Hey guys. I am looking for some carb tuning help. I have always used, and am familiar with holley mechanical double pumpers. For the Model A I decided to go with a vacuum secondary Holley Street Avenger 670. Well since I received it I found TONS of articles about issues with this thing with similar issues as what I have. I have been trying everything I have read but just cant get it right. OK so the engine is a SBC 350 with a Howards Rattler cam (.480\.488 lift, 227, 235 @50), promaxx aluminum heads (64cc, 190 runners), with a edlebrock dual plane manifold. I am running HEI ignition with a 2200 stall. The problem is hesitation when going to WOT. I checked the vacuum and in drive I have about 8, so I installed the 3.5 power valve. I am running 66 pri and 72 sec jets. I have tried all of the secondary springs and the white, lightest one is the best. The car is a 31 sedan, which is light, and 2.73 gears (haven't changed them yet). When I stab the throttle I get a burbly heisitation, that to me seems rich. This is opposite of everything I have read about this carb. It is supposed to be lean. So I am stumped. It has a 31 squirter, and the plugs come out black and sooty, but the insulator is either barely colored or clean. Any help would be great
I have experience with that carb. The 570 runs way better on my SBF than the 670 did. With that said; put the original orange accelerator pump cam back in, and put it in the number 2 position. Then, replace the #31 discharge nozzle with a #28. The throttle response should a lot more smooth. Additionally; if you are running a vacuum advance distributor, make sure the diaphragm is not ruptured or leaking. Something like that can cause a part throttle hesitation.
The Orange cam is still installed on the number 2 hole. Does it seem right that I would need to use the white spring? Sent from my LG-H810 using H.A.M.B. mobile app
Well I put in the .28 squirter and have tried the pink and white cams and still have a bad stumble. The white cam was for sure worse than the pink. I have been reading on cams and there is a lot of conflicting info. Some say the pink is the smallest shot and others say the white is. Not sure what to do from here. Thoughts?
I'm wondering if your accelerator pump is adjusted properly. I am also wondering if there is a vacuum leak. I've tried every pump cam available (I had the assortment kit) and nothing worked as well as the one than came on the carb from the factory. Is this an instant bog off idle? Or does it go, then bog, then go?
I played around more and have it almost gone. I am using the 28 squirter with the brown cam (biggest) and there is barely a hesitation now. Maybe it just needed a longer shot which I think the brown with smaller squirter would do.
What have to done to the HEI? is it stock GM or after market? If it is an old Street Avenger you bought someone else's problems. they had so many problems from the factory that Holley had to back up and regroup. If it is a new SA you may just have an ignition problem especially if you are running a GM HEI.
It is a proform aftermarket hei. The carb is a refurbish from holley that I got from them. It seems good with the brown and 28 now.
Well I am still not satisfied with the carb. It is much better but still if I stab it I get a blurp of a hesitation. It clears fast and then screams but is still there. Brown cam 28 squirter and short yellow spring. Any ideas? Thanks
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