Bill00Formula

iTrader: (4)

Over the last 6 months I haven't used my car too much. Took it to the track 4-5 weeks ago and it seemed ok. Only ran once. It's a 2000 formula with a LS7 block.

About 2 weeks ago I try again and it starts acting up on the way to the track. I go about 5 miles and turn back. It's like it's running on seven cylinders.

This last Wednesday it's finally getting cool so I decide to try again. As a leave the house it moderately back fires and still acts like it's on 7 cylinders. So I go around the block come home.

I thought I'd change the spark plugs, check the wires and change the O2 sensors. I took one spark plug out (2nd one on the drivers side) and the electrode is gone (the bend and top part) I also see there is oil on the threads of all the spark plugs on the drivers side but the spark plugs are dry on the passenger side. I also noticed oil under the car. When I saw the oil I was thinking cracked block. I'm not 100% sure this is related but it may be.

Any ideas? What Should I check? Thanks

jdiddyws6

iTrader: (5)

n4results.

LS6427

iTrader: (2)

Well, a cracked block won't make the spark plug threads wet with oil. But bad valve seals on that side sure will.

As far as the electrode......on my 427ci once when I did a plug change I saw one of the electrodes on one plug totally gone. The engine ran perfectly fine, I never had any idea there was something wrong....lol
It just gets blasted out the exhaust onto the road somewhere.

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Bill00Formula

iTrader: (4)

Thanks for the response. Well that makes me feel a little better. I was thinking that whatever happened had to be pretty serious to break the electrode so it could have also broken the block. The oil issue still has me concerned. I assume oil had to get past the pistons. I have had the heads for a few years (TFS 235s) but they don't have too many miles, maybe 5 to 10 thousand miles.

1 FMF

iTrader: (1)

you said you have an LS7 motor (block) so i assume you had the computer reprogrammed to run that engine?
I would pull and inspect all spark plugs.
If the piston makes contact with the ground strap it generally bends it, you don't normally expect the wrong spark plug having too much reach. and if that were the case you would see a similar affect on all spark plugs. When the ground strap is gone it's usually from high cylinder temperatures from running lean or from the engine overloaded. that part of the spark plug cools fairly easy because it's all metal to the external metal shell of the plug which is threaded into the head, so there's a clear path of conduction for heat transfer. if the spark plug was the wrong heat range and ran too hot for the application you would see the center electrode and ceramic all white and blistery. but the ground strap if it's a projected nose type of plug acts like a heat sink and if cylinder temps get too high for short duration is the first to go. I would look for similar signs on all spark plugs, that would indicate a general tuning problem. if it's just that plug then i would look at a bad injector for that cylinder. running excessive cylinder temps where it melts the spark plug ground strap is also not good for the exhaust valve, among other things.

http://www.carcraft.com/howto/116_07.../photo_14.html

Bill00Formula

iTrader: (4)

Thank you for the information and link. Very informative. I never knew how to tell anything from the plug. I will look at them closely. Not sure how much they will tell me since they have been in there so long. I had taken them all out and that one was the only one damaged. I think it's unlikely that there was piston contact unless something broke. I was surprised that I had TR6s. I am installing TR55s.

Yes it was tuned when I first had it built. A Ls1tech member helped me with the tune again this past year. I will go back and check the timing table again but I think it was couple points lower than the original tune.

I just remembered that I blew out the drivers side valve cover gasket twice when I first had this motor. I put a breather on the oil filler tube after that. That's probably where the oil on the drivers side plug threads came from.

I'm still wondering where the oil on the ground came from.

LS6427

iTrader: (2)

When I found one of my plugs with the electrode missing it wasn't from piston contact. It just let go. I have always done my own plug changes since day one with my 427ci......all I would do is check the gaps of my TR55's with a gap tool and then put them in. It was just a mahufacturing defect because all the other plugs were like new when I took them out. I always did plug changes every 25,000 miles or so too.....so they were barely used.

For the oil leak.....I think the best way to find it is to put the front tires up on some ramps. With the engine warmed up about halfway (maybe idling for 15 minutes) and then blasting the entire engine UNDERNEATH AND ON THE SIDES, everywhere, with two full cans of Gunk engine cleaner foam. Do the top also, valve covers and heads too. Let it sit for about 20 minutes....to mainly let it cool down enough so you can then safely hose it off with cold hose water. Then drive it around and check it each day for a new oil stain. If the leak is bad you can probably try starting it up right after you clean it and lay under there for a little while to see if you see a new drip.

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