Greetings, quick question I hope before i pull all my ****** hair out and buy an Edelbrock 4 barrel what I have; 2 Holley 94s (model 59) on a Northwest dual carb to 4 barrel adapter on a 350 chevy its is a fairly mild build and pretty fresh. It runs around 18 to 20 on my vac gauge. There is NO power valve leaks. There is excellent float level in both carbs. New throttle plates from ****ster. Dont need to explain PV size or Jet size as my problem is in the idle cct. I can get the idle down to around 700 without stalling but when I look down the throat of the primary carb I see fuel dripping from the nozzle bar. Which is what the engine is actually running on by the looks of it. I have adjusted and adjusted, I have swapped nozzle bars from front to rear I have cleaned till it almost shines on the inside in every orifice, I have set the throttle plates in the bodys till they almost seal the best I have ever achieved on this model 94. I still cant stop that ****** nozzle drip. (only on primary secondary carb looks to be dry I cant swap it because I have blocked it all up as a pureley secondary carb) My thought: 350 CHEV TOO BIG?? Do I need to drill the primary throttle plates so i dont need to open the plates too far so as to give vac signal to the idle cct which causes fuel to go through the main gallery and into the main outlet of the nozzle bar? If YES what size holes If NO WHATS NEXT!! hello Edelbrock! please advise Andy.
I would check your fuel pump pressure first and see what reading you have. I am thinking you have too much pressure for those 94's. What I think is happening is that at idle you have the needle and seat not holding the fuel due to excess line pressure causing it to flood. Off idle the engine uses more fuel so you won't notice it so much. You may need to fit a pressure regulator to reduce the line pressure.
Sounds like a fuel pressure problem to me also. Put a regulator on it and set it about 5 pounds and see what happens. Don't buy one of those cheap dial ones as they aren't very accurate.
Or...it could well be too much flow going through as he suspects. On a 221 flathead, Ford says main circuit gradually takes over from idle and off idle between 1,000 and 2,000 RPM, his engine is 2 liters bigger, so entirely reasonble su****ion. I would personally try dropping the front float level a tad to lower draw in venturi first with his setup, but if starting over I would unblock or find a good throttle body for the secondary and run straight linkage. This will of course drop flow by half in each carb and should I think cure it. Remember that small flatheads do fine running 2 carbs, essentially all flatheads running dual Ford carbs use straight linkage. Air byp*** would be experimental and would be interesting tinkering, but I think straight linkage will clean everything right up.
Fuel pressure regulator and fuel pressure gauge close to the carbs. Set the pressure a 2- 2.5 PSI at idle max and you should be fine.
I'm no carb expert, but I try to learn as much as I can. I'd look at fuel pressure first, but you said "New throttle plates from ****ster". Do these plates have a beveled edge on one side (I believe 10 degree)? Are they properly installed? Some new plates are sold for use in secondary carbs and they are designed to seal up 100% when closed, as opposed to allowing some flow for idle. Reversing (or flopping) even stock ****erflies may cause a problem. I think drilling the plates is a risky experiment when you should focus on fixing what's wrong with the originally designed system before redesigning it. On the other hand, since the Holley 94 was designed to be used in Fords, perhaps you're suffering from organ donor rejection.
Thanks guys, probably should mention I have a regulator and gauge (reliable) running at 1.5 to 2.5 pounds, should be heaps to keep the bowls full. Bruce I think I might be prepared to tinker with the "speed hole" in the throttle plate, as you said there is a lot more volume p***ing by producing the signal and the idle cct to intermediate cct may actually, in my opinion, be in a transition mode too early. I would love to hear from someone with a similar setup on a similar Cubic Inch engine. regards, Andy
Do you have stock power valves in the carbs. You need to change power valves when you run multiple 94's. when you put more than 1 on the vacuum drops and the power valves open very early and cause a problem similar to yours, but usually as you open the throttle. You need lower numerical ones. I think stock are around 7's. My 2c's worth. I have 2.5's in mine and it runs perfectly. BTW mine is 331CI.
I think drilling is the hard way here...this is an under-carbureted motor, and straight linkage will cut the airflow at idle in half per carb. Also fixing the current secondary will get back the off-idle circuit, a good thing to have. I would probably start with stock or fairly high # PV because, again, this is kind of undercarbed, unlike a 221 with the same carbs, and should have rather stocker like vacuum characteristics. There is NO reason to go progressive...much smaller engines do fine with straight linkage and dual Ford carbs.
aussie and Bruce 2X, one 175 cfm carb is too small for a 350, two is better with 2.5 or 3.5 power valves in both carbs.
Revvitup to 6,000 in low and you'll see two 94"s pop inside out into the plenum! Woohoo! As it is, just go straight and you'll have something like a civilian lopo 350. I have known 136 CI V8-60's that were happy with duals and straight linkage...
I run six 94's and often had one or two drip for no reason. Float levels are too high, reduce the float height and the leak stops !
Since you're running a primary secondary with progressive linkage, did you fatten the idle jets on the primary? Also, drop your float level a 1/16". Where are your mixture screws set? While it's at idle have you covered the air horn on the secondary to see that there is no vacuum leak? Did you eradicate the mixture screws on the secondary or just "screw em' all the way in
Hey guys, thanks again, hmm undercarbed Bruce.. maybe. Disapearing act of 2 x 94s down a dual plane manifold.. THAT would be real site! lol. ****ster.I have fattened the primary up to 57s and secondarys are 50s, havent had a chance to test them yet though. I have the secondary idle ccts totally blocked off. and NO PV in there (blocked). I have reduced my float level somewhat as i suspected this early in the piece. When I cover the secondary carb up it does run a bit richer but not so as to stall the engine. I am now thinking about taking a "bin dive" into my 94 spares box and trying to find a salvageable 94 base and trying Bruces straight idea. I do believe thre may be too much air flow past the idle signal ports which is pushing the carb into the transisiton stage. This may be eleviated by sharing the flow with the secondary carb...perhaps those aluminium throttle plates I got from you for the secondaries seal TOO ****** GOOD LOL!! stll thinking......
Just a quick note with something I ran into on my shoebox recently. I kept having the same drip on my carbs. Countless times of setting the float level, measuring everything, I finally realized my problem. The angle my carbs sat at was about 5 degrees. This made the carbs tip too far back and as the fuel heated up in the carbs, fuel would drip from the nozzle bar. I ordered some 4 degree wedge adapters from Dashman here on the site. Problem solved. Worth a look with a angle finder?
Andy, I think you might have misunderstood me here. Not your main jets, which I think you may find a bit to big in the primary, but rather the idle tubes in the primary carb. To fatten it you want to increase the small hole in the bottom of these br*** tubes 1-2 drill sizes at a time, which should smooth out your idle.
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