[Fot] valve spring pressure on TR4 race engine

[davehogye]

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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