largecar379

talked with Moldex Crank today----

production time is now 20 weeks out.

cost approx $2650.

ouch........

--Russ

928SS

probably take that long to line everything else up anyway... the time goes fast... when I spoke w/scat 2yrs ago, they had no issue building a single crank fast. but I think moldex does a better job of hardening or uses a better steel... there is a debate on whether 6 or 8 counterweights is best too. I used 6, devek uses 8, others use 6 or 8 too... in fact, most everything on these is debated at one time or another

we're master-debaters, hahaha

Mike Simard

20 weeks will be here before you know it and you probably wont be ready anyway. I've found their projected date to be accurate.

largecar379

probably so.......sent you PM.

Thanks for your info!!

--Russ

largecar379

so now that I've got all these measurements, now I'm struck on a few things.

my block is stock deck height, 9 and 1/4 inches. (metric conversion...232.75mm +?)

if I use a 95.25mm stroke crank, and a 6 inch rod, what is the piston pin (centerline) to piston top measurement I can use? (remember, in this excersize, I am using 16V heads, to be flat tops with just two valve notches with zero deck protrusion)

Sterling is advising that the 6 incher will push into the ring package, so what are my options?

Piston diameter is no big deal, as there are a few Chevy 400 piston measurements that would work for ring sizing. That would make ring purchasing easier.

Anybody care to take a stab at this?

--Russ

atb

Deck height is measured from the main centerline to the top of the cylinder.
232.75mm

Take one half the stroke of the crank and subtract from the deck height and you will have how far down the cylinders the centerline of the big end of the conrod is at TDC.

95.25mm / 2 = 47.625 mm

232.75 - 47.625 - 185.125mm

Subtract 6" (rod length), and now you have how far down the cylinder the centerline of the small end comes to rest at TDC.

185.125 - 6" (152.4mm) = 32.725 mm

For zero piston deck height, the distance from the centerline of the wristpin to the deck would be 32.725mm (1.2884")

This may not be optimal depending on what thickness gaskets you run.

WARNING: I'm not an engineer. You rely on my math at your own Peril
At any rate, I think this will get you close Russ. Definitely double check my mechanics and my math.

atb

We have a local stroker that has 6" rods. He mistakenly purchased them because he assumed that's what was used with the stroker cranks. When the motor was assembled, the pistons popped out of the cylinders. The builder chose to turn the pistons rather than get new rods. I understand there are a million reasons why this isn't optimal, but the car is running fine.

Also, I think one of the Wisconsin strokers was running pistons where the wrist pin boss went up into the ring package. From the pic I saw, it looked like the scraper was installed after the wrist pin since it spanned the wrist pin boss. It looked pretty cool, I think it was a JE. Don't know if this would be considered a "streetable" set up, but it definitely looked "all business".

Jim bailey - 928 International

The GTS pin center to top of piston is I believe 39.07 mm , 944 2.7 liter 104 mm piston 40.75mm , the 3 liter 944/968 is 36.05mm , the 928 4.7 piston is 42.75 mm. You must use a short piston as well or the shirts hit the counterweights. The GTS and 3 liter 104 mm 968 pistons are much shorter than the 4.5,4.7 or 5 ltr pistons because they have to be . Short pistons are harder to keep straight in the bores and coupled with the additonal side loading of the longer stroke crank it is less than ideal but there is only so much that you have to work with.

atb

Jim wrote:
Jim, you have just summarily summed up the totality of what a stroker build up is all about.

Vilhuer

Only 968 piston will work without skirt modification when 95.25mm crank is used.

largecar379

Adam---

this is exactly the math I'm coming up with.

yes, the oil ring will have to be across the pin, but i will discuss this with JE nest week.

thanks all for the help and guidance.

--Russ

6.0-928S

Hi Russ,
You may want to look into Childs & Albert. Since you were a drag racer I'm sure you know who they are. They have a lot of experience making high quality pistons with the rings in the pin boss. The piston section in their catalog on their website shows some examples. Check 'em out.
Regards, Hammer
http://www.childs-albert.com/catalog...om_pistons.pdf

largecar379

Crap---that's right Hammer...completely forgot about them.

too many numbers going thru my head to keep this straight anymore---must be old age or something...

Thanks---Russ

atb

Hi Russ,

I found the pic I was referring to, it's one of Todd's builds:

http://www.erik27.com/todd/427/Pisto...s/_DSC0492.htm

Same idea as the C&A pistons Hammer posted a link to.

Just a reminder to make sure to calculate your static C/R before ordering up the pistons. If you've built domestic motors in the past, its easy to take for granted that you have a wide variety of head gasket thicknesses to dial in your C/R, you don't have options like that with the 928 (unless your willing to go with Cometic gaskets which have a checkered history with the 928). I know I'm probably stating the obvious to you Russ, just want to make sure you've got a heads up on things like this. Things that can be taken for granted on a domestic build will sneak up on you when building one of these stroker motors.

largecar379

as I have said, anything you guys can think of is great help-----

I'll should know something about piston builds later this week (from JE and C-A).

Thanks-

--Russ