I have an 03 Z with vortech sc running 10 lbs boost. After missing a shift at track day last year I lost the fire to two cylenders. Limped the car home to find out the spark plug gaps had been closed on two of the 12 plugs. (just kidding 2 of 6 gaps were closed) Plugs were changed out for new ones and a week later I was driving agressively in town and another gap was bent closed.

I have an 03 Z with vortech sc running 10 lbs boost. After missing a shift at track day last year I lost the fire to two cylinders. Limped the car home to find out the spark plug gaps had been closed on two of the 12 plugs. (just kidding 2 of 6 gaps were closed) Plugs were changed out for new ones and a week later I was driving aggressively in town and another gap was bent closed.

New plugs again installed and this time the mechanic shimmed them up with washers to keep them form being bent again.

Been waiting for months now for a new local shop to open to see what can be done. I had the car dyno’ed and have come down from 375 at the wheel to about 280 at the wheel. The new shop says all I can do is have the engine rebuilt or basically have all the internals replaced.

Mechanic says rods may be streched and therefore piston is striking and closing gaps?

Does this seem correct? Sounds like 3 to 4 grand to get it back to new stock internals.

Anyone seen this before? Any ideas from those who understand engines would be highly helpful.

robby

 

hello

 

Sounds like time for a built motor to me...

 

You posted this 6 mins ago and you are bumping your thread right away

 

Sounds like ur facked buddy, If the gap on the plug is being closed, that means the piston is actualy making contact with the plug... Sounds like a lower rod bearing failure.

 

Are the plugs that close the gap always in the same cylinders? Do the gaps close as soon as you put a new plug in? Does your motor make any new, strange noises? Are there any metal flakes in the oil?

I've never heard of rods stretching like this and then continuing to run without any other issues. Usually a rod that stretches this much will bend and come out of the block or the big end will spin the bearing. I wonder if it could be some kind of carbon deposits?

Curious...

 

Thanks for the helpful comments guys. Can you explain what you mean by carbon deposits?

 

Thanks for the bump!

 

i guess what happened to ur engine can be caused by detonation...

 

drop the cats,use top end cleaner and try a fresh set of plugs.i wouldn't call it dead yet.if the motor is really fat,carbon could be closing the gap.

 

You might to do a few simple tests, before declaring the engine dead. Your power loss could be a lot of things. I have seen collapsed or worn cats cause big bottlenecks and big power losses, for example.

I would do an engine health check first...compression and leakdown. Start there.

If she is, in fact..dead....let us know if we can help.

 

It's possible that carbon deposits could have built up on the piston domes and be what is actually closing the plugs. Maybe it is way too rich or something and carbon built up.

I think it's wishful thinking, but who knows...

 

Thanks Sharif! You did a tune on my first 350 back in Charlotte. Also I think George from National Speed may have called you today about this issue. Thanks for the advice. No cats and HKS exhaust so probably not holding me up there.

Top end cleaner. Another good idea. Would that clean carbon buildup from the top of the actual piston?

 

You beat me to it. Thanks. We will keep checking these things.

 

What is a "fat" motor?

thought it through... opposite of lean. got it.

 

yes

 

Usually the spark plug is at the top of the combustion chamber in the head. I find it hard to believe that the piston is making contact with the spark plug without bending any valves or causing any other problems. Like Sharif suggested compression and leakdown tests will help in figuring out the problem.

Furthermore, even with rod stretch, which is unlikely to this degree, the combustion chamber is concave and the piston would probably never make it to the very top of the chamber anyway. I am not intimately familiar with the design characteristics of the VQ engines as I have not had one apart, but the likelihood of the piston making contact with the spark plug and nothing else is slim to none IMHO. Get some more information is you want some serious help.

 

what spark plugs are you running? Are the the first to plugs you lost the first time the same ones now?

 

This is exactly the information I was looking for. Thank you for your time. I am going to see if I can find a cutaway diagram of the vQ engine to confirm this analysis. Thanks again.

 

The second set of plugs was a different type but I don't know what kind. I believe the same pistons went down both times.