need carb help and opinions

[kidatforty]

My new engine is running and I'm working the bugs out. It fired right up and ran reasonable in park. When I took it for test drive, it had no performance from idle to transition into mains. It would back-fire and die. Iknow that it is not the accelerator pump. As some of you know, I changed the power valve to a 35 and down-sized my jets for altitude. Helped a little. I installed the HEI distrib. and it now has a smoother idle. Then I went online to find info on troubleshooting carb. I found good info. What some people do is open up the idle restrictions to get more fuel through the transition slots. I opened them up about .003" and opened up the main jets. I installed lighter advance springs in the distributor. I just took it for a test drive and it is the best it's been so far. Pretty close to what it should be. It runs stronger but still has that falling flat above idle. On carbs i've worked on in the past (german ones), I've always been able to play with the idle restrictions with no problem. They are removable so you can always go back down in size if it appears that you are going to large. I feel I need to open up the idle restric. a little more but I'm afraid that I will not be able to go back down if I need to except for turning some new ones on my lathe. Just to freshen memories: Holley avenger 670 cfm carb, buick 350, TA cam w/ 4 deg overlap, TA manifold, 3" 2 into 1 exhaust, 8" manifold vac.,5 deg btdc timing. Does anyone have any advice? I almost feel that the carb is too large but I sure don't want to go buy another one.

[kidatforty]

I guess I'm on my own.

[timmirvin]

Hey man, you are not alone......I am reading.....

[timmirvin]

First of all, a 670cfm is not too large. Have ran a couple diff Holley 750's on Chevy and Olds 350s...with success.

Have you checked and re-checked float adjustment??

Are you thinking the dead spot between idle and acceleration is too much gas or not enough.....??

[timmirvin]

Is this the new Truck Avenger carb.....?????

And what has Holley had to say about all this???

What about your secondary springs and the vacuum supply to those secondaries????

[kidatforty]

Thanks for responses. Really. I've been stressing it out a bit. I e-mailed Holly 2 days ago and no reply. I decided to go ahead and open up the idle restrictions and mains a little more and it improved alot. I don't have back-fire anymore but it still has a little bit of hesitation still off-idle. Because this hesitation was occurring with a back-fire it would be attributed to lack of fuel. Yes it is the truck avenger. I called Holley after the last mod. and left a message. They called back! I thought I might get chewed for fiddling with the idle restrictions but the tech rep said they do it at the factory sometimes. He recommended going to larger accel pump discharge nozzles. The transition into the secondaries is fine with original spring. I guess it's time to order more parts and wait for arrival.... again. When I have this thing 100% I will be sure to have all the tested and proven tips and specs on fine tuning the avenger. Thanks again guys, I needed to here someone's voice.

[kidatforty]

Oh yeah, the float level is right on.

[timmirvin]

I sure hope I don't have all theses problems with mine for heaven's sake!!!!!!!!!!!!!!!!!

I may be yelling for help next week!!!!!!!!!!!!!!