Sami951

Never mind that, how's this:
"Motor: Vierzylinder-Reihe, wassergekühlt, Vierventiler, zwei obenliegende Nockenwellen, ..."

Four cylinder watercooled, four valves, two overhead camshafts?? Surely not?!

Al P.

and turbo charged to boot, 410 hp as I recall.

1981 LeMans 924(944)GTP

the factory did indeed build a dual overhead cam 4 valve turbo-charged motor

Sami951

Confusing... the Porsche website is however describing the 944 turbo cup car, not the 924 GTP. I still believe the 944 turbo cup is 2-valve single cam design.

Bengt Sweden

It's not the first time data are mixed up on a web site. I just thought that the sentence refering to reinforced bearing perhaps could be confirmed by someone.
Bengt

keith

YES! We just installed a motor with a lightened/knife-edged AND perp-drilled crank that failed in FOUR hours of track use. #2 bearing seized and snapped the cast rod, destroying the bottom end.

So, they can still fail.

(We did not build the motor or do the crank work)

Al P.

Keith,
That sounds ugly. Just a few questions, no problem if you aren't sure but try not to quess if you know cool if not no problem.

What was the oil pressure at start up?

Was the engine pre-oiled before starting? In other words did the builder assemble it with assembly lube and before starting it spin the engine over with the plugs out till oil pressure showed on the guage.

After reaching operating temp what was the oil pressure?

Did the pressure remain realitivly constant during the four hours?

what happened just before the bearing sized?

sorry for all the questions but in researching this your failure doesn't sound like the normal failure seen but rather an assembly issue.

keith

As I mentioned, we didn't assemble the motor. The customer purchased the new motor and brought it to us to install in his car.

After startup, all gauges were normal.

The failure occured at the track the following day. Neither of us (from our shop) were present for the failure.

Upon disassembly, there WAS oil in the motor, it was reading low on the stick, but it was reading on the stick if you know what I mean...
The teardown revealed a very blue #2 rod journal, a bunch of little pieces of rod/piston/rod bolts/rod cap, and a nicely pocked block. The head was virtually damage-free. The other rod bearings also showed substantial scoring.

Additionally, we had a track-proven 944S fail exactly the same a few months ago right after banking and during hard braking at Lowe's Motor Speedway. The 944S did NOT have a modified crank, but DID have a modified oil pan/trap door from one of the aftermarket tuners.

Same failure, same rod, same damage (except the 944S sent the rod through the oil pan - no way to verify the oil level at the time of failure).

The 944 (modified crank) was on 410# progressive springs/30mm torsion bars, and the 944S was on 400#/400#+stock torsion bars. Both on somewhat grippy tires.

Jim @ EuroWerks

The engine had oil pressure almost immediately when spinning over. We did have some signs on the biulding side that were less than empressive. Looking back I still think the perf ( if thats what you guys call it) drilling is at least part of the answer. I still think that there should be a limit to how much weight comes off. Also I don't want to go over board with theory but what about harmonics? Now I will ck the rest of this post to see if I have just said something Stupid. I think theres deffinately more than one cause and I think theres more than one thing to correct to alleviate the issue. Good luck to us all!

M758

Sorry to hear about your failure guys.

I suspected that drilling and knife edging is not 100% certain fix. Too bad really.

I just finished my first weekend with Amsoil and a 2 hr enduro.

Saturday my car ran warm inspite of cool air temps (50-65F)
Water temp was the last line before the "hot" zone. Not over heating certaily but too warm for those cool air temps. Oil pressured stayed at 3.8 bar. My engine on Mobil 1 woudl run about 3 bar at those same water temps.

I pulled the t-stat for the 40 min race. Car ran cooler (mid gauge) and oil pressure was 4 bar for entire race. I ran hard for 40 vs Paul Bloomberg racing down to the wire. Paul took the win.

Sunday I ran the 2 hr enduro and oil pressure stayed at 4 bar throughout. Coolan temps were mid gauge. At the 1 hr 16 min mark I came in for my 5 min pit stop. I added 4 gal of gas and 1/2 quart of oil to bring level back to slighly over full on the dipstick. Went back out on track and car ran like gem to the end of the race.

I will stick the Amsoil. It may not prevent every rod bearing failure, but based on the oil pressure in my car and that another 944-spec finished the 2 hrs at only 1/2 way on the full level on dipstick with no issues seems to me that this stuff is worth the extra money.

I don't feel I am immune, but after 20 races this year I will pull the motor and replace rod and main bearings before next year's first race.

Al P.

M758,

Congrats. on the race and good to hear that the Amsoil seemed to perform as advertised.

At one time I was told pulling the thermostat messed with the way the water flowed through the head.

M758

Pulling the T-stat is temporary. I did want to overheat the car and it seemed like it t-stat was going bad not allowing enough flow to the radiator. You know how hard is pull one of those things. I tired for 5 min and a said screw it. I grabbed a long screw driver and ripped it out and left the snap ring in. It worked fine for the event. I'd rather run with one and will put one back in before my next race. Never heard about the head thing, but it does take little time to get some heat in the motor when cold.

Al P.

sounds like exactly what I would have done.

Did you chant the "special" words while prying it out? :-)

M758

I did that trying to get the #$@$%@ snap ring out.

The just used a BIG screw driver and the t-stat came out in seconds.

smokey

I'll try Amsoil next season.