analogmike

We ran my low mileage 2004 engine on a dyno when it had one cylinder leaking at 30%. It had two more horsepower than a new 2005 engine. Another 2004 with many more hours had a few more HP than mine. Basically they were all the same.

Nordschleife

Well,

Let me explain what I know.

It wasn't Louis the Lip or Harry the Horse that got in the car, it was "Spit the Dummy", so as not to cause any extra offense I'll just call him Spit for now.

Spit got in this lovely shiny Supercup championship winning car and proceeded to phuque his gear changes all round the track, in front of all the factory guys, like the champion Spit ain't. Well something had to give, I think I saw 10,900 on the Motec data and sure enough the Check Engine Light came on, so we pushed the car away and did not choose to rebuild the clutch that day, 'cos Spit woulda done it again. The phuquer has the coordination of a wobble board on speed. And who was going to ask the boys to pass up lunch in these circumstances, so the job was done back home.

Checking on what was done, I specifically asked about engine/valve damage and was given a little card with the leakdown values on. I thought, hmm, these do look a little low, and some of my buddies also thought so. I can't exactly recall the numbers now as I sent them off for Spit to frame in his den. And to complicate things the values were not presented in a way that was familiar. So apart from checking a dubious rolling road printout that showed an unfeasibly large bhp. I let it rest there for a few weeks when prior to shipping the car I had it tested at Weissach. To cut a long story short. The engine power as tested on an engine brake was spot on, ie it was on the high side for cars of that year, which you would expect as it was the best engine of six in the workshop. So despite my misgivings about the leakdown values, everything was OK. I asked about this at Weissach and was told that they would have worried if they were too good. In order to get specific, nail the jelly to the tree type data out of Weissach, you need to spend several hours and a drink/dinner to get rid of the vagueness and get something to hang a hat on. in this instance, I didn't have the time, so I'm stuck with a vague, 'they do read low'.
Ther will be two explanations, there always are.

R+C

Larry Herman

Silly me. I always thought that the more compression a motor had, the more HP it made, and leaking compression rings weren't the hot setup for making HP. Combustion gas does assist with ring sealing, so maybe there is something to the feeling the cup car motors don't produce as good leak down numbers.

jrgordonsenior

Thanks Randy I just spoke with Bob and he also said those numbers were too high. Bob said the RS motors he sees/builds typically have 3% or so with 5% on the top side.

What's really weird about this is the wide range of opinions from reputable sources. PMS saying they see up to 15% leakdown as acceptable, this particular mechanic saying 25-30%, and most other mechanics saying 2-5% maximum. Very wide range of opinions and all for trusted sources.

I like this car. It's been sitting for 3 years so it's possible it just needs to be run for a few hours. I think I'll ask the owner to take it up to WSIR for a test day and then either re-test the leakdown numbers, or put it on a dyno and see what HP it's really putting out. If there's a real problem it should show in the HP numbers. Of course this would cost me a set of tires as I don't think I want to run WSIR on 3 year old slicks....

38D

Btw, when I went to Jerry Woods' engine class, he stated that bad leakdown numbers do not always indicate a problem. He liked to use several different tests including dyno runs and compression tests.

paradisenb

A car that has sat for 3 years needs (desparately) to be drvien hard for some time to get any good data, good or bad. Leak down is certainly not the only thing to look for, but I would not buy a car with bad #s. The risk would only be acceptable to me if the car was priced 20k under market. That should cover an engine refresh. If all else looks good, it would probably be worth a set of tires. You could always use them later for DEs. If you buy a Cup Car.

jrgordonsenior

Thanks Randy I agree. just e-mailed you a pic of this car.

Sometimes it's hard to keep a impartial perspective when you find a car that appeals to you. There's a lot of older cups out there, unfortunately most appear unreasonably priced I think because of the success and appeal of the IMSA series. 05' cars were delivered for $125k. So why then do 4 year old cups, with lots of racing hours behind them, command $115 asking prices? Lazze faire....

JJayB

John
Did Henry at PMS tell you the factory recommends a top end rebuild at 24 hours. An engine with 20 race hours may have a few issues.

paradisenb

John. A local guy bought an 04 Cup car for $105k. Bought it when they sell them at the end of the series. His car had been wrecked but they put a brand new tub on it. No frame damage. I think the motors are freshened for sell also, right?

Nordschleife

you meant 'caveat emptor'? otherwise I don't recognise your French ;-)

R+C

jrgordonsenior

Too funny, you're absolutely right!

My only excuse is that I'm born and raised in Los Angeles, now Ellis Island West for the 21st. Century, and I often confuse my new-found multi cultural linguistics.....Thanks for the help, I suppose I shoud be embarassed but then again, I'm in Los Angeles and I.......

jrgordonsenior

Hi Jim,

As always I appreciate your thoughts and you're probably right. Although I didn't specifically ask that of Henry, I have heard a variety of opinions on when they should be torn down. I heard the shorter hour durations are more specifically for the "R" and "RS" motors, while the standard cup motor has greater longevity though that's all speculative. Galen just tore the motor out of the #100 car that ran at Cal Speedway with PCA in March. It had made it through 70 hours of racing and only had 2 cylinders that leakdowned 18-20%. I found that pretty impressive for an 03' cup motor that's been raced hard.
Hopefully I can get this one on a dyno next week at Precision MS where it was tested and run it awhile to see what it's producing.

38D

Aren't "new tub" and "no frame damage" mutually exclusive?

Larry Herman

I guess that if the tub is new, then any "frame damage" should be gone, right?

gpennington

Sounds like you have issues with the unknown. Let me resolve this for you. I have a 2003 car for sale with a perfect engine. You can call me. 803.622.5282. or you can all Greg Loles at F/G Motorsports.