Scott,
I just went thru this on a TR4 - I assume your dealing with a Spit,
so my #s won't help you. But... contact your cam manufacturer for the
specs. For the TR they were 100lbs at 1.625" installed height. They
didn't give a spec for rate so I didn't worry about it. However, the
very cool, computerized, "spring dyno" I used, calculated the actual
rate at about a 293 average for all 8 [sounds like a very nice number
but actually means nothing to me!].
To measure, you need to mic. the retainer thickness [in my case .
135"] and add that to the installed height. The total will be the
number you're looking for and at that [installed] height you want the
spec number given. Mine were a bit stronger than spec at 109lb avg.
but within my comfort zone.
Measuring the [actual] installed height is the tedious part. It is
hard to get any measuring device in where you need it, so make
yourself a gauge. I took a piece of straight, stiff wire and cut it
to 1.625". The idea is to measure between the spring landing at the
head and the landing step for the outer spring on the retainer. One
method [easiest] is to install the valve, retainer and keepers but no
springs and pull to full extension and measure - I found it much more
accurate and only a bit more time consuming to assemble each valve
using only the inner spring. Now stick your gauge between the spring
landings and use feeler gauges to figure the gap - this number will
be the height of any shims you may [probably] need.
Remember that no two valves are likely to be the same. How much each
valve and seat has been ground dictates the height.
This is just my way of doing it. I'm sure others have different
[easier?] ways. Hope it's of some help.
Greg "Lunker" Hilyer
TR4 #314
Albuquerque NM
On Jul 15, 2008, at 8:59 PM, Scott Cypher wrote:
> Can someone walk me through how to test a valve spring? I have the
> spring tester you put in a vice as well as the kind you use with a
> torque wrench. In either case, I need to know the compression length
> (I think) of the spring in order to determine the spring rating, and
> I don't.....
>
>
> Thanks
>
> -Scott Cypher
> spitfireracer@xsmail.com
> SCCA #57 HP Spitfire 1500 #362573
> Reading, PA
> http://gallery.mac.com/srcypher
>
> 1971 Spit MkIV/1500 RaceCar
> 1971 TR6 TBD
> 1976 TR7 Street
> 1968 GT6 Vintage
>
> "I'm so excited I can barely sit still or hold a thought in my head.
> Its the excitement only a free man can feel. A free man at the start
> of a long journey, whose conclusion is uncertain"
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