help with stroker questions........please
01-21-2008, 01:34 PM
#46
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be careful about the calcs. your deck ht will also be affected by casting and block machine/prep work, so it's not a solid number and will vary from block to block. I did a mockup w/some 968 copies, after all the machine work was done, then spec'd the pistons w/JE so I'd get a perfect 0 deck ht when assembled. kind of an *** backwards way to do it, but it did let me use a standard rod length, and since I knew I'd get custom pistons anyway, it worked out perfectly.
je claims there could be a piston wobble/sideloading issue w/putting the pin too high. I didn't think the diff between 5.85 and 6 was enough to warrent bothering w/shoving the pin up and dealing w/all that. but who knows? every one of these seems to be a bit unique somehow, so there's not really a ton of data on any specific design. we're all crash test dummies to some extent
je claims there could be a piston wobble/sideloading issue w/putting the pin too high. I didn't think the diff between 5.85 and 6 was enough to warrent bothering w/shoving the pin up and dealing w/all that. but who knows? every one of these seems to be a bit unique somehow, so there's not really a ton of data on any specific design. we're all crash test dummies to some extent
01-21-2008, 06:03 PM
#47
Rennlist Member
I dont know exactly what parts are being used by the Wi Guys build up of the Rennlist engine for the Holbert car. (Ill leave those details for Tim and Co. to report when they are ready, and that should be any day now)
But, as far as I know, because the 968 pistons are so expensive, but can be used with a bored and just alusiled block, they can be used with standard dimension 928 rods and a stroker crank set up for porsche bearing dimensions. (right?) But if you use after market pistons, like JE 968 copies, then you dont want to mess with the porsche coating so they work in the alusil bores (right) So, this means, Nicasil is the next best choice, but its a messy process. (clean block, remove all steel parts, bore, and then plate with nicasil for the very hard cylinder coating) then, the rings become the question mark.
some are saying that the rings normally used in an alusil bore are too hard and tear apart the nicasil coating. (right?) anyway, I think Tim and Todd have this worked out for the holbert stroker engine project.
It will be very interesting to see how this turns out and to see how much power it makes and how long it lives!
mk
But, as far as I know, because the 968 pistons are so expensive, but can be used with a bored and just alusiled block, they can be used with standard dimension 928 rods and a stroker crank set up for porsche bearing dimensions. (right?) But if you use after market pistons, like JE 968 copies, then you dont want to mess with the porsche coating so they work in the alusil bores (right) So, this means, Nicasil is the next best choice, but its a messy process. (clean block, remove all steel parts, bore, and then plate with nicasil for the very hard cylinder coating) then, the rings become the question mark.
some are saying that the rings normally used in an alusil bore are too hard and tear apart the nicasil coating. (right?) anyway, I think Tim and Todd have this worked out for the holbert stroker engine project.
It will be very interesting to see how this turns out and to see how much power it makes and how long it lives!
mk
01-21-2008, 06:20 PM
#48
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As I recall to run porsche length rods the stroke must be about 94 mm not the 95.25mm used on all the scat/devek cranks plus a stock Porsche rod big end has clearance issues to the block. Anderson ran Carillo rods on his first stroker which previosly were used in a 5 liter so had the shorter stroke and used 968 pistons but that was a long time ago