Thread: 383 spark plug tempuratures

Tweet

hi, i could really use some help and havent found anything on this site that addresses my problem. i have a 383 that has roughly 3,000 miles on it. its running 10:1 compression with a 236/242 520/540 at .050 110 load, 106 centerline camshaft, ported and polished performer rpm heads(1.50 rockers), topped with an air gap rpm and a 1" open spacer with a 750 speed demon(vacuum), hei distributor with a msd 6al. im having problems with the cylinders all running different temps (at least this is what i think). #1 and #2 cylinder spark plugs are always wet (threads soaked all the way) #3 and #4 are the same but not as bad, #3 is actually worse than #4, #5 and #6 are totally dry with the upper ceremic bone white, #7 is dry but is showing rich, #8 is running rich and the threads are wet until the last 4 threads. i thought it was an intake leak until i changed the carburetor from the break in edelbrock to the demon with a 4 hole 1" spacer ( i originally used a 4 hole and then changed to an open spacer hoping to break up the air a little better, which it did a little) anyways, with the edelbrock, cylinder#s 1, 2,3,4 were wet all the time while 5,6,7,8 were bone dry, borderline detonation. what the hell do i have to do to solve this problem? what steps do i take to identify the problem? any help would be greatly appreciated,,,,,, john

John, I might be thinkin' plug wires, but that's just a guess at this point. Have you verified a good connection at the cap on all wires? How about doing a resistance check on 'em? Are all the plugs gapped the same?

hey tech, no i havent run a resistance check on them, but i will. i do know that all of my connections are tight and i have gapped them all at .045. what do you think about the possibility of an intake leak?

Could be a number of things, but I think tech has you on the right path. You said you have 3,000 on it now? Is this a new problem? An old wise man once told me when troubleshooting go from simple to hard. It is usually something simple going wrong. I would check all wires and connections , cap, rotor, resistance on plugs first. Doesn't take much to foul a plug out with wet gas and ruin the resistance. You've got the front half wet and the back half dry, try shooting some brake kleen or WD-40 or something around the intake while it's running and see if it changes your idle, but I would go ingnition parts first. Simple to hard, troubleshoot it out.

urotu, as far as being a new problem, no i dont think it is, but im not sure. the engine is in a 79 nova which belonged to my brother for the past 15 years, he had the engine built (spent an ungodly amount of money on that) and i just purchased it from him 3 months ago. having said that, ive been going through everything and am finding out he half assed some things that i am now correcting. i didnt quite understand why he put the cheapy edelbrock on it, i guess it was a matter of money at the time or the fact that he just wanted to get it up and running. i agree with you guys on troubleshooting from simple to complex, but i didnt know exactly where to start. thanks for the suggestions and i hope you guys stick around to help out. john

ok, i checked the cap, rotor, and wires for resistance with a multi-meter and everything looked good. i changed the spark plugs (autolite 3924) and sprayed the intake with carb cleaner - no fluctuation in idle. i want to believe this is a carb issue..... just becuz of the differences of the spark plugs between the non spaced edelbrock and the 1" spaced demon...... im sorta scared to jet down the primaries becuz i dont want to lean out #5 adn 6 more than they already are, but on the other hand #1 and 2 are frickin swimming....... john

Dude, let me think this one through. You are having wet problems on the front half, is this right? And the back half seems normal, were the plugs black in the front half or just wet? Did you try sprayin' the carb base also? does it use any liquids? ie. oil, antifreeze?

Have you pulled the valve covers to see if all the valves are opening fully? Could there be some packing material in the rear manifold runners? I'm running out of ideas.

Doesn't that Demon have 4 corner mixture adjustments? I know on my old race demon I could adjust each corner if I found the front or rear cylinders running rich or lean.

pro60, yes it does have 4 corner adjustments and i have used a vacuum gauge to adjust them all to highest vacuum (15 inhg). all four screws are only set out a little over 1/2 turn from bottom.
tech, i just gave it a valve job and they all opened and closed properly, as far as the packing material goes, i dont know. i will check that.
urotu, yes #1 and 2 are wet and black down the thread side only. the porcelean has a greyish, reddish color down to where the procelean goes into the threads, at the same time, #5 and 6 are black down the thread side(, but the porcelean is bone white, #8 is black down the sides and the porcelean is dark grey down about a 1/3 of the way. i need to borrow a camera and just show what im talking about here.......bear with. the engine doesnt seem to be using any liquids, i have been checking them after every time i drive it.
on a side note, my brother told me that the older gentleman that built the engine said to call him and he will send a custom ignition for this engine (my brother was in the air force and came home right after the engine was built). apparently my brother paid for the ignition, but decided to give it to the guy as a tip, so no custom ignition. ive tried calling the shop, but no answer. what does this tell you.

Just on a whim, call the BG tech line and present the situation to them. They are pretty good at diagnosing if it is a carburetor mixture problem. It's worth the phone call just to eliminate that as a possible area.

firing order goes with the cam right, dont rule out the simple stuff

Try a different carb. Sounds like fuel distribution to me. Take a carb off an engine that runs good and try it.