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Pontiac of the Month

4 bucket 67's 1967 GTO

2023 December
of the Month

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Hi all. New here and I will complete my profile as soon as I can. I am completely outside my wheel house here and have spent most of my time tinkering with newer sports cars. Recently I came across a 66 Lemans for a great deal and decided to pick it up. This car is completely a mismatch of Pontiac parts and I will do my best to lay it all out for ya in the hopes of getting a solid answer as to why I seem to be lacking in the power department. The car is a 2 door Montereo red Lemans that has been dressed like a GTO.

What I have

1- Pontiac 400 motor code YD and from what I can see this was a 290HP variant from a Pontiac executive. I had this motor completely stripped down and reassembled with the following:

2). Stock pistons (motor has never been bored. New bearings bla bla bla

3) the CAM springs and lifters were all changed to comp gear with the cam being:

Comp xtreme energy with
268/280. 477/480

4) the intake manifold is a Holley street dominator

5) the carb is a Holley 750 double pumper with mechanical secondaries that’s do indeed work as they should. I verified this morning along with the throttle linkage

6) msd dizzy with built in coil. 10 degrees of timing
7) long tube headers not sure what model magnaflow mufflers 
good spark plugs and wires
9) the heads I’m unsure but I will post some pics of the numbers on the sides
10) the tranny is a 4 speed saganaw. Completely rebuilt but still a weak point
11) the gearing I’m not sure but I found a receipt for 373 gears from the previous owner 

She sounds great and drives real nice. It just seems to be lacking a lot of get up and go. I can’t even spin the tires without dumping the clutch. I’m guessing the problem is to do with the cam being a bad pairing with the heads ? Maybe over carbed? Any help on which direction I should go would be helpful. One last thing, it seems like fuel supply is not the issue



Edited by DustinMitchell
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Hi DUstin. Welcome to FP.

Your photos are appreciated but they are just missing key information we need to help you to help identify the heads.



There should be a two or three character designation where you see the 5C in the picture above. Or there is a six or seven digit casting number that usually begins with "5" or "9". Either one will tell us what Pontiac head you have and what cc's they are (assuming they are stock). I suspect you are correct that the cam and heads are not well matched to each other or perhaps the double pumper is a tad too much fuel.

What is your goal for the car? Mainly street usage?

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