rob rossitto

brenden,
106mm? as they'd say down in the hood, thats phat!

since I sure can't find 104mm 968 mahles for less than $2500.00 (yet) - and coating custom JEs ($1050)with the mahle feriwhatever (iron)looks sketchy (although 928developments offers a tempting magic coated weisco for $1500/set) - your piston prices sure got my attention....are you planning to just nikasil or sleeve and forget about alusil?

also, if you are going to stroke & boost it, be careful - I've been warned several times lately(different builders) about boosting a stroked motor - something about rod angle stress/side loading being a bit high and stroked piston speed issues if you are going to really rev it up to take advantage of the higher RPM/HP (centrifical) boost curve....I'm definately no expert - just what I've been told, so I'm just wondering if you've got a way around that stuff - 'cause it'd be cool...

my motor is out & being hot tanked, prepping for stroking & boring to 104mm if it'll take it, cheby type rods, 10.5:1 compression...perhaps 968 sized stainless valves if I can verify they won't kill bottom end performance...keeping stock 85 cams, extruded intakes & TB, RMB & adding cats/xpipe, reprogramming my aftermarket chipset...maybe a little porting/cleanup on the factory headers...no boosted firebreather, just a little smog-**** proof hair under the hood... so I've been following/struggling along with some of the other rennlister's exploits -mainly the piston/coating/block material challenges....$600-$700 pistons, eh???

Toejam

It's not recommended to supercharge a stroked 928 engine is it?? Just considering options... dont mind me

Jay Wellwood

Oh....I don't know - ask Tom F - he now owns the 'Tilo' car - which is a 6 Liter supercharged model. Do a search for 'Big Bird'.

Jim bailey - 928 International

The "problem " with a stroker is getting the compression ratio down far enough to be able to run much boost . You only have so much room between the top of the block and the crankshaft soooo ....you run short pistons (not a positive thing) , move the wrist pin higher on the piston , run shorter rods (not a good thing) , trim down the counter weights on the crank so they do not hit the piston skirt when the piston is all the way down .......... all of this may need to be done JUST to get a stroker to run on pump gas ; besides when you get 450-500 HP in a street driven car it will keep you amused for a long time !!! Yes I know Brendan NEEDS MORE !!

BC

My ideas here entailed running a crank hournal size on a custom crank that could use Chevy parts. That would allow chevy pistons.

But If I stay with my OEM crank, then it will be 1800 for rods, and about 1000 for pistons, pins, and rings, as you stated.

The sleeved idea is for more bore then I can get with the stock walls. Also, it is ductile iron - good for boost, and the sleeves let me run uncoated JE pistons (or Arias, Wiesco, etc).

I'll also be using this: www.dtafast.co.uk

Its taking a while, piece by piece, but the car can be back together by the end of the year hopefully.

BC

Its all really a tossup. If I had all the money I needed, I wouldn't even try going that route, but right now I am trying to find out where the most value is.

Ah, but I have only found Domed, flat, and Valve reliefed pistons on summits product lists. If I have to use a machine shop to change the piston top, then the reason and cost structure change back to just using a stock crank.

The rod ratio is a big issue. But with a bore of over 105, that ratio changes I think, in the positive direction.

Anyone know where I can find out how to do the math to figure out what stroke I would make the custom crank so that I could use chevy pistons and 5.7 rods?

atb

BC wrote:

Does this help?

http://www.mortec.com/borstrok.htm

BC

Yes, it does help Adam. Thanks.

mark kibort

Cant we just pull the pan, bolt on a GTS crank and put in the right pistons and use the stock rods?
Trying to think of a cheap way to get to 375ish rear wheel hp

MK

Jim bailey - 928 International

NOPE

BC

Yeah, what Jim Said.

How much IS a 928 GTS crank, anyway?

Jim bailey - 928 International

GTS crank new was $ 5,000 - 6,000 as I recall ....used ??? who has one ?

Carlos

I hate to break this news but Mahle is now advertising custom pistons for Fords in the "Race Pages" which is the publication for the National Mustang Racing Association. They are priced competetively with JE, Ross & others. So maybe if you just ordered a set by the specs & didn't tell them they were for a Porsche, you could get them at $800 to $1000 instead of the "bend over I'll drive" $3000 or $4000 for the Porsche part #.

Jim bailey - 928 International

Mahle USA is a custom piston maker they were breaking into the NASCAR market (to run in the nikasiled blocks) . They are "supposed" to be making copies of the 104 mm 968 pistons ........... as well . We have not seen any ......yet . In some preliminary discussions their comments about piston coatings seemed unusual .

rob rossitto

seen their aftermarket stuff around too- lots of it and it's competitive w/weisco, etc - but it's not compatible w/the OEM 928 cylinders...

"unusual"??? don't just tease us!!! do tell all!!! (does P_L_E_A_S_E help?)