Vilhuer

Got block back from machine shop today. It had been there for over six weeks. They bored all eight holes to 104mm. They said it took 15 hours just to do drilling and lapping. After recent discussions about pistons needing work to clear crank etc I desided to try immediatelly how much work there is in this case. Looks very good infact. 968 pistons do seem to clear Moldex 8 counterweight crank, barely but they do.







Cheap Eagle 5.85" H-beam rods I have also clear lower half of the block better than stock GTS rods for example.



Although bolt head is extremely close to opposite side cylinder wall when passing it. That was small surprise as I was expecting lower half be by far closest spot.

atb

Beautiful Erkka.

Bill Ball

Looks like you're just about ready to let her rip, Erkka!

Vilhuer

Still long way to go. For starters need to have piston tops cut for valve clearance and entire rotanting assembly balanced. Not to mention have to clean up storage grease away from the crank. After that real fun part of assembly can begin. That is if I have modified main bearings on hand by then. Seems it takes months and monts just ot get parts together for this kind of project. Unlimited budget could help but still its much longer process than bolting SC in. At least there is more time to clean up casting marks from block lower half. This is something I would do on any engine rebuild.

drnick

erkka, bolting in my supercharger is taking months and months...

svp928

Stan, bob weight for balancing is figured as follows:
Add together weight of:
piston and pin
rings
rod complete
rod bearings
oil est. (usually 2-3 grams)

then, add the weight of the BIG end of the rod, bearings, and oil

These weights combined make up the bob weight for one crank journal on a V-8.

Steve

slate blue

Thanks Steve, that is more good info for the information bank. Nice looking car you have there, I like the way it sits!

Greg

Stan have you had any progress? If you are looking for another piston rod combo PM me but you will need to change both.

Stan.Shaw@Excell.Net

Thanks Steve, but I knew that as my first post provided that information from the machine shop. I am looking for the balancing equation.

Stan.Shaw@Excell.Net

Thanks Greg,

I intend to figure out how to use what I have, even if in two separate builds.

For those following and interested in balancing. I found the following , which seems to be in sync with everything else I have gathered http://www.automotiverebuilder.com/ar/eb40634.htm

Right now I know the Carillo rods would reduce the weight by 50.5g (24g rot and 26.5g recip) and possibly 25g with JE pins (recip). I will see where this gets me.

Anyone out there using this crank? If so, with what components, and what was you bob weight?

svp928

Stan, I guess I don't know exactly what formula you are looking for? Did you mean the dynamic overbalance on 90 deg v-8's? Most shops won't do it, because it usually ends up causing a vibration somewhere in the rpm range...
Your linked article is a good one, it explains pretty well how it all works.

Greg, thanks for the compliment on the ol' crate...

928SS

ck out the the A series carillo. they are the lightest. H beams take over 600chp but are heavier. I used A series, cause I doubt I'll ever get close to 600chp. block does need some clearancing, but not a lot..

Stan.Shaw@Excell.Net

Sorry, I am not looking for the dynamic over balance information. I did find that and it is interesting to consider though.

I am looking for a way to determine how and where reductions in component weight affect the balancing. I can determine the new bob weight but I suspect the crank needs to be spun with it on to get the amount of change in weight needed (on the crank).

Stan.Shaw@Excell.Net

I am hoping 600chp won't be sufficent for my needs. The Carillo rod I am considering is what Greg B. suggest (thanks Greg).

mark kibort

so when they use 968 pistons on strokers, do the skirts always need to be clipped for the counterweight clearance? I never realized how close together all that stuff rotates.

mk

FlyingDog

Erkka's pictures are unmodified 968 pistons. It's 944 S2 pistons that would need to be modded apparently from the pics.