Another valve spring advice question
Turbo Mini Forums

I'm currently converting my 5 port turbo back to Naturally aspirated, as I have acquired another SC 7 Port head new for a bargain price. Plans are new pistons to bring CR up to 11.5. STR930 camshaft from my previous NA build. Probibly 1.3 Rockers, but do have a new set of 1.5 if needed.

Now my question is what are the best valve springs and retainers to use?

Soft rev limit at 7600rpm.
Current fitted spring height is 1.260 / 32mm with kent cams alloy retainers. Most after market springs need approx 1.350 for required seat pressure of 85-95lb.
Total lift will be 0.425thou with 1.3 Rockers. Or .490 with 1.5's.

Specialist components now supply a combination of Kentcams VS39 springs and matching retaining to give a 34mm fitted height @ 90lb with up to .510 lift @ 250lb. This seems like the best plan, however not cheap.

Can any body recommend any other options, Or details of MED Race springs.

Edited by alaskanow0 on 24th Jan, 2014.

Class C 3rd Place Avon 2011 14.18 @101mph

As you know Matt you need the leest pressure springs what will get the job done, my recommendation. Are minispares 526 double springs, good for lifts up to 0.575" and 8000 plus rpm check them out and they are under 25 billys

The Mini spares 527 springs fitted at 1.250 with current alloy retainers would give a 130lb seat pressure. Lift would also be reduce to .445thou. So not really suitable

My problem is the current spring height. The problem is the head is either designed with smaller spring height to start with or the retainer top caps sit to low and reduce spring height.

Do all different top caps give different spring heights. Or is it best to machine another .125tho from the head.

Edited by alaskanow0 on 23rd Jan, 2014.

Class C 3rd Place Avon 2011 14.18 @101mph

The springs need to be set/shimmed, the head machines or a combination to give the correct pressure for your chosen cam profile. So the follower rides the profile {more agressive profiles & RMP's requiring more pressure} I'm not familiar with that cam, do you know what's recommended ?
As Steve said you want the least you can get away with, as obviously "overspringing" will gain you nothing.

Phil.

Edited by Turbo Phil on 23rd Jan, 2014.

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Kent do recommend the VS39 at a 34mm installed height. The cam is similar to MD296. They also recommend Titianium top caps.

Phil, have you measured your spring heights on your 7 Port.

Edited by alaskanow0 on 23rd Jan, 2014.

Class C 3rd Place Avon 2011 14.18 @101mph

Matt you may gain a little with using STD to caps try them, if not as Phil says,

Edited by BENROSS on 23rd Jan, 2014.

WWW.TURBO-MINI.COM

Thanks guys, I think I'll give JohnK a call today to see if it's ok to remove some material from the head spring seats. If so I may be able to use the Minispares 526's springs with 1.3 Rockers, providing I keep the revs below 7500rpm.

Class C 3rd Place Avon 2011 14.18 @101mph

Ok so it not advised to machine the head. SC manufacture special valve spring retainers to give the required 34mm installed height. Designed to be used with kentcams vs07 or vs39 springs shimmed accordingly. But I guess other springs could be used for milder specs.

Class C 3rd Place Avon 2011 14.18 @101mph

Good info, cheers.

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