Hello.

I would like the assistance of those who have more lower end engine knowledge to give me their advice on how I should proceed.

My sc300 has been turbocharged for around 10k miles, and started to smoke white. I did a leakdown test and it lead me to believe my headgasket was blown. Once I removed the cylinder head, I inspected the cylinder bores as well for evidence of ring wear as well. All looked well except for Cylinder #2, near where the cyl is at top dead center, on the right side of the bore looking from the front of the engine, appeared some scoring, I could catch my finger on it as well. As I looked closer, below the scoring was a line going al the way down to where the cyl was a bdc. All the other cyls had this as well, but it could not be felt from touch, and a fingernail cannot be caught either.







My question is, is this salvageable, or will I need to bore it, hone it, get a new block, etc...

thanks!

 

How does the head look (bottom) on #2 as it appears you have some light detonation and will probably have some signs of peppering on the head as well.
In past experience there will be more damage to that piston that you can not see while in the bore pending on the amount of damage will need to be bored and honed how much boring will depend on the amount scoring.

 

Engine thread moved to engine forum.

 

thanks for the move. The head looks ok, not much peppering, ill take a pic for you

 

Whenever I see scoring like that I usually recc a .20 over bore as honing is questionable if your fingernails can feel it

 

is the any real benefit to get a GTE block? im not pushing big numbers.

 

Different piston design for lower compression...and the oil squirters can be debated as a benefit. Other than that, same block.

 

so those who say the supra gets lower comp from the head gasket are wrong?

 

it does get lower compression from the headgasket but the piston design brings it even lower than just the headgasket alone. NA piston with TT hg gives you roughly 9.2 to 1 and TT piston and TT headgasket is roughly 8.7 to 1. With a standalone and a good tuner you don't really need to lower compression like back in the day. You can get away with a higher compression than TT motor and still be safe and get less turbo lag.

 

tt hg DOES not lower compression on gte setup . its solely the piston dish design in conjuction with cc of combustion chamber depth ( which is different then ge head) that achieves 8:5:1 compression which is so old school in todays time when we have full control of timing and fueling and fuels like e85 .. they made tt hg thicker to accomodate a safety factor for boost to defend against detonation but designed this way back in 1990's with 87/89 oct in mind..

todays time the correct way to do this is 9:5:1 gte dished aftermarket piston or higher and for na-t same gte styled piston with ge metal hg and arp studs ..

mostly all new builds these days in the supra world are going for 9:5:1 or better .. my next motor personally will be close to 10:0