Is this a custom crank? Please help with ID
 

Well I finally measured and sourced the bearings for this 2.0L crank.

The motor is a 2.0L case with 84mm P's and C's. The crank takes .25mm over/under bearings for the mains and strangely, the rod journals are sized for a 3.0L (53mm) and it has 3.0L rods making it a short-stroke 2.0L.

Was there such a crank produced? ...or was this a custom dealio?

How many flywheel bolts?

It scares me to write this. . . with an 84mm bore, the only crank that gets you two liters is. . . a 60mm. . . which only appeared in . . .



. . .

Typ 935/79, 935 "Baby", 71 x 60 (1425cc x 1.4 turbo multiplier for two liter class)

http://forums.pelicanparts.com/uploa...1118169139.jpg

Is it April first again?

No sirs.. No joke.

It's a 6 bolt crank. Alright, well either he doesn't know the true displacement (not that any racer ever "forgets") ... or what, it's a 935 crank? :eek:

Looks like I'll be measuring the stroke today. :)

Chris

Keep us posted on this potential J A C K P O T.

Chris, I would NEVER accuse you of joking about a thing like THIS. It's too serious.

And it wouldn't be just a 935 crank, it would be a "Baby" crank-- the rarest of all!

The question (this should be answered by Grady) is was the 935 crank ever a six-bolt? I would have thought it would have been nine bolt by then.

Then again, if you measure the stroke, it might just turn out to be a 66mm crank, which would make it a bone-stock 2.0 liter. NOT that anyone's ever accidentally run 84mm jugs in a 2.0 class . . . :)

I assume it is counterweighted? If it weren't, I couldn't imagine it being a 935 crank.

Yeah, it's counterweighted. So a 66mmx84mm would make it a 2.2... I'd be shocked if it were 60, but i'll check in an hour or so when I get back to assembly..

excuse my ignorance but are they like really really rare? what sort of money would a usable 935 crank be worth?


Andy

An initial eyeball says 66mm, but I'll put a caliper on it and measure exactly when I drop the crank back in tonight... Dang...

Still, the 2.2L didn't have 3.0L sized rod journals...

Chris, a few specs from Wayne's book might be helpful.

Wayne's book is WRONG, on page 204 it claims a D1 dimension fir the 2.0 and 2.2 (66mm crank) of 57.010-57.059mm for the main bearing BORE, 56.971-56.990 SHAFT. According to the 2.2 spec book, its 57.020-57.059 BORE, 56.971-56.990 SHAFT. Now, the 2.0 spec book says 56.971-56.990, so that checks OK. That's a 6-bolt.

2.4/2.7/3.0 Turbo crank (70.4) 6-bolt, 57.020-57.059 BORE, 56.971-56-990 SHAFT. OK, that's the same as the 2.0/2.2 crank.

3.0SC 9-bolt (70.4mm) 60.020-60.059 BORE, 59.971-59.990 SHAFT.

3.2/3.3 Turbo 9-bolt (74.4mm) 60.020-60.059 BORE, 59.971-59.990 SHAFT. So that's the same as the 3.0.

Funny how Porsche changed critical dimensions barely through the 35-year run of the 911.

OK, you say it has 53mm rod journals. The rod journal is what the factory calls dimension "D2."

66mm- 57.020-57.059 BORE, 56.971-56.990 SHAFT
70.4mm- 52.020-52.059 BORE, 51.971-51.990 SHAFT
70.4 (9-bolt) 52.020-52.059 BORE, 51.971-51.990 SHAFT
74.4 52.020-52.059 BORE, 51.971-51.990 SHAFT

So, all the rod journals are the same after the 2.4-on.

That suggests to me it's either custom, or a ground undersize 66mm?

The mystery continues. . .

Wow John, I think I inhaled too much carb cleaner to get all that in one reading. :D I didn't get a change to measure the stroke (assembled the short block this evening. I'm chomping to find out, but will have to check tomorrow. Thanks for the great info!

I really enjoyed reading this thread, and will be sure to check back soon.
Great info.


Alan.UK

Damned if I didn't bolt the heads on before I remembered to measure it! Argh! Well I'll try and get a feeler probe down in there to ballpark it later. I'm really doubting that it's 60mm though from when I looked at the dimensions earlier...

damn you... you tease! ;)

And it shall remain a mystery until the NEXT rebuild. . . .20 years later, some young mechanic will tear it apart. . . kind of like the singing frog cartoon!

don't you want to be sure...

you could sell it to raise funds to fund your racing endeavors for the next decade... ;)

MJ

"Everybody do the Michigan Raaaaagggg!"

http://forums.pelicanparts.com/uploa...1118454675.gif

You are a bad, bad man... ;)