New liners, rings, cams - best running in procedure?
Discussion
Totally rebuilt engine. New cams, springs, liners, pistons, rings, all bearings, etc.
Given the potentially opposing views on getting rings to seat versus minimising load on cam lobes, what is the collective PH wisdom in terms of running in a new engine (after cranking for OP, setting initial timing, etc, etc).
Let it "fast idle" (2-3k rpm) for 20 mins to let the cams bed in, or take it straight out and give it full throttle followed by a quick lift several times to help bed in the rings and get rid of any high spots, etc?
Given the potentially opposing views on getting rings to seat versus minimising load on cam lobes, what is the collective PH wisdom in terms of running in a new engine (after cranking for OP, setting initial timing, etc, etc).
Let it "fast idle" (2-3k rpm) for 20 mins to let the cams bed in, or take it straight out and give it full throttle followed by a quick lift several times to help bed in the rings and get rid of any high spots, etc?
Bed the cam in first. This is absolutely crucial to the life of the cam. You really need to be certain that the engine fires straight away and get the revs up immediately regardless of any other problems - if necessary switch off rather than let it idle while you fix that water / oil / fuel leak. This doesn't take long so won't compromise your bedding in the rings.
While bedding the rings in vary load and revs, avoid extremes of load and revs but do load it (briefly). As I understand it, it's while the engine is loaded that most of the ring bedding-in occurs but you want to keep the load brief to avoid overheating.
While bedding the rings in vary load and revs, avoid extremes of load and revs but do load it (briefly). As I understand it, it's while the engine is loaded that most of the ring bedding-in occurs but you want to keep the load brief to avoid overheating.
Bedding in the rings to the bores is the most critical aspect on a modern engine as the tolerances throughout are designed for two parts to run together separated by a film of oil (think cam lobe and follower). The rings/bore are designed for minimal oil separation to prevent oil consumption and are designed to bed in to their running tolerance. The surface finish and material of the bore surface and the ring material are chosen to allow them to initially wear to give a consistent sealing finish on the full circumference, essentially removing the high spots on the bores and rings. The wear is a function of speed and pressure.
The speed is rpm, simple. The pressure is combustion pressure and this is generated by load (combustion pressure forcing the rings against the cylinder wall). We need to be careful not to apply too much of either as we will get too much localised hear on the high spots of the rings and this can affect the properties of the ring material and prevent the bedding in process. Likewise insufficient load will cause glazing of the material surfaces and prevent any further bedding in to the surface being too smooth. Adding a little more load and little more speed incrementally is the best way to go.
Start up and run the engine at the lowest engine speed to achieve max oil pressure (when the oil pump pressure relief valve opens). Run at this speed for 10-15mins, but be aware that as the oil temp increases the engine speed required to maintain max oil pressure will increase.
Drive normally normally towards a decent mile plus long well sighted, quiet straight road.
Select a fixed gear if auto, or 3/4th if manual.
Accelerate at 50% throttle from 1200rpm to 2/3 of peak rpm, lift off, change down and coast back to 1200rpm. Repeat 5 times
Accelerate at 60% throttle from 1200rpm to 2/3 of peak rpm, lift off, change down and coast back to 1200rpm. Repeat 5 times
Accelerate at 70% throttle from 1200rpm to 2/3 of peak rpm, lift off, change down and coast back to 1200rpm. Repeat 5 times
Accelerate at 70% throttle from 1200rpm to 3/4 of peak rpm, lift off, change down and coast back to 1200rpm. Repeat 5 times
Accelerate at 80% throttle from 1200rpm to 3/4 of peak rpm, lift off, change down and coast back to 1200rpm. Repeat 5 times
The coast down is important as this removes pressure from the rings and oil past the oil control ring to aid lubrication and cooling
That should be 50 or so miles
Then use normally gradually increasing load and rpm over the next 250 miles.
I would then change the oils as all the particles which have worn off your bores are now in your oil and filter.
Anecdote 1; A couple of years ago I built a BMW S14 engine and fitted a magnetic sump plug. After the break in period, I dropped the oil and found the magnetic sump plug looked like a Christmas tree! Mag sump plug obviously of limited use in an ally blocked engine!
Anecdote 2; Earlier this year I bought a 2007 330i daily driver with N52 engine which have a reputation of using a drop of oil. Turns out the first owner was BMW UK. Guess what, doesn’t use any oil! My guess is that it was not babied from new due to the user not being the owner.
The speed is rpm, simple. The pressure is combustion pressure and this is generated by load (combustion pressure forcing the rings against the cylinder wall). We need to be careful not to apply too much of either as we will get too much localised hear on the high spots of the rings and this can affect the properties of the ring material and prevent the bedding in process. Likewise insufficient load will cause glazing of the material surfaces and prevent any further bedding in to the surface being too smooth. Adding a little more load and little more speed incrementally is the best way to go.
Start up and run the engine at the lowest engine speed to achieve max oil pressure (when the oil pump pressure relief valve opens). Run at this speed for 10-15mins, but be aware that as the oil temp increases the engine speed required to maintain max oil pressure will increase.
Drive normally normally towards a decent mile plus long well sighted, quiet straight road.
Select a fixed gear if auto, or 3/4th if manual.
Accelerate at 50% throttle from 1200rpm to 2/3 of peak rpm, lift off, change down and coast back to 1200rpm. Repeat 5 times
Accelerate at 60% throttle from 1200rpm to 2/3 of peak rpm, lift off, change down and coast back to 1200rpm. Repeat 5 times
Accelerate at 70% throttle from 1200rpm to 2/3 of peak rpm, lift off, change down and coast back to 1200rpm. Repeat 5 times
Accelerate at 70% throttle from 1200rpm to 3/4 of peak rpm, lift off, change down and coast back to 1200rpm. Repeat 5 times
Accelerate at 80% throttle from 1200rpm to 3/4 of peak rpm, lift off, change down and coast back to 1200rpm. Repeat 5 times
The coast down is important as this removes pressure from the rings and oil past the oil control ring to aid lubrication and cooling
That should be 50 or so miles
Then use normally gradually increasing load and rpm over the next 250 miles.
I would then change the oils as all the particles which have worn off your bores are now in your oil and filter.
Anecdote 1; A couple of years ago I built a BMW S14 engine and fitted a magnetic sump plug. After the break in period, I dropped the oil and found the magnetic sump plug looked like a Christmas tree! Mag sump plug obviously of limited use in an ally blocked engine!
Anecdote 2; Earlier this year I bought a 2007 330i daily driver with N52 engine which have a reputation of using a drop of oil. Turns out the first owner was BMW UK. Guess what, doesn’t use any oil! My guess is that it was not babied from new due to the user not being the owner.
Prime the oil pump first to get circulation to the bearings etc. Onc the engine's fired pressure will rise very quickly. On a rover it can be worrying waiting for the oil light to switch off so if you bottle it try several starting attempts. Been there, done that plenty of times. Get the initial revs over 2k and preferably nearer 3k. I've never managed to do a 20 minute stint in one go as I'd have to check for leaks etc.
After that, I used to drive a circular route near my home taking in more distance as I grew in confidence. Definately load the engine and then snap the throttle shut for the initial few miles. The engine needs to work and gradually build up the revs and time it's under load. After a few hundred miles change the oil but I wouldn't go synthetic straight away. I'd use halfords 20/50 for a while.
After that, I used to drive a circular route near my home taking in more distance as I grew in confidence. Definately load the engine and then snap the throttle shut for the initial few miles. The engine needs to work and gradually build up the revs and time it's under load. After a few hundred miles change the oil but I wouldn't go synthetic straight away. I'd use halfords 20/50 for a while.
Thing is, the cam doesn't really care about "load". For a typical high performance cam, what you need to avoid is the low speed scuffing damage at first start, where before the sliding surfaces have bedded, high spots and machining surface finishes can lead to pickup and scuff.
Ime, the cam cares about the literally the first 10min of running, after that, it's all about the ring pack. On modern engines, all i'd avoid is continuous high load running too soon.
Ime, the cam cares about the literally the first 10min of running, after that, it's all about the ring pack. On modern engines, all i'd avoid is continuous high load running too soon.
stevesingo said:
Strange that it appears that you disagree, but don't directly say so.
Running in cams requires the avoidance of idling, good oil flow and the lowest load possible. Hence minimum rpm for peak oil pressure.
Plenty of online resources from cam manufactures suggest similar.
It's the 'minimum rpm' part of your comment that has me puzzled. The cam obviously doesn't care about engine load. Low rpms is the worst case for cam lobe tip wear and I thought it was accepted practice to keep the engine in the middle of the rev range for the first 10 - 20 minutes to reduce the peak load on the cam lobe tip while the cam / followers bed in. This is based on inertial forces in the valve train acting against the valve springs and the need to keep up sufficient speed in the oil film; just having oil pressure isn't sufficient, although it's obviously necessary.Running in cams requires the avoidance of idling, good oil flow and the lowest load possible. Hence minimum rpm for peak oil pressure.
Plenty of online resources from cam manufactures suggest similar.
Hence it seemed to me that the procedure you described could lead to the cam not being bedded in optimally which made me wonder whether you assumed this had already been done.
McVities said:
Could you not bed in the rings on the old set of cams and lifters, then swap over to the new stuff?
An option, but the lash setup for the old and new cams, and also timing, is completely different, so a bit of a pain to swap things over....I was thinking of removing the inner valve springs to remove some of the spring seat pressures to give the lobes an easier time.
Thanks for the suggestions so far.
PS i've been recommended not to run flat tappet cams (i.e. bucket and shims) on synthetic oil by the cam designer as they need ZDDP (or equivalent) to protect against potential follower scuffing (there is no DLC or equivalent hardening on the top of the followers)
How radical is the cam profile you are needing to bed in?
The issue with slow running and extreme cams is that at low speed, the valve inertia is low, and as you'll have "heavy" springs to get the valve closed quickly, at peak lift and slow speed there is time for the oil film to get squeezed out the gap between cam and lifter, leading to scuffing. (at high speed everything is slamming open at speed and so the valve spring load is busy getting used to decelerate the valve at peak lift, not pushing into the top of the cam lobe)
Unless you are running something truly radical, like say a lofting profile, i've never had an issue with a short 10 to 15m fast zero load run (say 3krpm) then get the engine under some load to start other components bedding down)
The issue with slow running and extreme cams is that at low speed, the valve inertia is low, and as you'll have "heavy" springs to get the valve closed quickly, at peak lift and slow speed there is time for the oil film to get squeezed out the gap between cam and lifter, leading to scuffing. (at high speed everything is slamming open at speed and so the valve spring load is busy getting used to decelerate the valve at peak lift, not pushing into the top of the cam lobe)
Unless you are running something truly radical, like say a lofting profile, i've never had an issue with a short 10 to 15m fast zero load run (say 3krpm) then get the engine under some load to start other components bedding down)
Boosted LS1 said:
Actually, in over thirty years over rover friendship etc, I've never heard of anybody screwing up a camshaft or ring pack. Just get it driven and don't be soft with it. It'll appreciate a bit of abuse :-)
This x 6. There is far too much carp written about running in on the internet, it's mostly overblown garbage.
In the real World people just get in it and drive it normally and it's done in a few miles.
You'll do more damage by pussy footing around whilst trying to follow some instructions.
Max_Torque said:
How radical is the cam profile you are needing to bed in?
The issue with slow running and extreme cams is that at low speed, the valve inertia is low, and as you'll have "heavy" springs to get the valve closed quickly, at peak lift and slow speed there is time for the oil film to get squeezed out the gap between cam and lifter, leading to scuffing. (at high speed everything is slamming open at speed and so the valve spring load is busy getting used to decelerate the valve at peak lift, not pushing into the top of the cam lobe)
Unless you are running something truly radical, like say a lofting profile, i've never had an issue with a short 10 to 15m fast zero load run (say 3krpm) then get the engine under some load to start other components bedding down)
Not crazy.The issue with slow running and extreme cams is that at low speed, the valve inertia is low, and as you'll have "heavy" springs to get the valve closed quickly, at peak lift and slow speed there is time for the oil film to get squeezed out the gap between cam and lifter, leading to scuffing. (at high speed everything is slamming open at speed and so the valve spring load is busy getting used to decelerate the valve at peak lift, not pushing into the top of the cam lobe)
Unless you are running something truly radical, like say a lofting profile, i've never had an issue with a short 10 to 15m fast zero load run (say 3krpm) then get the engine under some load to start other components bedding down)
Engine is a 1969 2 litre Alfa Nord engine, and will be running 12.7mm inlet @ 261 degrees duration (0.05" lift), with a "modern" profile, i.e. the flank accelerates the valve very quickly and the cam has a relatively "broad" nose. The exhaust is 11.7mm lift with 247 degrees duration.
Thanks for the advice. I think I'll give it 10 mins at 3k rpm, then take it for a drive to get the rings bedded. Red line will be hard limited at 7k, so will limit the running in to say 4k for 300 miles or so (on 40w mineral oil), then swap to something better.
OH! its a bucket and shim engine? 
you will be hard pushed to f
k cam break-in with that motor far more tolerant than a conventional push rod motor like mentioned dont sweat it just drive it like mentioned already not seen a bucket and shim motor suffer cam or bucket failure to date due to improper cam break-in yet
you will be hard pushed to fk cam break-in with that motor far more tolerant than a conventional push rod motor like mentioned dont sweat it just drive it like mentioned already not seen a bucket and shim motor suffer cam or bucket failure to date due to improper cam break-in yet Gassing Station | Engines & Drivetrain | Top of Page | What's New | My Stuff