All Plugs Fouling on Right Bank

-
clifftt

clifftt

Well-Known Member
Joined
Nov 13, 2007
Messages
2,420
Reaction score
969
Location
Concord, CA
Help! All right bank plugs (2,4,6,8) are fuel fouling on a newly built 273 Commando Formula S, have a black soot. Left side plugs are clean. Besides running in the driveway, I've only run the car up and down the street a few times. It idles rough.
Solid lifter cam is just a bump bigger than stock and degrees during the build. I'm using the stock manifold and AFB. Exhaust manifolds are stock, and the heat riser is opening as it warms up. Stock dual point dizzy. Initial 14*, 35* with vacuum.
The heads were resurfaced and when I assembled the engine, I found the intake wouldn't quite fit. Took it back to the machine shop and had the manifold surfaces shaved a bit and I was able to bolt up the manifold. I was thinking maybe the manifold isn't sealing against the right head. I ran the engine about 1000 rpm and sprayed brake clean where the manifold and head bolt together, and around the carb, but there was no change in the idle.
I'm looking for ideas... Thanks for all who reply.
 
I would look for a vacuum leak affecting that side.
 
the only thing I can think of is the AFB. Either an air bleed is clogged on one side or the rod hanger is bent and not letting the rod set in the jet at the right height. All the plugs have been changed to new ones I assume. You may need to check the manifold also as said above. Smoke test or other. {you could actually use plastigage to make sure the gasket mating surface is even}. How about the valve adjustment? Just thinkin' out loud here. Good luck.
 
all on one side...sucking oil from the intake manifold.......
 
What year 273?

Don't use brake clean as a vacuum sniffing agent, ones containing chlorine can be deadly when vaporized by heat, they will produce phosgine (sp?) gas, the same stuff used by the Germans in WW1.

Black soot dry, would be carb problem, black soot wet could be sucking oil or too much fuel, sniff the plug; does it smell like gas?........as already stated, could be speck of dirt in air bleed, possible bent hanger
 
I'm not up on my trivia....

Single plane or dual plane manifold?
 
check for stuck heat riser if you have stock exhaust manifolds also like others have said intake manifold ,try to retorque it first.
 
I would also be looking at the carb,if it is the heat riser check flow at the tail pipe,if its sticking you should feel a difference.
 
Exhaust crossover plugged in the intake? With a working hear riser......closed while the engine is cold and carboned up crossover......
 
I'm thinking the intake manifold has issues. Since you didn't post pics...if the crap on the plugs is wet and shiny, it's oil. If it's dry and fluffy it's fuel.

And you dont have near enough total timing if you only have 35* WITH the vacuum advance. You should have that much PLUS the VA.
 
Last edited:
Spark plug pics attached, two from each side of the engine. To reply to some of your posts: Spark plugs are new. The manifold is a stock open plenum, so if there was a carburetor issue, I think I would see fouled plugs on both sides. (If it was a dual plane, I could see that as a possibility.). It's not the heat riser, I noted the position before and during warmup, and it's open when hot. Exhaust crossover is not plugged, I had it cleaned out when all was machined (it was hella plugged!). Yellow Rose: how much timing are you running? That doesn't sound right.
So far it sounds like it might be sucking up oil. Check out the pics, please.

image.jpeg


image.jpeg
 
Your idle circuit is dead rich. That looks like fuel. What plug is that? I can see it's a Champion, just can't see the numbers.

You need 35* total timing PLUS whatever you have in the vacuum can. I don't know what you have for a distributor, so I have no idea how much advance you are pulling with the vacuum advance.

Just like a "power valve" in a Holley, which should have been called an economizer valve, the vacuum advance is there for economy. At a cruise, you can run more timing than you can under load. That is what the vacuum advance does. It's an economy thing. As a result, you need to make sure you have 35 total with the VA, all in by 2500 if it's an auto, 2k if it's a stick. You can reduce the amount of advance the can pulls. Seems to me if th can is pulling any more than 10* you need to cut it back some.
 
show the manifold
are you saying that it is a factory single plane?
 
Rose: Thanks for the clarification on the timing. The plugs are Champion RN12YC. The dizzy is a factory dual point.
Cudafever: Its a factory cast iron single plane...

image.jpeg
 
ok that's a single plane. Problem is in the carb on that side of carb.
 
I guess you could still have a vac leak on the leaner side plugs. is that the hose to you brake boost or you pvc on the back left side of the manifold.(left side looking at it from the driver side.
 
Cudafever said:
I guess you could still have a vac leak on the leaner side plugs. is that the hose to you brake boost or you pvc on the back left side of the manifold.(left side looking at it from the driver side.
Click to expand...

Back left side, with the white cap is for the brake booster. The hoses and clamps are new, but the valve is original ... That's a thought. I took you another carb photo.

image.jpeg
 
Yah, pull that hose and plug it. If the left side gets rich looking like the right. You have a bad brake booster. if not......still think the carb need to be open up to find the problem.

You have tried adj the idle air fuel screws in front of the carb right??
 
Booster Dewey rebuilt the booster, I doubt that's it, but might be the white check valve. I'll tackle that end. And I did try adjusting the idle screws, set as the manual said at 1 1/2 turns out at first, then moved it with a vacuum gauge attached, but the adjustments made almost no difference ... Vacuum hardly changed and idle didn't change.
 
What is it idling at? try and lower the idle and then re set the idle fuel mixture screws.
Sure sound like a carb problem. time to buy a carb rebuild kit and go thru it.
 
AJ: I popped off the metering rod covers and found the right side rod not set down into the jet. I'm hoping that was it.
The engine broke in without a problem, but I did go back into the carb afterwards to rebuild it. Perhaps that's the problem.
I'll make enemies in my neighborhood tonight if I try running it. And besides, I'm watching my Giants getting swept by the Cubs here in the 8th inning. I'll report back...
 
If it don't, i will still help a lot!!!!!!
I think you found your problem. as long as that metering rod is not bent now.......
 
Well that is not supposed to happen by itself, so make sure the rod is not bent and that the cover fits properly.
OOps, already said, sorry Cudafever....

The cover is what locates them properly, so it has to be down flat and tight.On occasion,I have had to bend the mounting ears down a tad.
 
Last edited:
You must log in or register to reply here.
-

Back
Top