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Re: type3-d Digest V01 #673

Gene Berg said that he liked the chrome-moly pushrods because if you get the
engine hot the increased valve lash would create noise that is obvoious to
the driver. He said (and I may be paraphrasing here) "I prefer to be warned,
how about you?" I have a set for my 2110 that I'm building (but I have no
practical experience as of yet.)

The Amazing Kelly Pitt.

> Subject: Re: [T3] Further research and experimenting material!
> Chromoly push rods expand  about half as much as stock alum. PRs. I know, I
> tested them in my oven and used my 12" dial calipers. Alum @ 200F grew
> .016", CM @ 200 only grew .008". Same length push rods.
> Tom
> Tom's Old VW Home
> http://home.att.net/~drsowatt/index.html
> ----- Original Message -----
> From: "Hal Sullivan" <tristessa@pon.net>
> To: <type3@vwtype3.org>
> Sent: Tuesday, November 06, 2001 10:37 PM
> Subject: [T3] Further research and experimenting material!
>> At 08:32 PM 11/6/01 -0600, Jim Adney wrote:
>>> The way I see it, however, the biggest contribution comes from the
>>> differental thermal expansion of the various parts and the fact that
>>> the cylinders and head studs are steel while the pushrods are
>>> aluminum (which expands 3x as much as steel.)
>> Now *this* I want to check out.  I'm using chromoly pushrods in one of my
>> aircooled VWs --  I'm going to have to start measuring my valve lash both
>> cold and hot, keep a chart of what I find.
>> I've heard theories that the reason for the valve clearance is due to the
>> different expansion rate of the aluminum pushrods relative to the rest of
>> the engine.  Following that theory, chromoly pushrods should expand at the
>> same rate (or nearly so).  If that's the case, would the 004/.006
> clearance
>> be as necessary in engines that use chromoly pushrods?

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