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Discussion Starter #1
Had a misfire on cylinder 4 after some high rpm 2 stepping, compression is around 32 while all others are at a normal 155 reading, there’s no smoke but there is some oil on top of the piston and the tip of the spark plug, and my valve cover gasket is fine so it makes me believe my valve seals are bad, what seals do you guys recommend? I saw some on the speed performance website are those good?
 

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The oil in the cylinder would be due to the piston thats broken. Time for a rebuild.
 

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Discussion Starter #3
The oil in the cylinder would be due to the piston thats broken. Time for a rebuild.
Will a leak down test tell me for sure? I put a camera down there there was no visible damage to the piston but there was a layer of oil, could it be just the rings?
 

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These engines have issues with the ring land cracking/breaking. You MAY have screwed up a valve, but the much more likely issue is a busted ring land. Just leave the engine off until you diagnose the problem for sure (pull the head and/or drop the crank and pistons). Might mean the difference between honing/over-boring the cylinders to clean them up from some fine scratches vs an entirely new engine from fully grenading the piston and destroying the cylinder wall, among other things.

For example:. Exhibit 1
 

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Discussion Starter #5 (Edited)
These engines have issues with the ring land cracking/breaking. You MAY have screwed up a valve, but the much more likely issue is a busted ring land. Just leave the engine off until you diagnose the problem for sure (pull the head and/or drop the crank and pistons). Might mean the difference between honing/over-boring the cylinders to clean them up from some fine scratches vs an entirely new engine from fully grenading the piston and destroying the cylinder wall, among other things.

For example:. Exhibit 1
Thanks so much for the advice I think your right otherwise there wouldn’t be much of an oil problem, gonna get inside and check it out. Should I replace anything else while I’m in there?
 

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@Trey Anderson yes, a leak down test will for sure tell you where the compression is going, and would still be a good idea to do while its still together. @rob99rt is on the money though, and 99% chance what you're going to find.
 

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Just curious, but how many miles on the car? If you're under the 60k powertrain warranty, you may be able to get a dealer to fix it with a new engine assembly. Some dealers are more mod-friendly than others, so you may want to find other FoST owners in your area (if you can) and figure out which dealership(s) are more likely to fix it without denying the warranty claim. The extra few days (week maybe?) of homework could potentially save you thousands of dollars, though, so consider it a job that could pay you hundreds of dollars per hour of homework.
 

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@rob99rt he mentions "high rpm 2stepping" which means he's at least tuned, which throws warranty out the window.
 

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Thanks @TurboGT ... didn't understand what he meant with that. Curious who he's tuned with then.
 
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