3.6 crank in a 3.2?

asphaltgambler · 11-13-2004, 11:35 AM

Has anyone put a 3.6 crank in a '85-up 3.2? In street motors usually more throw in the crank will yield a 'big-motor' feel. Does JE make pistons with the proper pin location for this set-up ?

If I go to 98mm P/C and consider the 3.6 crank what would be the build plan? Has anyone done this specific engine?

Carrera3.5L · Carrera3.5L's Garage

Quote:

Originally posted by asphaltgambler
Has anyone put a 3.6 crank in a '85-up 3.2? In street motors usually more throw in the crank will yield a 'big-motor' feel. Does JE make pistons with the proper pin location for this set-up ?

If I go to 98mm P/C and consider the 3.6 crank what would be the build plan? Has anyone done this specific engine?

My personal motor is a 3.5L from 3.2L using 100mm Mahle's with the original 74.4mm 3.2L crank (short-stroke I guess you can call it). Never DONE or SEEN a 3.5L long stroke (98x76.4) but HAVE seen plenty 3.6L versions (100x76.4) in Carrera and 930 motors when working at Andial.

Since Andial is one of the Mahle distributors, you won't see a JE piston in their shop. JE will build anything you ask of them, just make sure you provide them with the correct information.

Andial has both 98mm and 100mm Mahle pistons/cylinders for the 3.2L crank with 23mm wrist pin. The same sets are used for the longer stroke 76.4mm 3.6L crank, just additional piston machining is required.

If seriously interested, I have the drawing needed for the 100mm piston mods to make a 3.6L from a 3.2L. However, I don't have a drawing for the 98's. Sorry.

Ralph

asphaltgambler · 11-14-2004, 07:04 AM

Ralph, thanks for your input. I want to keep the 98mm P/C's. Looks like to me after that bore size things get thin and I worry about flame travel since I'm not doing the twin plug deal.

Since Porsche street engines are relatively mild RPM (below 6800) for even aggressive cam profiles, it would seem to me that this combo would be a no-brainer.

In other air cooled engines a modest increase in the throw AND the bore yield amazing results w/o seriously comprimising reliablility.

The first problem is that will the 915 flywheel and clutch assy bolt up?

Henry Schmidt · Henry Schmidt's Garage

We built the engine you're talking about back in the early 90s. It produced huge torque but no rpm. In fact it blew 2nd gear right off the main shaft (early 915). We encounter some clearance problems and because of the excessive rod angularity that makes piston side loading an issue we gave up on this spec for our performance engines. These cranks are designed to run with a dual mass flywheel and a harmonic balancer and without them balance also becomes an issue.
We just took apart a turbo engine built by Andial with a 3.6 (76.4 x 100) crank. This engine has exploded at least 3 times so we removed the crank and reconfigured the engine in an attempt to keep this engine alive. We'll let you know how the new configurations runs.

asphaltgambler · 11-14-2004, 07:54 AM

Being that there is always a optimum equation of bore/throw/rod length probably in this case the rods are just too short.
I also know that as the stroke increases the piston speed increases and the piston dwell time at TDC makes for increased chance of detonation.

Well. just a thought on a possible build. I'm glad that someone else has already tried this, even if it wasn't successful