Dolph88sc350TPI

Hey, just wondering if anyone ever removed their emissions equipment and plugged off the lines on your q-jet?
Did it cause a lean condition?

For some time now I've been chasing a knock problem and this has to be it, maybe nothing to do with emissions but its gotta be lean, my exhaust gets too hot to touch even at the very tip.

Could a bad base gasket cause it to run lean?
Or should I drill the idle circuits bigger?
Float need adjustment?

Its an 79 m4me that was on the car when I bought it.
Any ideas???

Thanks,
Dolph

Dolph88sc350TPI

after close inspection of the vacuum lines they don't leak, Its running wayyy too lean still.

I get a steady 21" in vacuum @ idle, but that doesn't mean the intake isn't leaking right?

No matter how much I back the idle adjustment screws out I'm still lean off-idle, part throttle, and "sometimes" WOT.

Could it be a base gasket leak or intake gasket leak?

Also, how low should I be able to get the engine to idle at?
Right now it won't go below 550-600rpm with the throttle plates fully closed and the curb idle screw all the way out.

I'm thinking about changing the intake gaskets, carb base gasket, and enlarging the idle discharge ports.
Should I do this?

chymos

don't modify the carb yet....before you do that, I suggest a basic rebuild, so that you can see if there's anything wrong in the carb itself (ie worn out float, bad gaskets, etc). This will also give you a chance to see what metering needles and jet sizes it has.

Also, if you don't have one, I learned quite a bit using the Haynes Rochester Carb manual. I know the Haynes vehicle books aren't all that great, but their Techbook series seems to be very helpful if you don't really know much about carbs, etc.

A bad base gasket would cause a lean condition, yes. Any leak between the carb and the combustion chamber will cause a lean condition.

With the Q-jet the idle screws are just that: idle mixture ONLY. They do nothing for the off-idle or any other circuit except idle.

I'm not sure what idle vacuum should measure at, but I'm guessing 21" at idle would indicate it's not a leak....

Have you done a search for "engine knock" and "hot exhaust"?

IIRC, it was posted in a thread a while ago that a rich condition could also cause hot exhaust....but don't even think about quoting me on that