Crankshaft questions, FWD turbo hybrid

[turbokinetic]

Hey all I'm finally getting back on my project car. It is a FWD transverse engine car. Original post here.

Turbo Buick 3.0 FWD

Had it running, everything was doing fine after fixing the bearing but wiped 4 lobes off the cam. Now have a roller cam now, a 258HR.

I'm still in the process of gathering parts. I have the Turbo 3.8 crank and rods but crank has the RWD flange for the driveplate. While I would love to use this, with its stronger bolt pattern and all, the offset on the crank flange is too much. It would require a spacer between the bellhousing and the starter would be questionable at best. Lets just say I don't want to go there.

I can get a reman FWD crank kit reasonably and have it overnight. This would be an easy solution because it would work with a factory 3.8 FWD driveplate.

How much would this "weaken" the engine by not having a turbo-spec crankshaft? Bear in mind it is a draw-through system and will be lucky to see 250 HP. My goal is to build something from mostly used parts, not build a race car. I don't think it will create a bomb to use a non-turbo crank but I want your opinions.

I turbo'd a 2.8, using a crankshaft from a junkyard engine. It was non-turbo. It has been running 13 to 14 PSI with intercooler, and has been turbo for 10 years and nearly 100,000 miles. So I am not expecting any problems with the 3.8.

If you're curious: YouTube - Modified 2.8l V6

Other than the crank issue, I need a lifter valley tray (holds the lifter antirotation bars) and a set of custom-length pushrods will have to be made. Pretty much have everything else ready to go.

One other note; our fair city now has an E85 store and I plan to retune the ECM for use of E85 fuel. The new cam and larger displacement will require a new calibration anyway so why not? It has a good octane rating and a higher mixture for better charge cooling. It will be an expiriment for sure and I will post how that goes.

Thanks in advance,
David

[cool 84]

I could swear the FWD motors I opened up had factory rolled fillet cranks...

[turbokinetic]

Originally Posted by cool 84

I could swear the FWD motors I opened up had factory rolled fillet cranks...

Good to know, I don't have much choice other than to buy a FWD crank so I will look closely. How can you tell a ground fillet from a rolled fillet? I looked at the old 3.0 crank and compared it to the 3.8 turbo crank. There is a difference in the fillet area but it is hard to tell.

The reason for the rolled fillet is to put built-in compressive stress in the surface layers of the metal. A crack happens when tensile stresses are applied again and again and fatigue sets in. If the surface layers are already in compression, the flexing of the crank will not be enough to place any tensile stress in the critical fillet areas. I learned that at some of my Caterpillar training but knowing how to "identify" it is another story. Are there any comparison pictures here?

Thanks,
David

[SHADOWII]

search on gnttype.com there should be some comparison photoes of the na and t cranks.

[Turbo1dr]

I know the 3.8L FWD engines all have rolled fillet cranks. The 86-87's are identical to the RWD except for the flywheel flange and the way they are balanced. I would not have a problem pushing a FWD engine with proper turbo pistons as much as a RWD GN engine....as long as the flywheel bolts don't sheer off.

[steveX]

Originally Posted by Turbo1dr

I know the 3.8L FWD engines all have rolled fillet cranks. The 86-87's are identical to the RWD except for the flywheel flange and the way they are balanced. I would not have a problem pushing a FWD engine with proper turbo pistons as much as a RWD GN engine....as long as the flywheel bolts don't sheer off.

I agree. FACT.

[63 Coupe]

pm sent

[turbokinetic]

Thanks for the re-assurance. Got a FWD 3.8 crank and driveplate on the way. Traded in the crappy 3.0 crank for a core.