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Re: Camshafts

To: "Charley & Peggy Robinson" <ccrobins@ktc.com>, "Charles Christ" <cfchrist@earthlink.net>
Subject: Re: Camshafts
Date: Mon, 9 Oct 2000 21:29:08 -0400
Cc: "Spridgets" <spridgets@autox.team.net>
Ya know, I read this earlier today, and I've bee wondering. (sorry have a 
cold, can't pronounce the n's too well) I recently readjusted the valves 
in the Midget. Man were they off. Now a few weeks later, I find metal in 
the oil. Tonight (third time in 2 weeks), I changed the oil an found no 
metal in the oil. But it is starting to show symptoms of the valves 
needing readjustment. You know, iccky idle, stumbles off line, etc. I 
have collected some oil to send for analysis, but I am not sure that 
helps me. Maybe help somebody else. 

I am still rebuilding an engine t' stuff in this baby.  The new engine is 
at the AAACHOO machine shop, (sorry had to wipe off the keyboard). and I 
am thinking I am gonn ask them to bore the oil galley, I have been 
advised to do this, unsure exactly what it acomplishes, but what the hey. 
It's only money. 

Still not convinced on the line boring and cam barins. I have yet to see 
anything other than anecdotal references to failure in this area. 
Explanations on how and why this might occur, yes, real failures - no.

Trust me, I am not a complete dunderhead (worked on industrial engines 
for yars), and I expect that I will have the cam bored, I just wanna know 
why. On a race engine that has to go time after time etc, sure. On a 1500 
Spitfidget, Nah. (oh yea, sanding the bearings - NO FREAKING WAY!!!!) I 
wanna hear from the engineers that designed this engine, or I wanna hear 
about a real failure, not some theory, not a ideal race prepped engine, a 
real world failure. One that says this design is f*%ked up. I have yet to 
hear that.

OK here is a real world reference. I have a Midget 1500 with over 90,000 
miles. Rebuilt once for new rings.  At about 30,000 miles. Went 3 years 
driven, 6 years parked (and that has to be good on the oil, even though I 
changed it several times in that span), 3+ years driven. Ran for nearly 4 
years with out a rebuild, now I find metal in the oil. Could be as simple 
as the thrust washer, could be mains or rods. Don't think so, as it ain't 
making a bunch of noise and the oil pressure is the same as it was 3 
years ago when I put a real oil pressure gauge in it. 'Stead of that 
freaking idiot light. 

(Sniffle)

Now it seems like the valves need to be adjusted again. That could be a 
cam failure, it could be that I just didn't do it right the first time. 

Not sure how the 948's and 1275's are set up, but the reality is the oil 
from the pump in a 1500 goes straight to the cam journals and a lack of 
oil in that area can only be from a lack of oil or a failure of the pump. 
Failure of the pump is not real likely in this situation as I have 75 lbs 
at cold (man I hate the sniffles) idle, and 20 or so at warm after a long 
run. And it ain't changed in 10,000+ miles. 

Real world failures only, no more theory.

Larry

>>>>On 10/8/00 10:45 PM so and so (Charley & Peggy Robinson) said. (And I 
quote:)

>Larry, et al,
>
>  Hmm,  I think thing need to be put into perspective here.  Most
>engines have separate "cam bearings" (sleeves) installed into the block
>for the cam to spin within.  Some don't.  The Spridget 1500CC engine is
>a case in point; its cam spins within machined bores in the block.  If
>the cam bores in the block get worn out of tolerance, the oil pressure
>could indeed suffer.  Also, if the bores wear too much, the cam will
>flex under the valve spring pressure.  The cam can break because of
>this, but the most frequent sign of this is that the valve lash won't be
>constant.  I had a Fiat 128 Spyder DOHC engine that manifested worn cam
>bores in this way.  The fix is, reputedly, to bore out the cam bores for
>bearings and run an XXX cam.  Take your pick; I've been told of several
>different to use.  
>
>  My thought is that I'd have to see signs of real probs in the cam
>bearing area before I'd bother.  By signs, I mean a real good going-over
>of the cam  bearing journals on the cam for signs of loss of alignment,
>out-of-round, etc.
>
>  Hope this clears it up a bit,
>
>
>  CR


Larry Macy
78 Midget

Keep your top down and your chin up.

Larry B. Macy, Ph.D.
macy@bblmail.psycha.upenn.edu
System Manager/Administrator
Neuropsychiatry Section
Department of Psychiatry
University of Pennsylvania
3400 Spruce St. - 10 Gates
Philadelphia, PA 19104

 Ask a question and you're a fool for three minutes; do not ask a 
question and you're a fool for the rest of your life. 


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