Breaking in rebuilt engine

[JSeaman]

Guys,

I will soon be breaking in my rebuild and wanted some feedback/tips on the best way. It seems that there are a lot of different opinions on this but any info appreciated.

So far I've heard that you should:

a) Start with a non synthetic oil, let the engine run at idle for about 10-30 mins then drain it and change the filter

b) Refill again with non synthetic oil. Then drive at varying speeds - no constant speeds because they are bad ... why?

c) Low revs and very low boost for about 1k

d) Change oil every 500 miles for the first couple of thousand (Switch to synthetic after 1k)

Any of this good advice/to be ignored?

Thanks

James.

[Bryank]

Guys,

I will soon be breaking in my rebuild and wanted some feedback/tips on the best way. It seems that there are a lot of different opinions on this but any info appreciated.

So far I've heard that you should:

a) Start with a non synthetic oil, let the engine run at idle for about 10-30 mins then drain it and change the filter

b) Refill again with non synthetic oil. Then drive at varying speeds - no constant speeds because they are bad ... why?

c) Low revs and very low boost for about 1k

d) Change oil every 500 miles for the first couple of thousand (Switch to synthetic after 1k)

Any of this good advice/to be ignored?

Thanks

James.
my two pence:

a) possibly. I think running for a few miles is a better idea. Idling for 10-30 mins straight after a rebuild is probably not so good as the oil pressure will be on the low side

b) to get the bearings & rings to bed in gently, (remove the high points) but have a little stress sometime to take the low points off the faces. Do not race or lug the motor either (ie driving up big hills in 4th gear at low revs)

c) yes, but not too low! after a couple of hundred miles, raise the revs a bit, then after another 100 a bit more etc.

d) depends how paranoid you are, but sounds like a good plan..

I wouldn't put synthetic in until the motor is well run in.

I know that running in a motor is a bit of an arcane art, but in all the motors I have built (10+ all different) the above has always worked. How a motor is run in will pretty much define how long/well it runs for the future. (Scariest running in period is for old Harley's: 5000 miles recommended by some!)


Cheers,

Bryan

[JSeaman]

Thanks Bryan, always useful to hear from someone with lots of experience.

[Nick]

It's a question that 2 people will never have the same answer I don't think.

Anyone go to TSC2??

There was a 200sx there that had just been rebuilt, the conversation went "and what method has he finally decided on going with to run it in"
"not sure, someone told him gently gently, someone else said thrash fook out of it"

Car launches off the line, with the engine bouncing off the limiter.

Everyone in chorus "looks like thrash the fook method then"

:D

[JSeaman]

:) Do me a favour Nick, don't tell Adam that!

[Bryank]

It's a question that 2 people will never have the same answer I don't think.

Car launches off the line, with the engine bouncing off the limiter.

Everyone in chorus "looks like thrash the fook method then"

:D
LOL pretty certain the bearings will die quite quickly after that then! suppose it depends if you want them to last 1 year or 10 lol

-- When I last had a crank reground, new bearings etc, i had a long talk with the guys who did the machining, and the engineer explained that when a new surface is prepared, it is in fact covered in *tiny* burrs from the machining tools.. these are what can cause problems..

In fact the machining must take place rotating the crank in the same direction as it would run in the motor, so the burrs are facing in the same direction as the bearing surface is moving, reducing the likelyhood of fouling.

Running a reground crank in is a bigger deal than just fitting new bearings, as these burrs have to be smoothed out by use, hence the warnings about not loading the bearings too hard initially.. If a crank has not been reground, just new shells fitted then the burrs don't exist (already smoothed out) so you don't need to worry so much :)

Part of the problem is that rings should be run in a bit harder than bearings, so it's all a compromise!

Of course, these are my opinions only, given my own experiences, and friends motors i have been involved with. You'll have to make your own decision:duck:

[Bondango]

when this topic appeared we started talking about my first job (16) i had back in 84 when i worked as a deisel fitter, namely on London Cabs FX4D's that used a British Leyland 25V (2.52 litre) engine.
A rebuild took us a day on the engine, i cant remeber once using a Torge wrench (did they exist) just a paper dial, everything soaked in heavy oil, built up and the next day fitted back into the cab.
After all the checks were made, it was fired up with a **** load of 'easy start' the pump timing was then set- by inserting a jammy bar between it and the engine block and revving the tits of it until they smoke wasnt as black as your boot.
Next day it was out on the road to cover another 150,000 miles :yes:

what is all the fuss these days about breaking an engine in :gay:


LOL

[Bryank]

when this topic appeared we started talking about my first job (16) i had back in 84 when i worked as a deisel fitter, namely on London Cabs FX4D's that used a British Leyland 25V (2.52 litre) engine.
A rebuild took us a day on the engine, i cant remeber once using a Torge wrench (did they exist) just a paper dial, everything soaked in heavy oil, built up and the next day fitted back into the cab.
After all the checks were made, it was fired up with a **** load of 'easy start' the pump timing was then set- by inserting a jammy bar between it and the engine block and revving the tits of it until they smoke wasnt as black as your boot.
Next day it was out on the road to cover another 150,000 miles :yes:

what is all the fuss these days about breaking an engine in :gay:


LOL
fair play, but an (olde but goode) archaic diesel motor with clearances you can put your fingers in is a little different to a high performance motor.. :p Would you REALLY want to do that on a turbo motor? (in 1984 I was mostly building custom bikes & engines .. the only turbo motor i have had direct involvement with was a GSX1100 bored out to 1270, with a Mr Turbo kit, hot cams and magneto ignition.. even firing that up was scary let alone thrashing it!!)

[JSeaman]

Well I'm glad this post has led to some happy memories being relived!

It seems that it's a toss up between rings being sat properly by thrashing it (Side effect is that bearings rapidly die), or being nice and gentle which makes the bearings happy but not so good for the rings. This fine balance can easily be overcome by buying a black cab it would appear!

Thanks for the help, it's been insightful :)