breaking in a rebuilt engine

[stack]

Hi, I am about to take delivery of my car after its engine (2.4S) rebuild (new cylinders, pistons, valves, etc). Rebuild done by independent P. specialist (not me!).
Any tips on dos and donts for the first thousand miles?
Thanks.

[cmcfaul]

Porsche runs their new engines to redline right off the production line. If it's going to fail let it fail while under warentee.

If it was me, I would keep in under 4k RPM's and 3/4 throttle for a 100mi then let it rip. I would also change the oil within 500 mi to remove any stuff left over from the rebuild and as a result of the break in.

Chris
73 911 E

[kenikh]

Dyno tune the motor, which will handle most of the break-in, in a controlled environement. Worth the money IMO.

[tfiv]

Your owners manual covers this, but there are lots of opinions. I dyno'd mine, kept it under 5500 for 500 miles, then let it rip.

[boxster03]

If I recall the owners manual on the old 70 it was about staying below 4k rpm for first 500 miles and not staying at the same rpm for any long period of time you were suppose to vari the rpms up and down.

[VintageExcellen]

From my experience, 90% with the 20+ 356/912 engines I have built:

Turn over with coil disconnected until oil press warning light goes out

Starts engine and run at 2000-2500rpm for 20-25min, watch for fuel/oil leaks, shut down and wait until engine is bone cold, 12hrs, then

change the oil, most of the break in gook/metal will be in the oil right now (yes this is an anal measure but if it is your keeper then who cares about extra work, adjust valves)

Start back up and set the rings by driving the car, I have little experience with 911 engines on this, run the car up in the rpms slowly then down slowly, make the engine & transmission push and pull on the piston rings a bit at a modest rpm, something like 6-8 times

drive the engine in city conditions or stop and go, little freeway, for 1000 miles, change oil, then

Slam the gas pedal and have fun!

I usually dyno tune the engine at that point, all the problems are worked out such as oil leaks, messed up parts, unforeseen errors (there will be some)

Good luck, have fun, I'm building my 2.2S engine sometime soon, but after that I am thinking 2.8 short stroke 280hp 8k MFI motor!

[Eric911S]

Hello: Some of the best running engines I've had were ones I built for the racetrack. Finished them up late Friday night and raced them the next day. Kept the rpm's down to 5000 for 3 laps then 7500 after that. Porsche used to do there engines the same way. You want those rings to seat in. Thanks, Eric

[Steve@Rennsport]

Dyno tune the motor, which will handle most of the break-in, in a controlled environement. Worth the money IMO.

Absolutely true, (IMHO of course)

[TEC69E]

I'm getting ready to break-in my motor soon and without the resources to dyno the motor it seems the procedure VintageExcellen mentions makes sense to me.

Just one question: How can you determine if the rings have properly seated? Is a leak-down test an accurate measure.

My config: 2.5 short-stroke with new Mahle P&C's (89mm)

Thanks,

Tom

P.S.

Steve - The twin-plug dist. looks even better installed.

[Steve@Rennsport]

Hi Tom:

Not many folks have access to an engine dyo so you are in fine company,...

Leakdown testing shows when the rings have seated so my suggestion would be to do an initial leakdown (the numbers will scare you) followed by further tests at 500 miles and every 1000 miles. When you finally see 2-3% on the guage, you'll know the rings have seated and the oil consumption will have stabilized, as well.

Glad you like the Twin-plug distibutor; send along some pics when you get a chance,...