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Old 06-09-2021, 02:03 PM
blackadder blackadder is offline
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Default Head comparison

Just wondering how 141 heads would compare to 77 heads? I have a 421 HO motor I am looking at building soon and the previous owner put 65 #62 heads on it. I am looking to get it a little closer to stock. I have a pair of 7K3 heads but was thinking of options.

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Old 06-09-2021, 02:39 PM
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It would be a toss up assuming both castings where in good usable condition.

The problem is there 68 or so CC chambers will with stock type pistons leave you with too high a compression ratio.

If it where me and I had the 7K3 heads already and wanted 10% more power then the early heads then I would grind off those 7k3 center port numbers and the casting date and run those, just watch out if your running more then .440” lift or so with the 421 pistons.

Also run the later 9.130” long push rods .

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Old 06-09-2021, 03:19 PM
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Problem with 72 7K3s is that they have no end exhaust manifold bolts and are very difficult to seal for long.

Still have 12s on my Judge but also add CD-2 (lead substitute) to every tank.. If ever needful have a nice set of 6Xs in big baggies.

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Old 06-09-2021, 04:50 PM
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If your just running exh manifolds it’s not a issue with sealing, but if you are running headers and the heads are off the car then the head bolt bosses at each end can be drilled and taped for 5/16” fine thread and then running headers is not a problem.

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Two pairs of brown leather flip flops, never seen more then 2 mph.

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Old 06-09-2021, 05:07 PM
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Thanks for the replies. The 7K3's are rebuilt just sat for a while. Will most likely need new stem seals. I am not overly worried about the dates or the casting #'s as I am planning to put the motor into my 65 GTO so accuracy is not my goal. just looking for a good streetable motor with some power.

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Old 06-09-2021, 05:37 PM
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Quote:
Originally Posted by steve25 View Post
If your just running exh manifolds it’s not a issue with sealing, but if you are running headers and the heads are off the car then the head bolt bosses at each end can be drilled and taped for 5/16” fine thread and then running headers is not a problem.
It's not difficult to do..
You have to drill the holes straight, obviously. I used a chunk cut out of a 2X4, drilled a straight hole through it, on a drill press, same size to use as a guide, marked the holes, checking with an exhaust gasket AND double checked with a manifold. I did this on a set of 11 heads..

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Old 06-09-2021, 05:48 PM
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I’d be looking for a proper #77 head for that 421.

Along with a Tri-Power to top it off.

Make it look like a 421.

Classic 421 HO.

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Old 06-09-2021, 05:54 PM
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"Along with a Tri-Power to top it off." BTW there were at least three different tripowers in the '60s. GTO high-rise with small center carb, GTO high rise with large center carb, and low rise B-body (421). GTO had three small pots limiting air flow and B-body had a single large air cleaner that could flow near 1,000 cfm.

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Old 06-09-2021, 06:02 PM
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Quote:
Originally Posted by padgett View Post
"Along with a Tri-Power to top it off." BTW there were at least three different tripowers in the '60s. GTO high-rise with small center carb, GTO high rise with large center carb, and low rise B-body (421). GTO had three small pots limiting air flow and B-body had a single large air cleaner that could flow near 1,000 cfm.
There are no low rise B-body specific Tri-Power intakes.

All Tri-Power intakes were low rise design until the first high rise design that started in 1964.

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Old 06-09-2021, 06:34 PM
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I'm pretty sure 141's are 326 HO heads...someone probably wants those for a 326.

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Old 06-09-2021, 06:40 PM
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Yes, the 141 casting is from that 326 ho motor only!

If your not concerned with the casting numbers and do not have a tripower set up to drop on then the 7k3 heads and a Edelbrock 2-4 bbl set up looks and runs a whole lot better!

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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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Old 06-10-2021, 02:41 AM
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Quote:
Originally Posted by padgett View Post
"Along with a Tri-Power to top it off." BTW there were at least three different tripowers in the '60s. GTO high-rise with small center carb, GTO high rise with large center carb, and low rise B-body (421). GTO had three small pots limiting air flow and B-body had a single large air cleaner that could flow near 1,000 cfm.
All 1964-66 Pontiac Tripower intakes are "high-rise".
All 1963 and earlier Pontiac Tripower intakes are "low-rise".
This includes B-body 421 engines.

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Old 06-10-2021, 02:00 PM
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I have a pair of #77 bare castings that would require a complete rebuild. I also have a 1965 dated tripower with all the carbs. I am just looking for options on heads. I am aware that the 7K3 heads do not have the outer exhaust studs but I can order brackets to fix that. There is a guy a few miles away that has the #141 heads for $500. They have been rebuilt and only ran for a summer.
Thought the 141's may work being valve size and CR are about the same as #77's but never thought of the bore dia difference. I also have a pair of new rebuilt 7K3's but had them shaved 25 thou on a 428 I have to bring up the compression a bit.

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Old 06-10-2021, 04:26 PM
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Quote:
Originally Posted by steve25 View Post
Yes, the 141 casting is from that 326 ho motor only!

If your not concerned with the casting numbers and do not have a tripower set up to drop on then the 7k3 heads and a Edelbrock 2-4 bbl set up looks and runs a whole lot better!
This is a personal preference thing but an Offy dual quad setup can be made to look almost identical to the '61-'63 inline SD setups. The difference in the spacing on the carbs between the read SD intakes and the Offy is only 3/8" where the Edelbrock intake jambs the carbs almost up against one another which does not allow using the SD air cleaners on them.

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Old 06-10-2021, 04:28 PM
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Same Head Bolts.
Maybey the same amount of Exhaust bolts, I dunno. You will want 6 Exhaust bolts per Head.

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Old 06-10-2021, 04:35 PM
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Sell the 7K3 heads.

Use the proceeds to help finance the #77 head rebuild.

Build a proper 421 HO.

It’s a fairly rare antique high performance V8 from the golden age of Pontiacs.

A mundane set of ‘72 heads or just as bad some 326 heads would just be wrong.

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  #17  
Old 06-10-2021, 05:07 PM
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Quote:
Originally Posted by padgett View Post
Problem with 72 7K3s is that they have no end exhaust manifold bolts and are very difficult to seal for long...
there are these great adapters that add a stud where an extra boss was previously tapped.

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