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MG MGB GT V8 Factory Originals Technical - Engine Break In

My motor is in the process of a rebuild Its a 3.9 rover 9.3.1 pistons stock intake 1404 edlerbrock carb Isky 262 cam.I just read about 10 articles on breakin and most said take it easy and dont go over 4500 rpm and speed up and slow down than after 500 miles your done.One said to run it hard from the beginning and doing so is what it takes.He said this is for all motors.Looking for your own breakin peroid experience.
dbw morris

Once the engine was ready to start, oil pump primed, I then ran it up to the required RPMís to bed the cam in. After that I tried to, sort of, take it easy but it sure is fun to step on the gas and be pushed back into the seat. So I really didnít take it too easy. Now 2 years on the rebuild of my Rover 3.5 and no engine problems.


My break in procedure is as follows:
* Keep the revs above 1/3 and below 2/3 of max RPM as much as possible.
* Avoid long periods of constant engine speed running and load levels on the engine.
* Vary the revs and load as much as possible and have at least six short bursts in a high gear at low speed with a wide open throttle to load the rings and bed them in properly or you will glaze the bores and this will mean a re hone.
* Change the eng oil and filter at 500 Klm.
* Change both again at 1500 Klm.
* Make as many long runs as possible without turning the engine off or letting it idle for longer than needed.
I put 1500 klms in 3 days on my car running it in and now have 460 000 klm on it with textbook oil pressure, compression and no leaks of any sort any where.

On a related topic: if you have not run the engine for the first time after the rebuild ; remove the spark plugs and spin the engine on the starter until oil pressure shows on a gauge. Then fit the plugs and fire the engine and keep the revs about 1500 / 2000 for about twenty minutes to bed in the cam or follow the cam suppliers recommendations if they differ to these.

Cheers, Pete.
Peter Thomas

I am reliably told that with a hand-built engine, once the cam has been bedded (20 min.) and it has reached normal operating temp., you are good to go. The run-in process is relevant to assembly-line motors that are not built to the same tolerances. This from a friend who is a truly master mechanic and muscle-car enthusiast.

IMHO the run in period is important on ALL engines that use steel piston rings in cast iron bores ( I have no experience of ally ceramic bores - which may well be different).

The whole point of running in an engine is to allow controlled initial wear of the rings against the cylinder walls. The fine cross hatching of the honing process leaves the surface rough enough to retain oil whilst the rings and bores bed in to each other.

Use of anti friction additives or insufficent revs will result in the tiny peaks of metal being bent over rather than cut off, resulting in long term oil usage and poor gas seal (bore glazing).

It is important to use running in oil and to vary the engine speed and load.

It doesn't matter how close the tolerances are - unless the rings and bore are properly bedded in you will have a lousy engine.......

Chris Betson

Whilst most of the discussions so far have been on bedding the rings and if the engine is being totally rebuilt , which I assume it is , then this is only one part of the running in equation albeit an important part.

The main, big end and small end bearings, tappets,valve rockers and so on are also being settled into a running pattern at the same time hence the suggestion for the oil and filter changes.

Good luck, Pete.
Peter Thomas

All I can add to that is that I used the electric drill method on the oil pump drive to get the oil pressure up - waited until it appeared on the rocker shafts - which took quite some time.
Then after first start,(following a full rebuild of everything), I did 45 miles in the garage on ramps in various gears at various speeds to make sure it was all working OK. Finally, the shakedown run was 250 miles at up to 80mph on occasions. Tickover had increased in that time from 750 to 1500rpm which indicates a significant loosening up early on. There was little change to the tickover after that.
And keep the oil simple (non synthetic)for the first 10,000miles.
Dave Wellings

This thread was discussed between 02/01/2003 and 03/01/2003

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