Holley '94's,same old problem

I've got a 276 cube flatty,Isky 400 Jr. cam,modified Chev dizzy,headers,presently running one Holley '94 carb until the engine is broken in. The carb has a good rebuild kit in it,there are no warped or twisted mating surfaces,no gasket leaks,fuel pressure is 2 lbs,running the stock 51 jets,accelerator pump rod in the #2 hole,throttle shaft is tight with just a bare minimum of play,no vacuum leaks anywhere,timing is 4* BTDC.Problem.. too rich,no adjustment on the idle mixture screws,runs gangbusters at part choke,Ive used 4 different powervalves ;2 @3.5 and 2 @4.5. No difference,there seems to be gas in the powervalve chamber when I dissassemble the carb. The powervalves are not blown and have been modified by Vintage Speed.The plugs are definately fluffy black.I've done a search for guys having similar problems but I'm no further ahead.What am I doing wrong?..and I just know it's going to be a simple fix !!
Thanks for any tips to remedy this;it's driving me nuts!

 

Why do you have no adjustment on your idle screws? Does it run if you turn them all the way in? It shouldn't... Those power valves sound kind of low for a single carb set up (at least to me).
Do you see any fuel leaking anywhere when it's idling, inside or outside the carb?

Flatman

 

i have had a similar problem the power valve was not seated good where it screws into the carb, was very hard to get it to seal, finaly used a soft copper washer , that did the trick,
bill

 

Flatman; Thanks for your response.The engine runs with the mixture screws all the way in or out,no change.There are no external leaks and it appears there's no internal leaks that I can spot. I've run a 7.5 powervalve with the same results.
Oldcarnut;I've run a teflon washer provided by Vintage Speed,same problem as when I ran an original fibre washer.
I'll go out to the shop tomorrow and recheck everything from the beginning;it's obvious I've screwed something up;I'm wondering if the float level is a tad too high,maybe drop it a 1/16".
Thanks for your input.

 

I believe the stock power valve were around 7.5. I would start from there although I am not sure that it will solve your problem. The power valve you are using on the single carb is for a two carb setup.

 

Multiple alarms...
First, troubleshoot idle system end to end: Idle jet, passages in body and over the nozzle bars, the two little bleed hloes (TINY holes at bottom of fairly small holes, one is idle, other is main) , passages down into base.
Float--lower is better, I've posted numbers here before, could find again if necessary.
Power valve--go back to stock...but only way they can affect idle, since they feed at venturis, is if they leak at gasket or are otherwise blocked open somehow...checkemout.
First, fill carb with gas and set on table. See if gas trickles down through that passage, if you can't see anything repeat with base off and carb blocked up level. You really need standard valves, too. My last NAPA kit came through with the no-fit late holley valve, I noticed...a recent post lists a crush washer that compensates for the crude fit somewhat. This could be a real problem.

 

Also, do the flog with NO AIRCLEANER, when problem is cured then see if aircleaner could also be a problem. Both original and hotrod cleaners can be clogged or simply inadequate and act as chokes. Big, ugly late model filter with good brand paper filter is probably the right way, and some Mopar and Ford truck paper filters have a reasonably vintage look.

 

Gents; Thank you all for your information and tips;it's been a godsend. The problem is fixed;I went back and went through the carb again.Everything is superclean and no blocked ports.I set the float level about a 1/16 " lower than the 1 11/32 " called for on the rebuild sheet.I'm using one carb until the engine is broken in and will switch to the dual manifold later this summer.The engine fired right away and ran pretty nice with no leaks. The main problem was the sealing of the powervalve gasket;after much pimping around it finally sealed right.I used one of the washers supplied by Vintage Speed. They have to be pretty tight and doing this caused me several anxious moments.The carb idles down to about 850-900 rpm,plenty of idle adjustment,running a #6 powervalve with about 15 Hg on the vacuum gauge.The #6 valve is all I have on hand (its an original part that was still useable),all the others are rated too high and my new ones for the dual carbies are 3.5 and 4.5. I'll clean the plugs and play with the timing now;I certainly feel better today as I was really bummed earlier.
Any comments on using a #6 powervalve?

 

Thanks for shairing your experence with getting a 94 to work right,I will soon be doing the same and know more about what to expect. The HAMB just rocks!