Yes! Let's hear some wisdom on this subject from Santa Cruz. Greg, please guide
us with your knowledge.
DH
----- Original Message -----
From: "Jason Ostrowski via Fot" <fot at autox.team.net>
To: "Peter Vucinic" <pvucinic at netspace.net.au>
Cc: "FOT" <fot at autox.team.net>
Sent: Tuesday, February 14, 2017 7:52:41 PM
Subject: Re: [Fot] valve spring pressure on TR4 race engine
This post has been swirling around in my head all day... Since We have always
run 65 lbs closed pressure for the GT6 motors with several different cam lift
scenarios... My initial thought and answer for Tim's inquiry would have been
that 85 lbs seems just fine. I almost posted 85lbs seems just fine as if I
really know what I'm talking about. And as I thought about it; the variables of
stroke, size, height, wet liners, etc. may have all types of influence on the
settings. With all that in mind I figured that I didn't have any reason assume
that what we do with the GT6 would be at all applicable to the original
inquiry. But I really wondered why his machinist would think that 85lbs is
"light".
Then the trusted voice of my mad German speed demon pipes in and says that it
should be higher by an off the chart amount of poundage!
Since he runs so well with a certain amount of reliability and obvious speed;
it remains of interest to me (with now less understanding than prior to the
original post) to fundamentally backtrack the inquiry of spring pressure
theory.
It seems that a huge # would yield a stronger bounce that would have certain
benefits. It also seems that a stronger bounce would meet certain limits of
stress on components and result in dangerous scenarios. Thus, there must be a
line to cross, a minimum and a maximum.
Dear Confucius, what say ye to the boundaries of such...and please, oh great
one, present the essential expose.
The formulaic dynamic as to the characteristic makeup of proper spring
pressures is???
I always look to the west for such guidance, perhaps some wisdom exists in
Santa Cruz?
Jason Ostrowski
Friendly Ghost Racing
1969 Triumph GT6+ Racecars
Sent from my iPhone
On Feb 14, 2017, at 7:32 PM, Peter Vucinic via Fot < fot at autox.team.net >
wrote:
I would be EXTREMELY careful with too high a spring pressure. Been there, done
that! If you go by all the STD calculations, theories and what you ?should
have? texts. It will tell you need HIGH springs pressures. Destroyed a couple
of cams that way! I just went back to springs with about the seat pressures you
are looking at. Haven?t had an issue with cams/cam lobes since.
"You can Make a Small Fortune From Motor Racing. As long as You Started With A
Lage Fortune!"
Kind Regards
Peter Vucinic
TR4 - TR7 V8 - Spitfire MkII
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From: Fot [ mailto:fot-bounces at autox.team.net ] On Behalf Of timmmurphh---
via Fot
Sent: Wednesday, 15 February 2017 6:56 AM
To: fot at autox.team.net
Subject: [Fot] valve spring pressure on TR4 race engine
I have 85 lbs. pressure on the intake valve with the valve closed and it sits
at a height of 1.655 inches. At .400 lift, I have 190 lbs. of pressure. We only
run to 6000 RPM with the gearing we have and the engine we have. The valve
springs are double springs and the machine shop says they are all about the
same, very consistent. What pressures would be recommended? The machine shop
thinks these pressures are light for a 6000 RPM engine. Any advice will be
appreciated. Thanks.
Tim Murphy
1961 TR4 #317 BRG
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