swapping heads
April 10th, 2012, 08:29 AM
#1
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swapping heads
Could I put the heads off of a 72 350 onto a 77 350? Would it make a noticeable difference? I am using the intake and carb from the 72 on the 77 already. Just wondering if it would be worth the time to use the better heads too?
April 10th, 2012, 04:39 PM
#3
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If I recall, the '77 motors had 14cc pistons, while the '72s had 24cc pistons.
The 14cc pistons of the '77 block plus the 64cc heads of the '72 block should result in a compression ratio of about 9:1, much better than the 8:1 of either the '77 or the '72 engines.
(Check me on this: 350 dish volumes were 0, 6, 14, and 24cc, for 10.5:1, 10.25:1, 9:1 [or 8:1 in 1973 and later], and 8:1 [in 1971 and '72 only] respectively, right guys?)
- Eric
April 15th, 2012, 11:18 AM
#5
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If you truly have a 77 block (casting 554964) that you want to install 7a heads on, you would be pulling off 3A heads, which have a 75cc chamber with 1.875/1.5 valves.
#8 heads came in 73-76 350 engines and have 7/16ths head bolts, your 3A heads will have 1/2 inch head bolts. The 7a heads will have ~69cc chamber at best (not a 64cc chamber), with a larger 1.56 exhaust valve, using the early 7/16ths head bolt.
You will have to have the head bolt holes opened up with a 17/32 drill bit in a drill press or a mill to use the #7a heads on a 77 block. Do not try this with a hand drill.
If you use standard head gaskets, you will gain around 1/2 a point of compression using the stock pistons.
#8 heads came in 73-76 350 engines and have 7/16ths head bolts, your 3A heads will have 1/2 inch head bolts. The 7a heads will have ~69cc chamber at best (not a 64cc chamber), with a larger 1.56 exhaust valve, using the early 7/16ths head bolt.
You will have to have the head bolt holes opened up with a 17/32 drill bit in a drill press or a mill to use the #7a heads on a 77 block. Do not try this with a hand drill.
If you use standard head gaskets, you will gain around 1/2 a point of compression using the stock pistons.
Last edited by Warhead; April 15th, 2012 at 11:22 AM.
April 15th, 2012, 11:39 AM
#6
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SBO head CCs
... And the '72 heads are most likely 7A's with 64-ish cc chambers.
If I recall, the '77 motors had 14cc pistons, while the '72s had 24cc pistons.
The 14cc pistons of the '77 block plus the 64cc heads of the '72 block should result in a compression ratio of about 9:1, much better than the 8:1 of either the '77 or the '72 engines.
(Check me on this: 350 dish volumes were 0, 6, 14, and 24cc, for 10.5:1, 10.25:1, 9:1 [or 8:1 in 1973 and later], and 8:1 [in 1971 and '72 only] respectively, right guys?)
- Eric
If I recall, the '77 motors had 14cc pistons, while the '72s had 24cc pistons.
The 14cc pistons of the '77 block plus the 64cc heads of the '72 block should result in a compression ratio of about 9:1, much better than the 8:1 of either the '77 or the '72 engines.
(Check me on this: 350 dish volumes were 0, 6, 14, and 24cc, for 10.5:1, 10.25:1, 9:1 [or 8:1 in 1973 and later], and 8:1 [in 1971 and '72 only] respectively, right guys?)
- Eric
The #5, #6, #7 incl the small capital A in 1972 are all measure 68-69ccs unless the heads have been milled.
You will also have to drill out the early heads for the larger head bolts required to bolt them onto the later 350 or 403.
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