04-13-2006, 06:04 PM
I have just bought a Holley 4160 600 cfm carb, put it on my Edelbrock eps manifold, and the off idle stumbles pretty bad. It gets up ok on the freeway, and when I get on it a bit, but even still is a bit rough. it acts like it is choking out a bit, and when I get on it hard, it accelerates smooth enough, without the "pause", but kinda peeters out when the down shift is almost coming off, kind of a hesitation feeling. The top end goes like hell, but that off idle circuit is stumbling unless I bump the throttle harder than needed. HELP ME!!! this is killing what little gas mileage i have.
05-08-2006, 06:02 PM
Hey Crazy Mike!
Did you figure this out? I just had a new Vortec 350 engine put in with a Holly Carb and I'm dealing with the same rough idle situation. It was great coming down the California Coast yesterday on the freeway, but this morning I was gunning the gas at every stop to keep from stalling. Is is as simple as increasing the idle speed? If so, how does one do this? I'm learning as I go.
05-08-2006, 06:28 PM
Are you getting black smoke when it "stumbles" as you put it? Exhaust smell rich? Are the plugs dark/sooty/getting fouled?
If yes, I'd check 2 things:
1) See if the fuel level's too high in the front (primary) bowl. You know how to check it? If it's high, try adjusting it lower. If it won't adjust lower, replace the needle/seat.
2) Also sounds like it might be the power valve (could either be blown, or isn't the right one for the amount of vacuum you have.). Blown power valves seem to be common Holley malady. 'Happens sometimes when they backfire. Fortunately they're easy to fix. Talk to your local speed shop or racing expert to find out which power valve you should be running. My 4160 has a 6.5 I think (maybe it's an 8.5).
If it's not overly rich, maybe it's lean. Did you forget to plug one of the carb or intake's vacuum hoses? Or do you have a carb-to-manifold gasket leak?
Let us know what you find.
05-08-2006, 08:58 PM
Go to the Holley website and look up the instructions for your model carb to install and tune it correctly. Otherwise you'll end up with a hundred diferent opinions on what to do and you'll be chasing your problem for a long time.
05-09-2006, 06:45 AM
Your hesitation sounds more like a lean condition, not too rich. If there is a long duration camshaft in the engine, it can cause the idle speed adjustment to be out of range, and into the transition stage at idle. We used to fix this by drillilg a 1/8" hole in the primary throttle plates, allowing the idle speed screw to be backed off, thus covering the transition slots at idle and getting rid of the "bog".
05-31-2006, 05:45 PM
I ran into a similar problem recently trying to get my new engine tuned in. The carb was giving me fits. It was brand new out of the box, and I tried everything I knew of to get it to operate properly. I finally made a call to the manufacturer's tech line and it turns out I had had all of the proper settings in place, but never all at the same time. Those guys really know their stuff.