Align Bore Advice Needed

[C J Murray]

So you do a spot on perfect case and install a camshaft that is FOURTEEN DEGREES WRONG? That must give a great result.

Hey, you started it Dad.

[Jacques Lefriant]

yes but i have to give CJ a hard time sorry for the rant.
j

[C J Murray]

Sorry if my question initiated any ill will.

But if I am reading Jacques' recommendation correctly and taking in Vic's, CJ's and Dick's inputs: while I'm not prepared to strip my customer's case mating surfaces to lap into spec, if I can make sure the new bearings are NOT steel-backed, then we should be okay without boring.
Is this correct?

Jacques just likes to wind people up. No harm done. We enjoy it.

The steel vs aluminum thing is not a big deal to me but it is to some. Measure the bearing ID with the case torqued and see what you think.

[Jacques Lefriant]

CJ
That aftermarket cam has been around for at least 30 years every shop that has replaced a camshaft has used them. When someone takes a cam to a cam grinder they usually opt for a regrind with a little more performance.
j

[C J Murray]

Jacques, I will bet you one of your Carrera 2s that the faux stock cam makes less power than the factory cam.

What still baffles me is that you are talking about "better" and "more performance". S_T_O_C_K is defined pretty clearly and stock is not what the faux "stock" cams are. They aren't even close.

[Jacques Lefriant]

CJ
I don't use faux stock cams for the Carrera 2 the other cams that are available make more power anyway.
i know that the aftermarket 356/912 cams are not stock but almost everyone seems to like them. Also if you like numbers the stock .002" or .05mm of crush will vanish at 100*C/212F if you use the steel backed bearings yes the ID will be better but the case will pound out and require rectification. I consider the bearing/line bore issues to be of more importance to the longevity of the engines than camshaft specs. I hope that our readers will benefit from our discussions and i only wind you up to keep it interesting keep the faith and AMDG
j

[C J Murray]

I consider the bearing/line bore issues to be of more importance to the longevity of the engines than camshaft specs.

With your "stock" cam you need to keep the rpm around 7000 to move the car so you had better have a good bottom end!

[Jacques Lefriant]

roller crankshaft ti valves etc

[Olivier Auvray]

Just one question: why the factory had a very tight tolerance for the main line bore?

[Jacques Lefriant]

Salut Olivierm
I would think that the crush and roundness are important if your oil pump is working well even extra clearance is no big deal.
j

[Steve Hatfield]

Me again, line bore question but a different engine but also for the street:
Case #s over”
Main no. 1: .0005”
no. 2: .0025”
no. 3: .001”
Align bore or no? If no then
Looking for alloy std case, first over (.010”) 50mm B (solid #3) vintage mains.
If yes then.010/.010 s
Thanks

[Jacques Lefriant]

try EBS racing in Reno I think they are out of +10-10 but they have alloy bearings. I always say first under on the crank but you are correct that the shell is bigger.
j

[David Nicholls]

The camshaft doesn't have any bearings to support it in the case.
There's a lot of emphasis on crankshaft measurements and line bores, but little or none regarding the camshaft.
I would have thought that you cannot do one without the other.

A great discussion, thanks gentlemen.
David

[Ron LaDow]

The camshaft doesn't have any bearings to support it in the case.
There's a lot of emphasis on crankshaft measurements and line bores, but little or none regarding the camshaft.
I would have thought that you cannot do one without the other.
A great discussion, thanks gentlemen.
David

The cam does have bearings; the cast-iron cam, well oiled, spins in aluminum bearings, exactly as the Cosworth DFV cams operate, for instance.
Back when the cases were not as 'used' as they are now, the typical process was to lap the case halves on the mating surface and re-cut the mains to standard size. In which case the cam bearings were cut back to standard also.
More recently, when the mains need a cut to oversize, the cam bearings aren't affected at all.
The loads are not drastically asymmetrical as are the mains and the rods, and then they are generously-sized and get a good supply of oil. So there's rarely a reason to fiddle with them.

[Craig Richter]

Thanks for the terrific discussion. Reminiscent of many talks with Ray Litz years ago, which always left my little pea-brain spinning. What a pleasure it was to work with such a great machinist, and you guys are cut from the same cloth.