Cliff Harris

I know about that one. Blown head gasket resulted in this (note the end of the plug (#7) on the far left compared to the others):



This is what my engine looked like right after taking off the head (#7 steam cleaned):



I think a camera would show you the bad cylinder.

desertmike1

Attachment 47855178There might be Aluminum heads with "Flat" counter bores.. 93-95 LT heads aren't one of them..


http://www.ecklerscorvette.com/corve...1993-1995.html

Hot Rod Roy

When I look at DesertMike's post, #18, and at Cliff Harris's post #21, I see signs that the tapered seats of these plugs have been burnished by the tapered seats in the heads of these engines. When I look at JimNina's post #15, I don't see any signs on any of these plugs that they have been in contact with any tapered seats in the heads. The tapered areas of JimNina's plugs are all dirty and contaminated. Were these plugs just loose in the heads (all eight of them?)? Or are they the wrong plugs for this engine? Is this the original '94 engine, or are these the correct heads for the car? Something doesn't look right!

desertmike1

I noticed the same thing, plugs don't look like they were seated properly..

I recently had a plug come loose on my C1500, and it clearly caused an engine miss, strange thing about it was; I didn't hear anything at all!

jimnina

First,
Thanks for all of the replies.
On the pictures I actually did have the plugs numbers, but the pictures were too big so I cropped them. Pic 1 (Cyl 1&2) Pic2 (Cyl 3 & 4) Pic3 (Cyl 5 & 6) Pic 4 (Cyl 7 & 8). I will repost pictures of the plugs at a correct angle. Some of the questions asked I don't know the answers too, Correct Engine, Correct Plugs, etc. I did hook up a data logger program when I first got the car and the readings were all over the place. Timing retarding and advanced at the same time. Rich O2 left and then O2 right and back and forth. When I took the plugs out some of them were loose. I thought the plugs looked pretty bad for the amount of miles but I also know the car hasn't been 100% the whole time. I did check on line EcklersCorvettes and the AC-Delco 41-906 are the correct plugs for the engine. Again thanks for all your responses.

86C4Z51

Just saw this thread and agree, those plugs look really nasty for 1500 miles. Hell, for 10,000 miles. A good-running engine's plugs should have maybe a little light tan or light grey on them. Anything black means rich-running or the cylinder is pushing too much oil.

They may be black if you had mixture problems, i.e. running problems not necessarily related to a faulty ignition system. Plugs taken out of an engine that was started and not allowed to warm up several times may be darker in color, but I haven't seen much of that in injected engines.

Are you noticing blue smoke on startup? While it's running? Some smoke on startup will indicate oil leaking past valve stem seals, while constant blue is a ring problem (you may also see evidence of excess crankcase ventilation). Some of us older guys will remember the sniff test, too, using your nose to detect unburned hydrocarbons or burning oil. I didn't catch how many miles are on the engine.

After getting the water out of the tank you may want to add some fuel-drying agent to the tank for a while. This is a good regular practice for any injected fuel system.

jimnina

I did due the old smell test and there was no noticeable oil but some fuel smell.
The engine only has 115K but I don't know if its easy or hard miles. When I looked at the data logger output files it was saying that the o2 banks were rich and then lean, back and forth? The logger files weren't much help.
I did upload a second set of pictures of the plugs that are at a better position to see. I have not tried oiling up the one low cylinder to see if it brings up the compression. I have owned other LT1's but they were both in 70's model vehicles and was much easier to diagnosis. The first one 70 Monte Carlo was MUCH easier to work on much, much more space under the hood. Going out of town this weekend, BIG RV show here in Tampa, so I won't have time to do any other testing until next week. Thanks for all of the replies.

MRPVette

Cliff mine blew on #7 as well how many miles on your car when it blew?

86C4Z51

Jimnina,

Is it the pics, or are all the gaps MONSTROUS on those plugs?

wsherrard

I'm going to toss this in for what it's worth. The plug pics do look nasty. Now my tale... a couple of years ago my 91 L98 developed a "knock", well it turned out that the material in the precats had broken loose and was banging around in the housing, really sounded bad! Replaced the front Y pipe on the L-98 and the problem was solved. I don't know if your model has the precats but if it does that might be something to think about.

1lndonr

Theses plugs are very clean indicating a lean condition. A rich condition colors the white porcelain insulator black.

cadmaniac

Yes, but if the optispark wasn't firing correctly, wouldn't that also contribute to the fouling of the plugs?

Also, If the engine was hydrolocked it would have a bent rod/cracked piston more likely than a bad bearing.

DinoBob

I agree with a previous poster that the gaps look enormous. The plugs look rough but fairly consistent.

jimnina

Thanks for the replys.
I did get the plugs changed. #8 was really impossible to replace, but I went under the vette and it was very easy. Unfortunately the new plugs didn't help the engine knock, so I guess I will be checking the bearings.
I'll report back when I get a place to pull the pan.

86C4Z51

Bummer.

Sometimes the knock is in the cat, or somewhere along the exhaust. I hope this is the case for you -- something simple (read: not expensive).