Fitting brand new camshafts

[wader3]

I've got some new old stock camshafts and after fitting without valves, will not turn. I noted the journals of the new ones are black, whereas the old ones are obviously polished - is there some prep work to be done on new ones does anyone know? I re-fitted the old one to check and turns fine.

[flying farmer]

First measure the bearings on the new and old camshafts, you may find the old bearings are different sizes along the length of the shaft.
If the new shafts measure ok then it is probably your heads that are warped.
When heads are skimmed after warping, it is only the face that is straightened, the camshaft bore remains bent.
What usually happens is that the cam wears its way into the bearing caps, and some metal is lost from the camshaft itself, until it can turn freely again (unless the timing chains snap with the extra load)!
The heads can either be line bored back to straightness, or it is possible to carefully rub down the high bearings with fine emery wrapped around an appropriately sized socket, then flat off the base of the bearing caps to correct the clearances
I find this is necessary on most of the engines I have rebuilt
The best way to check for straightness is to place the new cams across the bearings without the caps fitted, and see if they will rock from end to end. I normally find the high spot is in the middle rater than the end
Neil

[V Mad]

If they are black it sounds like they have not been machined. Measure the old and compare with the new. I suspect the new ones will be much larger.

[wader3]

Thanks Neil and Chris, a quick measure suggests it's the same size as the old one, and can't detect any rock, which is why I was thinking it's something to do with the matt finish. There not completely black Chris, more grey matt but smooth. The old ones are more like a mirror.

Rob.

[stagmuffin]

Thanks Neil and Chris, a quick measure suggests it's the same size as the old one, and can't detect any rock, which is why I was thinking it's something to do with the matt finish. There not completely black Chris, more grey matt but smooth. The old ones are more like a mirror.

Rob.

the reason they are a matt dark finnish is as a result of the hardening process they are ground and heat treated .the surfaces of your old cams have been polished in the bearings over many thousand miles hence shiny. as niel says warped head possible .you could blue the cams in the bearings without caps to see what result shows and identify the fault or just get a machine shop to rectify via line boring .

[flying farmer]

I would tighten down the bearing caps one at a time and see if it is just one that is tight, or all of them.
If it goes tight on just one, see if you can get a feeler gauge under the shaft in case the bearing has sunk at that point.
You could always give the cam bearings a polish using some 1200 grit wet and dry
Neil

[Bandit1200]

I can recommend a good machine shop with extensive experience of Stag. I have no connection other than that of a satisfied customer. PM me for details
Steve

[elvimto]

Your head should be completly stripped no valves etc. put the cam in the head and feel if it rocks that should tell you if the head is warped. You can use marking blue to tell if you are making contact. i replaced a cam on my car same thing the colour is from the hardening process, just give it a light touch with some fine emery paper, set it in the head and apply some blue to the cam bearings and turn it, remove the cam and check for contact it should give you an indication of your cam fit. Get the top half of the bearing caps and start to fit them torque them up one at a time and feel how the cam turns this will tell you if you have a tight spot and where it is. The end bearing cap the one furthest from the timing chain will have a bit more clearance than the rest due to the fact that its the last one to get oil and it tends to wear a bit. I think the clearance is .0015 thou you can check this with plasti gauge or feelers just as Neil says you may have to do a bit of tuning or you can have the camshaft bearings line bored I think Paddocks sell liners for this job. Good Luck

cheers Stuart

[wader3]

Thanks all, it seems to be the end one that locks it up, so I'm hoping just a bit of fettling will cure it. For a break I put the crank in which turns lovely.

Rob