Camshaft bearings

[gundersen]

I just got my new VVC head taken apart to install the piper vvc-to-solid cams conversion, and I am not sure I like the looks of the camshaft bearings.

I am not an expert, by any definition 😬, so could some of you gurus have a look at them here and see if they look ok?

[gundersen]

97 views and no replies...have I finally succeeded in muting the mighty POBC?

Don't let the "guru" part hold you back, if you have looked into an engine more than once you are at least twice as experienced as me

[Klunk]

I'll have a go then ,

 

I've not had my k series apart (yet!) but based on what I can see that looks more like porosity. I'm basing this on the fact that if it was debris it would have worn a groove right around the bearing. Also if you look at the last picture where the oil feed is, between the two bearing surfaces, you still have the pitting despite this being a non contact area. However, there do seem to be some grooves on the bearing surfaces in that picture, or is that just the lighting? What do the surfaces feel like?

 

Compared to a zetec head I've got in the garage, the surfaces look awful but that's like comparing apples with pears. Any luck with google images? Failing that, hopefully Oily will see this - might be worth dropping him a line.

 

Regards,

 

Giles

 

Edited by - Klunk on 29 Dec 2012 11:35:25

[gundersen]

Thanks for giving it a go Klunk

 

As you mention with the Zetec head, I was expecting to find a mirror like finish on these...so I was a bit disappointed to find this lunar crater landscape

 

I have tried running my fingers across it, and while it in no way feels like a mirror it does not feel as bad as it looks.

[Klunk]

Another thought Do you have the original camshafts? If so, what's the finish like on their bearings? I appreciate it's less likely to mark than the head but there should be some indication if debris was present in the oil.

 

Giles

[Mankee]

I am no means an expert, but I am subscribing to this thread with interest! 😬

 

Did you buy a complete engine, Bo? The first VVC 160 lump I bought was absolutely trolleyed; 120,000 miles, probably about 2 oil changes in its life, head had gone soft, even the block had gone soft. I can't remember exactly what the camshaft journals were like, but they were probably much worse than yours. And the engine was running "fine" before it was removed.

 

I think there might be some clearance data in the Rover K-series engine rebuild manual. What's the rest of the head like, especially the gasket surface?

[gundersen]

@Klunk: Good idea :)

Exhaust end

Exhaust middle

Inlet end

All bearing lands (is that what they are called on the cam?) have groves that you can feel if you run your nail across them ☹️ I suspect this is not good.

 

@Mankee: Yup, I bought a complete engine that was running "fine" Supposedly it should have done 45,000 miles. The rest of the head looks fine, and there is no pitting or anything on the gasket surfaces. It has the upgrade 160 pistons, so I was hoping to get a low 200bhp from it...

[Klunk]

Just googled "camshaft journal pitted yotatech". It's not a k series but the same issue. Click on the picture of the journal shown and read the thread (quite along way down). Interesting reply by someone.

 

Giles

[Mankee]

I think this may be the thread that Giles speaks of:

 

http://www.yotatech.com/f115/22r-head-gasket-replacement-251427/

 

Post #15.

[gundersen]

There is also this thread which shows some of the same symptoms, how ever it is on a bike engine

 

Just to be clear, it is the cam journals/bearings that has groves in them, the cam lopes are fine and without scratches or marks of any sort.

[gundersen]

I have dealt with many old school machine shop guys and i would ask about a pit or a scratch somewhere...and they would always tell me that it is just another place to capture some oil and lubricate the part better...

Heheh, perhaps it is just me being pedantic. The guys in the bike thread where also very laid back about a bit a groves...

[Klunk]

Thanks Mankee, that's the one - I struggle to do the link think on my phone!

 

The cam does look worn on the journals. If you were keeping it as a vvc I would throw it back together and run it till it rattles! My guess is you're going to a solid cam and I'm not sure I'd want to risk knackering a brand new cam. That said, you may not notice for many thousands of miles!

 

That thread does remind me of a mod to a camshaft bearing on my old vauxhall nova. You had to drill a hole half in the end of the camshaft and half in the head to improve lubrication. Given my lack of knowledge when I did that, the car lasted for many years before it died of something completely different.

Giles

 

Edited by - Klunk on 29 Dec 2012 12:35:54

[Roger King]

It's never possible to be certain from photos, but you may be OK.

 

You need to measure both the journals and the bearing surfaces for wear. If they are within tolerance, you may be able to mount the cam in a lathe and polish the journals clean with very fine emery. Quite often, this sort of apparent wear is far smaller than it appears visually (even if you can feel it) and it will clean up quite easily.

 

The pitting in the carrier bearing surfaces may well be just because of voids in a poor casting. In themselves they won't necessarily cause problems and, as others have mentioned, may actually hold a little oil and assist with lubrication. There are quite definite score marks there which would be indicative of poor oil filtration, but the question is whether or not they are as bad as they look. If you clamp everything up and measure the sizes of the bearing surfaces you'll soon see if there's any actual wear there. I would suggest that if they are within tolerance, they'll be OK to go again provided there are no horrendous score marks that I haven't noticed. I'm not recommending this, but it is sometimes possible to clean up such marks with a light going over with a Scotchbrite pad: if they do clean up like this they are really only superficial.

 

Edited by - Roger King on 29 Dec 2012 16:55:25

[diggerman]

The bearing surfaces are not that good. Looks to me like at some stage the cam has suffered poor lubrication and that there has been a tendency for the the bearings to 'pick up'.

 

The old cam would probably go on for ever but the new cam will suffer mirror image damage to the current state of the head journals. That probably wouldn't be catastrophic but during the run in stage may result in rapid initial wear.

 

If you go ahead with installing the cam, I would make sure that the oil supply to the journals is not impeded in any way and that the new cam, installed with no valves, turns freely with no apparant tight spots.

 

Hope it goes well.

 

Peter

[gundersen]

Hi Roger and Peter

 

Thank you both for your input.

 

@Roger: The old cams are going in the bin (or perhaps free of charge to a needy soul), so I am not too worried about them.

Am I correct in assuming that to "measure the sizes of the bearing surfaces" I will need some Plastigauge?

 

@Peter: That was exactly my fear, that I will (as Giles put it) knacker the new cams.

 

The scoring is not that deep, so I guess I will measure the clearance and see if it is within tolerance, and if it is go ahead and give it a shot

[Roger King]

These are not bearings in the sense of being a shell with a soft white metal or lead/indium facing. They are just bores in the aluminium so it is perfectly acceptable and more accurate than plastigauge to use a bore micrometer for measurement. It is however important that all parts are clamped together with the correct force at the time.

 

Plastigauge will give nothing more than an indication of the running clearance, but it will tell you nothing about the actual size of the bore. For example, if you had and oversize bore AND an oversize cam the plastigauge could still show an acceptable reading.

[gundersen]

Ok, but isn't the clearance the important bit here? Just asking because I am unable to find the actual size measurements for the cam "bearings", I can only find clearance tolerances

[Roger King]

True, the clearance is important, but plastigauge is a bit vague to say the least. I would suggest measuring your new cam journals and then measuring the bearing bores to see if sizes are OK.

 

You also need to check the bearing bores are in line. In the absence of the correct equipment for this, first check the running clearances are fine on all bearings and then assemble the cams into the head without the valves. The cams should turn relatively freely if all is in order. This isn't a perfect check, but it gives a good indication.

 

Edited by - Roger King on 30 Dec 2012 00:51:18

[gundersen]

Hi Roger,

 

Thank you for the advice, it is much appreciated 😶‍🌫️

 

I am off to the local version of Halfords to get the necessary tools, and in the words of the Guvenator "I'll be back!"...with an update when new years preparations and pregnant wife allows

[gundersen]

Our local Halfords clone (Biltema) didn't have a micrometer, so I had to do the measurements with a digital caliper

 

New cam sizes:

Inlet: 40.00mm

Exhaust: 24.52mm

 

Bore size, clearance:

Inlet, front: 39.94mm, 0.06mm

Inlet, back: 39.95mm, 0.05mm

Exhaust, front: 24,54mm, 0.02mm

Exhaust, back: 24,49mm, 0.03mm

 

According to the service manual, the clearance service limit is 0.1mm and 0.15mm, so this is within specification even accounting for the lack of liquid gasket between the two surfaces 😬

I gave the bearings a couple of "scrubs" with 1200 grit wet sandpaper, and that cleared up most of the groves. So I suspect that they look much worse than they actually are.

 

Then I removed all springs (what a pita, I need a better spring compressor as it can't reach the middle four springs 😔), and mounted the new cams.

The exhaust cam spins freely, while the new inlet cam is locked quite tightly in place. I can barely move it without the cam carrier on, but as soon as that is fitted (not even tightened) it is unmoveable I applied fresh engine oil to all journals and bearings before the test...

 

Is this the point where I throw in the towel and ask someone who actually knows what they are doing to have a look at the head?

[Bio]

Just try fitting the OLD inlet cam and see if it spins freely, if it does measure the diameter of the journals and compare with the new cam, if all looks good the end float could be too tight.

 

John

[oilyhands]

It could be endfloat but It is not uncommon for one piece cams to have a problem turning in a VVC head,this is because the cam bearing machining is not done by conventional line boring from one end as this is not possible with the stepped bearing sizes, the outer bearings are machined from each end in turn and this can lead to a mis alignment of the front and rear bearings. In the VVC system the front and rear cams are separate and are driven independently of one another so any misalignment is unimportant provided the cam clearances are OK. I suspect that this has happened in your case and that the reason the cam locks is because the bearings are slightly out of line.

 

When this happens is is necessary to ease the bearings in the head and ladder a little, I normally bolt the ladder down with some thin paper between the surfaces and then turn the cam, this will mark the bearing where it needs relieving. Normally I use a large diameter mandrel and some 800 grit wet/dry to ease the bearing in the areas that are tight. It is an iterative process which culminates in doing the same with the paper removed. Once the cam turns perfectly with the paper removed and the cam ladder properly bolted then things are pretty much as good as you will get them.

 

You will find that the smaller diameter bearings will need easing here and there as well.

 

Try turning the cam with the ladder off, then put the cam in the ladder on its own and do the same, this may help determine exactly what the problem is as the end float is governed by the ladder and the width of one of the cam lobes

 

Oily

 

Edited by - oilyhands on 31 Dec 2012 10:19:22

[Jason Plato]

from my learnings, when the head is finally bolted and torqued onto the block the whole lot of clearances all change again ...

[gundersen]

Thank you Dave (both of you ), the advice is much appriciated. I will give it a go and see if I can get it spinning.

[diggerman]

You need some of this. Engineers blue

 

Smear it on the bearings. Assemble as described by Oily and when the cam is turned it will rub off the blue at points of contact. This will help identify high spots.

 

Peter