atb

I've been looking around for an alternate valve spring for my stroker motor. The 968/944S2 spring is costly, which isn't too big of a deal but on a high lift cam I've been told that they are close to coil bind. Failures? Haven't heard of any, but I thought I'd still look around.

Surfing the net I started with the physical dimensions of the Outer spring O.D. (30.32mm), the inner spring I.D. (16.10mm), and the installed height (35.5mm).

It turns out that our mighty S4 springs are almost identical to.....
FORD PINTO SPRINGS.

Yup, here's the specs for Ford's P-car:
Outer spring O.D.: 30.73mm
Inner spring I.D.:17.40mm
Installed height: 35.56mm

So, in physical dimensions the springs are a pretty close match.

The Pinto spring is stronger, which I am looking for.

Louie had measured the seat pressures of a set of S4 springs (used I believe) at 61lbs intake and 71lbs exhaust. The Pinto stock spring is 85 lbs for both, and the racing spring is 91lbs (albeit the installed height is shorter by .100" than stock).

The stock Pinto spring has a spring rate of 270 lbs/inch, the racing Pinto spring 337 lbs/inch. I don't know what the Porsche spring is rated at.

I found on the web that the weight of the Pinto intake valve is a hefty 101 grams, where the 928 Intake [edit: should read "968 Intake"] is only 69.9 grams, which would explain why the Pinto spring is stronger.

The good news is that these springs cost $60 a set, and you need four sets for a total of about $240. That's about a third of the price of what I could get the 968/944S2 springs for.

Check it out: Pinto Valve Springs
So, I thought when I ditched the T-handle shifter in my S4 I would be free of Pinto legacy that has followed me through life, it looks like I'm right back in it.

heinrich

Dang Adam, that is some serious sleuthing you did. So, what are the components of your stroker motor so far, what is still outstanding, and how close are you to completion? Mind listing a parts list?

BC

I found aftermarket springs for the 2V (ford I think), but I just used the 944S2 springs that I bought from 928intl for the 89 head. The spring seats need to either be cut down or used from the 928S3 - as I am using S3 cams. If you go even better lift then that, I am not sure why you wouldn't be able to just cut more from the spring seats, stay in the good closed-pressure rating, and be okay?

heinrich

Brendan, interesting also. With my S4 heads, will I need S3 springs for the S3 cams, and will I need to modify?

Mark Anderson

Adam the 944 S2 springs are only $12 a set and they have lots of proven miles in this application. Nothing against Ford but do you really want a Pinto part in your Porsche?

Vilhuer

Are 944 S2 and 968 springs and other related parts same or different? Too lazy to check from PET.

atb

Heinrich, this is where I'm at on the stroker:

Block: '87 oil sprayer
Overbored to 4.095" (104.1mm)
Square decked

928 Int'l Stroker Crank
Oliver Rods
Ross Pistons for use in Alusil bores (on order)
(Waited 12 months for Mahles, no show)

Heads: All new valves -968 Intakes
-S4 Exhaust
New guides
Ported

Induction: Ott ITB intake

928 International Stepped Headers

That's about it for now.


Brendan,

The S3 spring seat is 1.5mm thick, not too much to be taken off of that is there? Even so, I don't know how sensitive the seat pressure is to changes in the spring seat height. Have you taken any measurements? I think I'm going to have to invest in a gauge. My inclination is to believe that when the 944S2 spring is set for correct seat pressure, that it will be stacked too short at full open and approach coil bind. If machined to avoid coil bind, then doesn't that mean that your seat pressure will then be too soft? I haven't personally worked with the springs, so this is all just speculation based upon what other's have told me. If you could let me borrow a set for a couple weeks, that would be awesome. I could mount them up and take measurements.

If you haven't already mounted up a set Brendan, do it and take some pics. I'd be curious to see how much clearance you have between the coils and at 11mm lift.

Again, lot's of guys are using the 944S2 springs in high lift motors without incident, but does it make sense to use an expensive spring that you may have to machine to fit over a cheaper/stronger spring that you don't?.

How much did the springs cost ya?

atb

That's good to know. When I looked up the part #, I got the same part # for the 968 as I did for the 944S2.

$12 per set is a lot easier to take than $22 per set.

atb

>>>>>but do you really want a Pinto part in your Porsche?

Mark,

Just ask the PacNW guys about my 928 and Ford parts, it's a long story.

Mark Anderson

With 11mm of lift you are far from coil bind on the S2 spring and they do not require any machine work. You will need some of the 85/86 hardware to use them.

BC

I have the springs in the heads already, Garrity rebuilt the heads, and assembled them. I may be disassembling the heads though. Are you saying you want the coil spacing when the cam is at full lift?

atb

>>>>Are you saying you want the coil spacing when the cam is at full lift?

That's what I was asking for, but Mark says it's not a problem. No worries.

Looks like 944S2 spring is a good option for price and fit.

heinrich

Helps to have some experienced heads together.

V2Rocket

Sorry to revive an old thread, but how well do S3 springs in an S3 head, handle 11mm of lift? Can they even lift that much without binding?