[redneckgmc]

I just bought a new Holley Truck Avenger for my 81 chev 4x4. My other one was leaking and idling rough and was the only thing not done to the engine. It was a rochester q-jet and before it started misbehaving i had no problem with it. My new carb, is amazing. I can slam the gas and it doesn't stutter or anything it just picks right up and i am getting great performance. However, i used to be able to roll around in a corner in 2nd gear (3rd for you car guys) and the idle would drop round 1000 and i could slowly cruise around the corner. Now when i do that the engine bogs down and almost stalls and runs all rough then once i get back up to rpms its beautiful. Its a truck, i like the low end. It worked fine before. The carb is adjusted good from factory but says i may need to adjust it. I'm thinking of the mixture screws, will leaning/enriching the mixture cure this? Or is there something else amiss. Please help as once this problem is cured my truck is back to being trouble free.

ps, 15k on a new 350, performer rpm cam lifters manifold bored .030 over

 

[Max Keith]

falling down

What size engine are you running? what other mods have you done to it? What size carburetor are you running?

OK got the rest of your thread. 350 cubes, cam and intake. Back to what size carb?

is it vacuum secondary or mechanical secondary carb, also what brand?

 

[redneckgmc]

sorry i thought i posted it. Its a holley truck avenger. vacuum sec, elc choke

 

[Max Keith]

bogging carb

what is the CFM rating?

 

[redneckgmc]

670

 

[Max Keith]

carb

It doesnt sound like you are seriously over carburated. I would look at the power valve. Its a good possibility you have a mis match. I dont remember the formula for figuring out what power valve you need, but the first step is to run a vacuum test on your carburetor. Your local hot rod shop should be able to tell you what size you need. Just because its new doesnt mean it cant have a problem.
I would also check around for vacuum leaks, as well. Check all your hoses, and on your intake and carb, be sure all the hoses are connected or that any nipples that dont have a hose to them are capped off. Lastly be sure you have your vacuum lines connected to the correct nipples.
Vacuum leaks can wreak havoc with your air intake signal in the carburetor.

 

[wildman926]

You need to tune your carb according to HERE.

You will be glad that you did. As Max Kieth said also, check for vacuum leaks as well.

 

[redneckgmc]

i have tuned my carb. i plugged my vacuum gauge in and it was round 40 i adjusted the fuel/air mixture as directed and it would go up to about 44 and then drop down so i backed it off and 44 was my highest. progress was made, but still having trouble. adjusted everything from the float bowls and readjusted my choke (inapplicable to this problem but it was coming off too soon). Truck is running better but damn that bogging down is still there. I have adjusted timing from 10-16. It was at 14 before (what the cam specs say to run) then i adjusted the idle to 10 like the hotrod builder advised. At 16 i was pinging and it was obvious i had too much advance so i backed it down to about 12 and thats where i am at right now, the middle ground where i can still cruise round a corner in 2nd round 1000rpm and not bog down the motor. There was an advance curve kit put in do you think I am going to have to change the advance curve? Please help this is driving me nuts!