camshaft in a V8

[landybehr]

Hi,

I´m wondering about the strict procedure for running in camshafts on the RV8 when the engine is first started after a rebuild. It´s said that idling is forbidden. Rather you should rev it to at least 1500U/min, otherwise the cam would not get enough splash lubrication and had no chance to bed in correctly. Later camshaft wear will be the consequence.

Now .. if the camshaft is that much dependend on splash oiling in the first 15minutes of it´s life - why should that change later in it´s service life. It will have to face a lot of idling in traffic driving, and would get little oil then right as much as it does on the first startup of a rebuilt engine.

So .. I´d be inclined to think that premature (compared to the old 4cyl engines up to the TDI which have a very good roller-arrangement in that area) camshaft wear is related to the design of the block.

What do you think ?

[Paul Woodward]

I believe that's the recommended procedure for starting any engine for the first time, not just the RV8.

[bill van snorkle]

There never appears to be a great deal of oil circulating around the upper section of Rover V8's. Oil pressure and filtration is not as good as the old 4 bangers either, which never build up sludge or carbon on the moving parts even when they are absolutely knackered, burning lots of oil and never serviced. Doesn't seem to stop many of the V8's from accumulating some impressive mileages however, They do demand regular oil and filter changes however.

Bill.

[tacr2man]

A lot of the trouble is due to wear on the rocker shafts, that causes the drop in oil pressure, also the high temps in OZ dont help. I had extra oil cooler , no aircon rad infront of the normal rad and used 5/50 synthetic . Towed a big tandem axle caravan in 45c no trouble.

If you go to engine shops there is a special grease that you can get that you use on the cam when rebuilding just for the dry startup reasons.

[101nut]

If the cam doesn't get lube in the first few seconds after startup it'll be knackered which is why the special moly lube is sold for initial startup.

That doesn't explain the long period of high rpm though. It's nothing to do with splash lubrication as the oil drip feeds down the push rods from the rockers directly onto the followers and cam lobe. I think (and I'm happy to be corrected) that this high rpm is to make the bearing surfaces between follower and cam lobe work harden. At idle there is little stress on the parts, they rub together and wear. At higher rpm the stresses are much higher and change the surface structure of the metal surfaces causing them to work harden. Once hard (it only needs to be done once) they have a longer life ... This explains why if you get a reground cam they may wear badly due to break through of the hardened surface if not rehardened.

AndyG

[Andrew V8 RRC]

Hi , I have rebuilt a few V8 in the past years, and i always prime the whole oil galery befor startup by useing my modifide distributer on a drill to prime the system by powering the oil pump without starting the engine.

a new camshaft from a reputible company will come with the first start grease use it.

once your engine is set up to bee started go ahead and once it runs take it straight to 1500 RPM this wil give the best luberication and force out eny air keep the engin at this rpm for 4 or 5min.

This is also essiencial if you have installd new piston rings, the increased RPMs allow the rings to properly bed in in the important first few minutes.

If you need more information take a look on the RPI site , many tricks and tips to be found here.

cheers Andrew

[landybehr]

Hi AndyG,

I cannot recall where I read it. It was an US-internet-site, maybe from Piper or something. They said that the stress on the cam lobes is higher at idle than at higher revs. They explained it but I didn´t bother to remember Something to do with inertia (of the valves or springs) or so.

Unfortunately I had no special grease with my camshaft which came from one of the UK dealers. I used some MoS2 additive tp enrichen some MoS2 grease and mixed that with synthetic engine oil and hoped for the best. Too late to change anything by now.

[ENGINESPECIALIST92]

Hi AndyG,

I cannot recall where I read it. It was an US-internet-site, maybe from Piper or something. They said that the stress on the cam lobes is higher at idle than at higher revs. They explained it but I didn´t bother to remember Something to do with inertia (of the valves or springs) or so.

Unfortunately I had no special grease with my camshaft which came from one of the UK dealers. I used some MoS2 additive tp enrichen some MoS2 grease and mixed that with synthetic engine oil and hoped for the best. Too late to change anything by now.

The runing in procedure for camshafts with hydraulic lifters is diferent from solid lifters, The rover v8 engine is well known for having low oil presure on idle so when you fit a new camshaft and hydraulic lifters as you should, the hydraulic lifters have air in them so to help bleed the air out and to lessen the stress on the components you run the engine at aboul 1500/2000 rpm for about 20 minutes.

This is how it is done by profesionals, Weekend warrior/part time grease monkeys may do otherwise at there own peril !!!!!!!!.

[Bull Bar Cowboy]

The runing in procedure for camshafts with hydraulic lifters is diferent from solid lifters, The rover v8 engine is well known for having low oil presure on idle so when you fit a new camshaft and hydraulic lifters as you should, the hydraulic lifters have air in them so to help bleed the air out and to lessen the stress on the components you run the engine at aboul 1500/2000 rpm for about 20 minutes.

This is how it is done by profesionals, Weekend warrior/part time grease monkeys may do otherwise at there own peril !!!!!!!!.

Well, if you really are an engine specialist then I’m glad that you haven’t built any engines for me as that’s a carp answer that is a long way from the truth ……..as it has FA to do with oil pressure, and is not peculiar to just the RV8.

The cam running procedure of 2000 to 2500 rpm for 20 minutes or so applies to ALL flat tappet cams ………….it is to correctly bed and work harden the surfaces ………….and to ensure that the ‘splash’ lubrication of the lobe to tappet surface is adequate ……… this applies to ANY engine with a FLAT tappet cam whether it is solid (follower type) or hydraulic.

IIRC it is because modern oils (and I’m talking in the last 10 years) contain very little zinc, which is imperative for the bedding in process. During the build, if you don’t have any specialist cam lube to hand then a little moly slip (that is oil soluble) will do the job.

Yes, RV8 engines were renowned for very bad cam wear on inlet ./ Ex lobes for cylinders 7/8, however, much of this was due to inadequate oil changes throughout the engine life……… and this is also tied into the ‘tilted head’ problem that used to allow the head gasket to slightly blow into the valley and quickly contaminate the oil.

The Rover oil pressure is adequate to do the job when the engine is in a serviceable condition ……………..

Here some reading material…………. I’ve have got an in depth explanation from one of the cam manufacturers somewhere ………….I’ll try to dig it out.

FT_Cams.pdf

Ian

[Hybrid_From_Hell]

Spot on Ian.

If you can Soak hydraulic lifters pre fitting in a tub of oil pre fiiting, a week did mine, rattled only then for a few secs on starting

Nige

[Bull Bar Cowboy]

There is actually an issue with pre-priming the lifters , especially if you are using a very high lift long duration cam ........... it is posible to get an hydraulic lock and the lifter may hold valve open with disastours results ............... very unusual but it has happened in the past, mainly on ford V8's ............................ an easy way to overcome the problem is to fit the lifters empty, but align the oil priming hole with the priming oil gallery. Before starting the engine, prime the oil system by using the electric drill method on the pump to create a respectable pressuse that forces oil into the lifters .................. then manually turn the engine over by hand for at least 2 revoultions ..................

Ian