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Old 08-30-2010, 04:48 PM   #1
makgreens
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Default mopar help again...360 heads on a 318

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
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Old 08-30-2010, 05:10 PM   #2
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Default Re: mopar help again...360 heads on a 318

"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.
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Old 08-30-2010, 05:42 PM   #3
makgreens
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Default Re: mopar help again...360 heads on a 318

heres some pics of the heads

J head





the other head


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Old 08-30-2010, 06:13 PM   #4
ChryslerRodder
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Default Re: mopar help again...360 heads on a 318

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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Old 08-30-2010, 06:33 PM   #5
makgreens
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Default Re: mopar help again...360 heads on a 318

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?
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Old 08-30-2010, 06:47 PM   #6
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Default Re: mopar help again...360 heads on a 318

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.
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Old 08-30-2010, 06:49 PM   #7
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Default Re: mopar help again...360 heads on a 318

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Originally Posted by R Pope View Post
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.

did ya bore out the block?
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Old 08-30-2010, 07:06 PM   #8
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Default Re: mopar help again...360 heads on a 318

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
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Old 08-30-2010, 07:15 PM   #9
makgreens
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Default Re: mopar help again...360 heads on a 318

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Originally Posted by pdq67 View Post
May i point out that the sparkplug locations appear to be different if it matters to you?
pdq67
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
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Old 08-30-2010, 09:25 PM   #10
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Default Re: mopar help again...360 heads on a 318

Measure the exhaust ports and combustion chambers. the heads are different but will work. I would get a matching set.
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Old 08-30-2010, 09:36 PM   #11
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Default Re: mopar help again...360 heads on a 318

intake and exhaust ports are the same and the combustion chambers are the same
maybe they were machined to match?
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Old 08-30-2010, 10:04 PM   #12
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Default Re: mopar help again...360 heads on a 318

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
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Old 08-31-2010, 01:39 AM   #13
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Default Re: mopar help again...360 heads on a 318

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
It would put you back in your seat pulling out to pass someone and punching it.
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Old 08-31-2010, 01:54 AM   #14
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Default Re: mopar help again...360 heads on a 318

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.
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Old 08-31-2010, 03:42 AM   #15
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Default Re: mopar help again...360 heads on a 318

Quote:
Originally Posted by pdq67 View Post
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
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.
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Old 08-31-2010, 07:35 AM   #16
Dolmetsch
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Default Re: mopar help again...360 heads on a 318

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.
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Old 08-31-2010, 08:05 AM   #17
fstfish66
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Default Re: mopar help again...360 heads on a 318

Quote:
Originally Posted by moparmonkey View Post
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.
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,,
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Old 08-31-2010, 08:14 AM   #18
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Default Re: mopar help again...360 heads on a 318

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!
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Old 08-31-2010, 01:54 PM   #19
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Default Re: mopar help again...360 heads on a 318

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Originally Posted by coolbreeze1340 View Post
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!

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
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Old 08-31-2010, 02:05 PM   #20
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Default Re: mopar help again...360 heads on a 318

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!
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