new motor issues

[buffblazer]

never got a response from my last thread so here we go again

motor is a 74 4bolt main 350 in a 86 k5. full rebuild with stock heads and a edlebrock performer intake, comp cams truck cam. holley truck carb and msd box.

the truck run pretty good at idle and when in neutral if you rev it up it seems to sound smooth.

but when you get it on the road, if you lightly cruise it runs good but if you smash the pedal when it hits about 2000-3200 it bops and bangs out through the exhaust then kinda clears itself out but not completly

im running a sm465 so it does it in every gear. only under load though not when sitting still.

then after its nice and hot at idle it will kinda rev a little if its idling at 850, it will drop to like 500 then pick itself back up and keep doing it. but once cruising it runs fine.

timing is a 6 degrees, cant find any vaccum leaks. new fuel filter, plugs are all clean.

could this be a missfire due to running way to rich in the carb? had a shop set up the carb but from the second i left the shop and mashed the pedal it was doing this.

what yall think?

 

[K5dreamer]

bangs and pops can be backfire, or afterfire.

backfire is caused by a misfire

afterfire can be caused by an over rich mixture, or an exhaust header leak.

the bogging under throttle could be either too rich, or too lean, hard to say. im not an experienced carb tuner, but im sure someone here will chime in.

 

[bp71k5]

Could be a bad vacuum advance as well.

 

[mnstrburbon]

The secondaries are coming in at the wrong time sounds like. Its vacuum secondaries correct.

 

[buffblazer]

how do i adjust the secondaries on a holley the shop still has the book and i dont have time to run up there during the week, so if its something i could adjust myself easily than great

 

[USSkoval]

If it's a Holley Truck Avenger, it should have the quick change vacuum secondary housing. Just two screws and change to a different spring. Probably should use a spring with a black or brown paint dab.

 

[mnstrburbon]

If it's a Holley Truck Avenger, it should have the quick change vacuum secondary housing. Just two screws and change to a different spring. Probably should use a spring with a black or brown paint dab.

Bingo here.
pull the spring out its under the black cover on the pass side and put in a stiffer one there should be a chart that came with the carb or search the web, or check them by hand.