general thoughts on the 2.4 engine

[rfuerst911sc]

I want to solicit the experts opinion on the 911 2.4 T engine. I am thinking about useing this engine for a project 914 conversion but I don't know too much about the earlier engines. So what's the opinions on this engine? And to convert to S specs is it just changing cams or is there more to it? Probably a bump in compression also?

[Jeff Higgins]

I absolutely love mine. It's an all original spec '72 still running on the MFI. I have dyno'd it at 135 hp and 141 ft lbs of torque at the wheels, so it's no powerhouse, but it is a sweet running little motor. I think because it is so relatively under-stressed it is one of the more bullet-proof early motors out there, probably rivaling the 3.0 SC motor in that regard. Mine has just over 30k on the last rebuild and I have put most of that on it myself. It has never missed a beat, even running it on the average of a dozen or so track days a year and driving it fairly hard on the street.

Conversion to "S" spec is more than just cams. I don't think the "T" pistons have enough valve clearance for the higher lift. The valve sizes are all the same on every 2.4, but port sizes got bigger from "T" to "E" to "S". The stacks and throttle bodies are the same as the ports; different sizes on the different motors. The MFI pumps have space cams specific to the motor as well, so that would have to be rebuilt if that is what you want to run. If you run Webers you can ignore all the MFI changes.

Lots of guys ignore the port size differences and use the "T" heads very successfully when upgrading everything else to "S" spec, especially on a street motor. It will be a little torquier on the bottom end, while giving up a bit on top. I hear the "T" heads are more desireable if you want to get them ported, as they have more meat for the head porting guy to play with, giving him more freedom to re-shape them.

The compression is quite low. Most guys put the 2.2 "S" pistons and cylinders on the 2.4's for a good bump in compression, like up to almost 10:1. JE has 84 and 85mm pistons that will do the same thing if you want to keep your cast iron cylinders and save some money. They all have deep enough valve pockets to clear "S" cams, so you get a bump in compression and the ability to run hotter cams all in one fell swoop.

Most guys will recommend losing the cast iron cylinders on any hot-rod build. They don't dissapate heat as well as the old biral or the new nickasil. I'm not so sure it makes that big of a difference, but I defer to the experts on that one. One thing I will say is that the CTE (coeffecient of thermal expansion) of the iron cylinders more closely matches that of the head studs than any aluminum cylinders. You won't hear of many "T" motors pulling studs. Of course if you are getting into it deep enough to replace the P&C's, you will want to time-cert the cases anyway, so that may be moot.

Anyway, that's my take on them. I think they are a great little motor. It would be a lot of fun to have one in a light little 914. My 911 is appraching 2200 pounds, far more than a 914, and it is lots of fun in that car.

[Lukesportsman]

I have RS P&C so I can't vouch for clearance, but the E cams are a great street cam more punch than the T esp. with some compression, but torquier than the S.