Solex Cams on 2.4T

[Brrrrp]

I have been told by one of the "larger" 911 engine builders that I can run Solex cams with my 7.5:1 T pistons. They claim to have done this before with no problems.

Has anyone out there tried this? I have read comments stating E or Solex cams can't be used with T pistons unless they're cut. However, "all T pistons are not created equal", and the 2.4Ts DO have the lowest CR of any normally aspirated 911. This has to result in more distance between the piston top and the valves.

On the other hand, the Solex cams have lift that approaches the S cam, close to 1.5mm more than a T cam.

Thanks.
Roger

[jcbear]

Brrrp-
See Wayne's book (Wayne's Top Engine Picks {page 112}), a 2.4 with "S" cam's IS a recommended upgrade modification. Also see the following thread on this forum click here.

You may also find this site helpful - which states that putting 2.8 RSR pistons and cylinders in a 2.2, which results in a 2.6 liter engine runs great with Solex or S cams.

I'm going with one of Wayne's picks that does not involve machining [i.e. cutting the case spigots and heads} by making my 2.2 --> a 2.4, by putting a 2.4 crankshaft & rods in my 2.2, using "S" p/c's, with Solex cam's, - it's not together yet, just picked up a 964 oil pump this week. I am really interested in what you decide, as I'm sure are ALL EARLY 911 rebuilders.

You might also see Bruce Anderson's Porsche 911 Performance Handbook, pages 138-139 which specifically talks about piston/valve clearance tolerances and measurements.
Welcome to the the Pelican Engine Rebuilding Forum

[Brrrrp]

For clarification, I am NOT planning on replacing the T pistons. The basic longblock is in good shape, starts and runs great, 135 comp all around, uses very little oil, and the valve guides are still in good shape. All I am looking to replace is the cams and the MFI with Webers.

Before you ask, "why bother", I use the car primarily for DE events. The stock T motor is pretty lifeless past 5K. I have the priviledge of living reasonably close to Road America. I would really like a bit more top end for long tracks like this one.

Thanks.
Roger

[jluetjen]

I guess the only 2 concerns that I'd have about your approach since you use the car for DE's is that the low CR of the engine will make the engine "cammyier" -- ie. weaker when off-cam. Solex cams are pretty weak below 2000 RPM anyhow, and start to sing in the 3000-4000 RPM range. So expect your car to be kind of sluggesh off the line or when leaving a dead stop. Having a 2.4 though should help that problem a little. The other issue is to confirm the piston-valve clearance so that the valves won't kiss the pistons. Be sure to do this before you put the engine together, otherwise the first crank on starter could be awfully expensive.