340 & 360 Cylinder head CC specs

[PRH]

It depends on how close you want the “guesstimate” to be.

In round numbers……..
For a v8 around 400 cubes and in the 10:1cr range…….a change of 1cc works out to about a tenth of a point in compression.
So, 5cc is half a point……….10cc a full point.

 

[furrystump]

“Reaches for can opener” If you are buying a new rotating assembly, I would buy a 4” stroke crank with probably a dished piston, but you might be able to run a flat top if the chamber is big enough and the piston is still down in the bore a bit. Maybe! I can see no reason (other than a very special use combo or a VERY tight budget) to buy less than a 4” stroke crank. It gives you performance room to grow. With only a slight difference in cost from a stock stroke aftermarket crank.

 

[ir3333]

4" stroke makes big power but not everybody wants maximum power.

 

[RustyRatRod]

I thought the op was getting a rebuild and wanted to know why the head cc number was needed.

I believe we've got that pretty clear for him. At least I hope so. lol

 

[Dartswinger70]

More about CR calculation... its math basically. You could for example mill the heads to bump CR up by making the combustion chamber cc size smaller

 

[PRH]

It’s MATH???

That’s it…….I’m out.

 

[273]

4" stroke makes big power but not everybody wants maximum power.

You can build a low power 4" stroke engine's too, look at a 76 500 Cadillac engine 190 net hp @ 3,600 rpm, to me if you want decent idle-4000 rpm NA power is to build a larger and or largest engine you can especially if want to run 3.23 or less gears.

 

[RustyRatRod]

It’s MATH???

That’s it…….I’m out.

That's my point. It's either right or wrong. Ain't none of this communist common core crap.

 

[33IMP]

If you really want to KNOW, you measure EVERYTHING. It's not that hard. I got a 6x6 piece of clear 1/4" plexiglass from work (for free) and a 100 cc. Syringe (used) from my vet (free). I use windex (used for other stuff around the house, so...free) to measure piston dishes, valve reliefs, and cylinder heads.
If I really want to KNOW, and didn't have my stuff, I'd buy a cc'ing kit.

 

[Plymouth65]

Thank you to everyone that responded, your information was greatly appreciated.

 

[33IMP]

I'm not very familiar with small blocks, but I know that the performance big blocks were often a half point to a full point less compression than they were supposed to be. Mostly cause the heads' combustion chambers were bigger than they were supposed to be, and the deck height higher than spec.

 

[MOPAROFFICIAL]

I'm not very familiar with small blocks, but I know that the performance big blocks were often a half point to a full point less compression than they were supposed to be. Mostly cause the heads' combustion chambers were bigger than they were supposed to be, and the deck height higher than spec.

The 340 would need the chambers to be 60-62cc to be a true 10.5 compression.

 

[Plymouth65]

The 340 would need the chambers to be 60-62cc to be a true 10.5 compression.

Machine shop told me the cc of the heads was 58cc

 

[Plymouth65]

I thought the op was getting a rebuild and wanted to know why the head cc number was needed.

The intent was to figure out what pistons to use with the heads I intended to use. I have found out that the 202 heads are 58cc. Now I don't know whether to use those heads or the 1.88 valve 360 heads.

 

[MOPAROFFICIAL]

The intent was to figure out what pistons to use with the heads I intended to use. I have found out that the 202 heads are 58cc. Now I don't know whether to use those heads or the 1.88 valve 360 heads.

If they've been milled that far, I hope they also milled the intake face of the head so that you don't have manifold fitment problems. Once the heads are on the engine unless you take them off, you'll have to Mill the intake manifold for it to fit. If they're a good machine shop they would have all your parts though and machine and mock assemble to make sure it all fits.

 

[CPDave]

Here's what I have for LA head spec's up to '86 or so, I'd appreciate it if someone could fill in up to the end of the pre-Magnum engines.

LA Small Block Cylinder Head Casting Numbers and Spec's
Through 1986 (From How to Rebuild Your Small-Block MOPAR
by Dob Taylor & Larry Hofer HPBooks 1987):

Engine ---- Year ------ Casting - Intake/Exhaust - CC
====================================
273 -------- 64-65 --- 2465315 - 1.78"/1.50" - 57
273 -------- 66 ------- 2536178 - 1.78"/1.50" - 57
273/318 -- 67 ------- 2658920 - 1.78"/1.50" - 57
273/318 -- 68-74 --- 2843675 - 1.78"/1.50" - 60 '69 last year for 273
318 -------- 75-83 --- 3769973 - 1.78"/1.50" - 63
318 -------- 77-86 --- 4027163 - 1.78"/1.50" - 63
318 -------- 77-84 --- 4027593 - 1.78"/1.50" - 63
318 FstBrn 85-86 --- 4323302 - 1.78"/1.50" - 62.6
318 Police 83-86 --- 4323345 - 1.88"/1.60" - 75.1
340 -------- 68-71 --- 2531894 - 2.02"/1.60" - 63
340 TA ---- 70 ------- 3418915 - 2.02"/1.60" - 65
340 -------- 72 ------- 3418915 - 1.88"/1.60" - 65
340 -------- 73 ------- 3671587 - 1.88"/1.60" - 65
360 -------- 71-72 --- 3418915 - 1.88"/1.60" - 65
360 -------- 73-74 --- 3671587 - 1.88"/1.60" - 65
360 -------- 75-76 --- 3769974 - 1.88"/1.60" - 65
360 -------- 76 ------- 3671587 - 1.88"/1.60" - 65
360 -------- 77-86 --- 4027596 - 1.88"/1.60" - 65
360 -------- 77-86 --- 4021051 - 1.88"/1.60" - 65

Note: of the unmolested heads that I've had CC'd they came in between 2 and 5 cc over spec, except for one set of ...302s which were 0.5cc under spec before chamber work and milling.

 

[MOPAROFFICIAL]

Here's what I have for LA head spec's up to '86 or so, I'd appreciate it if someone could fill in up to the end of the pre-Magnum engines.

LA Small Block Cylinder Head Casting Numbers and Spec's
Through 1986 (From How to Rebuild Your Small-Block MOPAR
by Dob Taylor & Larry Hofer HPBooks 1987):

Engine ---- Year ------ Casting - Intake/Exhaust - CC
====================================
273 -------- 64-65 --- 2465315 - 1.78"/1.50" - 57
273 -------- 66 ------- 2536178 - 1.78"/1.50" - 57
273/318 -- 67 ------- 2658920 - 1.78"/1.50" - 57
273/318 -- 68-74 --- 2843675 - 1.78"/1.50" - 60 '69 last year for 273
318 -------- 75-83 --- 3769973 - 1.78"/1.50" - 63
318 -------- 77-86 --- 4027163 - 1.78"/1.50" - 63
318 -------- 77-84 --- 4027593 - 1.78"/1.50" - 63
318 FstBrn 85-86 --- 4323302 - 1.78"/1.50" - 62.6
318 Police 83-86 --- 4323345 - 1.88"/1.60" - 75.1
340 -------- 68-71 --- 2531894 - 2.02"/1.60" - 63
340 TA ---- 70 ------- 3418915 - 2.02"/1.60" - 65
340 -------- 72 ------- 3418915 - 1.88"/1.60" - 65
340 -------- 73 ------- 3671587 - 1.88"/1.60" - 65
360 -------- 71-72 --- 3418915 - 1.88"/1.60" - 65
360 -------- 73-74 --- 3671587 - 1.88"/1.60" - 65
360 -------- 75-76 --- 3769974 - 1.88"/1.60" - 65
360 -------- 76 ------- 3671587 - 1.88"/1.60" - 65
360 -------- 77-86 --- 4027596 - 1.88"/1.60" - 65
360 -------- 77-86 --- 4021051 - 1.88"/1.60" - 65

Note: of the unmolested heads that I've had CC'd they came in between 2 and 5 cc over spec, except for one set of ...302s which were 0.5cc under spec before chamber work and milling.

675-318 heads were 68 CC's when I measured them. Pretty much every 360 and 340 head measured 72 with the exception of a couple measuring bigger because the exhaust valves were sunk. The 920 head measurement is pretty much spot on

 

[67Dart273]

North 40 outfitters and Cenex/ Co-op carry syringes, here

Also, I finally ended up buying to gigantic all GLASS ones when I was arguing the GMC brakes (which are still not happy) to use with gas/ oil, etc, as the rubbers in the others do not hold up. If you have a large enough one, you can easily temporarily use a syringe, without the plunger, as a burette by simply using a length of small hose and a clamp or some other valve, AKA aquarium valve or such

 

[66fs]

Here's what I have for LA head spec's up to '86 or so, I'd appreciate it if someone could fill in up to the end of the pre-Magnum engines.

LA Small Block Cylinder Head Casting Numbers and Spec's
Through 1986 (From How to Rebuild Your Small-Block MOPAR
by Dob Taylor & Larry Hofer HPBooks 1987):

Engine ---- Year ------ Casting - Intake/Exhaust - CC
====================================
273 -------- 64-65 --- 2465315 - 1.78"/1.50" - 57
273 -------- 66 ------- 2536178 - 1.78"/1.50" - 57
273/318 -- 67 ------- 2658920 - 1.78"/1.50" - 57
273/318 -- 68-74 --- 2843675 - 1.78"/1.50" - 60 '69 last year for 273
318 -------- 75-83 --- 3769973 - 1.78"/1.50" - 63
318 -------- 77-86 --- 4027163 - 1.78"/1.50" - 63
318 -------- 77-84 --- 4027593 - 1.78"/1.50" - 63
318 FstBrn 85-86 --- 4323302 - 1.78"/1.50" - 62.6
318 Police 83-86 --- 4323345 - 1.88"/1.60" - 75.1
340 -------- 68-71 --- 2531894 - 2.02"/1.60" - 63
340 TA ---- 70 ------- 3418915 - 2.02"/1.60" - 65
340 -------- 72 ------- 3418915 - 1.88"/1.60" - 65
340 -------- 73 ------- 3671587 - 1.88"/1.60" - 65
360 -------- 71-72 --- 3418915 - 1.88"/1.60" - 65
360 -------- 73-74 --- 3671587 - 1.88"/1.60" - 65
360 -------- 75-76 --- 3769974 - 1.88"/1.60" - 65
360 -------- 76 ------- 3671587 - 1.88"/1.60" - 65
360 -------- 77-86 --- 4027596 - 1.88"/1.60" - 65
360 -------- 77-86 --- 4021051 - 1.88"/1.60" - 65

Note: of the unmolested heads that I've had CC'd they came in between 2 and 5 cc over spec, except for one set of ...302s which were 0.5cc under spec before chamber work and milling.

From my experience those are NHRA minimum specs. I can tell you that it took .040 off "J" heads and "920" 273 heads to get down to those numbers. Also see Post#40 about milling the intake face. I also milled the intake face .038 on both the "920 and "J" heads, like thew book says and had no fitment problems.

 

[RustyRatRod]

If they've been milled that far, I hope they also milled the intake face of the head so that you don't have manifold fitment problems. Once the heads are on the engine unless you take them off, you'll have to Mill the intake manifold for it to fit. If they're a good machine shop they would have all your parts though and machine and mock assemble to make sure it all fits.

Yeah cause it AIN'T gonna fit with the heads milled down that far.

 

[RustyRatRod]

Here's what I have for LA head spec's up to '86 or so, I'd appreciate it if someone could fill in up to the end of the pre-Magnum engines.

LA Small Block Cylinder Head Casting Numbers and Spec's
Through 1986 (From How to Rebuild Your Small-Block MOPAR
by Dob Taylor & Larry Hofer HPBooks 1987):

Engine ---- Year ------ Casting - Intake/Exhaust - CC
====================================
273 -------- 64-65 --- 2465315 - 1.78"/1.50" - 57
273 -------- 66 ------- 2536178 - 1.78"/1.50" - 57
273/318 -- 67 ------- 2658920 - 1.78"/1.50" - 57
273/318 -- 68-74 --- 2843675 - 1.78"/1.50" - 60 '69 last year for 273
318 -------- 75-83 --- 3769973 - 1.78"/1.50" - 63
318 -------- 77-86 --- 4027163 - 1.78"/1.50" - 63
318 -------- 77-84 --- 4027593 - 1.78"/1.50" - 63
318 FstBrn 85-86 --- 4323302 - 1.78"/1.50" - 62.6
318 Police 83-86 --- 4323345 - 1.88"/1.60" - 75.1
340 -------- 68-71 --- 2531894 - 2.02"/1.60" - 63
340 TA ---- 70 ------- 3418915 - 2.02"/1.60" - 65
340 -------- 72 ------- 3418915 - 1.88"/1.60" - 65
340 -------- 73 ------- 3671587 - 1.88"/1.60" - 65
360 -------- 71-72 --- 3418915 - 1.88"/1.60" - 65
360 -------- 73-74 --- 3671587 - 1.88"/1.60" - 65
360 -------- 75-76 --- 3769974 - 1.88"/1.60" - 65
360 -------- 76 ------- 3671587 - 1.88"/1.60" - 65
360 -------- 77-86 --- 4027596 - 1.88"/1.60" - 65
360 -------- 77-86 --- 4021051 - 1.88"/1.60" - 65

Note: of the unmolested heads that I've had CC'd they came in between 2 and 5 cc over spec, except for one set of ...302s which were 0.5cc under spec before chamber work and milling.

Most all those numbers maybe except for the 273 are completely erroneous. I don't know why people publish stuff like that.

 

[CPDave]

Most all those numbers maybe except for the 273 are completely erroneous. I don't know why people publish stuff like that.

Those are the spec's the factory published, I guess they didn't blueprint the heads before they went out the door. Anyone building for performance, however probably should check/correct them.

 

[RustyRatRod]

Those are the spec's the factory published, I guess they didn't blueprint the heads before they went out the door. Anyone building for performance, however probably should check/correct them.

They also published the 68-71 340s at 10.5:1 compression. LOL