Spitfire Valve Springs

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Neil Verity

Well-known member
So, I have an older Triumph 1296 race ("Run-offs") motor that was built some (10-15 yrs ago) but was never run.... Top notch build, (Prather, Kline etc..). We have run it now a few races and broke some helper valve springs. Seems we can't find replacement springs (no record of what was put in motor 15 yrs ago) and Isky was unable to help us after I sent him the springs. Question... who is a good source for valve springs, either in general or for triumph 1296 race motors? FYI..These are some of the measurements I took:

Average Installed Spring height (no shims) = 1.54 inches, shims are typically 0.030 - 0.060 in height
Uninstalled outer spring height is ~ 1.6 inches, diameter of outer springs is ~ 1.13 inches
Resting installed height spring pressure is probably 90-100 PSI... but not sure on this number... could be lower..
~210 psi @ 0.5inch down from installed spring height, 240 psi @ 0.6 inch down from listed height
Total valve lift = 0.525 inches (measured form top of retainer using dial indicator and rotating motor).
Engine has roller rockers

Any help or guidance appreciated..

Neil
#83 HP MGB
#13 FP Spitfire
 
GT6... Thanks I'll look at the links.... no, the pneumatic valve spring F1 Triumph motor is still in development... These are just spring pressures measured on a gauge..

and to be clear. (sorry for some confusion in my post) .. although we only broke helper springs (inner 2nd coil) I am looking at replacing both inner and outer springs.. hence the spring measurements for the main coil and spring pressures taken off the dual spring set up..

Neil
 
Neil,

May be unrelated, but Comptune found that the Isky springs in the Sprite motors would not tolerate high lift applications, and often broke from fatigue. Comptune machined the spring pockets for larger diameter springs, and sourced some from a motorcycle application. Call Mike Miller (Comptune) or Craig Chima for details.

First check that the springs aren't going into bind at anytime in operation. Check inner springs independent of outer springs.

Ron Sorensen
 
I have tons of old stuff that I am going to be going thru soon.
Just don't have it in me anymore to keep it around.
PM me if interested.
 
Have performed valve spring archeology a number times as A-series heads come through shop. Have done very limited Triumph work. Some MGB. But, the efforts would end up similar.

Measure everything including valves themselves, springs (including coil bind and wire diameter), retainer, guide and anything else used on a single valve location. That way as potential spring candidates are identified, they can be evaluated against the existing installation. Think outside of traditional liquid cooled automotive installations. I've used air-cooled VW and motorcycle springs in the past. If the retainer manufacturer can be determined, that may provide a clue as to the spring supplier. Very few of the spring suppliers actually wind their own springs. Custom springs from someone like PAC are costly, but they are a premium manufacturer and made from the best materials. Comptune sourced springs have been used successfully many times by past and present National Champions.

One major consideration is that most springs developed in the 60's are made from Sili-chrome steels. Today's top tier valve spring steels are entirely different and a heck of a lot better. The better spring makers won't tell you what they use. A little investigation and review of industry documentation and presentations at places like AERA and PRndI will provide a lot of circumstantial evidence of what's being used.

Once a potential spring application is identified, then installation considerations need to happen. Spring seats and location needs to be considered. Physical adjustments may be needed to accommodate periodic servicing and aid in installation.

This wasn't a simple "buy this part #" or that number, but it usually never is. Figuring out what parts to use where makes it interesting and very fulfilling when things work out.

If I can help with your efforts, just contact me.
 
Mike's got it all. Personal experience over 30 years is to follow advice like Mike's and use the right parts. We've used Isky orange oversized spring sets for years on the high winding 948s and never had one break. BUT, you have to modify the heads in depth and diameter to insure the proper installed height and spring pressure is correct. I was lucky to start out with Hufaker and Comptune heads to get measurements etc. from. The two Comptune heads I have for my two remaining 948 9,000 rpm engines are a work of art and with the exception of a valve coming apart have been bullet proof.

Bob
 
Hi Mike, Bob, SW83gp

Thanks for the advise and encouragement....... looks like I have a little more homework/detective work to do. Mike, I'll drop you a line.

Appreciate all the help

Neil
#83 HP MGB
#13 FP Spitfire
 
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