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Calico coated Glyco rod bearings from the blue engine look perfect. This is after a lot of dyno pulls and some knocks as well. It’s clear that there hasn’t been any oil supply problems in the blue engine. The mark in the middle is from a Plastigauge test.
I've come to the conclusion that as long as the pickup doesn't suck air, the 928 oiling system works extremely well. All oiling system modifications in a 928 should be directed either to preventing the pickup from sucking air or mitigating the consequences of the pickup sucking air.
35 years of technology moving forward has lead to these kinds changes in pistons and rods:
I can’t however stress enough how remarkably overbuilt the early ‘87 pistons and the PPF rods are. They are virtually immune to detonation and can take huge amounts of boost. The only thing they can’t handle well is very high rpms. They are an ideal starting point for anyone building a forced induction motor.
might have missed it.
are you pulling pistons below deck now or longer rods to compensate?
Longer rods. The trick was to find a raw piston forging and a raw rod forging that together add up to the stock compression height plus stock rod height. The new rod is about 157.5mm give or take.
I've come to the conclusion that as long as the pickup doesn't suck air, the 928 oiling system works extremely well. All oiling system modifications in a 928 should be directed either to preventing the pickup from sucking air or mitigating the consequences of the pickup sucking air.
No engine will be happy if the pickup sucks air. The oil pan gaskets are not made by Mr. Brown, nor anything else in the picture.
Åke
Last edited by Strosek Ultra; 02-15-2020 at 03:51 AM.
As John is moving forward with building these two high rpm engines, we need some more camshafts.
The first test engine will get the existing Elgin 65-6 cams with the existing springs shimmed for higher seated loads. These cams worked great with the stock intake as the dyno graphs indicated. The existing spring setup did exactly what it was designed for, that is stock redline and up to 20psi boost. For higher boost, the exhaust valves need more seated load. For higher rpms, we likely need more load everywhere. Our calcs indicate that just shimming the existing PAC-1223L springs will work.
We need new cams for the second engine, so we ordered a custom set from Colt Cams thru Colin. These have a tiny bit more lift and duration compared to Elgin 65-6 cams, but are basically very similar in terms of valve events. (They should also work well with a normally aspirated 5.0 that has a rotating assembly to allow for a higher rpm redline, uses stock manifold, needs to idle well, and needs to pass tailpipe emissions.). Because of the slightly higher lift, these will get the standard PAC-1223 beehives.
Photos of the cams:
...and of course a photo of my cousin and me watching the Celtics beating Kawhi Leonard’s Clippers in a double-overtime game last night.
02-07-2020, 11:08 PM
