Thread: rebuild: how long until it's run in?

Would have thought the replacement of valve stem seals would have stopped smoke on the overrun from go!

Originally Posted by phuma

I have had my V8 rebuild at a reputable shop:
- new HC pistons & rings (was LC engine, but only HC available)
- heads checked, cleaned, new valve stem seals were fitted, guides were ok
- bores still showed the original hone marks, and were allegedly within spec (I was not there to check this)

How long should it take to run in? It is still smoking on overrun, and consuming the same amount of oil than before. I don't believe this is good. It's been 800km since the rebuild...

Running is not really to do with time , more so that the correctly engine loading cycles have been gone through .99.0% of all engines from new are dynoed to at least 90% of their maximum output within a couple of Hours after they are built . All racing / performamce engines hardly ever enjoy a running in period . Running-in per se is a nice antiquated idea . Every new car coming off the Production line is dynoed to full power , and has to be able to meet a certain spec, otherwise its over to the reject car park for fixing !!
In your case , it sounds like your engine reconditioners paid no attention to the Valve guides , as thats where your oil is coming from . Sometimes its just the valve stem seals they may have come off .
Do a wet and dry compression test , record the results and go back to your engine reconditioners and ask why this oil smoke and oil consumption is happening.

The rebuilder said the engineers did check the valve guides, and that they were ok. I had a misfire (bad new HT lead) yesterday, while we were checking that we 'revved' the vehicle a few times, and it smokes a bit black then - and then grey. And then it stops - if that makes sense!

No, not using coolant at all.

Originally Posted by phuma

The rebuilder said the engineers did check the valve guides, and that they were ok. I had a misfire (bad new HT lead) yesterday, while we were checking that we 'revved' the vehicle a few times, and it smokes a bit black then - and then grey. And then it stops - if that makes sense!

No, not using coolant at all.

You said originally , it was blowing smoke and the oil consumption was as it was before (the old engine ?) What is this excessive oil consumption in Litres per thousand Kilometers ?
I see you said the "engineers" checked the valve guides and they were Okay . interesting , how many Kilometers had this engine done before Re-conditioning ?

Engine had done around 197000km before rebuild. Consumption was definitely more than 1 litre per 1000km, and smoking heavily on overrun. During disassembly it was discovered the oil rings were stuck solidly on the pistons, so the assumption was that was at least part of the problem.

I don't know anymore

Originally Posted by phuma

Engine had done around 197000km before rebuild. Consumption was definitely more than 1 litre per 1000km, and smoking heavily on overrun. During disassembly it was discovered the oil rings were stuck solidly on the pistons, so the assumption was that was at least part of the problem.

I don't know anymore

Sounds even more like a Valve guide/valve/valve stem seal issue .
What causes rings to stick hard to pistons ? Yep excessive oil introduced in the induction cycle . There are few more ways this can happen . Not using any of that :valve saver" come destroyer stuff are you ?
Inlet manifold leaks can draw oil in from valley area . (where dors the IAC draw its air from , if fitted) Your PCV circuitry can do the same . Pull the Plenum top and see if its full of oil ,Theres allows Ring gap alignment , Another common one is running the wrong heat range plug .

A new engine will use some oil while it's bedding in, but the type of oil you use in the first 1000k's is what makes or breaks it.
Don't use synthetics or any thing heavyweight. Just a basic cheap oil is all that's needed.
The initial bedding in period is critical to the life. Use a syn or too thick oil will glaze the bores requiring a re-hone.
And don't baby the engine either, another big no no. It needs to be run with harder than usual acceleration, revved higher and engine speed varied as much as possible, ie no freeway cruising, take the backroads instead which is kinda the point when you have a Landy
start using a better oil once you have clocked up about 5000k's.

As for the oil on overun, most likely stem seals if the old ones were reused which is pretty shoddy work in my opinion. Been in the engine game for 20 years and regardless, you always change the stem seals.

Cheers

Andrew.

You should use a good Mineral oil for the initial 5K, do not let engine idle for longer than a minute, do not drive at a constant speed over long distance, vary speed. The engine should be run at higher revs than normal, try using a lower gear.
Reason: The combustion pressures get down between the rings and piston grooves and force the ring to conform to the shape of the bore, which quickly beds them in creating a good seal, if you let the engine idle or not work hard the rings may never bed in and create a good seal, the bores can glaze up and compression can get past the rings into the sump.
So drive it hard (keep the revs up) for a few 1000Klm's, use a good quality MINERAL oil (NOT SYNTHETIC) and change oil to Synthetic and a new filter at 5k and your motor should be run in, Regards Frank.