TTop Tony

Ever since I put a new aluminum intake and Holley carb my idle speed has been creeping up slowly. Last week one of the bolts had a little oil coming through so I pulled it and retorqued all the bolts. Now my Carb refuses to idle any less then 1800rpm. I have the idle speed screw all the way out. What did I do? I'm just about to pull the intake off and start again. Would a leaky intake cause this? Please help?

RMS73

Did you check the intake vacuum after the installation? Check for a vacuum leak under the carb and where the intake meets the cylinder heads. I use carb cleaner for this. with the engine running spray the fluid at the joints. If speed picks up or idle smoothes out you have found the vacuum leak. Carb cleaner can dissolve the paint if you put too much on. Ether based starting fluid is my alternate. Also check the cranckcase for vacuum. Put the vacuum gage on the dipstick tube. Any vacuum in the crackcase means a vacuum leak under the intake. When I corrected the vacuum leak under the intake on my Vette it idled smooth at 600 rpm, acceleration was greatly improved and the mixture screws on the carb actually could control idle quality.
Roger

gerry72

Throttle cable mis-adjusted and not allowing the butterflies to completely close. Or massive vacuum leak. It's easy enough to check either. Remove the air cleaner top and look down the venturi to see if the blades are closed. If they're not, remove the throttle cable from the lever to see if it will now close. This will lead you to a path where you can fix the cable problem. If the blades are properly closed, then start the engine and start manually closing the choak. If the idle speed starts to drop and stays smooth, then you're dealing with a vacuum leak. Based upon the symptoms, I'd say it's a throttle problem.

TTop Tony

Thanks guys that'll at least give me some things to start looking at.

daily_driver

dont forget to put permatex sealer on the bolt threads, then you wont have oil comming up through the bolts....

and dont forget that aluminum intakes need to be retorqed several times after u install it....

TTop Tony

Yes permatex sealer definitley this time ( I didn't know I had to keep retorquing it) and better gaskets. I wasn't thrilled with the cardboard ones I got last time.