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#1
10-02-2023, 05:20 PM
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1965 head difference
What is the difference between a 1965 77 and 76 head casting? On the surface they seem the same.
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#2
10-02-2023, 05:30 PM
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The ones I've dealt with: 77 has about a 64cc chamber, and 76 has a 69cc chamber. About a half a point in compression difference. Valve size is the same. In a modern build with dished pistons, the performance would be the same, all things being equal.
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Jeff 
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#3
10-02-2023, 06:19 PM
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Thanks I kind of suspected there was a slight chamber size difference or perhaps porting. I will hang on to them then.
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#4
10-02-2023, 07:08 PM
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If your running over .400” lift the bigger chamber head makes more peak power due to less valve shrouding .
The intake and exh ports are exactly the same. One of the craved in stone rules for making power is to never trade air flow for compression, within reason of course!
__________________
Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! Last edited by steve25; 10-02-2023 at 07:18 PM. |
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#5
10-03-2023, 04:21 PM
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Just was curious being I have 3 seats of 7K3 heads as well as the 76's and a fresh rebuilt pair of 64's. The 76 were on the engine in my 65 GTO when I bought it and was wondering if they were worth keeping. I also have a 65 421 I was thinking of using in the GTO as well as a 68 428. Investgating options as well as making room. Thanks for the replies.
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#6
10-03-2023, 04:28 PM
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The rebuilt 1970 455 #64 heads are supposed to be an 87cc chamber volume, more than likely starting out at about 92ccs but of course you need to verify.
That’s a nice head for a 421 or 428 with a flat top piston or one with a small dish depending on what your compression ratio target is. The 76 heads are kinda worthless and not worth putting money into, if they were the 77 heads used on GTO 389s and 421 HO engines they’d have value for restoration purposes. The 7K3 heads are fine at 96ccs for a 455 build but I’m really not a fan with the missing end bolt holes for use with headers.
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1964 Tempest Coupe LS3/4L70E/3.42 1964 Le Mans Convertible 421 HO/TH350/2.56 2002 WS6 Convertible LS1/4L60E/3.23 |
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#7
10-03-2023, 05:10 PM
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Well you have what you might need to build a 389, 421 or 428 so you need to decide.
Any of the post 1965 heads that you have will make far more power then 76 or 77 castings and dish pistons will not be needed.
__________________
Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
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#8
10-05-2023, 03:11 PM
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i agree with both your opinions. The one dislike I have for the 7K3's are the lack of the exhaust stud. I was thinking of the 64's on the 421 running tripower, dependant on the piston wear as onersize pistons seem to be a loooonnnng lead time to obtain. As stated I will need to CC them incase they may have been shaved slightly in the past. I have had others say that they may run a little higher temp on a 421 or 428 due to the wonderful gas we have these days. Has any one had experiance with the thicker Cometic head gaskets to gain a feww CC's if needed?
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#9
10-05-2023, 03:43 PM
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It easy to drill the needed lower outer exh flange holes.
Just bolt up a exh manifold to locate the holes. Just use a big enough tight fitting bit first as a center punch / locate point, then drill and tap for fine thread 3/8”. It takes no more then 1 hour to drill and tap all 4 holes.
__________________
Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
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