CAM Bearing Opinions (one for the engine builders)

Si.G · Postby **Si.G** » Tue Nov 30, 2010 12:11 am

Hi Everyone,

I have pulled apart my spare engine to rebuild and found the following -

It does not look like the bearing has 'picked up' and the bottom part on the head is spotless, which is further evidence to say it has not 'picked up'.

It looks like a casting issue, like there were bubbles in the metal. Has anyone seen this before?

Do you think I should get a new one or stay with this one??

Thanks
Si.

Si.G · Postby **Si.G** » Tue Nov 30, 2010 12:18 am

One another thought

When the bearings are machined in to the head, do they put all the bearing caps on and the boar the bearings to get a perfect match between the head and caps or machine the head and caps separately?

Obviously this will affect the decision to get a new cap or not
Si.

fattima · Postby **fattima** » Tue Nov 30, 2010 7:15 pm

I would say the head is bored with the caps in place, this is how it is usually done.

It does look like a casting issues as you say.

tbro · Postby **tbro** » Tue Nov 30, 2010 8:05 pm

Si.G wrote:One another thought

When the bearings are machined in to the head, do they put all the bearing caps on and the boar the bearings to get a perfect match between the head and caps or machine the head and caps separately?

Obviously this will affect the decision to get a new cap or not
Si.

Oh! Bugger,
Hope you haven't spent any money on this head yet, cause its kangaroo Ted.
You have 3 choices, (1) another head, cheapest way out (2) Have all the caps faced, line bore the caps to return to std specs, (3) machine caps to accept slipper bearing if you can find any to suit!!!.
For the price of a second hand head I think its probably the best way out, haven't seen a porous cast like that for bloody years but then it is a old casting :lol:

That type of casting remindes me of Lynx Engineering manifolds!!!!!!

Terry

Si.G · Postby **Si.G** » Wed Dec 01, 2010 12:03 am

tbro wrote:
Si.G wrote:One another thought

When the bearings are machined in to the head, do they put all the bearing caps on and the boar the bearings to get a perfect match between the head and caps or machine the head and caps separately?

Obviously this will affect the decision to get a new cap or not
Si.

Oh! Bugger,
Hope you haven't spent any money on this head yet, cause its kangaroo Ted.
You have 3 choices, (1) another head, cheapest way out (2) Have all the caps faced, line bore the caps to return to std specs, (3) machine caps to accept slipper bearing if you can find any to suit!!!.
For the price of a second hand head I think its probably the best way out, haven't seen a porous cast like that for bloody years but then it is a old casting That type of casting remindes me of Lynx Engineering manifolds!!!!!!

Terry

Bugger indeed, given that the engine is intended to be a high reving NA engine, my concern is that the rest of the cap has bubbles in and hence will be a point of weakness.

I am only in the processes of taking the engine appart, so no investment at least.

In terms of options, does an NB6 head fit a NA6 block? If so, I will get a head from the uk with solid lifters and kill two birds

Si.

manga_blue · Postby **manga_blue** » Wed Dec 01, 2010 11:21 am

Do you have a machine shop lined up yet for the head work? If so then I'd take the whole head down to them for an opinion, expecially if they have experience with sports engines from dodgy casters (ie italian cars). If it's just a cap then they may be able to bore in a replacement.

I've had problems buying a used NA8 head. They go soft, mainly on the head surface in the exhaust port areas. Softish ones are good enough for stock use but mightn't stand up to mods and regular track days. Corrosion, warping, cracks and overshaving are other problems you can encounter with used heads.

It worth getting them to test yours before you commit to anything anyway. As it turned out the shop that I used was able to source and test 4 or 5 heads for me before I needed to shell out for a good one.

bigdog · Postby **bigdog** » Wed Dec 01, 2010 2:49 pm

Are the marks are only on the one bearing cap? If so the head should be fine, just replace the bearing cap and have them line bored, then fit new oversize bearings to suit the bore size. As manga said - take it to the head shop for their opinion before you spend any $$.

Si.G · Postby **Si.G** » Wed Dec 01, 2010 10:46 pm

bigdog wrote:Are the marks are only on the one bearing cap? If so the head should be fine, just replace the bearing cap and have them line bored, then fit new oversize bearings to suit the bore size. As manga said - take it to the head shop for their opinion before you spend any $$.

this is the only cap has the casting issue, all of the others are in really good condition.

I think you are right. I need to take the bottom end to the machine shop anyway, so I will take the head along and get an opinion.

Si.

Postby **NitroDann** » Thu Dec 02, 2010 5:59 pm

As has been said they are line bored so you cannot just replace one. Buy a reconditioned head with solids. My B6 runs 8500rpm all day long with the solids but it didnt like that too much without them. Theres nothing practical you can do with that not considering the price of a recon b6 head from an astina or something .

Cheers,
Dann