How long must I wait?

[AW111]

I recently did a full rebuild of the engine in my MR2. It's a 1600 cc naturally apirated 4 cylinder.
I ran the rings in on the dyno, then changed the oil when I got home. Ran it for a week (about 250km), refitted the oil cooler and changed the oil again.

How much general running around do I need to do before I can -
1) Run it to redline (8,300 rpm) and regularly use WOT.
2) Change from running in oil (Penrite 15/40 mineral) to synthetic (I plan to use Penrite 5W/30 or 5W/40 full synthetic)

I am currently sticking to a self-imposed 6,000 or so rpm, but that's just where it really comes on song, and my right foot is getting itchy.

[Mignon]

http://www.pumaracing.co.uk/runin.htm

[Ilovejapcrap]

I'm in the process of a rebuild on a mr2 myself ( mk3)

http://www.mr2roc.org/phpBB3/viewtopic.php?f=88&am...

It should be done by next week so would also be interested in this.

[AW111]

Mignon said:

http://www.pumaracing.co.uk/runin.htm

That's pretty well what I've done - I'm about 350 km into the final "change oil again at 1000 miles" stage.

I did the initial break in (cams & lifters were unchanged) on the dyno.
All runs in 4th gear with a cool down period between each set of three runs.
3 x 3500-4500 rpm, 1/3 throttle.
3 x 3000-5000 rpm, 1/2 throttle.
3 x 2500-5500 rpm 3/4 throttle.

It doesn't smoke, and uses no oil.

I am itching to see what difference the valves & head work have made, but that will wait for another 1000km or so.

[stevieturbo]

Many race or performance engines are run in on a dyno....in a matter of minutes, maybe hours at most.

Lets face it, it is rather impractical to run many for hundreds of miles easy to do it, as some may never even do that many miles in a year ! lol

[AW111]

stevieturbo said:

Many race or performance engines are run in on a dyno....in a matter of minutes, maybe hours at most.

Lets face it, it is rather impractical to run many for hundreds of miles easy to do it, as some may never even do that many miles in a year ! lol

While that is true, I hope this build will last another 100,000 km, while competition engines tend to be rebuilt every few years or less. They also tend to have bigger clearances.

On the subject of bearing clearance, OEM bearings are available in 5? sizes to suit different block / crank clearances, while aftermarket bearings come in standard and undersize only.

[GreenV8S]

AW111 said:

How much general running around do I need to do before I can -
1) Run it to redline (8,300 rpm) and regularly use WOT.
2) Change from running in oil (Penrite 15/40 mineral) to synthetic (I plan to use Penrite 5W/30 or 5W/40 full synthetic)

1) I suggest you're already there. I don't see any benefit in babying the engine once the cam and bearings have had their initial bed-in period, and you have already bedded in the rings so no special considerations there. If I were you I'd already be using full revs and wot briefly to help the rings finish bedding in, and gradually transition up to normal unrestricted driving over the next few hundred miles.
2) Any time from now on.

[stevieturbo]

AW111 said:

While that is true, I hope this build will last another 100,000 km, while competition engines tend to be rebuilt every few years or less. They also tend to have bigger clearances.

On the subject of bearing clearance, OEM bearings are available in 5? sizes to suit different block / crank clearances, while aftermarket bearings come in standard and undersize only.

OEM engines last 100...200...300..400k ( well some do, some dont ) and you can be sure none of them are run for hundreds of miles prior to you getting them.

It would be totally impractical to do so.

[PeterBurgess]

Biggest problem we have, and all the professional engine builders I know and work with, is arrested running in due to pussy-footing and using oil which is 'too good'. We build our engines with 1/2 thou increase in bore size for the road so the engines are ready to go. Modern oils are really good at protecting engines and can cause the high points in the bore to bend over instead of wearing away. These little hooks hold oil and the engine happily burns this with no obvious tell tale smokey signs. We find if folk don't use the engines they can ruin them and cause them to use oil. Engines run in best at peak torque when there is max pressure on the back of the rings and it beds em in well. What can cause problems is labouring in high gears or seeing max speed in high gears when heat can build up and cause trouble. For this reason I, and many other pro builders, now supply our engines with Joe Gibbs driven break in oil. We have to move forwards and adapt to changing times.

I suppose I am trying to say the OP's engine must be fully bedded by now or arrested running in conditions obtain

Peter

[AW111]

So the consensus appears to be that the job is now done and I can get on and enjoy driving.
I will change to synthetic in another 1000 km or so.

Thanks all.