spark plug frustration

[vml7]

I am having problems trying to figure out why the same 2 plugs
keep fouling out rather quickly. other 6 look fine. car is 1971 dodge demon 340 4sp. ported w2 heads, 10 1/2- 1 comp ,holley street dominator high rise intake, holley 700 double pumper mech. sec., unilite dist. msd 6a, cam is comp. cams hyd. lift 494 dur 292 108 centerline. the 2 plugs that foul are very wet and smell like gas, no oil or water.

[dave571]

If it's the same two all the time, there must be a problem with coolant or oil getting in to those cylinders.

What colour? What do the deposits look like?

[Ram 1500 Box]

What cylinders are we speaking about? Are they grouped together? Are they on separate banks? What type, make and heat range?

[vml7]

spark plugs are auotolite 63s ,wet plugs come out of cyl. #3,5

[Ram 1500 Box]

Since these are not in the same pair in the head, I would not look for infiltration from the valley area. But, they are in the same pair in the intake (looking at the dual-plane manifold) and are the short side runners, and are slightly richer than the outside runners at #1 and #7 cylinders. The recommended plug is the #65, (2 ranges hotter than the #63's) and I would purchase a pair, run them for a while and then re-read the tip. If they go without fouling, I would consider moving all of the cylinders to #65's.

[skankweirdall]

If I read your post right, that Holley intake is a single plane right? In which case they are notorious for uneven distribution. You can epoxy in "popsycle" sticks on the floor of the manifold right at the entrance to those cylinders. What you are doing is building a small dam in front of the intake runner opening. Most of these dams are about 1/4" X 1/4" or 3/8" X 3/8" by how ever long the port opening is. Keep your cold plugs, this should even out your distribution problem.

[Ram 1500 Box]

If I remember right, the street dominator was a heated, dual-plane design and the strip dominator a non-heated, single plane, common plenum design.

I would always start with the recommended plug heat range LONG before I would start modifying the plenums in any way. Now, if it is a single-plane common plenum design, only after using the correct heat range and then reading them compaired to the remainder of the plugs would I ever modify the base of the plenum.

If you are running plugs 2 ranges too cold, cylinders #3 and #5 would be, by design, the first to cold foul plugs. (and why not, your running too cold a plug)

I would suggest rather that a person probe each of the cylinders at the exaust port with a gas analyzer to determine the correct mods to the intake plenum floor. I am aware of the "popsicle stick" modification on single-plane common plenum designs, and it is even recommended by the Direct-Connection folks, but you cannot adequately balance the cylinders, if it is in fact the problem, without proper gas analysis.

[skankweirdall]

Colder plugs run better with less chance of detonation. The other cylinders are fine with them so even if you put in hotter plugs you have not fixed the distribution problem with the manifold, you've only succeeded in masking it. He could also since these are on the same side of the engine drop a jet size in the primary on that side. It might help.

I guess we really need to find out if it's a dual or single plane manifold. I thought they were single planes.

[skankweirdall]

That manifold is not listed on Holley's site so I don't know.

[mtrv8n]

Have you checked that the plugs are firing??

Pull the plugs, put the wires back on em, and have a buddy crank the motor while you groung the plug on a header. You should see a big fat spark. If not, you know where to start looking for trouble.

I don't like the Unilite, but you could just have a coupla bad wires(burnt) or they might not be seated right on the distributor cap.

You could have bad plugs, broken ceramic. Maybe they weren't seated tightly when installed, and are passing gas (hee hee).

It's easy to break plugs when installing them, just a little crack and they're history.

[6 packin]

How about the carb? Whats the idle mixture set at? Count the turns to full seat so you can tell us and put it back. Make sure that when adjusting the idle circuit on that side, it should make a differance when you turn it in either direction. If is does not kill the engine the could be plugged. Take them all the way out, dont loose the little seal that holds it in place. (somtimes made of cork). Blow threw the passage with compressed air. Try it again. Also note the others plug condition and color. Just a idea.

[cuda66273]

It may be something as simple as not enough initial timing in the motor causing the plugs to foul or a carb adjustment.

You've got lots of testing to do from all this info...pick a starting point and work through it one step at a time and lets us know what you find.

Just thought of one more thing...your not running a cap with aluminum contacts in it are you?

[vml7]

thanks for the input, I changed plugs from 63s to 65s, but the same 2 plugs were wet. I then pulled the carb off, and disassembled it . about a year ago the corner of the base plate cracked , so I replaced it with the base plate from a older barry grant carb I have .(860 cfm, was to much for my motor) looking at the top of the base plate , i noticed a pin was inserted in the middle on both sides of what i believe is a fuel canal ? the pin seems to seperate primary and secondary canal. maybe because the bg carb had rear adjustable jets, ? that was just my guess.
well i drilled them out , and car runs great , no fouling , so I assume some how that was the problem