993 engine brake-in after top end rebuild

[mmasse]

First, let me state; YES, I read Wayne's book.

I have a specific question. My car is a track only car. The break -in method in Wayne's book seems to take quite some time before the engine is fully broke-in : 1000 miles. And would involved driving the car on public roads, which is not an option for me.

My intention is to have the car back on the track as soon as possible after assemblying it again.

So, is there any specific considerations for braking in an engine which will be use on track only?

thanks for your inputs, thanks

[john walker's workshop]

somewhat hard driving for an hour seats the rings as good as they are going to seat, if the P&Cs are in spec. the bearings are as good as they will ever be, so no break in needed there. no break in for the heads needed, other than if you went with adjustable rockers, you would readjust after 1000 street miles or one track day.

[mmasse]

Thanks John,

I can probably follow the first steps on Wayne's book, change the oil and then just take it to the track and drive it hard.

My main concern was that there seems to be a recommendation not to pass 5000 RPM for the first 1000 miles. On the track that's kind of impossible.

any thoughts on this?

[GaryR]

IIRC after my last full rebuild Dan Jacobs told me to run one session at 6/10ths to see if he forgot any bolts and if I make it through that drive it like I stole it.. I did, still runs great.

[MikeD930]

One of the worst thing one could do to break in the engine is to "baby" it. Doing this prevents the ring from seating into the cylinders properly. I read that it's the 1st 20 miles that is the most critical in seating the rings. It's best to run it hard (not WOT but around 7/10th) for the 1st 20 minute or so (also use engine braking as much as possible). Then change the oil and oil filter, check eveything out then you're done!

[KTL]

Running it in (don't say breaking....... ) on the track is the BEST thing you can do for it. You have the freedom to drive it as needed- varying acceleration and deceleration. Doing it on the street would be a pain with speed limits and traffic obstructions.

Ideally you could go out with a DE group for the first time and you can just fiddle around getting on and off the gas as you wish, watching the gauges (and listening for noises that freak you out...... ) and pointing people by.

The one thing that puzzled me at first was the recommendation for cam break in. I thought it was idling at a minimum of 2000 rpm for 20 min. The general rule is to not let the idle drop below 2000 rpm for the first 20 min. So that means driving it hard is certainly acceptable. Just don't let it idle too slowly, in order to ensure adequate lubrication to the cams & rockers.

Funny thing is, there's other stuff like clutch run-in that's bugged me. If you're breaking in the engine and a new clutch (replaced it while you were in there, as does everybody, right?) at the same time, the clutch is truly supposed to be babied for the first 500 miles. You normally want to avoid heavy throttle application to allow bedding the clutch disc with the pressure plate and flywheel surfaces. THAT's not easy to do on the track.

[mmasse]

Thanks KTL.

I am probably in the best possible scenario for track break-in, then. My clutch was not replaced. I replaced it right before my last track day, when I blew the engine, so it is already broken in!
Thanks again to all your inputs

[KTL]

I think the clutch break-in is typically for your more common organic friction material or carbon clutches? I have a "copper" sintered metal disc, so I don't think that's a worry in my case. But I threw the comment out there anyway, just to give people something to think about. Cooking a new clutch is not something you want to do while breaking in your new engine...