Flathead Running rich

bmwillia

bmwillia

Senior Member
I have been fighting an issue with my engine running rich.

Some background info:

I am running a Stromberg 97 Carb rebuilt by Max. I have a mechanical fuel pump with a sediment bowl. It is a new pump but I used the spring out of an older pump to get the pressure down to around 2lbs. I have checked the float and it seems to be good.

I have a strong exhaust smell like an engine that runs rich. When I rev the engine I get what sounds like back fires on deceleration out of the tailpipes. Other than that, the engine ran pretty good until about 100 miles ago when it started missing and lurching a little while driving at lower RPMs. I had to put about 5 gallons of 10% Ethanol in it to get home from a trip and I attributed the missing and lurching to that gas, but I have ran two tanks of 100% gas since then and the problem has gotten progressively worse.

Yesterday I pulled the plugs and found they were all black and crusty some worse than others. These are new plugs with just over 1000 miles on them.

Screen-Shot-2021-04-19-at-11-25-30-AM.png



I am going to get new plugs but I am not sure where to go from there. Any ideas would be appreciated.
 
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A "Max rebuilt" carburetor? That brings an old saying to mind, "90% of carburetor problems are ignition related while most ignition problems are caused by a faulty fuel system".

Are you sure your coil, condenser, and points are good?

Jack types faster than me.;)
 
#2 and #3 are probably correct, however if the power valve at the bottom of the
acc pump well leaks ( who knows why...it happens ) you will run rich. Max will be here
momentarily.
Charlie
 
I have converted the car to 12v and it is a new coil. I am using the helmet distributor and points that were fresh when I started driving the car. I am using a 12v adapter plate on top of the distributor. It and the condenser are new.

I'm not saying those things are not the problem just giving you all the info.

What is the best way to check the condenser and coil?

What do I need to look for with the points?
 
I recently learned the hard way that when condensers go bad they don't just cause burned points. They can cause missing and lurching and fouled plugs. I also went down the carburetor rabbit hole. Had a little problem mounting it because of size, but the Tubman condenser cured the problem. Seems like every other condenser is a crap shoot. Check out this thread (page 2) to see if some of it applies to you.

https://www.fordbarn.com/forum/showthread.php?t=296287&highlight=drolston
 
I did not but I bought a conversion kit from Vintage Auto Garage and it is a 3 ohm coil with internal resistor.
 
Just a thought or a "wild" idea. How did you check you carb settings? what kind of engine vacuum readings are you getting.


It could be completely electrical.
 
When you get a chance pull a plug wire and crank the engine you should see a really strong spark if not pull the distributor.

That is another thing to check also the distributor has two sets of points if for some reason they are not set correctly the dwell period will be all meshed up. Remember the points overlap each other to proved the necessary dwell period.
 
Yes the plug looks bad . . . but it isn't necessarily the carb. Unless the power-valve is leaking, I'd suspect you have other issues - most likely ignition related.
 
I think I am going to start with ignition. This project has taken me several years and many things have changed over that time.

Thinking back to when I ran the engine on 6V I don't seem to remember it running rich or back firing. I'm going to start with ignition and go from there.

First is a new condenser along with new plugs. I have already reached out to Tubman for one of his. I may check my local NAPA for one as well while I'm waiting on Tubman's to come in.

Any recommended brands, or any to stay away from?
 
bmwillia said:
I think I am going to start with ignition. This project has taken me several years and many things have changed over that time.

Thinking back to when I ran the engine on 6V I don't seem to remember it running rich or back firing. I'm going to start with ignition and go from there.

First is a new condenser along with new plugs. I have already reached out to Tubman for one of his. I may check my local NAPA for one as well while I'm waiting on Tubman's to come in.

Any recommended brands, or any to stay away from?
Click to expand...

It was a new condenser from MAC's that caused me grief. I am sure many of them are okay, but I would not take that chance.

What kind of spark plug wires are you running. If carbon core or spiral wound, they are prone to connection failure at the ends.
 
I am really not sure what spark plug wires I'm using but there appears to be a single copper core in surrounded by a white insulator.
 
In ref to post # 18.....I use Tubmans big brass condensers for most Mallory
and hot rod applications. The IH 200 however is easily adapted to stock front mounted
distributors and has little eye appeal. Tubman's baby is way cool.
Charlie ny
 
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