torque and HP at lower rpms so don't try to run them like a small block chev, they won't live and don't need high rpm to get it!

    Dave
     
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  12. porknbeaner
    Joined: Sep 12, 2003
    Posts: 40,902

    porknbeaner
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    You won't get much grief from me. ;)

    The 360 Magnum heads are good heads and less pricey that 340 heads. They may be a lot of head for the 318 but given that the other components are up the task they would make a real improvement.
     
  13. Rusty O'Toole
    Joined: Sep 17, 2006
    Posts: 8,925

    Rusty O'Toole
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    I agree that the heads you have now are good enough to be going along with, and your money can be better spent elsewhere.

    They did make a police 318 with 360 heads, I don't know if they changed the combustion chamber or pistons to keep the compression up. 360 heads will fit but I suspect, lower compression.

    Your best bet would be aftermarket heads but, as others have said, probably not worth the cost for street use.

    I have seen articles in hot rod magazines where they got 400HP out of a 318 without doing anything very exotic.
     
    Last edited: Mar 4, 2019
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  14. whateverit takes
    Joined: Sep 5, 2013
    Posts: 34

    whateverit takes
    Member
    from new york

    My previous set up in my OT 68 Coronet Station wagon was a 1986 318, w/ Edelbrock Performer intake, 600 cfm Edel. carb and EQ Magnum heads w/stock 1.92 I and 1.625 E valve sizes. The EQ Magnum heads are a direct replacement for the 5.2 (318) and 5.9 (360) Magnum which are prone to cracking issues. Mopar uses the same magnum head for either 5.2 or 5.9 engines so the flow is there. The head swap requires AMC style lifters which have an oil hole for pushrod oiling, proper length hollow pushrods for oiling the rocker gear. Comp Cams carries the pushrods and most lifters now have the oiling hole. I added a Comp Cams hyd flat tappet 20-221. You will need to purchase the stud-mounted rocker arm kit for the magnum heads as well as a specific head bolt kit for the magnums. You can re-use your valve covers however magnum heads have a few more bolt holes. My wagon has 2.94 gears and moved along nicely. There are easy-to-find forum write-ups on the swap as well.

    Ernesto
     
  15. An Edelbrock performer 318-360 intake with a 600 cfm carburetor will wake up your stock 318 nicely. A stock 340 cam with matching valve springs would be the next upgrade if it were my project. That and improving exhaust flow with headers and duels.
     
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  16. JCash56
    Joined: Mar 3, 2019
    Posts: 7

    JCash56
    Member

    Thank you all for the very informative information, I’m currently piecing together prices on parts that most have you suggested. Do any of you think the stock pistons would work fine with the setup I’m doing? Planning on using the stock heads so I wouldn’t see why there’d be a problem but I wouldn’t take my word over people who know what they’re talking about.


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  17. gene-koning
    Joined: Oct 28, 2016
    Posts: 1,122

    gene-koning
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    The stock pistons and rods will be fine, as long as they are in good shape. Like Slayer said, the 340 production cam and a 600 cfm carb, with dual exhaust will wake up your 318. Put some 3:23 or 3:55 gears in the rear end, with a Sure Grip, or limited slip and some good smaller tires (26"-28" tall) and have some cheap fun. If your doing long hauls on the highway, an over drive, or taller tires (don't go overboard with too tall of tires either) are better then 2:76 or 2:45 gears, those gears just kill the low end power.
    Too many people think they need a big carb, and the 340/360 heads to make power for a street motor and they are wrong. Both will kill the low RPM pull the 318 was designed for. Gene
     
  18. ^^this. I ran a 318 in an off topic car that weighed around 3200lbs with the exact combination that Gene laid out for you and it was extremely peppy, not a race car by any means but was a lot of fun. And it did have 2.76:1 gears in the rear with a short tire, would have been even better with lower gears.


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  19. ffr1222k
    Joined: Nov 5, 2009
    Posts: 1,010

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  20. Rusty O'Toole
    Joined: Sep 17, 2006
    Posts: 8,925

    Rusty O'Toole
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    The only thing wrong with stock pistons is they sit low in the cylinder causing low compression. So you need small chamber heads. You can up compression with custom pistons that sit flush with the block but this can be expensive. So, be careful of what heads you use, 360 heads might give you bigger valves and ports but low compression.
     
  21. 73RR
    Joined: Jan 29, 2007
    Posts: 6,179

    73RR
    Member

    If you have some money to spend and time to do the work mentioned then I will echo what Squirrel suggests; buy a 360. More torque without opening the engine and you start off with better heads and, if you shop around, a 4-bbl.
    Add the 1970-340 cam and you have a great package. The factory hot-rod 360 was called the E-58 option and was used in cop cars as well as the Lil Red Wagons.....not a slouch. IIRC, in 1979 the Lil Red Wagon was the quickest production car sold in the US...
     
  22. JCash56
    Joined: Mar 3, 2019
    Posts: 7

    JCash56
    Member

    Alright thank you. The rods and pistons seem fine, just gonna replace the rings and hone the cylinders, will sure save me some money. I’m hoping to do dual exhausts this summer maybe. Pretty sure the previous owner put the transmission in there from the same car they got the block so I’m guessing 3 speed? Unsure of the actual transmission but I plan on taking that out too soon and clean it up, so hopefully I’ll know what kind.


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  23. Your next post will surely be - what new rear end will swap in my 56 since I blew up the stock one ? Join the 55/56 mopar thread - on the HAMB - for more info.....
     
  24. Roothawg
    Joined: Mar 14, 2001
    Posts: 18,502

    Roothawg
    Member

    In high school we bought a 1979 Dodge Aspen Highway Patrol car. It had a 360 in it. The castings had HP on the heads. We didn't know if that was high performance or highway patrol. It was quite a sleeper. We had a lot of fun with used tires...a lot of used tires. It was the best $125 we ever spent.
     
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  25. grimmfalcon138
    Joined: Jan 14, 2010
    Posts: 139

    grimmfalcon138
    Member
    from az

    I run the 5.9 litre Magnum heads on my 318. A set of aftermarket pushrods with the oiling holes and a set of AMC lifters solves the top end oiling issue. Then the other issue is you need to run a Magnum specific intake, or have the heads redrilled for a la intake.
     
  26. JCash56
    Joined: Mar 3, 2019
    Posts: 7

    JCash56
    Member

    Yeah I’ll have to keep the rear in mind, might have to swap out a new one, I don’t think I’ll be making too much power that it should be a problem? But I’m not an expert on differentials. I’ll have to take a look at that thread for sure


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