Break-in after rebuild? What's the proper way?

I will be stabbing motor/tranny in my 80 SC this weekend after doing a light rebuild (rings, head work, head studs, gaskets/seals, etc).

What is the proper way to "break-in" this motor? Also, how many miles before I should check the valves and head torque?

Thanks.

Ron Milliet
Petal, MS
87 325is http://www.dcslink.com/bmw3/index.htm
86 325e
80 911 SC http://www.dcslink.com/porsche/index.htm

I'm going from memory here, so be careful (Warren is sure to have the definative answer).

In the factory manual, there is a well detailed procedure for running the engine on a test rig. Unfortunately, mortals like us don't have access to one, and the test rig allows the engine to be under partial load.

None the less, here's what I recall of the procedure:

1) Set up the engine ready for running. Set the idle slightly higher than normal. If you've replaced the rocker-arm adjusters, set the gap to 0.15mm (not the usual 0.10) to allow them to bed in.

2) Start the engine, check dwell angle, and make sure the oil pressure guage rises a second or two after start. If it doesn't rise almost immediately SWITCH OFF and investigate.

4) Assuming all is well, run at 2000 rpms for 10mins, 4000 rpm for 10 minutes, and 6000 rpms for 10 minutes. Check during this time for excessive temps, oil leaks, unusual noises - all good common sense stuff.

BEWARE: That's for the engine running under load on a test rig.

In reality, I wouldn't run it at those speeds immediately. Instead I'd run it at 2000 and 4000 (max) only and follow the "break-in" or "running-in" procedure in the handbook.

Again going from memory, this suggests restricting your rpms to 3500-4000 max for the first 500 miles, and not using max rpms (eg 6000+) for another 500 miles (it may be another 250 miles). During this period use the gear-box and the engine freely, try to avoid driving for long periods at the same rpms. I'd suggest you use "normal" roads wherever possible rather than freeways during this period.

After the first 500 miles you must change the oil and check/re-set your rocker-arm gap.

I'll try and reply again tomorrow when I have the specific info to hand. In the meantime, it seems possible to construct a sensible sort of break-in schedule from the above info.

Well done of getting all that engine work done.

Good luck,

- roGER

i agree, like the vw vr6, you need to use the engine, but not at constant speeds, you must change rpms, id try going through twisties, and running it hard to about 4K rpms at the most, and drive it like 4K is your redline. If you leave the motor run at the same engine speed for too long, rings etc will not seat properly, causing oil burning

I'd agree with all this too. I'd probably baby it during the first thousand or so. I would drive it pretty easy.

Also, while I've never rebuilt a Porsche engine, most other engines are prelubricated in a couple of ways. Greasy goop is put on the bearings and cam and stuff during assembly. then, before starting the engine, you turn the oil pump by hand to get the passages filled and some pressure up. Unfortunately, this is usually done by turning the motor, which is not easy. Much easier with the spark plugs out though.

------------------
'83 SC

All sounds like good advice. I remember breaking in my first full rebuild...a 72 MGB, 4 cyl, 1.8ltr. The book had similar suggestions ,but I remember particularly this step:

On an open road, in 4 th gear, use FULL throttle from 30mph to 60 mph. Do this as much as possible for the first 50 miles. Normally this would be a 2-3 shift, but this was a way of loading the engine whithout too much rpms.

Thanks for the help.

Ron

I'm breaking a top and bottom rebuild in right now. My mechanic said not to be overly concerned, not a real technical process on my part- keep the revs under 4 grand, keep it in the city, don't baby it, check the oil at each fueling and pay attention to anything that seems unusual. Make sure you check that oil, I think I burned off a lot in the first 250 miles. Either the car was not completely filled or I went through 2-3 quarts during this time period.

At 8-9 hundred miles he will change the oil, retorque the heads, adjust valves and go over the motor carefully.

Joe
'80 SC Targa