I am running a Holley 2 brl 500 cfm on my stock intake with a Clifford adaptor and I was messing with the motor when I noticed that if I crimped the PVC line the idle drops way down. I've had a problem with the idle being too high, so high that I don't have the idle adjuster screw even touching the linkage, so I am wondering if my PVC is somehow causing the idle to be so high. Yup, I've checked the timing, throttle linkage movement, vacuum leaks, etc... and I'v never been able to determine why the idle was so high. I've never messed with the PVC hose on any other engine I've had so I don't know if that is normal (to crimp the PVC line and have the idle drop). The hose iteself is new as is the PVC which itself isn't stuck or gunked up. Any ideas? Thanks!!

 

Check that line for any vaccum leaks, also check the baseplate gasket. Make sure you have a good throttle spring shutting that carb all th way all the tiem too. Sometimes they could get stuck open and give you that high idle

 

Thanks for the reply! I installed an extra spring on the trottle linkage and even that didn't help, it still idles high. If I drop the timing way down then I can set the idle using the adjuster screw but I shouldn't have to do that. I checked for vacuum leaks but maybe I am missing something, it just seems strange that if I pinch that PVC line the idle drops noticeably.

 

i had the problem with my holly 390. i installed a new edelbrock 500 and it fixed it. little spendy easy fix but i needed a new carb anyways.

 

 

I know that you already installed another throttle spring and checked your linkage, but try disconnecting your linkage and see if it brings your idle down. When I installed my 390 carb I was positive that I had the linkage adjusted right, but the idle would not go down. It turned out that the linkage was just slightly to long, just a hair and after disconnecting it the idle dropped down.

 

I'll give that a shot, I was monkeying with it today and it couldn't decide wether to idle high or idle so low it wanted to die! Thanks!