I recentley installed a street avenger 670 cfm on my car. I don't seem to be getting much vacuum, but I don't really know what would be normal. I have about 10" at idle and it drops right off to zero by the time you put your foot about 1/3 into the throtlle. Taking off from a stop it will really bog down unless I try to keep the rpm's up to about 3000. It's a 1971 350 4 speed with a TA 212 cam and 10:1 pistons. I have the cam set 6 degrees advanced per their recommendation. I have a 3.5 power valve in it and the plain spring for the secondaries. I've looked pretty throughly and can't find any vacuum leaks on the intake or any where else. What circumstances would call for larger squirters on the accelerator pump?
A low rpm bog or hesitation is sometimes an indicator that either (or both) pump cams & squirters need some attention. It's handy if you can find someone with extra parts for experimentation. Did things work better with a different carb previously, no other changes? What's the ignition timing look like, initial and total advance? Devon
I have a 670 street avenger on my 78 403 olds with a comp. cam exe 262. My vacuum at idle is 16" and 13" in drive. Cam was installed "straight up". No bog or hesitation whatsoever. Use a stethescope, maybe a vacuum leak.Oh- i have the lightest spring that came with the carb installed now. Carb performs perfectly!
I didn't have so much of a problem with the original Q jet but a friend gave me a 4160 750 cfm that I tried first and it was the same story. I just figured it was too much carb for the engine so I got the 670 instead but same story. The timing is 14 degrees initial I think 34 total. I haven't messed with the timing since I set up the engine sometime ago. The MSD has been so good since I set it up I haven't touched it. I know it seems like alot but with that cam it really wants it and you can tell in the performance.
