Technical Flathead 8ba dry fouling plugs

I'm running an 8BA with Offenhauser heads and intake with two 94's with 51 jets, solid linkage and 3.5 power valves and the only problem I have is the stumble off idle. I tuned the carbs with a vacuum plate and it ran worse than when I set them by putting my hand over the carbs, I've tried the accelerator pumps on all three settings and basically no change. When I put it on the street I was running air scoops and it ran better than when I put air cleaners on it. Runs better with the choke pulled about 1/4", thinking about putting in a lower power valve to give it a shot of gas when the throttle opens.

 

What a small fuel pressure regulator help. Seems your fuel pump is overpowering the carbs. You might have to drop the fuel pressure a bit.

 

You will figure it out keep at it. Did you put a vacuum gauge on?

 

So my fowl breath is actually bird-breath?

 

A friend disconnected the accelerator rods and his runs and idles better. I would not believe it till i saw it.

 

It needs more fuel in power mode, probably snaps back through the carbs on occasions because it's lean. I'm having the same problem on my bb chevy, it's all about fuel and air mixture. When you dump the pedal the flathead wants a gulp and it's not getting it.

 

Seems logical, if it runs better with the choke partially on, it's got a run lean problem.
2 X what pull toy said.

 

Is the engine getting up to proper operating temperature? Helps them to run better.

 

That's why I was thinking about a lower power valve, running two carbs lowers the vacuum on each carb since the engine can only draw so much air. Lower number on the power valve opens at a lower vacuum and hopefully dumps more fuel as the throttle opens. Not a bad stumble on my flathead but enough to be irritating.

 

Seal off one of the carbs so no air or fuel can get in. I had the same problem of fouling with original 97`s and progressive linkage. I cured the problem after finding out the secondary carb butter flys did not seal 100% at idle.

 

unisync for progressive carbs ?
Could you please explain how to do this ?

 

so are you running the smaller air cleaners that are effectively ‘choking’ it a little ?

 

A UniSyn is useful when multiple carbs are used when idling. If you are idling an engine with carbs like the factory 3-2 setup on a 348 58-61 Chevrolet which have no idle mixture screws and the butterfly’s are not open at all a UniSyn is not necessary.
If idle on more than 1 carb whether progressive or not the UniSyn is your friend. Every engine is different so the “red” ball is important to be at the same level on each carb. It is only used for idle. A synchronizer for a multi carb motorcycle engine can also be used by attaching a vacuum line to each carb.

As a side note the engines exhaust pipe or pipes should not be sooty and black. If left idling in a closed garage the carbon monoxide should do you in pretty quick.

 

Thanks - my first grade teacher said I couldn't spell my name - she was wrong....

 

I like that - little info that's cool to read - I was just looking over my grandpa's scrap book from the late 30's early 40's when he was in a gun club hunting bears and the like.

 

Always worth checking the depth of the spark plug holes. Seems many "late" versions of the old name brand heads are now set up for 3/4" reach plugs. Not sure the effect of short plugs in long holes, but it surely won't help.
Costs nothing to check.
Plug looks rich, but can also look black with ignition issues.

 

If your Malory distributor is an old one with a two-piece cap are you sure the spark plug wires are fully seated in the cap? If not you'll have a weak spark which will foul plugs the same way you're showing.

 

thanks,
my point was actually about the fact that the original poster is running 2 carbs on progressive linkage, - meaning a primary and a closed off secondary at idle. Just wondering how to use a unisync on those.

 

The original post said progressive but did not specifically say idling on only one. I know my dual quads will not idle on just the lead carb alone. All the 2-2’s on friends flatheads are straight. I’ve never seen 2-2’s progressive so far in my travels.

 

I agree with your comments, but generally the idea is to have primary completely closed off, (which may be the wrong way to go about it anyway).

I am also considering running a progressive 2 x 1&1/16 Holley’s on my stock flathead, - ( I have my reasons), inspired by this.......

 

Hello everyone, we finally got the problem fixed! After dumping the 9 super7's after finding they were our vacuum leak, we put two new Stromberg 97's on and we also replaced the advance springs in the Mallory unilite. Starts up and idles great, advance all in at 25k pulling hard in all gears! No more fouling of the plugs and lots of power under load. Thank you for all of your help and advice! Just in time for good guys show next month!

 

I got to know! How did you get a flat head to rev to 25,000 rpm without puking its guts out?
What gear ratio and speeds do you run? What block? I’m impressed, the most I ever heard of is 4,500.

 

My mistake, saw it when posting, thought everyone would know what I meant. 2.5k

 

We knew what he meant, especially since no conventional engine I know of can get to to 25K.

 

Yea, I knew what he meant. But I doesn’t mean we can’t get a little chuckle out of it. Too many people are too uptight these days.

 

Holley carbs usually need a PV ~1.5" below the idle vacuum amount.
In other words your 3.5" PV would be good for a ~5" idle vacuum ..... if you want a PV to open earlier you need to raise the PV number so it opens closer to the idle numbers.
The PV number is the vacuum level they open at.

 

you should be in the ballpark with what you have.
Question is, is your vacuum thingie on the carb hooked to the vacuum thingie on the dizzy. (distributor) , show us a pic from other side.
Mine isn’t hooked up and I also have a slight stumble off idle as you describe…..

 

thanks for reporting back , pleased that you got it sorted.
Did you go progressive or fixed linkage with the latest setup ?

 

I can definitely see a 2-2’s system like the one in the photo with progressive linkage like a 4 barrel since they flow into the same opening in the manifold. The ones on friends I know are individual carbs to individual openings.