Plymouth65
Active Member
Looking for the CC specs for 340 heads casting 3418915B and 360 heads casting 3769976.
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340 & 360 Cylinder head CC specs
- Thread starter Plymouth65
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MOPAROFFICIAL
If it has tits, it's a liabilititty.
72cc chamber, 155-160cc intake port
90's cc exhaust port
Its 894, 974, ... i think you mixed up 974/596
90's cc exhaust port
Its 894, 974, ... i think you mixed up 974/596
Plymouth65
Active Member
These are the pictures of the heads that I have. I found a guide to Mopar V8 Cylinder Heads and Block Casting Numbers, it indicates the following 3418915 – 1970, 340 LA-series small-block, 2.02/1.60 valves, 63cc-73.5cc, T/A. I am assuming the 63cc is the standard head and the 73 would be the T/A
Dartswinger70
Well-Known Member
The 895 casting number heads will say 340 on them the 915 J heads will say 360. I suppose a purist would say the 894s are the 340 heads... ? but yes the J heads were used on later 340s etc.
PRH
Well-Known Member
When you really want/need to know……you measure them.
MOPAROFFICIAL
If it has tits, it's a liabilititty.
As i said.
A quick verification if they're still stock or within only ,you know...' a few thousands of stock' ... stack some feeler gauges in the shallow side of the chamber or use the tail of a mic and you should get about .100 deep which is a tell of 72 cc
Plymouth65
Active Member
They do say 360 they are also marked Z and O with 2.02 valves
Dartswinger70
Well-Known Member
I do believe Google will tell you x heads are 65ccs Js may be 72 ccs etc. that's combustion chamber volume but it varies if you want exact I agree cc them and measure it the cc kits are cheap IMO.
Dartswinger70
Well-Known Member
Yes they did have different casting marks the actual number if last 3 of it is "915" its a 360 head etc. but there are also later 360 castings also I believe . The "915" was the early 70s LA head released in 1971 then to add to the confusion if you ar ereading up, there is a big block 915 head also
MOPAROFFICIAL
If it has tits, it's a liabilititty.
Good luck OP
Over n out.
Over n out.
Dartswinger70
Well-Known Member
Ill drop this here just to stay on track may be some good info but keep in mind to get "surgical" you'd need to measure and flow test etc. Small Block Cylinder Heads 'Stock Specs'
Unmilled “J” virgin heads measure about 72-73 cc per chamber. Only listen to Moparofficial and Perfacar so far. I assume the 974 heads are the same chamber size, as “J” heads but I have not personally cc’d them.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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I've NEVER seen or heard of a factory stock, 65cc big-port, sbm head.
But, I admit, my experience is limited, lol.
But, I admit, my experience is limited, lol.
That ^^^^^^^
Because what they say they are and what they really measure are 2 different things.
Plymouth65
Active Member
Please excuse my ignorance, but how important is that in determining what pistons to put in my 360. It has to be bored 40 over and while looking for a new rotating assembly I was asked about the the cc of the heads in relation to compression ratio.
ir3333
Well-Known Member
Head cc total determine static compression ratio. I've read Mopar rated them a t 63 or 65 cc so you could blueprint them to 63cc / 10.5 compression and be NHRA legal. Stock they were all around 72 cc's and about 9.5 compression.
Those are NHRA minimum specs. It takes approximately .040 mill to get that small.
ir3333
Well-Known Member
so .020 mill would be around 68cc. Would that be about 10:1 compression?
Yes, you need to know piston to deck measurements and head gasket thickness also for compression calculations. I usually shoot for 9:1 myself as I run factory exhaust manifolds a have a street car.
No, it's not "just the head". The head, the piston crown, how far the piston is at TDC (deck clearance), head gasket thickness and cylinder head cc all add up. So unless it's all measured, compression is unknown. Also, one thing almost everyone forgets to add in is the space from the piston crown to the top piston ring. Although a small amount, in order to be accurate, that must be included as well. That's why I use the .500 down method when figuring compression. It includes "all that".
Right and "MOST TIMES" milling the heads that much requires milling the intake or the intake sides of the heads for proper alignment, so it's best to check. I've normally "gotten away" with around .025" or so before bolt alignment becomes an issue.......but port alignment may not be perfect if that's what you're aiming for.
ir3333
Well-Known Member
I thought the op was getting a rebuild and wanted to know why the head cc number was needed.
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