pontiac 1967 400CID manual engine rebuilding

Dedek963

The European guy
89
1
8
Prague
I have a Pontiac GTO 1967 4 speed manual.
I bought this car last year in NJ from a guy who serviced the car for 27 years. (I am european, living in Europe so it was a bit difficult for me 😊 )
I have been looking for that car for many years to get it in very original shape. The only not original thing is the engine.
O have been told that this is 1968 GTO 400 engine and it seems to be truth.

Production date seems to be D158
Block casting number 9790071
Engine code 623216 WT

Camshaft 540 / 253 (i have no idea what those numbers are), another numbers 521? / 31 / A /? /D
Crankshaft 9773524 / 107 / N
The diameter of connecting rod journals is 2,241 which means that the crankshaft was at least 2 times repaird (Am I correct?)

There are correct heads 670 (L216)

What is weird is the bore of the cylinders we measured: best value 4,106, worst value 4,118
Also used pistons 9787610 they used to be a part of 421 CID engine

I have no idea how this can happen. A 400 CID block with bore smaller than 4,120. Do you have some explanation for it?

Piston rods: there is no single same number. It seems that there were used piston rods from different engines with the same stroke. The connection rod lenght seems to be 6,625

All the data above seems to allow me to rebuilt the engine to the very original shape.

What I would like to have at the end is an engine better than a factory one with more than 360 HP and 450 Lbs torque. Max safe RPM at about 6500 (BTW: I am using 95 octane fuel)

What I would like to do is:

Change the crankshaft to the right one with a standard (factory new) diameters of journals
Increase the bore to a standard 4,120
Change the pistons and connecting rods to some of better quality than original
If the camshaft is correct, then to keep it. It is mosly untouched. If not then change for the right one
Change the rocker arms (used up) for roller rocker arms
Change valve springs for another with at most 300 lbs (but also not much less)
Of course oil pump and all sealings and gaskets

Might you please help me with yours experience I am lacking to find the right way how to do that and to find the right parts for that purpose?

Many thanks in forward

 

Dedek963

The European guy
89
1
8
Prague
If the engine was really a 389, 4.062 bore stock, 4.092 with .30 over pistons and worn out bores.
The 421 pistons are 4.093 so they would roughly fit a .030 bored 389.
With your aim of 6,500 rpm and the collection of parts you have you would best served to contact this company
https://butlerperformance.com/rt-5038-the-pontiac-engine.html
Hi,
You are right... if it was 389 CID engine, the answer would be exactly like this... but the numbers say, it can not be 389 engine...
The only thing what we could imagine was that ... someone could buy an unfinished new 400 CID block and bore it less than 4,120, because he had some 429 pistons...
I have no other explanation...
 
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Dedek963

The European guy
89
1
8
Prague
melsg5 thank you for the link. I already contacted them.
:)
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melsg5

Staff member
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everything points to a 68 400 even the crankshaft number is late 67/early 68 400.
Any chance the measurements you have are not correct?
another shop you can contact is www.wallaceracing.com
good luck and let us know what you end up doing with the car, if you can post pictures that would be great
 

Dedek963

The European guy
89
1
8
Prague
everything points to a 68 400 even the crankshaft number is late 67/early 68 400.
Any chance the measurements you have are not correct?
another shop you can contact is www.wallaceracing.com
good luck and let us know what you end up doing with the car, if you can post pictures that would be great
My first feeling was, the measuring is wrong (despite all other measurings were correct). So I used also another device to be really sure.

Here are the photos of the measurings. please note > one is inches, the other in mm (inch> cm = 1 x 2,54)











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melsg5

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very puzzling, Butler had no ideas?
have you tried contacting Wallace?
could you post a picture of the back of the car?
 

Dedek963

The European guy
89
1
8
Prague
Yes very puzzling > dismounted to the very last bolt. I want to do it really bottom up and get it into the shape of a new engine.
Some photos above are before cleaning, some after.

Butler has no ideas so far. Maybe because of the weekend.
Wallace will I contact today.

The back of the car corresponds to the date of production > June 1967. Or did you have another reason for seeing it?
 

melsg5

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I just wanted to confirm the year and the back is the easiest way to determine a 66 from a 67. I have seen some strange things happen with vehicles imported to other countries.
Interesting picture your GTO, a 442, and what looks like an American Indian teepee.
The production code D158 cannt be D156? I assume not since the block code 9790011 wasnt used for 67. Since Wallace and Butler deal with engine blocks all the time I was hoping they would know if there were any unusual combinations they have come across to help explain your findings.
 

Dedek963

The European guy
89
1
8
Prague
Some strange cars I have seen in Europe was the reason Why I went to US to personally choose the car.
What I could not see was the engine inside :)
All the other things are original.

The picture was taken 3 weeks ago on a gathering of US 900 cars. I found there this 4-4-2.
The production date is 99,99% D158 eventhough the D and 8 are bit worn out. If you look the last digit closer, you will see, that the missing curve is still noticeable.
The block number was not used any before 1968 (of course it could be 11/67 or 12/67 but it is not this case)

I have the first reply from Butler. But they also do not have the explanation for this unusual combination.

well.. at least I can go for 4,150 bore to match with butlers pistons.
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melsg5

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have you made any decisions concerning other components such as oil pump, I would recommend the Ram Air IV pump. How about the camshaft? Something similar to the 068 cam which was used on the Ram Air III and HO engines. I would not recommend the Ram Air IV 041 camshaft, too rough for a street driven car. Good luck with your project and keep us posted on it's progress.
 

Dedek963

The European guy
89
1
8
Prague
I am trying to communicate with Jim Butler regarding the engine set up. But we are at the very beginning.
Because I want to have a perfect setup, I have to have really lot of information.
(Are pistons T shaped? If yes (according to the picture it seems so) what about durability? what piston chamber to use? Standard or -3? or more?
According to that what camshaft and the compartment...
I send the pictures of the camshaft from my engine I can not determine.
Could you please look what it is?









 

melsg5

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I have not come across the term "T" shaped piston before. I do know you want forged not cast and you already have the GM part number for what is in the car now. https://www.pontiacdiy.com/pontiac-v-8-pistons-and-rings-performance-guide/
CWC on the camshaft is Cambell, Wyant, and Cannon a foundry that made camshaft blanks for many different cars. The 540233, (that is the number?), is from a 61-62 389 Super Duty mechanical lifters. Scroll towards the bottom of this link
http://www.wallaceracing.com/camcode1.htm.

It really seems like somebody was trying to create a 421 type engine for your car.
 

Dedek963

The European guy
89
1
8
Prague
Standard piston looks like this



T shaped pistons are used mostly for racing purposes. They are lighter, have less momentum, allow higher revs, but their durability is almost mostly shorter, because they have often more play.
T shaped pistons look like this

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Dedek963

The European guy
89
1
8
Prague
If I am correct, in the .txt file are now the cam I have in the car and 2 cams from GTO...
I am trying to resolve why my camshaft has been used.
...and simultaneously figure out what the numbers say.
 

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melsg5

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The only benefit of that cam appears to be more duration, lumpy idle, but it is a very old design. I'm sure Butler could recommend a camshaft but they need to know more information. What rear end gearing you have, mention the 4 speed, what type of driving, racing, cruising, intake manifold, carburetor, heads, any other modifications.
 
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