car stumbes at 3,000 rpm

[chrisfrom nj]

i recently converted my car from tbi to carb i changed everything intake, carb, dist, now at around 3,000 rpm it sumbles a little the carb is a holley 650 the dist is a msd it has a vacume advance,and the intake is a team g intake it allso has a 2 inch spacer please help me fix my car

[bubba428]

turn you distributor clockwise about 4 degrees timing (thats 2 degrees on the dizzy), and richen the mix just a little bit....then use the throttle set screw to hold the motor at 2000rmp and adjust the timing. counter clockwise till it runs crappy then clockwise till its smooth. then with it still at 2000rpm turn you adjustment screw in the same maner tighten till it stumbles and loosen till its smooth. repeat as necessary. there are better more exact ways but thats the best way for a quick tune by ear.

Did I miss anything?.......


O check all your vacuum lines for cracks and other leaks...I think you may be either lean or to far advance...do what I said, that should get you closer to 100% depending on your ear

[chrisfrom nj]

Originally Posted by bubba428

turn you distributor clockwise about 4 degrees timing (thats 2 degrees on the dizzy), and richen the mix just a little bit....then use the throttle set screw to hold the motor at 2000rmp and adjust the timing. counter clockwise till it runs crappy then clockwise till its smooth. then with it still at 2000rpm turn you adjustment screw in the same maner tighten till it stumbles and loosen till its smooth. repeat as necessary. there are better more exact ways but thats the best way for a quick tune by ear.

Did I miss anything?.......


O check all your vacuum lines for cracks and other leaks...I think you may be either lean or to far advance...do what I said, that should get you closer to 100% depending on your ear

thanks bubba im going to try that tomorrow

[chrisfrom nj]

my car still stumbles and cuts off at wot

[crainholio]

What jet size are you running in the primary metering block? Secondary block?

What power valve # are you running?

[chrisfrom nj]

the stock jets that the holley 650 came with

[crainholio]

Originally Posted by chrisfrom nj

the stock jets that the holley 650 came with

I guess it's possible that Holley sells a carb properly jetted for your exact engine. But that hasn't been my experience.

The mixture adjustment screws on the metering block only fine tune, if the jets aren't properly sized the screws can't make up the difference.

Time to pull & read your spark plugs, or hit the dyno with a wideband O2 rig. After you've used a timing light to properly set your distributor to 8deg BTDC advance w/ the vacuum advance capped.