Ok, this post ended up longer than I expected, but.....I've tried to find some information over the last few days and haven't found any satisfactory answers for a few questions.

I'd like to keep this discussion technical and not an opinion session.

- What spring pressure is really needed for "Semi-aggressive" cams?
- What Retainer material is best?
- Why don't I see seat shims in most sets to provide a choice on seat pressure?

Assuming kelford 272 cams (presumably similar to GSC S2's in lift and ramp rate), 30 psi of boost, and only 8000rpm redline, what seat pressure would you really want to see from a proper set of springs?

Obviously you'd want to have a seat pressure that allows for some weakening of the spring over time (even if manufactures claim they won't... operating in a save stress range for fatigue life), pressure enough to seal against boost pressere on the valves, some margin for accidental over-rev, and not so much seat pressure that you'll put unnecessary wear on the cams, etc.

Kelford website says (for evo 272's):
Use the factory spring base for Street/ Strip applications up to 8000rpm and 23.5lb(1.6 bar) boost, over that use the supplied spring base to increase seat pressure to 110lb

GSC says:
Part number 5041 includes new 4340 Chro-molly spring seats (these won't crack like others aluminum seats) and GSC’s Titanium Retainer set. This kit is capable of 11000RPMS, with as much as 12.5mm of lift (or .285" of camlift). This is a must have for anyone pushing the limits. If you have had problems with valve float or throwing rocker arms this is the spring set that will cure your problems for good...

Spring pressure:
Seat at 1.46"= 95 pounds
.300"= 200 pounds
.400"= 250 pounds
CoilBind .560"

Part number 5039 includes a set of GSC Beehive Springs for use on the stock seat and OEM retainer. This kit is capable of 8500RPMS (or south of 9k), with as much as 11.4mm of lift (or .259" of camlift). These are designed as a drop in spring to use with the S2 camshaft set.

Spring pressure:
Seat at 1.56"= 68pounds
.300"= 160 pounds
.400"= 210 pounds
CoilBind .625"
Max lift 11.4mmof lift (or .259" of camlift)

So, what am I missing, how does Kelford say I need 110lbs spring pressure over 23.5lbs boost, when GSC says 68 lbs is acceptable with S2's, at 8500rpm without knowing my boost, and 95lbs is ok for "any" cam, 11000rpm, and "any" boost level?

Why does nearly every spring set have Titanium retainers when titanium isn't as stiff? Presumably the retainers are operating at a safe stress where they won't approach their fatigue limit. Why am I paying more for neglible weight reduction(neglible performance gain)? Is this just marketing of TI because it's "sexy"

Can I get valve seat shims if I want to increase my seat pressure?

 

Anyone?

 

Bueller?

 

so you know...I will attempt to keep this very short. Mostly because it's late and I want to got to bed!lol

We do not have any experience with the companies you mention, so will speak from an experience standpoint only, and not try to decipher what the companies are trying to convey.

We usually set up our springs between 85-95lbs on the seat. Not discounting manufacture reccomendations, but we don't run anything above or below that for the street(mitsubishi). That covers us no matter what the customer tries in his ride. 95lbs will handle 40psi and a 272...but a little more seat pressure won't hurt it. We have run 110psi up to 60psi with no issues..430 lift and 10.5rpm ..And if you find yourself in a situation where you need a little more, you can easily settle that with a shim, and you can get them from most machine shops, as we sometimes have to put a shim under the locator to get the required seat pressure.

 

From one of the head masters himself

 

Thanks for the info, It's good to have to get some data from experienced people.

 

Back to titanium retainers...

Can one get away with just using titanium retainers along with stock springs for less chance of valve float at higher rpms (I plan on running up to about 8k, if that (road race)). Is titanium recommended for motor that will go 100k miles or do you have to keep an eye on them and replace periodically. Thanks.
Dan

 

My assumption is that Ti retainers may have a marginal effect if they are really lighter than stock retainers. It may be a move in the right direction, but I think it's probably small.

I haven't seen any other good information on Titanium other than the fact that it has infinite fatigue life like steel if the design limits stress below a certain level. If they are designed correctly, they should go 100k.

Springs are fairly cheap and easy to do. I'd be inclined to do them if you are going to run sustained high rpm, or larger cams.

 

It's not that I am afraid of the difficulty involved with installing springs. I am more concerned with longevity of the motor. Essentially, is there more concern of increased wear due to a heavy spring or more concern for valve float if run with stock RPM with a cam such as the Brian Crower 272s.
Dan

 

The reason GSC's spring pressures are lower is the fact that they are using a beehive spring.For those who don't know what a beehive spring is it's a spring that is smaller at the top of the spring then the bottom.It has a taper that makes it look like a cone shape I guess is the best way to describe it.
With this design it uses a much smaller retainer then a conventional spring does.Also the fact that the spring gets smaller up top means that the weight of the spring itself and retainer is lower and consumes less power to open and close so you don't need as much pressure as a conventional spring to resist valve bounce/loft.

 

the 5039 is a stock replacement spring that is designed for the S2 camshaft up to 8500 rpms and basic operation of the motor.. these can be used to 25psi with ease. going to 30psi we would suggest the use of our 5040 kit and north of the 8500rpm limit we suggest the 5041.

As far as comparing the kelford and our S2 camshafts the only person that has seen both of them together on a cam doctor is martin @ AMS and i'm not sure if he would be able to explain why each cam would require a different spring..

the use of titanium has 2 benifits one is that it is stiffer and just as light as the oem aluminum retainer and our ti retainer allows for a higher lift (retainer to valve seat clearance). We have used Chro-Mo in the past on some other retainers but do to the weight of chro-mo vs ti we decided to use the Ti on the new beehive spring.

our 5041 kit can take up to .060 spring shim to raise the pressure even higher. not unless the engine is taking 60+psi and 11k rpms would we suggest running that much seat pressure but it is possible.