Piston to spark plug contact. Any ideas?

01STG2ROUSH

New Member
Nov 3, 2005
28
0
0
I have an 01 Roush thats pushing about 11psi. I've had the blower on the car for about 1,000 miles now and last week I started to have a miss. I pulled the plugs and found one of them had been pinched off by the piston. I installed a new set of NGK TR6's @ .037 and drove it fine for about 75 miles until I jumped on it again and of course at 5700rpm it seems the piston has tagged a plug again as I have my same ol' miss back.

I'm going to pull the plugs again to confirm but I am almost positive it's going to be gapless again. Is there a shorter plug I should run or am I a victim of rod stretch soon to become rod break? What have you guys done to remedy this? Is there a better solution than installing some quality rods? -Trent :shrug:
 
  • Sponsors (?)


I have an 01 Roush thats pushing about 11psi. I've had the blower on the car for about 1,000 miles now and last week I started to have a miss. I pulled the plugs and found one of them had been pinched off by the piston. I installed a new set of NGK TR6's @ .037 and drove it fine for about 75 miles until I jumped on it again and of course at 5700rpm it seems the piston has tagged a plug again as I have my same ol' miss back.

I'm going to pull the plugs again to confirm but I am almost positive it's going to be gapless again. Is there a shorter plug I should run or am I a victim of rod stretch soon to become rod break? What have you guys done to remedy this? Is there a better solution than installing some quality rods? -Trent :shrug:

Are you running 11lbs of boost on the stock internals? How much HP are you putting down?

Sounds like something is very wrong. You need to gap those plugs at .30 too. And shifting at 5700 with the stock valves/springs is very bad for the engine. If I were you, I would stop driving the car, and take it to a mechanic.
 
Are you running 11lbs of boost on the stock internals? How much HP are you putting down?

Sounds like something is very wrong. You need to gap those plugs at .30 too. And shifting at 5700 with the stock valves/springs is very bad for the engine. If I were you, I would stop driving the car, and take it to a mechanic.

First off, yes it is close to 11psi with 373hp to the rear wheels on a stock bottom end.

Secondly, I came onto this board with the intentions of getting some good ideas from fellow members who may have experienced this problem as I know some have. I perform most all work done to any of my toys and I can already hear what a "Mechanic" would say. I'm sure I could shift it at 5000 all day and run less boost and so on and so forth but thats really not why I have the car. I'm sure I could tear the motor down and throw in a decent set of rods, perhaps an indexing washer at the plug or maybe there is a plug with a shorter reach? I would just like to hear some feedback from experienced members who may even perhaps be a "Mechanic". Sorry to rant, just a frustrating thing thats all...

Any input? :shrug:
 
First off shifting your car at 5700 is not terrible for it, I have no idea what the previous poster is talking about, Its harder on the valvetrain then 5000, but our cars are re-lined at 6050, and even then some people bump their near stock engines (ie no forged internals) red-lines up to 6500 (hotmustang for one) and have no problems at all. I wouldnt be sitting there bouncing off the limiter but afew seconds of acceleration most definitly shouldnt hurt it.

Now on to your problem, are you sure that the piston is hitting the plug? I haven't heard of anyone else having a problem with that on these cars. What kinds of plugs are you running? Is there any damage to the insulator on the plug in question?
 
The first set of plugs were Autolites gapped at .045. I pulled those and installed a set of NGK TR5's at .037. Neither time has the porcelain been damaged but the gap is completely closed up like the ground strap was rolled over. Would detonation really close the gap up? I heard no pinging but the cylinder directly beside it was lean at one time as the ground strap had melted at some point. I thought it might have happened when they were tuning it the first time so I didn't worry bout it. That plug is still intact but is pretty white thats for sure, however it is only 50 miles old too... Am I barking in the wrong direction?
 
I'd start out and do a compression and a leak down test on the cylinder that keeps bending the plug. It will give you an idea if the piston is damaged or if you have bent a valve. My guess is part of the upper ring land is breaking off the pistion and hitting the spark plug.

And just an FYI I rev my 00GT to 6,200RPM on a stock short block and a blower for over 5 years.
 
I just picked up a new plug and pretty cool flash light from Checkers and after looking down the spark plug hole I can see where the piston is marked from contact. I suppose now it's a question of rod stretch or perhaps something else?

:shrug:
 
there's no reason for the piston to be hitting the plug. you've got something damaged. if you continue to drive the car before getting a new rotating assembly, you risk doing further damage. sorry about your luck.
 
Yeah I agree with the above poster, if the piston is marked up from hitting the plug you have a serious problem with your internals and will end up needed to replace at the very least the rod and the damaged piston. If you continue driving the vehicle this way you risk taking a chunk out of this piston and possibly scoring the cylinder walls which would force you to replace your block too. Sorry for the bad news.
 
I have seen detonation close up plug gaps and mark up the tops of pistons. The only way the piston could make contact, is if the rod bearing was so wore out, that the piston could come up far enough to hit. Then it would be knocking like no tomorrow.

I would do a compression test, if it turns out ok, then have some timing taken out of the tune. Make sure you use good fuel, and try it again.
 
^yep....I think thats detonation. Its closing the gap on that plug, so you may want to check that fuel injector out...could be dirty and not allwoing the fuel to spray correctly.

I see the valves smaking the piston before the spark plugs if something was THAT wrong. Tim @ MPH had my rev limiter @ 6500 wheil I was N/A and I did TONS AND TONS of 6200RPM shifts, ran to 6400 in 4th, and hit the 6500RPM limiter a few times. 0 problems doing that and never a closed plug gap.
(BTW since adding the turbos, Tim @ MPH set my rev limiter down to 6200RPMs)

Oh and one more thing....DONT GO WOT UNTIL YOU FIGURE OUT FOR SURE WHATS WRONG!
 
Detonation can close plug gaps and damage piston tops. what cylinder is it that this is happening on

If it's the drivers side rear cylinder #8 then this might be caused by the lack of coolant flow near that cylinder, there is ways to fix that so if it's number 8 let us know and for now pull some timing out.
 
Detonation can close plug gaps and damage piston tops. what cylinder is it that this is happening on

If it's the drivers side rear cylinder #8 then this might be caused by the lack of coolant flow near that cylinder, there is ways to fix that so if it's number 8 let us know and for now pull some timing out.
[/QUOTE]
Just came across this thread....I just put a turbo kit on my 90 302... being impatient and not getting a good tune, I took her out for her first drive, and went Wot, upon Decel I had a bad loud ticking noise coming From driver side rear of motor. Pulled my plug out and it was smashed, with a indentation of obvious impact. Help?
 
Having the same issue.. running MMR long block fully forged 4.6 strokes to 5.0..Was missing, just pulled all plugs and cylinder 1 was closed. I was also running e3 plugs with multiple electrodes.. no contact mark though? Kenne bell running 17lbs of boost.. detonation possible.. maybe need to run race fuel, or have it retuned.. timings advanced around 11 right now.
 
Having the same issue.. running MMR long block fully forged 4.6 strokes to 5.0..Was missing, just pulled all plugs and cylinder 1 was closed. I was also running e3 plugs with multiple electrodes.. no contact mark though? Kenne bell running 17lbs of boost.. detonation possible.. maybe need to run race fuel, or have it retuned.. timings advanced around 11 right now.
First things first, throw the E3s in the garbage (or at the forehead of the counter monkey that sold them to you) and put some real spark plugs in the engine.
 
First things first, throw the E3s in the garbage (or at the forehead of the counter monkey that sold them to you) and put some real spark plugs in the engine.
what would you recommend.. had this happen once before, and was trying something that was a little more stought.. also was trying to run a little cooler plug...really thinking it’s detonation..will verify tomorrow with camera.
 
what would you recommend.. had this happen once before, and was trying something that was a little more stought.. also was trying to run a little cooler plug...really thinking it’s detonation..will verify tomorrow with camera.
A quality copper plug a step colder than stock. NGK is good, so is Denso or Motorcraft.

E3 plugs are absolute garbage. Their quality control is a joke, and you have no control of the flame front with them.
 
what would you recommend.. had this happen once before, and was trying something that was a little more stought.. also was trying to run a little cooler plug...really thinking it’s detonation..will verify tomorrow with camera.
Look up what plug your heads call for. Was probably detonation.i ended up having a bearing or something go in the turbo and made its way to #8 cylinder. No good lol.