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Old 12-05-2010, 02:01 PM
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Pontiac Head

I am looking at a few different charts about cylinder head volume and was looking for some solid advise. Wallace racing site lists a #94 and a #96 cylinder head (1971 350 -94 1971 400 -96 ) both as having a 96 cc volume. And kens speed and machine lists it as # 94 - as 80 cc s and the #96 as 96 CC s .
Does anyone know for sure which one is right?
I dont have the funds to buy a buttload of cylinder heads just to see. I can CC them and I am going to open up a set to about 87 CCs and I need to know what to start with. The #94 heads would probably work fine if they are 80 CCs as I could do a little work on the chambers and end up with 87 CCs which is the magical number in my build. ***.

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Old 12-05-2010, 03:40 PM
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The 73-74 4C-5 & 46 heads were rated, by the factory, at 86cc.
The early 75 5C-4 & 5C-7 and the 75 or later 6X-4 were rated at 93cc.
These are the factory ratings, so the heads must be checked to be sure of the exact combustion chamber size. I have found them, usually, to be close, but almost never exact. For example, the 722 RA-IV was rated at 71cc, but my over the counter heads were 77cc.

Bill
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Old 12-05-2010, 04:56 PM
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Anything close would be great. I can open them up a little if I am careful.I just cant seem to find consistency in the different sites and I cant buy a bunch of heads just to CC them to find they arent what I want. Not to many sellers will CC thm either LOL
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Old 12-05-2010, 07:15 PM
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If you were to find a good pair of either 46 or 4C secondary code 5 heads, you would know that they are close to 86cc, so buy them and take them home to cc them. In my opinion they would be the best factory head that you could get.
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Old 12-05-2010, 07:23 PM
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Quote:
Originally Posted by WDCreech
If you were to find a good pair of either 46 or 4C secondary code 5 heads, you would know that they are close to 86cc, so buy them and take them home to cc them. In my opinion they would be the best factory head that you could get.
Thank you bill. I'll keep a look out for those.Do you mean the #46 set with a date code for 1969 (400+428) or date code for 1973 (350).
I know right where there is a set of 46 on a 73 350.
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Old 12-05-2010, 07:33 PM
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A little hint, All 73 350s will have 46 heads. 74 350s wil have either the 4C-5 or the 46 head and the GTO will have 46s with screw in rocker studs.
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Old 12-05-2010, 07:34 PM
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Kens speed and machine shows the 1973 #46 head at 89 Cc. Completely accptable but the same number is used on a 1969 428+400 and they are shown by ken to be 72 CC. Thats too small.I can cut .010 off of the 89 CC heads to get to 87 CC if need be, but opening up a set from 72to 87CC would probably not go well.
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Old 12-05-2010, 10:14 PM
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latech, You have to check the date code of the head. There were no 72 cc 46 heads in 73-74. Pontiac used the same numbers, in different years, for heads with different specs. Go to the Wallace site http://www.wallaceracing.com/headsearch.htm and scroll down to the drawing for code locations. Casting for a model year generally started in July of the previous year, thus GXX3 woud be for the 1974 model year.
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Old 12-06-2010, 06:03 AM
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I knew about the date code, but didnt have the valve cover off. Then salvage yard owner said it is a 350 and someone wrote 69-350 on it. I am sure that is wrong as the block casting number is a 488986 which is indicative of a 73 350. Next I saw the date code on the head was a G273 which should be july 73. I was freakin out when I first saw the head code as that number does appear on the head for a 69 400+ 428. BUT...then reality set in and the numbers crashed my little dream.Guy wants 250 for engine and turbo 400 both running when set there years ago.He only garanteed them to be rebuildable cores at this point. Cover His A**.Still not bad. I will be going for it. Thanks Bill. Linn
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Old 12-06-2010, 06:28 AM
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Any chance the heads have screw in studs? If so, grab that deal.

I might would do it anyway, given that there's a TH400 thrown in (it'll likely have the dog sprag, though ) but that casting date gives it a slim chance of having been used on a '74 production engine. And IF (big "IF") it was a '74 "GTO" (X-body Nova clone w/a hood scoop, horrendous stripe package, 'ground effects', and little else), it may have the "good" heads.
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Old 12-06-2010, 12:20 PM
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It is now in the back of the pickup. I opted not to take the turbo 400 but I am going to call him later and tell him to hang on to it untill spring.
The motor turned over and all the cylinders seemed to make real good pressure.Its a 2 barrell motor, probably not the gto (darn) . He said it was a good motor when he put it in the building years ago but he said he was selling it as a rebuildable core. It has 5 pads for motor mount bolts and they are all drilled and tapped for bolts.
It had good looking coolant running out of it when I kicked it overon its side, so I am pretty anxious to get the heads of so I can CC them. I sure hope they are the right ones.
I am going to save the bottom end for later, I have a good running 1971 350 2 barrel engine in the car that runs good, I am building the 389 to perform somewhat, I will keep the other 350 bottom maybe to get squirrelly and put a stroker kit in it...who knows.At least I will have some spare motors and such.Thanks for your reply
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Old 12-06-2010, 07:26 PM
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Well , I have not only got the 73 350 with the number 46 heads date coded july 1973 I bought... I got a set of 7H1 heads also. They show to be 80 CC s .
I cant seem to get any truly concrete answers for the chamber sizes of the heads for my build. Its no ones fault, it is just dated information.
So I cant pass anything up.
I am doing just what I said I did not want to do.I now have a shed full of heads. I will open an E Bay store soon . LOL
I am going to CC all the heads I have and I will post the results.If anyone is interested.
I am dissapointed that so many different websites give so many different specs. Its a wonder anyone can build **** that actually runs as designed.
I also read somewhere that the same head the same secondary code can actually have a difference of 6-8 CCs depending if the engine was destined for an automatic sled or a stick.The stick usually got a smaller chamber than the auto.I also read that pontac chambers are machined so if they have enough meat they could take a raw casting and vary the end chamber size with a flick of the wrist on the mill. Hmmmmmmmmmmm
I wont fill my Beret with Kool Aid you can bet.

Last edited by latech; 12-06-2010 at 07:32 PM.
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Old 12-06-2010, 08:01 PM
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I believe the 7H1's are "4-bolt" heads, that is, they have only 4 exhaust manifold/header bolt holes. I don't recall if the boss/pad is there and can be drilled and tapped or if it's like the 7K3 head that lacks the pad altogether.

There's an "L" bracket available that allow$ a header to be bolted up if the pad is missing.
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Old 12-07-2010, 05:22 AM
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Quote:
Originally Posted by cobalt327
I believe the 7H1's are "4-bolt" heads, that is, they have only 4 exhaust manifold/header bolt holes. I don't recall if the boss/pad is there and can be drilled and tapped or if it's like the 7K3 head that lacks the pad altogether.

There's an "L" bracket available that allow$ a header to be bolted up if the pad is missing.
You are correct, these the 7H1 and the 46 heads BOTh are 4 bolt heads. I was so concerned with all the rest I never noticed that.
Can they be drilled and Tapped, are they meaty enough?Thanks Cobalt
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