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Cylinder head interchange
Posted: Thu Feb 06, 2020 7:43 pm
by custom76
I have an opportunity to buy a pair of good 1971 heads off a 360. Is their any difference or downside to putting these on my 1976?
What do these typically sell for?
Thx
Re: Cylinder head interchange
Posted: Thu Feb 06, 2020 8:41 pm
by Stuka
No clue what they sell for, and that really depends on condition.
But, 71 could be one of two different heads. 51cc or 58cc. Both will raise your compression, and both will also have the dog leg exhaust ports like your current heads.
Re: Cylinder head interchange
Posted: Thu Feb 06, 2020 9:02 pm
by custom76
Stuka wrote: ↑Thu Feb 06, 2020 8:41 pm
No clue what they sell for, and that really depends on condition.
But, 71 could be one of two different heads. 51cc or 58cc. Both will raise your compression, and both will also have the dog leg exhaust ports like your current heads.
Do you know what compression ratios I would have on these and is having the seats hardened even an issue with AMC motors? It’s kind of a big deal on Pontiac motors if you jack up the compression and run ethanol added gas.
Thx
Re: Cylinder head interchange
Posted: Thu Feb 06, 2020 10:48 pm
by Stuka
71 would need to have hardened seats installed if you didn't want to have to worry about it. Since you would have them off, it wouldn't hurt, it doesn't cost much (They are like $6 each).
And the compression ratio would depend on what pistons you have, so I cannot answer that.
Re: Cylinder head interchange
Posted: Fri Feb 07, 2020 7:08 am
by will e
Exhaust bolts may be different. On the older heads all 6 exhaust bolts were the larger size (I believe 3/8 inch thread). On the newer heads, don't ask me when they started this, the outer bolts are smaller than the inner bolts which remained at 3/8 inch thread).
Also, the hole for the alternator bolt is typically larger on the older heads too. I believe 7/16".
So if you do decide to use them, verify the bolt sizes before you assemble them onto the engine. You might need to get replacement bolts.
Good luck!
Re: Cylinder head interchange
Posted: Fri Feb 14, 2020 8:57 am
by MReese Wagoneer
will e wrote:
Also, the hole for the alternator bolt is typically larger on the older heads too. I believe 7/16".
So if you do decide to use them, verify the bolt sizes before you assemble them onto the engine. You might need to get replacement bolts. !
I can tell you the alternator bolt is different , no one makes the Delco alt with a 7/16 hole on the 2” mount , I drilled mine out along with 2 mount brackets and the 2 inch spacer
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Re: Cylinder head interchange
Posted: Sat Feb 15, 2020 3:10 pm
by custom76
will e wrote: ↑Fri Feb 07, 2020 7:08 am
Exhaust bolts may be different. On the older heads all 6 exhaust bolts were the larger size (I believe 3/8 inch thread). On the newer heads, don't ask me when they started this, the outer bolts are smaller than the inner bolts which remained at 3/8 inch thread).
Also, the hole for the alternator bolt is typically larger on the older heads too. I believe 7/16".
So if you do decide to use them, verify the bolt sizes before you assemble them onto the engine. You might need to get replacement bolts.
Good info, thx
Good luck!
Re: Cylinder head interchange
Posted: Sun Feb 16, 2020 12:38 pm
by fulsizjeep
This may be helpful to you.
Re: Cylinder head interchange
Posted: Mon Feb 17, 2020 11:10 am
by custom76
fulsizjeep wrote: ↑Sun Feb 16, 2020 12:38 pm
This may be helpful to you.
Many thanks, very helpful.
Re: Cylinder head interchange
Posted: Mon Feb 17, 2020 11:17 am
by custom76
Stuka wrote: ↑Thu Feb 06, 2020 10:48 pm
71 would need to have hardened seats installed if you didn't want to have to worry about it. Since you would have them off, it wouldn't hurt, it doesn't cost much (They are like $6 each).
And the compression ratio would depend on what pistons you have, so I cannot answer that.
I was told by PO engine was freshened with new rings on the stock pistons. The RH cylinder head has a small crack that was repaired by some PO at the far rear bottom corner. Can’t tell without getting closer if it was welded or epoxied.
It’s more of a minor nuisance with some oil burn off and I may try an epoxy patch first, think I can get to it in order to prep and repair if I pull the outside heater box.
I realize head replacement is preferred, but any suggestions on a brand or type of metal epoxy?
Thx