levic482

I have a 77 with a stock 350. I installed a edlebrock air gap intake manifold and a holley 670 street avenger 4150. Ever since I instilled them I have a hi ideal, its around 2000 RPM. The total timing is 32 degrees and the fast ideal screw is completely backed out. I was thinking about changing the jet size but first I wanted to see if anyone has any suggestions or what jet size to use or something else to check.

Thank you in advance for the advice

davidchristopher

idle- The word you're looking for is idle. Edit your title with the correct spelling so you get better traction on the post.

Sound like you might have a vacuum leak? Difficult to diagnose over the internet, but I'd make sure you're not leaking vacuum anywhere as a start. You should be able to get the idle down to 700-900 range easily.

Other things to look at- throttle linkage.

Might be useful to post a pic of your throttle linkage, the vacuum lines and choke as a starting point.

Bikespace

I'm not familiar with that carb, but is it possible you overlooked a high-idle cam, separate from the low-idle adjustment, that isn't disengaging? On the Q-Jet, this cam is tied in with the choke. Can you post some photos?

Otherwise, @davidchristopher's suggestions seem right on the money. I'd suspect your vacuum leak to be at the carb base, or possibly at the intake manifold base.

BTW, only a moderator can edit a title, but changing it for better visibility is great advice. Perhaps PM @vettebuyer6369 or one of the other mods to change the title to "High Idle with New Carb" or something.

davidchristopher

Ah- I've never had to edit a title. Sorry.

Also, wasn't tryna be a dick about spelling, but I clicked on the thread thinking it had something to do with the philosophical morality of owning a vintage sports car. Or something like that, anyway. Regardless, I wasn't thinking it was a carb issue.

Hope you get this hammered out enough to lay some rubber dude.

Rescue Rogers

ry disconnecting the throttle cable to see if theres not enough slack in it to get to a low idle

4-vettes

I ran a Holley 670 street avenger for about 15 years on a RPM Manifold. The street avenger series of carbs come jetted really close for a stock 350. And yes I too have a 77 Vette. I'm also thinking you have a vacuum leak. Do you know how to check for a Vacuum leak?

Jebbysan

Make sure the choke is disengaging. Is the throttle lever touching the stop? I know you said the screw is backed out but is it touching....? If the throttle blades are completely shut then you have a vacuum leak somewhere.

Jebby

derekderek

You have to ask a moderator to edit a thread title. First unhook throttle linkage to make sure it is not holding throttle open. If idle thays high, then remove the carb and check the base gasket. Could be carb problem, but more likeley is the install. Fixed copiers for 35 years. As good at it as anybody on this planet. I would still screw up a detail and have to refo what i just did.

Rescue Rogers

There was a thread last year about throttle blades hitting a certain intake manifold

HeadsU.P.

Not sure about the carbs butterflies actually hitting the Intake, but certainly some were rubbing ill-fitting base gaskets.

No expert on Holley ST. AV cabs, but with a primary idle screw all the way out, always suspect the secondary throttle blades refuse to close. Find out why.

Other Holleys have another adj screw hidden for the secondaries.

Rescue Rogers

I think it was a miss match between square bore and spread bore....I don’t remember the particulars but a spacer/ adapter is indeed needed along with the correct gasket