I've got a 600 vac sec Holley I bought off of eBay a few years ago. I tried it on the car when I first got it running but it wouldn't idle and the accel pump was shot so I stuck it on the shelf for a later rebuild. I finally got around to rebuilding it a while back. I totally disassembled it with the exception of the throttle shafts and soaked it real good in a gallon of carb cleaner. I then washed it real good with soap and water to kill the remains of the cleaner, and blew out all the passages with compressed air, 150 psi. I then put it back together with a Holley kit, new gaskets, power valve, etc. Set the floats dry, mixture screws out 1.5 turns. Put it on the car and then wet set the floats, first with just the electric pump running, then with the engine running about 2000 rpm. It will not idle below 2000 rpm, and if it does idle, floods like crazy. Made sure that gas would just trikle out of the sight holes, even lowered the floats so no gas would trickle out, no difference. Mixture screws have no effect at all, can close them or take them out and it still floods! Only way I could get any kind of idle out of it was to leave the large power brake vac port open. From idle to about 2000 rpm, it sounded like a drag car idling, but from 2000 rpm up, it was smooth, no flooding whatsoever. What the heck is going on with this thing? Throttle shafts close, work smoothly with no binding. Choke is open. Jets were clean, size 62 IIRC , has a metering block in the secondaries.. Power valve is new 125-65, made sure I used correct washer under it. I'm stumped. I'm thinking my vac will be low at idle due to the 272-284 cam, so I don't think the power valve is the culprit. New Holley needles and seats. Gas is not pouring from the vents into the throttle body that I can see. It is exactly just as it was before I cleaned and rebuilt it, with the exception of the acell pump which now works right. Oh, and no vac leaks on the intake, car runs fine with my old Ford Holley. It's getting way too much gas to idle, but why? Any ideas from you guys that fool with tuning Holleys? Sorry for the long post, but wanted to try to get all the facts as I know them out there for ya'll to make a decision on....
my first thought is that the power valve is leaking fuel. shouldnt with a new power valve and gasket. when you have it idleing with the open vac port, look down the venturies. with that amount of fuel going into the carb you should see it coming out of the venturie boosters. if you dont see it coming out the boosters then i would think the metering block is leaking into the power valve chamber. i would think that if you took the front bowl off and metering block off right after running you would be able to see if the power valve chamber is wet or dry. if its wet then the problem is either the metering block or power valve.
I had a similar problem. super flooding. When I did my re-build, i accidently put 2 gaskets on the power valve. they didnj't line up and caused massive gas 'blow by' I felt pretty stupid when I found the problem.
I know you asked for experts, and that ain't me, and I'm struggling with my own Holley tuning issues now, so I should just keep quiet. But, can't help myself ... doesn't the power valve open under LOW vacuum? Seems to me that COULD be your problem.
Are you positive the secondary throttle blades are closed??? Check em. If not... you may have to remove the carb to adjust the secodary throttle stop unless its allready been turned over...Good luck!!!
Are you sure you used the correct gaskets? Did you match them up with the old ones? Several carbs are serviced with the same kit so you run the risk of getting the wrong gasket between the metering block and the body.
Metering block. Hadn't thought of that. Could be bad. Doesn't seem to be pouring fuel thru the boosters, so you may be onto something there since it did it before and after the rebuild. That should rule out the power valve. Yep, matched them up with the old gaskets to be sure I had the correct ones. Now it might have had the wrong gasket on it to start with, but I made sure according to the instructions to use the one that matched the metering block, so it should be the right one. It matched the old gasket and the line ups on the body and metering block.
Yep, checked that on and off the car. Both blades close, primary and secondary. I'm beginning to think like Bryant, the metering block is screwed up, because it did this before I took it apart,and after too.
I'll bet you've got a metering block gasket on backwards. Or possibly the base plate gasket is backwards. The reason the mixture screws aren't responding is you've got the transfer slots exposed with the throttle blades open that far. Take it apart again, you've got something put together wrong. Make sure the gasket behind the powervalve is centered when you tighten the valve. Verify the powervalve is functioning by sucking on the front side and see if the piston works in and out while you're sucking on it.
When I get time, I'll tear this thing back apart and see if any gaskets are put on wrong, but I don't think that they are. I'm leaning toward something wrong with the metering block since the carb does exactly the same as it did before I cleaned it and put the kit in. That would explain the mixture screws not working, I did have to turn the idle way high just to keep it running. Any less and it would flood completely out. If I can't figure it out, I'll just sell it and buy a Summit or Edelbrock. I'm not much on tuning, and sometimes not very patient. The old Ford Holley on it right now runs fine, just sometimes it doesn't want to idle in gear, so I may just leave it like it is.
dont give up on holley just because the used one you have is bad. ive used lots of different types of carbs and i will have to say my favorite is the holley double pumper. get one the the right size for your motor and it will respond faster than anything else.
I had this problem on a stock 600 on a 85 Mustang. Seems it had been rebuilt before and who ever did it some how warped the metering plate in the secondary circuit. Replaced the plate, gaskets and steel plate and it worked fine. Make sure you use a clutch head driver and tighten the plate evenly a little at a time to avoid this. Just a thought.........
