Running-in a Rebuilt V8

**Tank** · 5th August 2017, 10:59 AM

I don't know why this subject has so many different ideas about running in, here are some facts.
Piston rings need to bed in (conform) to the bore surface, the bore surface has been cross-hatched honed by the machinist to suit type of rings used and type of engine.
This pattern on the bores is designed to hold some oil and provide a softer surface for the rings to shape.
The way rings work is the built in clearances are designed to allow Compression from the ignition and exhaust stroke (upward stroke) to move down past the top of the piston into and behind the top ring, which has a step cut into the back of the ring to allow this to happen, compression gasses then force the piston ring into the surface of the bore, making a good contact all the way round and sealing the gasses from running down the sides of the piston.
So when you hear people saying labour the engine or idle it for ages, you now know they have no idea what they are talking about.
A few tips for running in or should be "seating in the rings to the bore", if you idle the engine too long or labour the engine you will Glaze the bores by not applying enough pressure to keep the rings hard against the bores and the cross hatch hone pattern will wear off.
You should use liberal amounts of CAM LUBE to coat the cam lobes and lifters before start up.
Do NOT use a Synthetic oil, use a good quality 30 grade Mineral, wind the engine over (petrol) with the coil lead out for about 5 or so seconds.
Plug the coil lead in and start engine, maintain revs over 1000rpm for about 20 minutes, this is optional but once you feel cam is run in, turn off engine (don't let it idle).
Drain the oil and replace the filter, refill with oil and filter and drive the car for the next 500klms before changing oil again, use mineral oil up to 1500klms, then if you wish go to manufacturers recommended oil, synthetic oil can be used.
Driving, just drive normal except for long idling, lugging the motor up a hill in too high a gear, don't drive at a constant speed on a freeway, vary speed up and down, around town leave the gearbox in a lower gear than you would normally use, occasionally give the engine a wring of the neck, high revs and back down, not all the time just when you get the need for speed. Main thing is don't let the vehicle idle in neutral for long periods, when cold, start engine and drive off asap, don't sit there on cold mornings revving the ring out of it (no load), just start it and drive.
Keep a sharp eye on oil consumption, park in the same spot each time you dip the stick, oil consumption will be slightly higher in the first 1000klms and should settle to normal around 1500klms.
I would do a compression check at 1500klms.
Remember, Don't idle excessively, don't labour (under load in to high a gear), use mineral oil till your happy the engine is run in, Good Luck, Regards Frank.

**PAT303** · 5th August 2017, 04:09 PM

Good post Tank.

**Blknight.aus** · 5th August 2017, 06:57 PM

Keep the revs to it and dont load it too much. Vary the engine speed

**Meccles** · 16th August 2017, 01:13 PM

I remember Pete Brock explaining how they used to run in their XU1 torana's - which were road registered. They used to drive Melbourne to Phillip Island.
That south gippsland hwy fits the bill, winding road - reasonably flat to begin with. Then hills towards Phillip Island.
Said it was perfect running in road. Just saying is all

My engine, I've got Penrite break in oil, will run at 2000-3000 rpm for 20 -30 minutes. I've used a heap of cam lube and primed oil pump.
Then drive reasonably normally for 500kms -putting under some load but not max rpm, varying speed. Mind this will be a bit hard as car is not yet registered.
Then change oils filters.
Just water in as coolant until I'm sure I've got no major leaks/issues

**Pedro_The_Swift** · 17th August 2017, 04:32 PM

Nice post Tank,, thats exactly how I did mine,, even the mineral oil out to 1500kays,,

**rick130** · 19th August 2017, 10:20 AM

I'm not sure what Frank's thoughts are on this, but what we did with either road engines on road or race engines on the dyno was first, run in the cam.

This was critical on an OHV flat tappet engine.
1800-2000RPM for 20 minutes.
Not ideal for rings, but critical for the cam and lifters.
It keeps the lifters rotating and stops galling.
As Frank said, use gobs of moly assembly lube.

A mate made a cam running in device for Formula Ford's.
An old engine block with an electric drive to the cam.
Worked a treat, then all we had to worry about was bed rings.
Are one point we were having issues of not enough taper on can lobes and some lifters with insufficient radius.
After careful checking this extra step helped reliability and extended engine life, especially when my rebuild limit was 5% leak down.

For road engines, find a hill, use a relatively high gear, and really load the engine up.
Full throttle from relatively low revs, one run.
This seats the rings.

Then drive normally.

Long runs at constant revs aren't great, keep the engine moving up and down the rev range.

On the dyno we didn't spend much time at all. It was all about getting a decent ring seat, then get it racing.

**DiscoClax** · 20th August 2017, 08:48 AM

OK I'll wade in as most have had a go... this is based on a lot of experience, research and direct testing over decades with various car and truck vehicle and engine manufactures and designers. It was my speciality as an engineer until the last decade when it became more of an expensive hobby...

Excluding (flat tappet) cam break in time where crank - thrown splash lubrication requires that the engine sits between 2000-2500rpm for its first 20mins of life (critical) and high ZDDP oils...

The simple rule is keep the engine between 1/3 & 2/3 rds of max revs with as much load as you can apply (ie. heavy throttle). That avoids both labouring and over speeding the engine and also keeps the combustion pressures high to push the rings into the bores for rapid bed in, with good oil pressure to cushion the bearings and flow to flush through.

Simple example: Engine designed to redline at 6000rpm. Keep it between 2000 and 4000rpm. For an engine designed to max out at 4500, it would be 1500 to 3000rpm. If that engine is turbocharged and 1500 is under the boost curve then use the lower end of full boost revs as the minimum instead. Keep it 'on the boil'. You'll feel by seat of the pants where the engine is happiest (near max torque).

It's all about high combustion pressures and moderate revs. Light loads are bad, over-run is very bad (avoid active engine braking), idle is bad, very high revs are bad. But only for the first 100-200 kms or so (depending on how effectively you can follow this). After that (and oil and filter change) drive it in a varied manner. No synthetics for the first few thousand kms.

My recent stroker RV8 motor? Run in on a dyno, but only because I could. As soon as it fired (pre-primed oil) it was brought up to 2000-2500rpm and heavily loaded up for the first 20 mins (cam and rings). Modern 1.5mm ring pack and plateau honed bores in mine so that first 20 mins pretty much did the job for the whole engine. After that it was some moderate run ups and then straight into full throttle pulls after a filter change. When installed in car the first drive was with a 1.5t trailer hanging of the back.

A mate's similar stroker was done in car. Did that out in the country and fired it and immediately drove it under load (left foot braking where required) keeping the revs up for the cam. Three may have been a smallish trailer attached for that time, too...

By two-bobs...

**Pedro_The_Swift** · 20th August 2017, 09:15 AM

and the figure from the "full throttle pulls" was ???

**DiscoClax** · 20th August 2017, 10:24 AM

A few ponies over 300, with over 500 torques in the modern units

but you'd expect that out of 4.9 ltrs / 300 cubes of bent eight goodness.

**DiscoClax** · 20th August 2017, 10:34 AM

Another added thing to note... Modern ring packs that are much narrower and use different materials and facing tend to bed in much easier / quicker and are less sensitive to method than older styles (cast iron, un-faced, wide, etc). Equally moden bores tend to be machined differently to suit those rings. What I wrote above applies more to the older engines, but still has relevance to any engine.

I get a new company car at least yearly and I consider it run-in by the time I drive it home ~50kms, but I follow the 'simple rule' on that trip home religiously. And always on the highest octane fuel I can find (if petrol) to ensure it isn't spark-retarding under load.

That works for me and what I posted would be my recommendation. But no offense taken either way if followed or ignored

Choice is a wonderful thing.

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