Breaking In the new engine

[Steve Bryant]

Hello all,
this may have been touched on before but I would like to have some discussion on the best way currently to break in the new engine  (re-bore, new big ends, bearings, valves, guides, etc.) so that the best performance can be had from the reconditioned engine.

Break in oil is now a favored method of helping to bed things in and the initial first uses of the engine are said to be best if the car is taken out and driven under load fairly vigorously (without thrashing it) so as to help  "set" things.

Loads are varied during the initial miles and the car driven about 500 miles to break it in after which the break in oil is changed for the oil of choice, clearances checked, and adjusted as required,head re torqued,  timing checked etc. so the car is now ready for its life on the road.

Is this what is now considered to be a good method of running in for our cars? Your thoughts ?
Thanks,
Stephen

[Chris KC]

Hello Stephen,

If you use the search pane at top right you will find this has been covered pretty thoroughly in previous threads.

I'm running in my own engine at present (and have done so successfully on a number of previous occasions - I won't say many as my engines tend to last fairly well...)

You will get many and diverse opinions but here's mine:

- Don't leave a newly built engine idling for long periods in the driveway, drive it.

- First start - be happy. Don't run it too long. Just walk around and see what's leaking, any nasty noises? A few minutes is enough. I put the coolant in immediately before starting the engine and drain as soon as it's stopped - this avoids an engine full of water if the head gasket isn't sealing well. Once the engine is COLD again re-torque the cylinder head nuts (especially if you have an ally head).

- First drives - keep them short. Go out at the crack of dawn (wake the neighbours) so you can have a quiet little road somewhere to yourself. Listen to the car and don't force it. First time out I wouldn't go over 35 mph, just be content to get up the road and back without stressing anything. The car will get hot so don't run too long. Don't rev the engine too fast but crucially don't let it labour under load.

- Early runs, again keep them short, 10 miles or so for the first fews. The engine will still be quite hot and you don't want to be too far from home if something drops off. Keep checking oil and coolant levels every time out.

- Slowly build up to longer runs. Aim to pootle along a lane somewhere at max 40 mph or so, using the gears liberally. Gently work the engine up and down, but again, don't labour it and avoid very high revs. Check the points gap now and then.

I'd aim to do about 200 miles like this, by which time the engine will be feeling much freer and you can start to extend to longer runs. I've completed about 465 miles now and the last two runs were 100 miles each. I found a nice little route down a quiet B road where I can do 40 - 45 or so without annoying anyone and have avoided main roads like the plague. You do not want your road speed to be dictated by traffic, go at the speed the car wants to.

On yesterday's outing I was letting the car run up to 55mph on downhill slopes and she feels sweet. Always gently. I don't plan to put my foot down hard till I've got 1000 miles under my belt.

I personally use bog standard 20/50 oil throughout the process. I would suggest changing it fairly early as it will get very dirty very quickly. I run with a modern oil filter and am about to do my first change, certainly sooner if you don't have a filter. I for one will use flushing oil at the same time, just to remove anything I failed to find when I cleaned out the crankcase. I have no qualms about this because the inside of my case was clean enough to eat off when the engine went back together. It's high time I checked the tappet clearances too.

That about covers it I think. Like I said - works for me; no doubt others will now tell you I'm all wrong!

[Steve Bryant]

Thanks Chris,
good information, much appreciated.

Having looked at past threads I was trying to get the most up to date methods  as suggested by others for  breaking in given that oils, pistons, rings and bearings are different now. Its just the engine design that is old.

Cheers,
Stephen

[Chris KC]

Thanks Chris,
good information, much appreciated.

Having looked at past threads I was trying to get the most up to date methods  as suggested by others for  breaking in given that oils, pistons, rings and bearings are different now. Its just the engine design that is old.

Cheers,
Stephen

Depends what you are running I guess Stephen - for me none of that has materially changed in the last 35 years.

[John Mason]

I am surprised that Chts advises to re tighten the head when COLD (I am not saying this is wrong) but I have always been taught to re tighten cast heads hot and ally heads cold.

John Mason.

[Ian McGowan]

I am surprised that Chts advises to re tighten the head when COLD (I am not saying this is wrong) but I have always been taught to re tighten cast heads hot and ally heads cold.

John Mason.

Perhaps John, it is worth noting that Chris specifically says "re-torque" not tighten. i.e. restore to previous settings the tension originally set in the retaining studs after the head has settled. To do this correctly the engine would need to be cold , as it was when the head was originally torqued down??

[John Mason]

Point taken.

John Mason