Cracked Fiat camshaft cap

[TipoBoy]

Hi,

I've noticed that one of my camshaft caps appears to be cracked. It's the one between cylinders 1 and 2 on the intake camshaft. I'm not sure why this camshaft cap is needed. All the other camshaft cams sit between each pair of lobes for the valves for each cylinder but this is an additional cap.

Will it be okay? If not can I get another cap machined or try and use one off a different head? I know they are machined together with the head.

If it fails what is the potential damage?

Thanks

John

[robert kenney]

Those don't really look like cracks but more like die casting marks. Have you removed the cap to inspect the bearing surface?
To make sure use a piece of fine abrasive paper and smooth the area to see if they are indeed cracks or not.

Robert

[TipoBoy]

Hi Robert,

Thanks for your advice. I removed the cap and the bearing surface was perfect. I hand sanded the area around the cracks using some fine wet and dry paper being careful not to go anywhere near the bearing surface. After 10 mins the marks were completely removed from one side and substantially reduced on the other side.

John

[Guy Croft]

You have done the right thing cleaning up around the cracks. It's called 'chasing out' and you do it to assess the depth and extent of the thing. Unless you determine that you can't repair. Your cracks may well be superficial ie: not deep and could be the result of casting temperature related problems and they are, in that case, (as I would say) 'not functionally significant'.

If actually cracks - and if they had been generated by cam seizure - which they can be - the housing would have distorted and melted and there would be extreme galling and pairing in the journal housing (the round bit the cam runs in). But aluminium alloy is so ductile that it tends to just wear away by those means rather than crack.

Cracks in non ferrous materials like alloy can only really be verified by dye penetrant but a thorough visual with a magnifying glass is a start. If - under closer examination the cracks have spread in any of the directions shown in my photo below (red lines) then the housing is unserviceable really. That said I have never seen significant cracks caused in normal - or even abnormal operation on those parts and would not expect to.



GC

[TipoBoy]

Thanks Guy,


John