I have a holley 600 4 bbl 80457-3, on a 350 chevy in my 50 chevy truck. It only wants to run at full throttle. I had it off today and cleaned it and set the float level, it ran okay for a while except for light throttle and when decelerating and coming to a stop. When under light throttle it acts like theres a flat spot or a little sputter and the idle drops way down when you come to a stop and it sounds rough, then will settle in to a regular idle. Now it wont stay idling and only wants to stay running if under full throttle, then it runs smooth. As soon as you let off the throttle is sputters and stalls. Any ideas?
Sounds like a power valve issue. Its diaphram is either old and hard, or its leaking. Replace it with a 125-105 valve unless you have a big cam in your engine. Bigger cam= lower manifold va***.You would then want 125-85, or 65 etc. When you take it apart check the metering plate gasket for a print, or sign that its making good contact at the accelerator pump transfer port. Its the round projection in the main body in the va*** well for the power valve. Some carbs have a small tube with O-rings for that function, so in that case its not an issue. If you can't see a good print it means the va*** in the power valve well is pulling fuel out of the transfer tube giving a very rich condition at idle. This is caused by a warped carb body. I have fixed many with a flat mill file. Use new gaskets to re***emble! Hope this helps. -Mike
If you've got access to a vacuum gauge you can pick a power valve that will work easier than guessing - use about 1/2 idle vacuum as a starting point and tune from there... From the description it sounds like you've got either a leaky gasket (or warped metering block) or just plain 'ol trash in the carb. I'd take it apart, clean it up, blow out all p***ages, and re-***emble with new gaskets and go from there. Last complete kit I bought from Holley was only $25 or so. (most say to use holley stuff as it's better than the imported kits - I dunno - I've used both and the last time I used a holley kit - it was what the parts store had on hand) 303 Garage - I can't stand Edelbrock carbs - they could never solve the hot start problem that 3 of us had (have) - and we tried everything they suggested from "isolators" (non metailic carb spacers) to jetting, float levels, idle mixtures, etc. Spent a ton of time on their tech support lines, with a wideband O2 meter, ignition setup changes, even took it to highly regarded carb tuner that does holleys and Q-jets only to find out it's a all too common problem they've got no fix for... they're blaming it on fuel quality and excessive heat - of course I didn't have the problem with the rochester's or holley that they replaced... I'd rather have a good running, easy to start engine than one that will crank for 8-10 seconds before even thinking about starting with the edelbrocks... OH and 2 of these were boats where typically you stop, sit for a minute picking up a skiier and start up again.... the extended cranking gets really really annoying when skiing.
If the throttle shafts arent worn out do what MikeC said, replace the power valve and flat file the metering block surface, they get bad from over tightening the bowl screws. Make sure theres no old gasket material blocking anything. $25 for a kit beats the **** out of $300+ for a new Edelbrock AFB. Check for vacuum leaks too with some WD40 sprayed around the base, make sure all the vacuum hoses are hooked up. Make sure EGR valve isnt stuck open also
the 80457's are good carbs and easy to tune IMHO. Check that power valve, check for any vacuum leaks, get a vacuum gauge and tune the carb with the mixture screw, make sure the electric choke is dialed in if wired up.
you could eliminate the power valve all together a lil epoxy but you have to go up 3-4 jet sizes and never worry again it does sound like that is the issue and check for vac leaks also as stated above
Try this. Pull the aircleaner stud off. Rev the motor HIGH and cup your hand hard and fully over the throat of the carb. Do this a couple times. If there's dirt in an air bleed, it'll **** it out. Don't laugh, try it.
I was going to mention the air bleeds - look at the top of the carb, you should see small br*** circles with holes in them on the bowl side of the bores. Spray well with carb cleaner or brake cleaner & use something like a soft wooden toothpick to ensure they're clear. Otherwise, looks like folks have covered most things. Arguing Holley v Edelbrock is a losing proposition. I prefer Holley, but currently have an Edelbrock on my Stude (may put a Holley on & see if it cures my surge).
I had a Holley (can't remember the number) on a Chevy pickup 350 and fought the problems you are talking about for years, it finally got so aggravating that I parked it in the weeds and let it sit for the last 6 years. My son needed a pickup for work this summer and begged me to get the old thing running, so I reluctantly put it in the shop and started working on it. Compression was good, ignition components were all new as I'd just replaced them before I quit driving it thinking I might have ignition rather than carb problems. So into the old Holley I went, and the old frustrations came right back and I thought "why in the hell would anybody use one of these things?" Everybody I talked to said, get an Edelbrock, so I went to the parts house to check it out, $266 later came home with a brand new Edelbrock. Took an hour to put it on, easiest carb installation of my life. Every part needed was in the box. Just enough cranking to fill it with gas and it started and ran perfectly! NO ADJUSTING, NO NOTHING! Bolted it on and it ran. Man, am I a believer now. I wouldn't wish a Holley on my worst enemy now. The frustrating thing to think about is that I could have been driving this pickup all these years, the vehicle was dead to me for 6 years all because of a POS Holley. I can't stress it strongly enough, throw yours away and go get an Edelbrock. You will thank me if you do.
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