Bore and piston wear boosted aplication
Discussion
Hello all!
I'm new here. A couple of years back i restauraten my car and supercharged it (eaton m62 blower at 10psi). Original it got 189 crank HP. Now it is at 310hp and 420Nm. It's an alfa 75 3.0v6 12v (1989). I rebuilt the engine. Now, 6000 miles on the rebuilt engine, i wanted more power so i decided to lower CR (was still original 1:9.5) so i could advance more timing. It was a knock limmited timing table. When i pulled the heads to mount a thicker headgasket i was disapointed to see there was a lot of wear:
I drove the car hard after a good warmup of course. It also saw some trackdays. But in my opinion this is exesive wear. No overfueling. I ot a wideband installed.
From my opinion the piston crown has a lot of carbon buit up. Has the carbon scuffed the cylinder walls? Or is this wear to distortion of the piston. It still has the original cast pistons.
Hope you guys can help me out!
I'm new here. A couple of years back i restauraten my car and supercharged it (eaton m62 blower at 10psi). Original it got 189 crank HP. Now it is at 310hp and 420Nm. It's an alfa 75 3.0v6 12v (1989). I rebuilt the engine. Now, 6000 miles on the rebuilt engine, i wanted more power so i decided to lower CR (was still original 1:9.5) so i could advance more timing. It was a knock limmited timing table. When i pulled the heads to mount a thicker headgasket i was disapointed to see there was a lot of wear:
I drove the car hard after a good warmup of course. It also saw some trackdays. But in my opinion this is exesive wear. No overfueling. I ot a wideband installed.
From my opinion the piston crown has a lot of carbon buit up. Has the carbon scuffed the cylinder walls? Or is this wear to distortion of the piston. It still has the original cast pistons.
Hope you guys can help me out!
Yes, the pistons were coated to fit the enlarged liner bore from honing. You can see trough the coating now... it has a piston to wall clearence of 0.12mm now and it should be no more then 0.06mm according to the specs. And it was 0.06mm after the rebuilt.
Crank breading was not the best. It was a the small original oil seperator no bigger then an espresso cup ( italian style
) i upgraded it to a better and bigger format 500miles back or so but i think harm was done already...
What do you mean with strange hone pattern? I see the pattern is gone on the thrust side.
Crank breading was not the best. It was a the small original oil seperator no bigger then an espresso cup ( italian style
) i upgraded it to a better and bigger format 500miles back or so but i think harm was done already...What do you mean with strange hone pattern? I see the pattern is gone on the thrust side.
I decided to pull the motor when i saw the cylinder marks. I lifted the head to lower cr.
These engines don't have a squish area so that's the reason for a thicker headgasket.
Top ring end gap 0.7mm
Midlle ring 0.7
Oil 0.82
0.55 is max for all rings, according to the manual, but i took some aditional play becuase it came as an NA engine from the factory and now it is supercharged. Don't know anymore where i sat the play. Obviously there is also a little wear.
I also see some piston rock not much . The skirt is a bit convex.
These engines don't have a squish area so that's the reason for a thicker headgasket.
Top ring end gap 0.7mm
Midlle ring 0.7
Oil 0.82
0.55 is max for all rings, according to the manual, but i took some aditional play becuase it came as an NA engine from the factory and now it is supercharged. Don't know anymore where i sat the play. Obviously there is also a little wear.
I also see some piston rock not much . The skirt is a bit convex.
My tuners sad the timing table was knock limited and i know some guys who lowerd compression saw 350hp instead of 310hp with the same engine.
These engines had 9.5 to 1 because in the days they where built that was the max cr they could run with these engines in my opinion so a litle cr drop isn't that strange i think.
Crank bearings which where fine before rebuilt still look nice. But some are bad. They where not in the best shape last time i saw them. I need a regrind.
Top ring lands look very nice.
I just saw some coating fractures near the top at the oil ring where the coating starts. I think the scuffing is from coating particles.
The coating should be bullit proof according to the company.... but it isn't..
In dirt particles i don't believe. I washed the engine over and over with solvent and flushed all oil channels. I worked realy clean.
These engines had 9.5 to 1 because in the days they where built that was the max cr they could run with these engines in my opinion so a litle cr drop isn't that strange i think.
Crank bearings which where fine before rebuilt still look nice. But some are bad. They where not in the best shape last time i saw them. I need a regrind.
Top ring lands look very nice.
I just saw some coating fractures near the top at the oil ring where the coating starts. I think the scuffing is from coating particles.
The coating should be bullit proof according to the company.... but it isn't..
In dirt particles i don't believe. I washed the engine over and over with solvent and flushed all oil channels. I worked realy clean.
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