I'll join in...how's this 2.4T rebuild/upgrade?
 

I've read the numerous "build me an engine" threads in the archives. I've been considering the 2.7RS upgrade, but for the sake of being unique, want to go the road less traveled.

Here's what I'm leaning toward. My 2.4L "T" engine needs a full rebuild. The #4 piston and valve became friends (possible over-rev by PO). So I need to figure out my P/C's direction.

My thought is to bore out the 84mm cylinders to 86.7, JE pistons, and build a 2.5L long stroke engine (I have a 70.4mm crank). I know I want to keep the MFI, and the existing case (unless I find issues after finishing the tear-down). Could I keep the "T" MFI calibration, and existing cams?? I plan to upgrade in the future, but wish to keep costs down now. I'd rather put money into "proper" machining and critical fasteners, to build the engine the "right" way, and do performance mods later. I figured no matter what I build, I'll want more power later on.

Should I do additional work on the heads to get better power, and prepare for future mods?? Is there work required on the heads for the larger piston bore? Also, where do I find out the cost of JE pistons? And what compression ratio should/will I have? I want to be able to run on 93 octane pump gas.

All machining work will be sent out, but assembly work will be done by myself.

Any comments are welcome.

Thanks!

I cannot help you much Jay but wondered which case came in a 2.4t engine from 1972. Any idea?

Thanks.

Jay, here's what I would do.

Bore the cylinders out like you planned.

Buy JE pistons that have enough valve clearance for S cams. (for future upgrades) You can get whatever C/R you want. 9.8/1 is my recomm.

The heads may need a little flycutting to clear the larger bore pistons.

Have the T cams reground by Elgin to E-spec.

Open the intake ports up to 32mm. (No, contrary to the factory spec book, a 2.4T intake port is actually 29mm, not 32mm. The exhaust ports are already 32mm though.) You could go a little more if you like, to 33mm or so.

Use your existing MFI pump as-is. A T pump can be adjusted to work with E cams and run just fine, assuming that it is in good condition.

This would be a nice 170-175hp motor with great streetability, and much improved top-end, and great around-town low-speed response.

Those are all great suggestions from Tyson. One question though. When I measured a T iron cylinder it didn't seem to have enough room to go out to 86.7mm without leaving enough material between the CE ring gasket and the piston. 2.15mm to be exact. Is this a large enough margin?

Did Porsche use a CE gasket on the 2.5 or not?

Any thoughts?

If your going to machine the heads (which you should) open the ports to 36mm.. (S spec) You will be charged the same by the machinist whether you specify 32mm or 36mm. With an E cam this will make a nice ballsy engine. And at a later date you could run a rad cam and have the breathing capability.

Also have the heads machined for twin plugs.. if you dont twin plug now, you may at a later date.. in the meantime put some old plugs in the lower position.

sounds like a fun project

Thanks to everyone for the info. I can see the motor taking shape in my head already. Bobboloo--I'll have to look into whether or not there's enough mat'l. This option was mentioned in an earlier thread that Tim (It9eek) talked about doing on his '72 T motor.

Any special case mods I'll have to do aside from getting it back to spec? (and the oil bypass mod. of course)

First, you have to decide what sort of motor you want -- AutoX, street hot rod, or racetracks. You shold also build the motor from the bottom end up. ie do the heads, etc. later if you dont do it all at once.

And, there are some tricks to boring out the cylinders. Get a machinist who has done this before on race engines, and talk to him.

I agree with Tim T except the 36mm port thing. It's a great idea, but wouldn't allow you to still use the stock T MFI pump, since the breathing would be quite a bit better than a stock E-spec engine.

I've seen cast iron cylinders opened up to 86mm before, and it worked just fine. The 86.7 may indeed be pushing the limit though, like Bobboloo stated.

Jay, if we can hook up, your welcome to at least a ride in my 72E with 2.7 RS pistons/cyls, E cams, and stock E mfi.

I won't be in northern Chicago though anytime soon

Dennis, I'm going to take you up on that before I make an official decision on the motor rebuild. My dad lives in Michigan, so I pass thru NW Indiana from time to time. Thanks!

Jay, sounds like a plan! Just give me some notice since we seem to go back and forth to Mishawaka every few weeks. BTW I'm planning on attending Thrown Hammers Car show in Sept. if we don't meet up before then. Other wise, until I find better employment, I'll be easy to get to at Purdue U. Hammond Campus just a block north of 80 2 miles over the border.

Its nice to have a reason to go for a ride:)

I just got around to installing my MSD ignition and adjusted my throttle rods so I am now getting more than half throttle ;)

I would have replied earlier but I was on vacation.I'm looking to do the same thing. To bore out my T cylinders out and install JE's and keep my cams and MFI pump the same. Then when I get out of college swap in S
cams and recalibrate the MFI pump.

Here's what I came up with on some of my calculations:
A 2341mL 9.8:1 T engine should make about 170 and 9.8:1 2397 mL(85mm bore) 9.8:1 T engine should make about 2% above that.. about 175 or so. A T engine with an 86mm bore would displace 2454mL and probably make somewhere in the neighborhood of 178hp or so.
I'm guessing a 2397mL 9.8:1 S engine should make about 200 or 205 and a 2454 mL engine should make another 5-7HP more than that.
How close do these #'s sound?
Is there enough meat on a T cylinder to bore it out to 86mm and still be reliable enough to run for 70K-100K miles? I'm looking for an engine that I know the engine will run well for a long time and still be quite fun.

Tim, remember, I'm the pig for this situation. I'm running my stock 72 case, 3-4-or5R, Don't remember which. I'm at about 10,000 after rebuild with no case issues.

PS, you may as well put in as much displacement as you can ie,2.7 or2.9 instead of stopping at 2.5. That displacement will give you another 20-30 hp and lower your useable powerband.

Then again, my old stock 2.4E was rather stout:)

Dennis,
I'm really really hesitent to bore out my spigots to accomidate the 2.7 pistons. I just don't think they can handle the stress. I think yours is ok since it's got E cams and not RS cams but I'd like to run the S cams in my engine eventually and I'd be really worried about my case cracking.

Can you check your case for me? I know I"ve got a 3R-4R case. If I had a 5R case I'd go with the 2.7 in a heartbeat but the 3R case is a weak one.

Aye Tim, will do!

I hear you, but I have faith, and hope that all will be well!

Remember, the early 70-72 2.3, 2.4, 2.5 race engine made up to 275 hp in those early cases.....

He!!, its outside, I'll go check!

Tim, and everone else, I just looked and it is indeed a 4R case.

Tim, if you have a spare set of early S cams, I'll be happy to see how long my case lasts with them in tow :)

I do use my car every day for daily transportation and it needs many things, but the engine is sound

hmm.. You're seriously tempting me.

Dennis,
Can you check the other side this time? I've got a 3R 4R setup but dtw's actually got a 5R 4R setup so it could be either.

Took a look, its the dreaded 3R-4R. 3R on the oil cooler side. My car was 0060 of the line, so late 71 production, hence 3R-4R

I'm tempted to go the 2.7RS P/C route. I have the 4R/5R case, so I guess I'm not too worried about stressing it. I don't plan on the full RS setup...at least not for a while! My engine has a broken exhaust valve that punched a hole in the piston. If the cylinder walls are too beat up, I won't even be able to bore them out unless I find a good used replacement in the right height group.

I'm trying to get a good understanding of exactly what machining I'd have to do for the case/heads. I can't quite follow what I'd need to calculate costs of going the 2.7 route. Does anyone have a good itemized list??

Dennis, I'll be out of town tomorrow (7/2) until Mon. morning. But I do have all of next week off from work. Drop me a line how next week looks for you. I won't be able to reply until Monday, but I will get back to you!

Have a great 4th everyone!!