59A Flathead Running Rich, Need Help
 

59A Flathead that was built by someone else.

This is what I was told that engine is internally:
276 ci
Isky 400 Jr cam. It has a bit of a rough idle so it seems like it is a 400jr cam or least something comparable since I can't verify the cam without going into the engine.

This is what I can say visually about what is on the engine:
Edmunds 2x2 intake
Stromberg 97 carbs
Edmunds heads
8BA timing cover with later model Dual Point Mallory distributor.
Fenton exhaust manifolds
2" exhaust to Porter mufflers

The engine seems to start up and run fine at idle and in the lower RPMs. The lower RPMs range that I mean is probably up to about 2000 RPM or so. But when accelerating harder or longer in each gear so that the engines revs up into the 3000+ rpm range, the engine's power falls off like a flat spot and then it starts loading up like it is getting too much fuel. It kind of jerks a little too. All of the spark plugs are sooty and black showing that is running way to rich.

When parked and just free reving the enigne, you see and hear the same thing. Low RPM's seem ok, but higher RPM's it is loading up, popping, and extremely rich exhaust smell.

What I have done so far to diagnose the problem without any real change:

1. Carbs had stock jets and power valves in them (45 Jets, 65 PV's), changed to 43 Jets and 71 PV's

2. Checked distributor timing. Recurved for better advance curves, Now has 22 degrees advance all in by 2500 RPM and 4 degrees initial timing. New points and condenser (tried three different brands of condensers just in case), but I have no way to test the condensers other than to make sure that they are not shorted to ground. It has solid core plug wires and checked each to make sure they are in good shape by checking resistance (less than one Ohm each, continuity, and none are shorting to ground.

3. Replaced coil with a new Beru Blue coil and made sure that the positive lead to the coil is 12V for the Beru Blue coil to work properly. I bypassed the ballast resistor on the original coil on the car. The Beru Blue Coil is the same as the Bosch 00012 coil and does not need ballast resistor.

4. Checked fuel pressure, have about 2.5 psi at the carbs with engine running at idle. Drops some to about 1-1.5 psi while reving it up high.

5. Still ran the same. So, I blocked off each carb individually to see if the dual carbs were the problem or to see if one or the other carb has an issue. Still ran the same.

6. Check the compression on each cylinder with the engine at operating temperature. All are 140 +/- 10 psi.

7. It had NGK B4L plugs in with only a few hundred miles on them. All of them are black and sooty. They are the shorter reach plugs for iron heads. I put new plugs in it just to see if there was a difference, but no change really.



It only sems slightly better with all that I have done where the extreme rich smell isn't quite as bad, but is still pops and loads up reving it up. The new plugs got black really quick.

What am I missing? I'm at a loss and looking for suggestions.

Re: 59A Flathead Running Rich, Need Help
 

Genuine Stromberg carbs or knock offs? Has your TDC mark been verified as correct?

Re: 59A Flathead Running Rich, Need Help
 

Yes, genuine original older Stromberg carbs.

Good idea here that I had not thought of. The TDC mark has not been verified. Would if the mark is retarded and timing is too slow, then it will not ignite the fuel quick enough to burn it all during the power stroke? Can TDC be located with a spark plug style piston stop meaning will it touch the piston or is the spark plug hole too far past the edge of the piston where you have to remove the head to use a piston stop across two head bolts?

Re: 59A Flathead Running Rich, Need Help
 

Are you using the gaskets for the power valves? They may be leaking. Have you checked float level? It's possible the accelerator pumps are supplying too much fuel. Is the accelerator link in the S-ummer position? Does the Mallory have any vacuum advance.

Re: 59A Flathead Running Rich, Need Help
 

Yes, the power valves have the gaskets. The pump arm is in the S-position. I need to check the float level. The Mallory is mechanical only

Re: 59A Flathead Running Rich, Need Help
 

What plugs are you currently running? I don't know about the 59A Edmunds heads, but the 8BA versions take a 3/4" reach plug (Champion "L" series or equivalent). The stock plugs are much shorter reach (7/16") and will be seriously shrouded. The 8BA Edmunds heads also have the spark plug moved just far enough to miss the exhaust valves, allowing for the use of extended tip plugs. I installed a set of Champion L82YC plugs in the Edmunds heads on the '51 Merc in my '51 club coupe when I installed the new engine in 2016. They haven't missed a beat in the last 8 years. I pulled them out a couple of years ago and they still looked good.

I find it unlikely that Edmunds would have used different combustion chambers on it's two series of heads. If you were to decide to use these plugs, I would still be careful checking the installation out on the slight chance the Edmunds could be significantly different.

Re: 59A Flathead Running Rich, Need Help
 

The NGK B4L plugs in it now are the short reach plugs. Longer reach plugs definitely would not hurt.

Re: 59A Flathead Running Rich, Need Help
 

I would suggest a plug change ASAP. Not only will the plugs be shrouded, but the shorter threads have a good chance of failing, as aluminum is not as strong as cast iron. There is a reason they went to the longer reach plugs in the aluminum heads.

As I said before, check first. I have tons of experience with 8BA Edmunds heads, but none with the 59A version. I can see no reason why they would be different, though. You should probably get a spark plug tap to clean out any carbon that has accumulated in the unused threads.

Re: 59A Flathead Running Rich, Need Help
 

What air filters are you using. The ones that are too small can cause rich running. If so try its with no air filters.
I think .043 jets are too small. A built 2 carb flathead usually needs at least standard .045 jets, usually one or two sizes bigger.


John

Re: 59A Flathead Running Rich, Need Help
 

No paper element air filters. Using the scoop and wire mess screen like these:

https://www.speedwaymotors.com/Strom...SABEgIpe_D_BwE