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Re: Valve settings

To: "Spridgets" <spridgets@autox.team.net>
Subject: Re: Valve settings
Date: Wed, 13 Feb 2002 08:21:21 -0500
References: <B88F1B51.AA3B%macy@bbl.med.upenn.edu>
Well yes, you will want to do it again.

I suppose that theoretically you could figure out what the cold clearance
was supposed to be if you have the hot clearance, expansion coefficients of
all the involved materials, knew what the "hot" temperatures were of each of
those items, and their relationships to one another. Remember, _everything_
expands when it gets hot. That includes the valve stem, rocker shaft
support, head, block, pushrod, lifter & cam (did I miss anything). Add to
that the fact that some are on one side of the rocker ratio and some are on
the other!

Undoubtedly, the reason that the clearance is specified hot is that it
eliminates the potential variation of all these, possibly
aftermarket/performance, items. The factory can specify cold because they
are working with known constants (within "normal production tolerances"
anyways ;-).

1972 Midget
1998 Safari
1999 9-3
1964 (Me)
I enjoy long walks. Especially when they are taken by people who annoy me.

----- Original Message -----
From "Larry B. Macy" <macy at bbl.med.upenn.edu>
To: "Spridgets" <spridgets@autox.team.net>
Sent: Tuesday, February 12, 2002 7:19 PM
Subject: Valve settings

> Call me a DCO.
> I have been a bit concerned about the way my car is running after I got
> new exhaust. Soooo last weekend I went and did some adjusting. I checked
> valve clearances and adjusted the carb (still the DGV, no SU's YET). Well
> set the valves to the stock setting and it seemed OK. But then I realized
> weren't quite right. DUH I put a modified cam in (JERK!!). So I went and
> checked Ted Schumacher's email he sent me, last year, about timing this
> Well, stock is .025 cold. Ted told me (memory is such an evil thing) .018
> intake and .020 exhaust HOT.
> Now if memory (see there is that THING again) serves correctly heat
> stuff. So I think Hot clearance should be tighter than cold settings. So I
> may not be too far off, but I am still off, I think. Will have to do it
> over again anyway, but thought I would ask, I didn't screw up too bad did
> I??

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