help me build an engine for my 72T. 2.4? (2.7?)

[jim72911t]

Hi Pelicanheads,
I'm a daily visitor but seldom post. After coming to the unfortunate conclusion that I could have done a better job rebuilding the engine in my '72T, (compression test, don't ask), I've decided to pull the engine and do it right. My goals for the car are occasional street driving, DE events (Porsche and BMW, as an instructor) , maybe an autocross here or there and PCA time trials.
The first thought I had was to just drop a 3.0 or 3.2 in and be done with it, but the idea of an original small displacement motor with some power seems more appealing right now. Plus, the problems with electrics, fuel pump, etc, seem like a hassle. A 2.7 RS conversion is also not apparently possible due to my car's 3R case.
My car is a stock '72 911T with MFI. I have come to the conclusion that I need to replace the pistons/cilynders. I would like to keep the stock T heads, which were rebuilt by a reputable Porsche mechanic with new valves, guides, etc, less than a year ago. Could I upgrade to the 911E pistons/
cylinders and cams without any problems? From the research I've done, the E has the same size valves (as does the S) as the T, with the difference being the larger port sizing on the S. I also realize that the E pistons/cylinders have slightly lower compression than the S pistons/cylinders, which may help in my intended application. I would like to upgrade either to an E/S MFI system, depending on application, or a set of Webers.
Any help would be much appreciated. The idea of building a fun, streetable, trackable motor sounds like a fun project for the off season. Build your dream motor based on what I have; just remember, it's my money you're spending, not yours!


Thanks,
Jim
'72 911T

BTW, If you have parts you'd like to sell that would aid in my project, feel free to email at jim@paulcomp.com

[kstar]

Hi Jim:

First, make sure that you don't talk to
Roy at Motor Meister. If you doubt my words, please peruse the PP archives.

I started out with a '72 911T.

I now have a short stroke 3.2 MFI motor that sees 7300rpms on each excusrsion - and an easy 300hp at the crank - courtesy of Black Forest.

You should stop by my house and we could talk motors. Call me at 858 759-9101.

I have nothing to hide. As long as folks like Ealrly S Man and Roland don't show up and party too much on my patio . . . . :>

Best,

Kurt

[Bobboloo]

You might consider boring your 84mm cylinders out to 86mm and getting some JE Pistons with a 9.5 to 1 ratio. Regrind your cams to S cams and recal your MFI pump. Build a 2.5L S motor so to speak. Should be close to 200 HP.

The spigots on the 3R case would not have to be bored in this scenerio.

This was a route I was considering until I found a good deal on a 2.7

Bobby

[stevef]

I'm thinking of doing just that....taking my 2.2 to 2.5. Figured I was going to get new P&C's. Are you suggesting reboring and leaving the bare surface without reapplying the wear coating.

[Ron,K]

You might consider boring your 84mm cylinders out to 86mm and getting some JE Pistons with a 9.5 to 1 ratio. Regrind your cams to S cams and recal your MFI pump. Build a 2.5L S motor so to speak. Should be close to 200 HP.


Steve,

I just completed this very same engine combination. You will not have to replate your cylinders as the "t" cylinders are cast iron and have no plating. After 1500 miles, I'm pleased with the combination.

[724doorE]

Cheap bang.... 2.7 Euro RS pistons and cylinders along with your stock heads. If your MFI system is a little rich it will probably be fine. The other thing I would change is from T to at least E cams. You'll have a very tractable engine that will scream to 7300 and pull from 2000-2500. Very nice in an early car. If you do it yourself, you should be able to get away with a 4-6000 dollar rebuild that will last a long time.

Ask me how I know

[jim72911t]

Thanks for all the help, guys. I had thought about boring my stock cylinders and using JE pistons as another possibility. Anyone have a source? I just did a search on their website and found no reference to a Porsche application.

And no, I won't be going with MM.

Jim

[zotman72]

I went down this path myself two years ago with my 2.4 MFI T motor. What I did was to build an stock 2.4 S MFI engine and boy am I happy with it. Do it right, you can come under $6K with you doing the assembly. Hardest part is finding the right MFI components (stacks, p/c, and cams). The rest can be built out your T parts. I do recommend sending your case out to Competition Engineering to make it right (oil bypass, decked, casesavers and general check out). Raceware rod bolts and teflon coating on your main and rod bearings. Get an SC oil pump and front cooler if you are serious about hitting the track. The 2.4S MFI engine is one sweet motor and a lot fun on the track. Sport muffler required. HTH.

[724doorE]

guys, I may be wrong, but.... from what I've read, the JE pistons are about 800-1000 a set, then you must get the cylinders redone.

Just buy a set of Mahle 2.7 RS p/c's for 1500-2000 and be done. Don't play games

[tobluforu]

I'm with 72fourdoore. I did what he did and I love the power band on my 72

[cegerer]

".... but the idea of an original small displacement motor with some power seems more appealing right now."

It will be even more appealing after you drive it. Ask me how I know. -- Curt

[Early_S_Man]

Actually, the RS 2.7 pistons & cylinders can be found for $1350 ... if you check around. IMHO ... JE pistons are currently overpriced by quite a bit! A couple of yeats ago ... at the JE website ... the most expensive 911 pistons with valve relief cuts were $117 each!

The 2.7 MFI build-up is one of the easiest 'upgrades' for an MFI 'T' engine, and much more rewarding than a transplant ... if you do the engine disassembly and reassembly yourself! The ONLY cams to consider are the factory early 'S' grind ... or GE-60 cams, since those are the tuning range most-closely matched by the rebuild of an MFI injection pump using the RS 2.7 'space cam!' Using 'T' stacks, throttle bodies, and heads would only cost about 10 hp on the top end, and give better mid-range torque ... though the 'stock' RS 2.7 torque equals or exceeds the peak torque of the 2.4S engine at 6500 rpm ... ALL THE WAY FROM 3300 rpm to 6700 rpm !!!

Ask yourself if 200- 210 hp (which equals the output of a USA-spec 3.2 transplant, and sounds & responds SO MUCH BETTER than a smogged post-73 engine ... it has to be experienced to be believed) is a sufficient increase from your 140 hp 911T?

And, just to clarify ... premium rod bolts and studs aren't required for a RS 2.7 spec engine, so that saves you $1000!

I would, however, strongly recommend 'sport' valve springs and retainers, though ... from AASCO, Jerry Woods, Andial, or EBS. They provide an insurance policy against mechanical overrevs from a missed shift in your 915 ... to 8500 rpm ... well worth the approx. $600 price tag!

Keep the MFI spirit alive! Good luck!

[Bobboloo]

The reason I suggested a 2.5 "S" motor was because he said he has a 3R case.

While I'm not familiar with why the 3R case would be unsuitable for a 2.7 conversion, it's why I suggested a 2.5 motor. Iron cylinders do not stress the case as much as the alloy cylinders since they match the expansion rate of the steel studs. The spigots could be left alone as well.

Also, I think the T/E stacks and throttle bodies would be fine in this scenerio as well as Warren suggested with a 2.7 RS motor.

If the case is suitable for a 2.7 conversion then the 2.7RS P/C's would be the way to go as the cost for cutting spigots is only $250ish.

Can anyone shed some light on the 3R case as in a real life testamonial?

Bobby

[CamB]

Yeah. Keep the MFI spirit alive - well I'm sorta cheating (MFI throttle bodies with EFI for best of both worlds IMHO). I still consider it in the spirit of an MFI engine.

I have always wondered where you get an RS space cam (or where guys like P-THOMAS got their 3.5 litre one, for that matter).

Are they pricey? I have always assumed so.

[Bobboloo]

Pacific Fuel Injection on the west coast (U.S.) can build a space cam for whatever motor you are building. There is also an outfit on the east coast but I don't remember their name.

Bobby

[Early_S_Man]

The RS 2.7 space cam is a readily available standard part in the Bosch supply system ... thanks to a 3.5 year production life for the 911/83 engine! It is my understanding that the cost to rebuild a MFI injection pump is the same, whether you rebuild it to stock 'T' specs, or RS 2.7 specs ... surely one of the bargains of owning an early car!

As far as the 3R and 5R cases go ... they were suitable for 2.4S engines, and have no reliability isues, AFIK. The issues regarding the 7R case are overblown, and sparked by problems with the development of the 2.8 RSR engine ... all 308 hp worth! If there had been a reliability problem with the 1972 2.4 911S engine and its' 190 hp with a 3R case ... wouldn't we have heard about it by now?

[jim72911t]

First off, thanks to all who have contributed. Instead of being angry that I have to pull my motor and do a teardown, I'm now actually looking forward to the project and the eventual (hopefully good) result.
After re-reading the article (Tech Notes II, Excellece) that I first read about the 3R (and 4R and 5R) cases not being suitable for a 2.7RS conversion, and reading all of your replies, I'm thinking that a 2.7RS might be a fun way to go. Also, I was originally thinking of ditching the MFI system entirely, but now I think I'll keep it just because it's so damn cool, and I can't give up on it. I do plan to retain the stock T heads, which may cost me some HP at high RPMs, but if that might save me a couple thousand dollars, and give me some midrange torque, I'll make the sacrifice. If I end up with a motor that can get me to work once or twice a week, and sound (and go!) like the early Porsches that passed me at Thunderhill a few weeks ago, I'll be satisfied.

Thanks again,
Jim

[J P Stein]

The spigot lands of the 3R case are about 5 mm wide.
Taking the spigot bores out to 97 mm from their current 92 mm.
reduces the land width to about 2.5mm. Land width of the 2.7L, 7r case, at 97 mm is about 5 mm. The 3r cases also lack the internal webing and the extra stiffening around the flywheel added to the 7r case. Some extra machining is also required on the 3r case for piston skirt clearance.

My understanding is that it can be done, of course, but the longevity is problimatic in 2.7L form.......the case cracks, or so I've read. I have no personal experience with the 3r case in this application.
.......but I have one in the shop.......real cheep.

The 5r case also has the wider lands, BTW, and extra stiffening
around the flywheel, but, alas, no internal stiffening.

Thas' all I know about this.

[724doorE]

Jim,

I think ( I'd have to look again) that my 72E has a 3R case. As I've said, I did the 2.7 RS thing and have had no problems. Just make sure you have all the proper machining operations done to the case halves. Typically, if they are slightly warped or out of shape down the center they can be shaved and then line bored back to the original spec ( my case). No problem with the 97mm spigot bore. My one drawback is that back when I did this in 1990 or so, Dilivar was still the rage and thats what I shelled out the money for. Today on a small engine like this I would just use stock or raceware studs. The small ports will be fine, or while doing the rebuild you cuold have the heads ported to S spec and then install S stacks when you can find some later. Also don't forget to have the oil bypass mod done.

Again I like Paul Tomas have NOT had our MFI pumps rebuilt or recalibrated. I have had no problems and as far as I know niether has he. I'm sure he could speak on that matter.

If you want to get rid your MFI I'd be happy to take it off your hands. Its an old antiquated syslem don't you know .

Oh well, got to go to work or something.....

BTW, if you have acess to a small Bridgeport type vertical mill, and a large set of balls, you can do the spigot mod and install case savers, and do the dowel pinning if you desire

Good luck and where are you located ?

[zotman72]

A brave man with a dremel can do the porting of his 911 T heads to S spec. I decided that was not me, but that is all my wrench (Eisenbud in Denver) did when he ported my heads. Similarly taking emory cloth (or your dremel) to your mag case to boattail it can be done but I again chickened out. Mag dust is quite nasty too. I used steel head studs on my case but I differ with Warren on the rod bolts. Raceware bolts I think is the way to go.

I am curious how many 911 engines, the folks on commenting on this post have rebuilt themselves. Me, I am at just two. Hopefully not another anytime soon. MFI does rock.