Another stroker question

N2O-SHARK · 07-26-2008, 08:37 AM

Searched and couldn't find too much info on the details of stroking. At least not on this site, though a few pop up windows offered places to go.

My question is, has anyone stroked the 5.0L with out boring and replacing pistons. I know it's a "While you're at it" but to keep cost down is there a way to keep the 5.0L bore and just add stroke? Just wondering if you can do it for the cost of the crank, new rods and balancing with out the block prep, boring, pistons etc?

I ask because I might have a line on a scat crank for about $1200. I can swing a little more for rods and balancing. I can't swing the full blown stroker right now. Thinking a mini stroker would still be better than a stock 5.0L.

For the cost of doing a full stroker correctly, I could put a new pool in the yard... But if I can get away with a mini stroker for under $4K, I'm in like Flynn. Just testing the waters before I put my Hybrid back together. BTW if I can do a stroker it will be with the Euro S top end...

SOmeone please edumacate me.

N2O-SHARK · 07-26-2008, 10:00 AM

Sounding like I should just stick with N2O or go Turbo.

If anyone has a 6.0L build and would like to PM me any details, I will be eternally grateful.

Does anyone know the rod length specifics for the 6.0L? Pistons are already fly cut for the Euro S heads, might get away with out dishing the pistons?

As for the balancing, I guess there is no way to tell untill I get it all to the shop to be balanced.

Danglerb · 07-26-2008, 10:17 AM

Stroking means the rod journals on the crank are located farther from the main bearing center line, which causes the rod and piston to move farther up and down in the cylinder. To keep the piston from poking out the top the combined length of the rod and piston must be reduced. My understanding is that it isn't good to take all the reduction in the rod, so new pistons with the pin located higher are typically used. Block also need to be clearanced for the greater swing of the crank etc. New pistons mean nikasil block and pretty soon not doing the full stroker seems like a waste.

Cheapest bump in power I can think of beyond the hybrid is to bore the block to 104 mm and have it lapped (no need for nikasil with Porsche pistons), and use 968 pistons for a 5.4L motor. I don't know if new rods are required for this or not.

rhjames · rhjames's Garage

Quote:

Originally Posted by Danglerb

My understanding is that it isn't good to take all the reduction in the rod, so new pistons with the pin located higher are typically used. Block also need to be clearanced for the greater swing of the crank etc.

usually the rod of choice is the 5.85 Chevy rod when building a stroker.
it's not the best rod to use, but it's the most common.

anything shorter than that, and the stroke/rod ratio gets really bad......

--Russ

Danglerb · 07-28-2008, 10:16 AM

A lot of strokers have been built using a piston with the pin located up in the ring groove, specifically I am thinking of the Ross 400 (I think), and over in Mustang land this resulted in a VERY bad reputation for a 302 stroked to 347. My understanding is that eventually the pin the in groove issues were worked out, but I think its still a case with the 928 that anything more than baby steps away from a proven variation can have both substantial risk and cost.

Even with a 5.4L based on 968 pistons its not clear to me if a new damper is required to the tune of $500+ and months of waiting for it.

Kind of makes me understand the appeal of chrome alternator style hot rods.

Danglerb · 07-28-2008, 12:05 PM

I think the damper is also optimized for rpm range, Porsche used a different damper didn't they for basically the same internals on the US and Euro motors. Mark used to use a factory damper and I think he has switched to an ATI, which of course don't mean it would do squat for me, but the factory rubber dampers are getting kind of old.

rhjames · rhjames's Garage

Quote:

Originally Posted by John Taylor

Damper = external balance. Rotating mass balance = internal balance. Other items like flexplate and flywheel also affect balance. If the internals (rotating mass) is correctly balanced, then the stock damper can be retained. For a 928 stroker, it's best to start with an 8 cw Moldex crank, fewer problems that way.

If you like chrome alternators and oil caps, you should spend more time at the Fairplex in Pomona.

IF you are going to internal balance, then all of the rotating parts should be balanced. Porsche says that with the internals being weight balanced, you can use the balancer as is, but I would not trust it. Better to do all of the parts at one time--- then you'll know for sure what you have. The 8 counterweight crank is easier to balance as it takes less add-on metal to pull it into balance.

crank, rods, pistons, pins, rings, flywheel-clutch assembly/flexplate, and the harmonic balancer.

Wrist pins located in the oil ring groove are nothing new, just require a little more $$$ and the knowledge of how to put it together (read: correct height measurements/engineering--your piston supplier can help you with this).

A longer rod will yield more power, and is better for rod/stroke ratio, but those who are building strokers are staying away from this due to putting the pin in the ring grooves.....(exception: the Green Bay bunch).

--Russ