Can a 70.4mm crank fit a 964 3.6 case?

[DV 993tt]

Anybody know if a 70.4mm crank can fit in a 964 3.6 case?

[Henry Schmidt]

It will fit and the result is a very nice short stroke engine.

[DV 993tt]

Thanks for the answer Henry. That's exactly my thinking. A very nice short stroke engine. If I use 102mm P&Cs with a 70.4mm crank, the bore stroke ratio would be 1.449 which exceeds your short stroke 2.8 ratio.

[kenikh]

Can you make the valve train light enough with those big valves to make it worth shortening the stroke? Seems to me that the only reason to shorten the stroke is to rev the sucker to 8K. You'd need titanium valves to stop float when coupled with a cam that would take advantage of the higher revs. Then again, the big bore of this motor could probably handle the overlap that lazy ramps would afford you, so it might work...maybe.

[Henry Schmidt]

Valve train is not an issue. We rev our 2.8 short stroke engine to 8500 RSR sprint cams and without titanium valves . The 2.8SS uses 49mm in and 41.5 mm ex just a little smaller than stock 3.6.

But if titanuim valves are desired we have Del West titanium valves in stock.

[kenikh]

So the answer is the large displacement (3.3 liters for a 3.6 on a 70.4mm crank) makes up for the low end power loss of using a cam with slower ramps like an RSR (when compared to something like a DC62). Makes sense.

[soupbone]

Quickie .....Will 3.0 rods on 70.4 crank hook up to a 3.6 piston?

[Henry Schmidt]

The 3.0 rod has a 22 mm wrist pin and the 3.6 piston has a 23mm wrist.
The wrist piston location in the piston or pin height is also different.
I believe the pin height is .8mm too high. This would mean you would have far too much deck height.
We encounter this same problem when putting 3.2 pistons on a 3.0 crank and rods.

[soupbone]

What makes sense here... Custom rods? Pauter? Or maybe stock 3.0 rods with custom JE pistons with 22mm wrist in the right place? Is that possible?

[cstreit]

You can also run 100mm and 102mm cylinders in a 3.0L case... Though with the 102mm your spigots are getting really thin. I am using 100mm cylinders from LNEngineering and there was plenty of meat left on the case for a nice 3.317L engine. Making over 312bhp at 7k rpm on 930 octane (twin plugged obviously)

[soupbone]

Yes indeed cstreit. I wondering about 104mm p/c 70.4 crank in 3.6 case for 3588cc or so. Is LN 104mm on a 3.6 case reliable in general? Can a 70.4 SC crank live at 8000 rpm like the 66mm in Supertecs 2.8?

[mcinturff]

Well if a 70.4mm SC crank will fit, then a 956 (or is it 962? or are they the same) will fit. 66mm stroke * 102mm bore = 3.235 liters. Anyone ever done this?

[atelier14]

Does anybody here actually uses a 70.4mm crank in a 964 or 993 engine with longer rods and JE pistons?

[kenikh]

No, it won't fit.

[356RS]

mcinturff, I'm in the process of building a 66 x 100, 3.1 liter on an early 930/02 case.
Hard part is getting the desired compression ratio of 11.2 or so without filling in the early SC heads.

[safe]

How high can you safely rev a stock 964 engine?

A couple of friends have fitted MAF-kits from FVD in Germany with 7200 rpm chips, to their 964 RS's.

[atelier14]

Mark, what 66 mm crank are you using?

Destroked 70,4 mm, 962 or other aftermarket?

[Henry Schmidt]

Originally Posted by atelier14

Does anybody here actually uses a 70.4mm crank in a 964 or 993 engine with longer rods and JE pistons?

Originally Posted by kenikh

No, it won't fit.

If the question is : will the 70.4 crank from a 2.4/2.7 (six bolt flywheel) fit in a 964 case? Kenik is correct, it will not.
If the question is: will a 70.4 crank (9 bolt) from a 911SC, 935, or 962 fit in a 964 case? the answer is yes.
It will fit and we have done it.

[Henry Schmidt]

This 66mm crank was designed to fit the 964 case or any case that uses a 9 bolt crank. The plan was to make a two valve 911 engine spin 9000+.
It uses GT3 Pankl rods and a modern oil supply system.

[356RS]

atelier14, I'm using the early 2.0/2.2 CW crank. Wish I could afford the 66mm crank Henry makes. Beautiful work Henry.