#7 Cylinder looks... strange... Please take a look.

Greetings,
Long story short, blown head gasket on my '91 GT (on RH side), replacing both... Took LH head off and found some strange marks in cylinder #7. See attached...

Scuffs with small gouges in the scuffs.

What could cause this?

(stock short block, go fast parts, blower... making over 475 hp w/ conservative tune. After tune I lowered rev limit to keep engine intact - 50k original miles on engine, less than 1k since boosted)

THANKS!!!
oz

KZGUNS said:

was this engine sitting for a while? kinda look like it was sitting and rusted where the piston was parked. Can you catch the scratches with your finger nail?

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Well, yes, I only drove the car a couple times last summer and the one time it overheated (and then I found the coolant was low). That's surely when the head gasket failed and started sucking in coolant... I didn't make the connection then so it sat all winter and spring - so yea, it sat 7-8 months.
Figuring out that it had a blown head gasket this summer, I used a borescope to check to see which cylinder had water getting in and #2 had a small puddle. I did not see any water in any of the other cylinders. #2 has no marks at all (it was only a couple weeks between the time it last ran and when I scoped it. I had also drained the coolant shortly after I last ran it... so not much time for water to pool.)
The spot in #7 does look like it could have been a little rust... My nail does just 'catch' a little when I run it over this area - and it's contained to the spot where a ring would have contacted the cylinder where water might have pooled...
So.... I'm thinking maybe the borescope didn't tell the full story and #7 had water in it over the winter.
I know there was water in at least one cylinder because when I started it the first time this spring it turned over strangely... started to turn then kind of paused and turned slowly then fired... I think it was purging water out of one of the cylinders. When running, the majority of the steam was out of the right side - so I was not surprised to see water in #2. #7 is more of a mystery...
THANKS!

KZGUNS said:

Its possible this happened long before you did any work, like before you owned it. If it was me and i wasn't ready to rebuild I'd probably just run it. Once together maybe do a compression and leak down test.

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I did have the heads off a long time ago and there were no marks in the cylinders. A compression test is a good idea as I do have numbers from before I put the blower on it. Should be a good comparison.
I was thinking of honing it a little... just push the piston all the way down (it's all the way down when #1 is at TDC so easy to do), put a 4" diameter piece of cork gasket material on top of the piston to protect it and just hone enough to remove the ridge that catches my fingernail... I just don't want to do more harm than good.

Noobz347 said:

Clean it out, oil it up, and run it.


I wouldn't use any more harsh than steel wool. The rings knock off anything in the way within the first couple of revs.

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Yea, that's my thinking too... My fear was combining this with boost and encountering an explosive event....

Noobz347 said:

Nah... You'll run a compression and leak-down test before installing boost anyway.

--or if you already have it, run it light then check compression.

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Yea, compression and leak down was all good when I added the blower. I'll run it a bit and recheck it.