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This topic was originally posted in this forum: Modified Tech Talk
Author Topic:   Carb Problem
Rook 78
posted April 08, 2004 11:28 AM     Click Here to See the Profile for Rook 78     
Let me preface by saying I know little about carbs, heck I cant even spell it. I am having problems with my carb, it is a 2 barrel 500cc. Holley. The problem is at idle, the right side is bleeding over and the left side I have no trickel of fuel at all. Took most of it apart last night at the track for play day, cleaned and blew out much of it, no help. Needle and seat appear to be working. Any thoughts? I am not sure what pump I have on it, bought motor complete with all parts, is it possible that I may be getting too much fuel pressure? No guage.

[This message has been edited by Rook 78 (edited April 08, 2004).]

posted April 08, 2004 11:58 AM     Click Here to See the Profile for KPLugnut   Click Here to Email KPLugnut     
Chances are, the butterfly on the side that is pulling over is open further than the butterfly on the side without pullover.
The idle transfer slot in the baseplate on that side is probably exposed a different amount than the one on the other side (if you look up from underneath, it's the vertical slot cut in the throttle bore).
Stock carbs from the factory often are poor in quality and precision when it comes to those slots and their lengths.
The next place you might check (after verifying 6-7lbs of fuel pressure at idle), is to start by properly dialing in the idle circuit and mixture screws.
You didn't mention it, but is there a difference in how the idle mixture screws are adjusted on each side? They are the 2 screws on the side of the metering block (behind the float bowl).

Let us know any additional info you can. We'll figure it out, not to worry...


Rook 78
posted April 08, 2004 12:23 PM     Click Here to See the Profile for Rook 78     
I was told to start at 2 turns out on adjustment screws. Also, if you would please explain idle circuit?? I will have to check out the idle transfer slots when i get home tonite. Not sure what I am looking for, but with your description I will have a place to look. I do have a fuel pressure guage somewhere at home, will have to hook it up to make sure it is right. I fear there may be a high volume pump in it, but the previous owner did run gas. Your help is appreciated.

posted April 08, 2004 01:51 PM     Click Here to See the Profile for KPLugnut   Click Here to Email KPLugnut     
2 turns normally is a bit on the rich side, but everything depends on the whole package, both inside and under the carb.
the "idle circuit", simply is dialing in the idle mixture screws, setting the throttle so that no more than about .030"-.035" of idle transfer slot is exposed under the closed butterflies, verifying fuel pressure at idle, and also setting float level to just a hair below the bottom of the bowl sight plug hole with the plug out and car idling.
Target rpm at idle for that kind of a motor will be in the 1200rpm range, give or take a bit.

Hope that helps, if ya need more info on idle circuit setting, search thru the archives and old posts of the forums, i'm sure it's in there. It's rather long to write out in full. :-)

If ya can't find it, let me know, I'll email you a file discussing it.


Rook 78
posted April 08, 2004 02:44 PM     Click Here to See the Profile for Rook 78     
I will give it a shot tonite, thanks for your help and insight!!! I will let you know how it comes out.

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