Cylinder leakage test

[Dan Bennett]

Probably stating the obvious, and may not apply to some racers but the years I worked with teams running Jenkins engines he had two things that he concentrated on. Yes, he was known for reading spark plugs - a lot of teams would send somebody over to our trailer so he could give an opinion on their plugs but first and foremost he had two things he insisted on.

First, the amount of leakage. He insisted on very low numbers. Second, on variation between cylinders. If he didn't like what he saw, he always asked for the engine back for a refresh. I remember other teams thinking he was being excessive (or maybe being too cheap or just didn't have the money) ignoring the request. And of course, they'd cry real tears when they started having problems qualifying.

This was not troubleshooting if the car had lost performance, It was checked regularly. We used to talk about a lot of things, but he would never discuss the hone finish he had come up with.


Came back to edit to include another example of how much he thought of keeping things where he wanted them. He told me that shortly after starting to use the ZL1 aluminum block, he found that heat cycles would quickly take the bores out of round. He then set up a system so he could keep a block heater running 24/7, even when in the trailer (or maybe ramp truck at the time, don't remember}.

[Adger Smith]

Dan,
The Grump could have fit right into the aircraft industry.
He would have been spot on how it is done.
Leakage for aircraft is low % per cylinder and close on the variation cylinder to cylinder

[rebelrouser]

Yes, a NA engine with tight end gaps should test better than 10% on a warm engine a cold engine will read slightly more leak down. A large gap nitrous or blower engine will leak more cold. What I do is leak my engines on the stand when fresh right after taking them off the dyno cold, save those numbers. Then you have a baseline, when leakage starts to increase, I know it is time to save my pennies for a rebuild. I don't race class just bracket and index, but I see very little loss in ET until leakage gets about 30%