So as some of you may know I have a 255 merc flathead bores out with heads,cam,port job, and a 2 deuce offy intake with dual 94s. They have .049 jets in it and stock powervalves. My air filters paper has been ripped out and just the fine bug next and larger bug net is left. What could this be. Everyone I talk to says they run .049-.051 jets in their carbs and it works fine. For me it’s so rich my boss said it was burning his eyes. And another thing is my plugs are fouled. And they are autolite 216 plugs. But the end of the ground strap is flush with the end of the threads. My boss is telling me this is wrong. And the electrode should protrude Into the combustion chamber to make a efficient burn. What am I doing wrong? Sent from my iPhone using H.A.M.B.
Check some of these things. Ruptured float. Needle valve not seating. Float level too high. Wrong type power valves, and/or incorrect gaskets. Damaged diaphragms in power valves. Distortion in lower body and throttle body causing vac leak into power valve chamber. All the above will cause an over rich situation. Don't worry about the plugs for now, you can't stick the electrode down too far or the valve will hit it. They won't cause it to be rich. being rich will cause the fouling if extreme. I may have missed something out but those things are where I would be looking first. Mart.
Float is ok. Checked the float height and re adjusted it, needle is seating 100% all new gaskets. All the gasket surfaces sanded flat. It has stock power valves in each carb. So thag might be the problem Sent from my iPhone using H.A.M.B.
That’s what I thought, and what most people are saying. That’s why I’m so confused Sent from my iPhone using H.A.M.B.
You're not jetted too big. It will run fine on 51s let alone 49s. It's too rich because of one of the things listed (I did leave out fuel pressure). What sort of fuel pump do you have? Do you have a fuel pressure gauge? You want no more than 2.5psi. Mart.
One thing I haven't seen mentioned, where did the jets come from? Just because they are marked .049 doesn't mean anything. They should be checked with a # drill set because it is very common to find drilled jets.
I am running a electric pump. And a offy tegulator. I forget what I have it set at. I will check when I get home Sent from my iPhone using H.A.M.B.
Power valves too big. I run 4.5’s in my dual 94’s on a 239 8BA. I think stock is 7.5. Make sure you have the correct ones that doesn’t have a radius at base of threads or it won’t seal good allowing fuel to leak past. Sent from my iPhone using The H.A.M.B. mobile app
Be sure to check your fuel pressure with a reliable gauge. The Offy-style pressure regulators are known to be unreliable and the numbers on them are not necessarily accurate. Using a fuel pressure gauge as your reference set your fuel pressure around 2 lbs. This should end your problems unless the regulator is faulty, in which case you'll need to replace it. You might need more fuel pressure if you ever go racing but this should be okay for general driving. Good luck!
The old speed manuals and I do believe Fix Your Ford (1958) recommends plugging 2 of the ports on the economizer valve in a 94 set up for duals.
what type of power valve is this. It came in the rebuilt kit. And it looks like it works backwards. Could this be used as a plug? Sent from my iPhone using H.A.M.B.
Not sure of the name but it isn't a power valve. On certain models it is on the front of the carb (or is it the back?) and is to do with the signal for the loadamatic vacuum advance. (Spark valve? something like that?) It is not intended to be used as a plug. What is your vacuum at a gentle acceleration? You need to know what it is so you can work out if your power valves are ok or not. I have a dual vacuum/fuel pressure gauge that is really useful to diagnose these issues. If you don't have one, maybe you could see if you can get one. Mart.
Plugging power valves are a bad idea. That was an Old way of bypassing a problem that can be remedied by finding the correct size for both carbs. They are designed to kick in during acceleration for progressive controlled power and economy. A good thing. I’ve run power valves for my two 94’s for decades. I have great power and get 16mpg. The best on this subject ever. https://www.jalopyjournal.com/forum/threads/motor-why-stromberg-97s-over-94s.4618/
the spark valve screws into the cast iron base on later model carbs. The correct economizer or “power” valve is pictured on the right with no radius at base of thread. Also beware of some valves that have larger plungers that can hang up on the side against carb body. Sent from my iPhone using The H.A.M.B. mobile app
Jetting, & powervalves, and general carburetor calibration are widely misunderstood. Now I'm not gonna argue I'm a carb guru, but a few hours spent going through the shop manual, and theory of operation and the setup and adjustment in the carburetor manuals will go a long ways. Most of the adjustments people talk about are bench settings that just baseline everything, so the engine will run after installation. They are the simply a starting point, by no means the final adjustment. The spark plug condition will tell the tale. With modern gasoline, they should be very, very clean burning if ignition and carb calibration is optomized.
Black! Dark dark black. My boss is a machinist. And he said the exhaust was burning his eyes it’s so rich Sent from my iPhone using H.A.M.B.
Lots of really good information in this thread, but 93 percent of all carburetor issues are ignition. Any tests on the ignition system? Jon.
Modern gas formula off pump will lie to you, plugs always look rich, look at new cars they're controlled by computer tail pipes are black, buy yourself a good wide ban O2 gauge it will lead you in the right direction once that's established remove gauge, My Flatty With twin carbs has 4.5 pv & 48 jets Pressure 2psi, initial timing 13 deg
I ran 51's and 4.5 PVs on 94's on my 1951 286 Merc flatty. Now granted...every set up needs fine tuning but mine ran great. Also ran an electric pump with a Holley regulator set at just over 2psi and a pertronix on a stock '51 dizzy with good wires and Autolites.
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