Other than a combination of too much boost and compression, I'm trying to figure out what caused some damage to my motor. I have no idea how many miles were on the short block before I got it. It survived about three years for me under boost.
Specs:
350 SBC
Performer intake
750cfm TBI with 4 160 lb injectors
291 heads, bowls cleaned up, port matched, chambers polished, 1.94,1.5
unknown cam 510/510 lift
L2256 forged pistons (9.7:1)
HX55 turbo @10psi
Air to water intercooler. The max temps I've recorded under boost were around 130F.
2500 rpm converter, 3.50 gear, 3900lbs
rev limited to 6k, rarely saw 5k. Usually short shifted into second around 4k. Street use only very rarely saw boost in third
MS-II
Solid 12.7 afr under boost.
Cold Compression Test
1 160lb 2 180lb
3 70lb 4 180lb
5 150lb 6 180lb
7 160lb 8 200lb
All of the pistons look normal in color and wear. The skirts and tops look good. The backs are clean. Some show some evidence of blow by on the second land. All of the driver side pistons had the top rings in five or more pieces. Number three was broken through the second land down through the pin hole and back up to the second ring land. The passenger side pistons and rings all look fine. The bores appear undamaged but the honing is all but polished away. Would the lack of oil break rings without scuffing skirts? I know this motor is a recipe for detonation but I never heard any, and it doesn't look like it. I didn't think 10psi through these heads would be enough to break a piston. What do you guys think?
Thanks,
Kevin
Specs:
350 SBC
Performer intake
750cfm TBI with 4 160 lb injectors
291 heads, bowls cleaned up, port matched, chambers polished, 1.94,1.5
unknown cam 510/510 lift
L2256 forged pistons (9.7:1)
HX55 turbo @10psi
Air to water intercooler. The max temps I've recorded under boost were around 130F.
2500 rpm converter, 3.50 gear, 3900lbs
rev limited to 6k, rarely saw 5k. Usually short shifted into second around 4k. Street use only very rarely saw boost in third
MS-II
Solid 12.7 afr under boost.
Cold Compression Test
1 160lb 2 180lb
3 70lb 4 180lb
5 150lb 6 180lb
7 160lb 8 200lb
All of the pistons look normal in color and wear. The skirts and tops look good. The backs are clean. Some show some evidence of blow by on the second land. All of the driver side pistons had the top rings in five or more pieces. Number three was broken through the second land down through the pin hole and back up to the second ring land. The passenger side pistons and rings all look fine. The bores appear undamaged but the honing is all but polished away. Would the lack of oil break rings without scuffing skirts? I know this motor is a recipe for detonation but I never heard any, and it doesn't look like it. I didn't think 10psi through these heads would be enough to break a piston. What do you guys think?
Thanks,
Kevin
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