Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

Idle problem

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429bbf:
cliff nice engine. i built a bbf 20 plus years ago. the flattops stuck out of the block  about .010  i used 72cc heads and .035 gasket . it had over 220 cranking compression. a little much . everything went could until i pushed the valves up through the heads . the idiot i hired to do the heads didn't put hardened seats in but charged me for them , long story short it ran about 10,000 miles and started missing . shortly after it started . once the lifters pumped up the valves wouldn't close. i ran it on pump gas but it liked to knock a little. had to use octane booster. fwiw

Cliff Ruggles:
We shoot for zero deck then use the stock Felpro head gaskets that crush at .039".

Hardened seat sure work well with this new fuel, nothing in it to keep the valves from receding into the heads like the old fuel with lead.....Cliff

dlphil10:
I'm not sure the hone was good on the motor. It had a really random idle which I'm thinking had to be ignition because a vacuum gauge showed a steady 17 inHg at hot idle (~22inHg cruising). The decent vacuum also makes me think that cam wasn't too bad for this motor.

I had an original 350 2 barrel that ran great, just got a lot of miles on it. Its compression should have netted around 8.8:1 in terms of actual calculated SCR. I think decking a block 0.041" seems extreme so im having my builder take a solid 0.023" of the deck and go ahead and take it out to 0.040" pistons. Im also going to reuse the same cam as it seemed to be fine. This should put me around true 9:1 and around 7.1:1 DCR (around 63deg. intake closing). It might not be the most efficient or all out motor, but it should be close to efficient as a stock build, no? This should be good to get more done to the car and then go for the 400, 428, or 461.

Thoughts on how the carb should be tuned?

Cliff Ruggles:
I would try it as-is and see how it works.  Should be pretty close for what you are doing.....Cliff

dlphil10:
What power piston spring should I use? I'm guessing it'll make around 15inHg in gear. Dark blue? I think I may have the orange spring in it now, for whatever reason.

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