mark kibort

All i could think of was gregs warning of oil starvation due to g forces,and then i remember all the talk with the open road racers about how long it took much of the oil to be in the heads due to high RPM and slower than pace, gravity return paths. was 30 seconds the limit? as you know, i had no issues at the track with 30seconds of near constant full throttle, and the highest of RPM levels AND lateral gs.... all i could think the entire weekend was this was the perfect storm.............but it survived and showed no signs of issues. for example, if 60 seconds was the time it took for the oil to fill up the heads, i would feel better about going back.
or maybe, the fact that the positive gs, for much of the later time period at near redline, might force the oil back to the pan faster. i mean, it is a real force and not a part of open road racing.
wasnt the issue with Dennis' engine something to do with the oil return or oil feed openings to the heads that were either too large or missing?
i would think that the separator /scraper is not a huge deal as i dont think the crank sees much of the oil, and the separator might be an interesting thing to investigate, but what would be signs i even have that as a problem?
thoughts?

James Bailey

Mark your cylinder heads were tested by Porsche in the privacy of the Nardo ring in Italy long before the 86/87 car was shipped to the USA for Holbert to run at Bonneville for the record attempt. That is a nearly 8 mile oval with about 3 minute laps. So they did extended high RPM runs at speed to be SURE the 928 would set the record before they went to do it !!
I still believe that your heads have 944/968 style check valves which also serve as restrictors to limit oil flow to the heads. Which might explain why your cam chains were eating teeth off the cam gears. Something which does not seem to happen much to anyone else.
Also when Kim Crumb get a letter from Porsche about racing his GT about 25 years ago one of the requirements was using the 944/968 parts.
If they went to the trouble of running modified 85-86 cams , fitting an external socket to swap chips easily and showing up a Bonneville with two different gear ratio transmissions that we know of I have to believe they knew about the oil issue at least by the time they got done at Nardo and fixed it.
Perhaps your luck was buying a preproduction modified hand assembled race engine from Porsche which kept your heads from filling up with oil and the bottom end from flying apart from oil starvation.. Then swapping those same heads onto your current stroker. That would explain why so many 928 engines have failed with track use. Kim Crumb blew up his GT twice as I recall.

mark kibort

So i have Magic heads.. if that solves all the issues with the car, you would think that all would want a copy of whatever the differences are. the bottom end was stock. nothing fancy, but if it was saved by the heads, When i machined them we checked them to see if there was any changes. ports were stock, valves were stock...... the oil check valve was said to be stock by the guy that does a lot of 944 heads. but who knows.

i certainly would think that if porsche found out something that worked for nardo and it was the first gen of the engine, why didnt it make it to the production version?

my cams losing teeth was a mystery. nothing has changed, not losing teeth now, and its been 15 years of racing these cams (stock 85s with bearing mods to fit S4 heads)

i would agree with the "luck" if my 84 wouldnt have lasted so long, as well as the 85 5 liter bottom end on the 84 part euro top end, AND Scot's version of that engine i built. No sign of any issues and the 84 pulled apart after 170k miles , and the last 40k while racing it, showed no signs of wear at the bearings.

But, if the heads are the reason, then we need to closely examine them when i pull the engine next. hopefully that doesnt happen for a while.

as a note... at nardo, when the car had run 180mph, i think it was running the 2.2 gear box, where at that speed, the engine is just chugging along at 5000rpm. when at Bonneville, their top speed was 172mph, so using the stock gear box 2.2, would also allow for the HP needed to make a top speed run. running a higher numerical ratio final drive would have increased the hp to get to near that speed, but maybe fell off too fast to get there. (peak HP is at 5500) so, the 2.75 might not have enough hp to get to 171, if it got its peak at around 180mph .. im sure they were working the numbers to put the gear box that matched the hp and goal. but in the end, if they used he 2.2.. there shouldnt have been as much time spent at over 5500rpm as i did at cal speedway.

anyway, i have lots of pictures if we can see the check valve in them and determine that it is different.. I dont know if it is or isnt. what i do know, is that if that is the reason the car has lasted as it has, all should install it!

Mk