72455

So I swapped out the 670 Street Avenger carb on my 72 U code Supreme for a 770 Street Avenger. She won't idle when cold without feathering the throttle, but is fine once warmed up. I had no problems with cold idle when I was running the 670.

From what I've read, it's a matter of simply adjusting the electric choke. My question is, do I adjust the 770 to the same setting as the 670, or will this not work because it's a bigger carb?

Thanks,
Dave

Vintage Chief

I'm not certain you can assume the 770 should be adjusted to the 670 setting; in fact, I don't believe I'd make the statement that any two 670 or 770 carburetors can be adjusted to the same settings. IMO, I'd adjust the 770 as per this video.

Olds64

That's a good video Norm. When you adjust the choke make sure you do it with the engine cold.

Vintage Chief

Dave, the only way to adjust any choke is when the engine is cold.

Oh hell, I thought I was responding to Dave - Sorry, I didn't realize it was Clark (Griswold).

Schurkey

Actually, I think the video is CRAP. The video may have been produced by Holley, but it's VERY limited. They show you how to adjust the choke COIL, but not how to adjust the choke pulloff piston, or the choke unloader, or how to synchronize the fast-idle cam to the choke blade position. In other words, they show you ONE adjustment (the easy one) and forget all the others which may be just as important, but harder to do.

Not showing how to adjust the unloader is forgiveable. It's the least-critical. OTOH, I've never seen a Holley that had the choke pulloff piston adjusted properly. They pretty-much need to be tweaked to suit each individual engine and operating parameters. It's a CRUCIAL adjustment, and Holley doesn't even include those instructions when you buy one of their electric-choke kits. For that matter, Holley doesn't even tell you the best way to route power to the electric choke. It's like they WANT you to have problems with the choke. I don't know what they're thinking.

https://www.chevelles.com/techref/Ad...tic_Chokes.htm

That MIGHT be an issue with the choke coil adjustment. It could be a problem with the choke pulloff piston adjustment. If the engine stalls immediately after starting--it's probably the pulloff. If it stalls 30 seconds or a minute after starting, it's probably the choke coil.

72455

Got 'er dialed in and she's runnin' like a champ! Everything was fine...I just didn't set the choke quite right with the throttle when I started it the last time.