I have an oddball problem with the Holley on my 283. Motor has a mild cam and pulls about 15 in of vacuum at idle. Every time I try to run the motor it floods right away, and by flood I mean fills the intake with gas and fouls the plugs. I've changed the power valve and the power valve gasket and fuel is still somehow getting into the back of the metering block and leaking down the power valve check valve port. Anyone else ever run into this issue? I figured I'd ask before ordering another power valve and a new metering block. Here's a few pictures of the carb for reference. Thanks in advance. Edit: It's a 600 cfm carb not a 650, if that makes any difference.
Check the flat carb body surface with a gauge block or good straight edge ..that surface almost looks like someone used a rol-loc disc on it...
Any particular reason why you have chosen a carburetor that is over 170% of what this engine is likely to need? There is only so much adjustability that can be taken advantage of here.
I was told a Holley 650 with vacuum secondaries should be fine with this motor but that shouldn't be relevant to the issue at hand anyways, which is gas getting behind the metering block into the power valve cavity.
Not sure who would have told you that. If you fix the issue at-hand, you might be right up against a tuning issue. Proper fuel atomization is dependent on the proper velocity of air moving over the venturis. If that velocity is not correct, you will not have proper atomization. This cannot be corrected with tuning.
I just realized I wrote multiple times that it's a 650 CFM carb, it's actually a 600. Still probably a little big for this application but if it doesn't work out I'll find another home for it.
Do you mean the power valve gasket or the metering block gasket? The PV gasket came with the new PV and the metering gasket is the blue Holley one. There were no obvious tears or issues with it but I have not replaced it yet. I'll do that next but I was curious if it was possible for the metering block itself to fail.
Had a similar problem a few years ago. I changed gaskets, metering blocks, float, etc. Turned out to be a hole in the fuel p***age for the needle and seat. Even though the float would lift and shut off the fuel flow, fuel would p*** right through the hole in the p***age, over flow the carb and pool in the intake. Sent from my iPhone using The H.A.M.B. mobile app
No kidding, that is an oddball problem. Did you have to replace the carb to fix it? I'll definitely check that out. Thanks.
Yes. Im running off a mechanical pump but I tested it off a hanging auxiliary bottle to byp*** the pump. The fuel is dripping right out of the power valve check ball / vacuum port, not the venturis.
X2 for wondering what the gasket looks like between metering block and main body. I was called about a similar problem a few years ago- just dumping fuel down the intake. Turned out to be the guy installed the wrong metering block gasket, which was causing the power valve p***age to leak directly down into the intake. Sent from my iPhone using H.A.M.B.
Thats your issue-- wrong gasket. See the U shaped cutout above the power valve-That gasket is for a metering block that uses a transfer tube to the main body.
^^^ What they said. This is the same problem I described above. Swap out that gasket for one that just has a hole for that p***ageway (no horseshoe) and you will be good to go. Sent from my iPhone using H.A.M.B.
What they said. Wrong metering block gasket. That gasket is for the carbs that use the o-ringed transfer tube.
Yes. I sent pictures of the issue to Holley thinking they might send a new carb body at a discount. They ended up offering me a new carburetor if I returned the defective unit to them. Pretty cool since my carb was way out of warranty. I guess in the early 2000’s they had a defective batch, prone to zink pest problems in the fuel bowl,(super dangerous) and they wanted them back and out of service. Sent from my iPhone using The H.A.M.B. mobile app
Did you have that new gasket on hand???... Did you get it fixed????.... How does it run????... Inquiring minds like mine want to know!.
I've ordered the gaskets and they're supposed to arrive at the parts store tomorrow. I will update the thread as soon as I get it put back together.
Put the carb back together tonight and things are 90 percent fixed. No more flooding the intake or fouling plugs. I've still got an intermittent hanging idle and a midrange popping issue that I need to resolve but I have a feeling the last guy who had this apart may have messed with the choke mechanism so I'll play with that and see if I can get it perfect but as of now it's pretty dang good. Thanks a million guys, who knows if I would've ever figured that out on my own!
Do a bit of looking at various dual throttle return springs & the way they're generally installed , might help your idle hang up . what I see currently is pretty rough . Once the choke is open , it has nothing to do with how the engine runs ,many times an intermittent miss can be traced to an ignition issue ...
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