Technical Carb problem

Hi I’m running a 364 nailhead with four big 97 Stromberg s , fuel pressure set at 2/1/2, seem like I’m getting way to much fuel in the manifolds, fouling out the plugs, I disconnected the back two carbs and I’d running better, I have them leaned out two 3/4 turn, do I need to rejet all of then , I believe jet size is 45. How much should downsize, any help would be much appreciated.


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how long have you been running this set up? always had this problem? have a pressure regulator? if so, what is it set at?

 

Cant help, but, that's a bitchen car.

 

Can you get a manifold vacuum readings?

 

This all completely new, built it from the ground up ... yes I have a regulator and is set at 2 1/2


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Yes but not since I disconnected the back two carb , I’m going to check it again today...


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Thank you, I have all the fenders for it , going to run it like this for awhile


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The manifold looks homemade to me. Has it ever been used successfully on another engine or car?

 

Those are Martin manifolds that got from Buick rodder out of California


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The problem is no heat in intake . When you drop pressure , across the throttle plates it wants to ice . Makes the fuel mixture droplets instead of making a vapor from the fuel. If you were running WOT , you wold love it .

 

Please excuse my ignorance. I have had no experience with nailheads, so I don't know anything about "Martin manifolds". So I will ask again, have they been run successfully on another car or engine? I would expect they were, but it would be good to know for sure so we can eliminate that as the potential problem.

 

If the plugs are black it's to rich.

 

Yes they have , I’ve seen six twos run on these manifolds. I’m thinking I need to get smaller jets for them ?


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What’s wot?


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wide open throttle

 

Yes I’m sure I would love it , unfortunately the speed limit is 45 on my island


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Check your float levels if all is good bottom all you idle mix screws then bring them back out only a half turn not 1 1/2 like it calls for on a single carb set up.


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Thank you I did check the float levels 1/2 inch from the top, I have the mixture screws at 3/4 turn . Car running pretty good since I disconnected the back two carbs, but would like to run them all, ordered smaller jets , hoping that will work ?


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With it running look down the throat of each carb and see if you see any of them dumping fuel.


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I hate to be a pest, but have you seen this particular manifold running on another car or engine? You say you saw one that ran with six carbs, but it was obviously not this particular manifold , since it has provisions for just four carburetors.

 

I'm assuming your trouble shooting running rich is at idle?

If so swapping jet size won't do anything for ya.


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I would get a vacuum gauge on it and set the ignition for the best reading, then adjust from there.

 

Hmmmm! I’m not sure it’s running rich at idle , and I also figured out today the air cleaners were restricting the airflow to the carbs and flooding it out under load


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I think deathrowdave has your answer.

 

Yes but how do I fix it ?


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I would suggest trying a hotter thermostat. Not sure it will solve the issue, but inexpensive, and certainly will not hurt.

You need to hook up a temporary tachometer to determine the RPM where you are having issues. Circuits vary, but ballpark:

Idle <900 RPM
Transition 750~1200 RPM
Main 1100 RPM and higher.

Note the circuits overlap.

While heat is probably the definitive answer, a possible "Band-Aid" might be in slightly leaning the circuit in play during the issue.

And while you have your regulator dialed at 2 1/2 psi, maybe hooking up a fuel pressure gauge as a check might be beneficial. Those regulators are about as reliable as the weather forecasts were when I was a youngster

Jon.

 

best advice I can offer is to talk to Clive at Stromberg or Uncle Max at 97express.

I emailed them both for tips on tuning up my stromberg 6x2 setup. both guys were very helpful and knowledgeable.

I'm still learning more about how to dial it in, but their combined advice was a good start for my application.

 

Can only lend you some advice that saved years of guessing.
Look in Summit for an Innovate fuel/ air mixture meter. Run you about $200. Will tell you exactly what circuit and when your loading up.
One more piece of advice, DON'T mount permanently, save as a tool for future projects

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Tough lookin' rod I'd might add!

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It's possible for a carb to run a lean idle yet pig rich at cruise, and vice versa too. The jets don't really factor at idle, etc. The porcelain "color" is just a part of what to look at. Deep down inside the plug where it meets the metal shell is the color indication of lean or rich AFR at wide open throttle. Heat range and ignition timing indicated on the ground electrode. Modern gasoline doesn't color very much either, if plugs are black and sooty with today's fuel, the mix is WAY rich!