73 2.4T rebuild/upgrade

[TargaT]

Hello Friends, I have decided to pull the engine on my recently acquired 73T. Although it only has 70K miles and has never been apart it has a multitude of leaks, requires a full exhaust including heat exchangers. I had a leakdown test and it averaged about 10%. I've read many threads re upgrading to S specs but from my overall assesment an E spec motor would be more suitable for me and there seems to be little info on this upgrade. From my research this is what I understand to be the differences.

1. compression ratio .5 difference. Assuminging my Ps&Cs are still useable is it possible to get this increase by shaving the heads? how much?

2. different cams. these seam to be readily available. can you recommend a source or particular part #s

3. MFI throttle body openings. Apparently Eurometrix can modify these- about 1K$

4. MFI stacks- look for used or apparently these can be bored? Eurometrix indicates he has the tooling to open them up to S specs. Will this work?

5. MFI pump space cam. Is this part available? is this something I can replace myself? or is there more to it than that.
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6. Heads- from what I can see the valves and ports are the same for T and E ?

Is this an all or nothing? i.e. is it possible to replace the cams and not modify the throttle bodies or stacks? Is the space cam change critical? and what is its function? timing and/or volume

Is this worth the effort or am I just asking for a lot of trouble i.e. should I just put it back togethor stock?

Lots of questions but I'm new to the Porsche world.
Thanks, any feedback and suggestions would be greatly appreciated.

Joe

[Tim Walsh]

Do a search, you'll find lots info on 2.4T's. I went with JE's @ 10:1 and E cams.

You should be able to get half a point from shaving the heads, but it's not an elagent way to do it. Do a search for tyson schmit(sp?) and dtw, both have done it sucessfully.

If the butterflys are ok (ussually not) then you can get away with just enlarging them, otherwise it will take a full rebuild at eurometrix.

The space cam is replaceable, but I've never heard of anyone actually replacing their own spacecam. Most just rebuild the pump and have the cam redone at the same time. I bought a used E pump and sold off my T.

Heads. All 72-77 heads had the same valve sizes. (40e and 46i I think) but the ports varied. T motors ussually had 29mm intake ports, E's had 32 and S's had 36's.

Frankly, it's more of an all or nothing kinda thing. If you change your cams, then you have to change your pistons somehow or you won't get enough clearance for your pistons. If you do that then you need to get enough air into the motor, requiring larger ports,t-bodies and stacks.


One option is to increase your compression with new pistons and leave everything else alone.

[dtw]

I got a theoretical .75 point of CR from shaving my heads. If I had it to do over again I think I would offset-bore my rod bushings.

[TargaT]

Hey, great website. I'll print off a copy of your rebuild guide to use along with Waynes book.How's your progress? not too many recent updates.
Could you tell me a little more about the configuration of your motor and how it's running if on the road yet.

Joe

[dtw]

Thanks for the positive feedback. I really need to update the site, a ton has been going on since the last update. The engine is indeed up and running nicely. Due to my prior 911 experience, I miss the torque of the large displacement motors, but the throttle response and cam profile of this motor more than make up for it. With a light '72 tub, 7:31 gearbox, and this engine, the car is a rocket ship. It makes peak power just over 6,000 rpm. I think there's more power and driveability to be unlocked from this motor, great as it is, with some careful CMA and dyno time. I drove the car for several months to enjoy the motor and break it in while I put the finishing touches on the car's mechanical restoration. When that was done I tore the car apart this summer and it is now in bare metal being prepped for paint.

I did a search confined to my name and the engine building forum and came up with these, among many other, threads relating to my engine:

Doesn't matter how many times you see one...

Snap...crackle...pop...ROAR!!

[Bobboloo]

First off, what do you plan to do with the car. Is it for the street or for the track?

If it's for the street I wouldn't touch the induction. Increasing the ports will make the car a dog on the streets. Just about the time you get to the power it will be time to shift. Even the cams would be better left as is IMO. Just bump up the CR to 9.8:1 with a set of pistons and an already great motor (the 2.4T in my opinion) will be even better. If you want to increase the cc's by boring the cylinders out and installing some larger JE's (85mm or 86mm) to have a 2.5T motor all the merrier.

If the car is for street and occaisional track then do the same mods as above but add a Solex or E cam and port accordingly if budget allows.

If the car is a track car then by all means. Change the induction and ports but forget about trying to make T stacks work. You have to go to with S stacks and ports. The displacement size will be governed by what class you want to race in.

I just rebuilt my 2.4T stock and I love it for the street. I just removed the 2.7S CIS motor (36mm ports) that was in the car temporarily and it didn't feel that much stronger than the 2.4T MFI although the numbers would show different. Had the motor been a 2.7CIS normal with (32mm ports) I'm sure it would have felt a lot stronger on the street.

Just my 2cents...