New(old) heads for engine rebuild?

[A38Valiant]

That poly motor is a good looking unit. I was going to mention magnum exhaust manifolds but I didn't know if they fit on c body, now I do. I wanted to do a complete magnum (5.2-5.9) and trans and ecu /efi basically the driveline from a junk late model truck but I never found a c body that some idiot stole the engine out of but haven't found that diamond in the rough yet and I have too many other things going on which is always the case.

Just remember that all magnums use the 360 size rear seal on the oil pan, and all those pickups and vans are rear sump. So even if you go with the 318 magnum, you still need a 360 car pan.

 

[70bigblockdodge]

So the old differences in pans between 360 and 318 didn't carry over to 5.2&5.9 in other words the radius of the pan around the ends of the engine?

 

[A38Valiant]

Correct. All magnums use basically a 360 truck pan.

 

[70bigblockdodge]

Cool that's awesome the oil pan on my 98 ram is rusted and drooling somebody gave me a oil pan from a 5.2 truck I never knew that. I just saved myself like 100+ dollars

 

[has2bmopar]

I definitely would not spend any money on your original '68 318 heads. They do not have hardened seats and were notorious for burning out exhaust valves for that reason. I would look for some mid '70s to '91 360 heads. They will already have hardened seats, bigger valves and the larger intake ports to match your 4bbl intake.

The Magnum exhaust manifolds sound like a good idea, but I would stick with the LA heads to avoid issues with oiling and stick with the rocker shafts. You would also need a different intake for Magnum heads over the LA piece that you have already aquired.

Engine mounts will be an issue to consider with transplanting a complete Magnum instead of an LA engine.

.... I think a 383 (even a bone stock 2bbl 383) with a 727 would be a nice upgrade over a 318/904 whether you intend on keeping the car or not... :shruggy:

 

[rjstick]

Thanks for all of the info - lots to chew on for sure. Still trying to decide whether to refresh to 318 with some upgrades or go ahead and transplant the 440.

The 440 seems like it would be more difficult to pull off.

Complete engine rebuild in either case.

 

[A38Valiant]

I definitely would not spend any money on your original '68 318 heads. They do not have hardened seats and were notorious for burning out exhaust valves for that reason. I would look for some mid '70s to '91 360 heads.



. :shruggy:

And with the larger chambers, they are an excellent way to drop the compression ratio from the 9.25 you have down to about 8.4. And just think of the great 7.5 to 1 blower motor one could build if these were installed on a 71 up 8.4 to 1 318......

No thanks. I would rather port 318 heads.

 

[has2bmopar]

And with the larger chambers, they are an excellent way to drop the compression ratio from the 9.25 you have down to about 8.4. And just think of the great 7.5 to 1 blower motor one could build if these were installed on a 71 up 8.4 to 1 318......

No thanks. I would rather port 318 heads.

A '68 318 has open chamber heads... little if any difference in volume, they also have smaller valves, don't have hardened seats and have much smaller ports....

Soooo, your recommending porting out the intake ports to match a 360, replacing the seats, at which point it would make sense to put in new 1.88" valves and you might as well replace the guides, because they have 143,000 miles on them... With the price of porting, machine work, new seats, valves, guides, springs, retainers, locks etc. that recommendation is an excellent way to be in up to your eyeballs into some awesome open chamber '68 318 heads, and just think of how great it will be when they flow almost as good as a $100 pair of uncut 360 J heads.

No thanks. For that much money I would rather buy new aluminum Mopar heads.

Just the money you have suggested in porting would buy an expensive set of pistons so you could put the compression ratio wherever you wanted.

I have a pair of '68 318 heads and some 360 LA heads. If you care to make it interesting I can check the CCs in both and see if they will change your compression nearly a full point as you have claimed...

 

[70bigblockdodge]

A buddy and I put a set of mid 70s 360 heads on his 318 with used composition gaskets, I would never use steel shims on a small block, and the cranking pressure barely made 100 in about 6 cylinders
I'm all for making a engine in a cruiser able to run on 87 octane but at less than a thousand feet above sea level your talking maybe 7.2/1 no thanks some quality time with die grinder on 318 heads way better IMO and if you ruin them well its not like you are working on date code hemi heads

 

[has2bmopar]

Again, there there is going to be little if any difference in chamber volumes, they are both open chamber heads.

Using a tired engine for a compression example?... And you should never reuse a composition head gasket. You could be low on compression for countless reasons like scored cylinders, low ring tension, broken rings, bad head gaskets, 30 years of use etc. The uneven compression you noted enforces this. Cam overlap will play a part in your cranking pressures as well.

Elevation has absolutely nothing to do with your compression ratio. It is taking 55 cubic inches of cylinder volume and crushing it into 5.5 cubic inches of space... 10:1 on a 440. Air density plays no part in the ratio. It seems everyone is pulling compression ratios out of their a$$ and not having any consideration to the deck clearance, piston dish, or the actual chamber volume difference in a '68 318 open chamber head vs a 360 head.

Anyone using this thread as any sort of reference in building an engine should first decide what head best suits their type of build, then check the chamber volumes, THEN buy the correct pistons, figuring compression height above the wrist pin, valve reliefs, gasket thickness etc. to get the desired actual compression ratio. The pistons are the expendable part in getting a proper compression ratio.

 

[moper]

"Again, there there is going to be little if any difference in chamber volumes, they are both open chamber heads."

Totally incorrect. The open chamber 318 heads are usually around 62-63ccs. The 340/360 open chamber heads are supposed to be as small as 68ccs but the normal ones are 72-76ccs. The difference is the edges of the chamber due to bore size. A 318 using the 360 heads will have a ton of dead space where no power can be produced from but volume exists to reduce compression. The '86 318 4bbl has a static advertised ratio of 8.4:1. The '86 318 2bbl has 9:1. The difference is the heads - the 4bbl used the 360 heads and intake. Knowing that they are both "larger" than specifications, the reality is closer to a full point difference.

I'll also agree is part with you on the order of operations - the parts have to be chosen to work together - but I use the total budget, expectations, and available parts as input long before the pistons or head choices are made.

 

[has2bmopar]

I definitely would not spend any money on your original '68 318 heads. They do not have hardened seats and were notorious for burning out exhaust valves for that reason. I would look for some mid '70s to '91 360 heads. They will already have hardened seats, bigger valves and the larger intake ports to match your 4bbl intake.

A '68 318 has open chamber heads... little if any difference in volume, (OK the actual numbers after checking CCs myself are 66 for the 318 and 70 for the 360 915s) they also have smaller valves, 1.50/1.78 vs 1.60/1.88, don't have hardened seats and have much smaller ports....

For the idiots that keep saying port your 318 heads... just the intake ports alone are 31CCs smaller... That is 248CCs of material to cut out in the intake ports alone to come up even with uncut 360 heads. Now add replacing the seats, larger valves, deshrouding the valves in the chambers, and porting the exhaust etc. = A herd of morons that cock off instead of doing some actual research.

Soooo, your recommending porting out the intake ports to match a 360, replacing the seats, at which point it would make sense to put in new 1.88" valves and you might as well replace the guides, because they have 143,000 miles on them... With the price of porting, machine work, new seats, valves, guides, springs, retainers, locks etc. that recommendation is an excellent way to be in up to your eyeballs into some awesome open chamber '68 318 heads, and just think of how great it will be when they flow almost as good as a $100 pair of uncut 360 J heads.

No thanks. For that much money I would rather buy new aluminum Mopar heads.

Just the money you have suggested in porting would buy an expensive set of pistons so you could put the compression ratio wherever you wanted.

I have a pair of '68 318 heads and some 360 LA heads. If you care to make it interesting I can check the CCs in both and see if they will change your compression nearly a full point as you have claimed...

I have checked the heads and they are 4CCs different... So I used the 3.91 bore, 3.31 stroke, the 66CC chamber volume, .039" gasket thickness and .027" deck with flat-tops to get 9.25:1 compression, as advertized for a '68 318.

When you add the 4CC increase for the 360 chambers you get 8.85:1.... That is 4 tenths, hardly a full point... Maybe some idiots can do some actual math before they get mouthy next time.

Totally incorrect. The open chamber 318 heads are usually around 62-63ccs. The 340/360 open chamber heads are supposed to be as small as 68ccs but the normal ones are 72-76ccs. The difference is the edges of the chamber due to bore size. A 318 using the 360 heads will have a ton of dead space where no power can be produced from but volume exists to reduce compression.

The '86 318 4bbl has a static advertised ratio of 8.4:1. The '86 318 2bbl has 9:1. The difference is the heads - the 4bbl used the 360 heads and intake. Knowing that they are both "larger" than specifications, the reality is closer to a full point difference.

The edge of the 318 chamber is about .075" farther away from the edge of the head gasket which are all over 4", so the void will be there regardless. If you replaced the seats and put in larger valves you would have to cut that area back anyway to deshroud the valves.

Totally incorrect.... The '86 318 302 heads were CLOSED chambered... The 360 308 heads were OPEN, Thus the larger difference in compression ratios. Maybe open a book or 2 and get your facts straight before you get snarky... :reading:

Also 7 tenths is not a full point and if they are BOTH larger than advertized, they BOTH would change equally not mysteriously change in the favor of your exaggerated compression loss.

Another funny thing... Dodge themselves opted to take nearly double the compression loss than the '68 318 will take in order to increase the HP for their 4bbl 318. Obviously tiny-*** ports and smaller valves are a larger setback than a loss of some compression.

 

[70bigblockdodge]

Okay I was wrong throw the 318 in the scrap pile get a big block now the heads are not a issue.

 

[has2bmopar]

Okay I was wrong throw the 318 in the scrap pile get a big block now the heads are not a issue.

...:yes: ... Now your talking... ccasion14:

 

[moper]

I didn't think I was being "snarky" - sorry you took it that way. As a matter of fact a lot of that post was F'ed up on my part...lol. I missed the part where you say you measured; and the use of the 86 model year was a "shoot from the hip" bad example...lol. The 302s came on the 86s...lol So my apologies to you and others for reading too quickly and overlooking critical parts of your post.
That all being said - instead of replying now from work I have some homework and i'll reply back with it. You make some points that I feel need clarifying.

 

[70bigblockdodge]

Fwiw if your still looking for head improvement/airflow on for a-bodies ony check out thead 318 head porting for the average joe. 1wildandcrazyguy did a fantastic job breaking this all down doing a little bit, a lot or somewhere in between. moper I can't believie you argued these points and didn't send him to that thread that you had posted on. I don't think he's looking for a race head just some more go out of what he already has.