Just wondering if anyone else has had issues with their vacuum secondary getting stuck and holding the throttle open. This happened to me a week or two ago when I blipped the throttle to let off the choke more quickly and my pedal just stayed to the floor (reved to 8,000 it's all good though amazingly). Then, the next day my cousin told me a story about his vacuum secondary also holding his throttle open, except he was on the highway. Is this just a rare occurrence if the secondary is not tuned right, and your throttle return spring is not strong enough? I just bought a new secondary by QFT that can be tuned by a screw driver, or would it just be better (and safer) if I got a double-pumper considering my setup so far? Chevy 350, aluminum holley street dominator single-plane, holley 600 vac. secondary, unknown cam 7in vac. @ idle (no vacuum leaks, massively lopey) and a 4spd. saginaw manual trans, all in a 1952 GMC My first time getting an engine all tuned up (was a long-block) so bear with me
You have not mentioned what brand of carburator you are using. All the ones I have seen have some type of mechanical return linkage incorperated into the secondarys.
Thats more than just a blip if you ask me, pedal stuck to the floor. At first I was gonna say throttle maybe be getting hung up at the intake. But with that combo I think not. Will stay tuned to see what comes up.
Oups sorry, it's a holley 4150 I believe, #65 jets, and a 3.5 Power Valve. Before posting this I put on a new dual return spring, disconnected the secondaries, and it ran fine So it sounds like my return spring was just simply not strong enough to pull it all back closed with the rush of air? Doesn't seem like a lot of people have been complaining about vacuum secondary carbs.
Yeah.....Check too see if your primary throttle valves are not over centering.....that with a weak return spring may get your attention...!!!????
sweet, I got all day tomorrow to mess around with it, my old return spring did not feel all that weak though... but anyways ill be putting my hand on my kill switch every time I tap on the gas, going to be paranoid forever XD... ohhh btw, what year is that? (in your avatar) looks nice in blue!
Helilog, I think your right, I did some more digging through older posts and found this: http://www.jalopyjournal.com/forum/showthread.php?t=655840&highlight=vacuum+secondary I did forget to add that I bought it as a used rebuilt carb, maybe it's time for a new base plate. I did some searching in the past but could not find a base plate for a vacuum secondary Holley for much under $100. I'll post a picture tomorrow morning of the carb I have currently, it's very clean I do recall that the shafts did have some play, but very little in the primaries. I never thought about it, but do Vac. secondary holleys work well with big cam's? I bought my long block thinking it was just going to be a stock 350, turns out I was wrong and should have asked the seller some more questions hahahah. I was also researching about EFI mostly for gas mileage reasons, ill want more than 8 MPG lol. maybe ill start an EFI, vs double-pumper, vs vacuum secondary thread
Wild guess, but I think it's a driver side motor mount issue. It happened to me way back when. The engine rocks over and stretches the carb link. Engine will stay wide open until the RPM peak out and the engine settles back down.
Throw the air cleaner in the trash,Notorious for one backfire and in flames ,I had one go up myself On the return springs I always had mine to the front of motor
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