Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

Dual quads

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Cliff Ruggles:
What are you goals for power production?

Difficult to get a decent compression ratio with those heads.

If the engine was built with the 8 valve relief cast pistons they will reduce the compression at least another half a point, so they have to be replaced as well......Cliff

chance:
I thought I might have to go with different heads, a friend of mine has a set of 65 389 heads but the valves are smaller? I want a low to mid 400 hp engine that I can drive on the street and some weekend drag racing, the car has 3:42 diff in it. I"m picking the engine up tomorrow so I'll be able to look it over more closely and see what's there and what the quality of the parts are.
I'll keep you posted, I'm going to try to build it this winter and install it in the spring so I have some time to look for what I need
Thanks!
God Bless!!!

Cliff Ruggles:
I wouldn't use heads earlier than 1967, they made big changes in 1967 and all for the better.  The early heads also mess things up for using a decent piston as well, and why the "generic" cast replacement pistons have 8 valve reliefs instead of 4.

The 8 valve relief pistons are garbage.  Not only do they reduce compression, most are .030-.050" below the deck at TDC.  Pontiac engines THRIVE on very tight quench and will run hot/overheat/detonate if you build them with too much quench area.

They also use cast iron connecting rods which are a disaster waiting to happen.

I'd put a good set of 4340 "H" beam rods and Icon or equivalent forged full floating pistons on my wish list for that engine.  The better pistons also come with a revised ring pack and are much lighter than factory replacement type forged pistons......Cliff

chance:
Yeah the engine I took out of the TA had those 8 valve relief pistons in it, the 67 block I'm getting today only has the 4, I haven't had a chance to look at the rods closely but I'm assuming they're 67 units. I'll no more tomorrow.
Thanks bud!!
God Bless!!

chance:
Well Cliff, you gotta love a friend of a friend story....LOL When I went to look at this 400 it was on a pallet with another engine stacked on top in a shed. I could see it had new pistons and the guy was a friend of my friend. so I said I'll take it, so he delivered it to my friend as he was going to Florida for 2 weeks. Long story short.... It's not a 400, it's a 68 350. so my Question to you is can I use the 350 and the parts of the 400 that I have to build a stroker motor, are the cranks the same can I put it in my 400 block, since I'm going to have to buy pistons anyway bore one of them to 455??? I haven't paid for the engine yet and I know he will take it back. Like I told you on the phone this is my first Pontiac build and I don't know them like I do the mopars and chevys What are your thoughts? I ordered the max performance Pontiac book that we talked about on the phone it should be here in a few days.
Take care my friend!!
God Bless!!

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