[Fot] Valve spring pressures

[LEE FOLLANSBEE]

Marty, how much over 7k are you taking your engine?  Valve springs are indeed a wear item, I replace them on the engines I build by probably the 3rd rebuild.  This is true for all makes of engines.  I have a very nice spring checker that I use and checking the spring pressures at install height and nose (max compression) is an integral part of each rebuild.

________________________________
From: Fot <fot-bounces at autox.team.net> on behalf of Scott Janzen via Fot <fot at autox.team.net>
Sent: Saturday, July 10, 2021 7:27 AM
To: marty sukey <trmarty at hotmail.com>
Cc: 'Friends of Triumph' Triumph <fot at autox.team.net>
Subject: Re: [Fot] Valve spring pressures

I shim mine to meet the cam maker’s requirements, and usually find there is a range of a few shims within which they are all set the same.  I also find that after two seasons the springs have lost about 30 lb seat pressure.  I routinely rev my GT6 to 7k (same valve train as your Spit) and figured out that at a typical race weekend at Summit Point it might go to redline 560 times (about eight times a lap).  your results may vary!

Anyway, a 30 lb loss is over 10%.  My settings are roughly 60 lb closed, 230 lb open at 0.523 lift.  I run the Isky VWE 005/SP116.  They also make a set with a softer inner spring (SP006) if you don’t need as much spring pressure.
I have a fairly radical cam, and these springs are adequate, have been running them for years.  Other manufacturers offer what seem to be similar but not identical spec springs, but if you open up the box  and they have orange paint on them, they are these Iskys.  It seems others re-package and sell them.  I’ve found this twice from other manufacturers, such as comp cams.

My guesses are:

  *   you may not routinely run over 7k and have not noticed this before.
  *   It may be valve float
  *   If it’s a recent change, look for a broken valve spring
  *   make sure your spring loads match the cam maker’s requirements.
  *   If you have been running these springs “forever”, replace them.  They are a wear item.

See you at Pitt race!

On Jul 10, 2021, at 10:07 AM, ralph hansen via Fot <fot at autox.team.net<mailto:fot at autox.team.net>> wrote:

I always set mine up with equal pressures at full closed. I would check them at full open and sometimes adjust them a bit to get better balance when closed. The pressure to open is more critical (told by a very old race tech from back in the day) to balance and smooth out the running at high rpm. Think of it as running through a series of eight spring loaded closed doors. If they are all the same spring pressure you fly through, with spring variances you get through some quicker, others impede your movement. I usually ended up with eight different shim stacks under my valves to achieve this but my under-developed 1147 would pull to 8k nice a steady and run a few ticks off the flyboys and ahead of many stronger cars.

On Saturday, July 10, 2021, 08:48:40 AM CDT, marty sukey via Fot <fot at autox.team.net<mailto:fot at autox.team.net>> wrote:


Hey all. I am trying to decipher some power loss weirdness I was experiencing on the dyno Thursday over 7000 rpm on my Spitfire. One of the paths I am going down is valve spring pressure at full open. I know its cam dependent but what are some of you other Spitfire folks running so I can get some ballpark ideas. Heading to PittRace on Wednesday.

Thanks,
Marty
_______________________________________________
fot at autox.team.net<mailto:fot at autox.team.net>

http://www.fot-racing.com<http://www.fot-racing.com/>

Donate: http://www.team.net/donate.html
Archive: http://autox.team.net/archive http://www.team.net/pipermail/fot
Unsubscribe/Manage: http://autox.team.net/mailman/options/fot/quikrx@yahoo.com


_______________________________________________
fot at autox.team.net<mailto:fot at autox.team.net>

http://www.fot-racing.com

Donate: http://www.team.net/donate.html
Archive: http://autox.team.net/archive http://www.team.net/pipermail/fot
Unsubscribe/Manage: http://autox.team.net/mailman/options/fot/sjanzen@me.com



-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://autox.team.net/pipermail/fot/attachments/20210710/a6f63c9f/attachment-0003.htm>