<VV> Cam Bearings, Proof is in the pudding

[Tony Underwood]

At 07:47 hours 02/06/2006, Smitty Smith wrote:

>
>From: JVHRoberts at aol.com
>Subject: Re: Cam bearings
>   ------------------big snip------------
>Building up the cam and boring the case is probably the simplest. Boring the
>case and fitting inserts is also a possibility. These would be the only two
>I would consider.
>   ----------------------------------------
>   Smitty says:  As long as we are using John's money, I don't care 
> how we do it.  I haven't investigated the cost of any of these 
> fixes so I don't know but if it gets into adding several hundred 
> dollars to the cost of an overhaul I will be looking for 
> options.  Like, I don't see the necessity of boring the 
> block.  Yeah I know.  The holes aren't round.  So which would you 
> rather have?  A shaft with .001 clearance in a square hole or a 
> shaft with .010 clearance in a square hole?  What is wrong with 
> getting each journal turned down to fit its own bore?  A lot of 
> people are talking about line boring the block but I am not sure 
> they have knowledge of tool availability to do the job.  Talking 
> about what they do for V Ws doesn't say the average shop can do it 
> for us.  I had a block in the 70s that had distorted Mains.  It was 
> only a couple of thousandths  I wanted to get it line bored to 
> clean it up and then use shims behind the inserts.  Couldn't find 
> anyone in Tidewater that would do it.
>  Tooling they said.  So next step would be for me or someone else 
> to get a cam done to fit a block, or prove the availability of 
> tooling to do a line bore.
>   When I asked this question in the first place, I asked what the 
> pros were doing about the problem.  I would prefer to not hear any 
> more from people who don't regularly build engines or from those 
> who built one 10  years ago and don't see a problem.  I can dream 
> up all kinds of solutions and in fact did address them to a friend 
> before I posted to VV.  So lets hear what you "have done" or what 
> you actually are "going to do", and get the word out on that.





OK... so far I've not heard anyone mention this:

...what about shaving something like .005 off each crankcase half 
along the parting surfaces to shrink the crank/cam bores, then line bore?

How far could you go with shaving the crankcase halves before getting 
into trouble with the hardware that bolts to the crankcase 
(bellhousing, front housing, top cover)?   I'd expect no issues with 
the head/piston/cylinder fit since the actual difference would likely 
end up ~.01 which is likely less than the production tolerances for 
pistons to head in the first place.   There's also enough slop in the 
bolt hole fit for the hardware to allow the engine to go back 
together without attacking the holes with a rat tail file.

If shaving .005 off each piece (.01 total) will get the tolerances 
between cam and bore within specs, why not do it?

Up through now, the issue seems to be an error/out of round bore of 
~.01.   The above machine work should fix this much  error.   Not 
cheap but it's gonna be less than welding/spraying the cam bores and 
line boring.



IMHO this is the reason for saving all those old low miles crankcases 
stuck in the rafters of the garage, on shelves in the barn, in 
corners of the basement gathering dust...

If the first go-around lasted 30 or more years before wearing out cam 
bores, wouldn't it be logical to expect at least half that much more 
life out of a good-original within-spec crankcase?    And just how 
many miles are typical Vair engines expected to endure these 
days?   (except for Smitty, whose half-million mile engines don't 
qualify on this logic)  ;)

Smitty's situation is where that good original factory spec crankcase 
in the rafters comes into play.


You can either pay for the welding/machining or stash a couple of 
good crankcases away for insurance.


Sure the military fixes crankcases by welding and machining.   Those 
guys get paid monthly and the rate never chances.   They do the work 
all day long, same pay, same product, same facilities, it's what they 
do.   They're in it because it's their MOS.

The guy at Boob's Automotive Machine Inc is another matter.   He's in 
it for the money and if he has little/no competition you're either 
gonna pay, or do without... or back up your parts stash with the 
stuff you will need to further the hobby pursuits.


I have good crankcases stashed away; for me this is all moot.


tony..