The car in my signature is having some issues. I had the motor rebuilt and installed my B4B and old carb over to this motor. I had a 74 Quadrajet that was recently rebuilt that i decided to install as it was built for this motor. I am showing 9" or 10" of manifold vacuum. It does not bounce around, i adjust the mixture screws and the vacuum stays steady. I thought that this was kind of low. Also it feels the same on the amount of power as my last 455, dont really notice that much of a difference. The old motor was a 73 stock block/stock pistons with a KB cam, I swapped the intake, carb and headers over to this engine and that was it. I figured i would feel a little more power. I am working on adding a different converter at a later date, along with a different intake. But taking it a step at a time. Any suggestions? Possible vacuum leak on the intake? I carefully sprayed carb cleaner around the base of the carb to see if there was any leaks, there was no rise in RPM when i did this.
Do you have another qjet that is known to be good to test? I've had several "rebuilt" carbs run like complete crap because they have wrong parts on them.
That's low vacuum for that cam. I would try another vacuum gauge also. Don't discount the intake not fitting correctly and creating a vacuum leak into the valley.
That’s what I was thinking also, it’s low. My first plan is a different vacuum gauge. Then thought it might have been the intake leaking. If I take the intake off and put it back on, any tips or tricks? I have The Valley pan cut to TA specs. Then have a gasket on the heads to intake, and the rubber gaskets in the front and back of the intake.
Before you take the intake off, pull the PCV valve and block it. Block off any breathers. Then run the engine. Put a piece of paper over the oil fill cap hole and see if there is vacuum present, see if it sucks the paper. It might be subtle. If there is vacuum, the intake is leaking.
Get yourself some carburetor cleaner start the motor up let it run and spray the base of the carburetor to see if the RPMs go up then spray all four corners of the Intake manifold if the RPMs go up you know your intake is not sealed.
Is there a vapor recovery charcoal canister on this car? They can create significant vacuum leaks if damaged or not connected properly.
