Built '72T enjoy's retirement pull on the Jerry Woods dyno...
 

On Monday night I made what I believe was a very sensible decision along the lifeline of my Gulf Orange '72 911.

This is a car I bought in 2000. It has been a Bay Area PCA owned car for most of it's 6 owners. It has been used for PCA GGR competition events for most of that time. Over the years it was developed a little, with the addition of SC flares, RS bumpers and duck tail.

Since we have owned it, the car has been used to test many of our products, allow Tracey to learn high speed driving skills, accumulated many minutes pressed up to the rev-limiter (7300) at Auto-X and 1000's of miles at track events.

The spec of the motor has always been a mystery to some degree, with the thick folio of receipts for the car showing several rebuilds, often preceeded by "car towed to shop - engine over rev", then followed by a significant invoice. As best I could tell, the motor is the original 911T case, 911E cams, 911E MFI pump with 911S plastic trumpets.

The decision to take this motor out of the car was purely one of timely preservation. Built many years ago it has delivered very faithful service - much as you would expect from this edition of the 911 engine. But time and hours were taking their toll on the motor, oil leaks, worn external components, deteriorating hoses, cracking heater boxes etc. In the scheme of things I would have been very upset to recklessly damage this finely balanced motor - so made plans for long block replacement for an interim - allowing this one a full freshen-up.

With that motor ('72 2.4 911S) ready to install later this month, it was time to retire the original motor with some dignity.

Straight from the car it made peak of 181 hp at 6250 rpm, falling to 160 hp at 7000 rpm, a test without the stock air cleaner made peak of 183 at 6500 rpm and still made 172 hp at 7000 rpm.

We also tested a stock 1972 muffler in place of my rare 1969 Abarth 911S muffler and made the same numbers.

http://forums.pelicanparts.com/uploa...1097079678.jpg

We did not fool with mixture (no lambda bungs) or timing - these were de-rig runs to see what we have been working with in the car and to check for any issues that might need repairs on parts migrating to the interim motor.

With 180 hp on tap we feel pretty sure there are 911S pistons in there (not E as we had assumed from the paperwork) But otherwise it seems like an honest little motor that has given great service and is going to be prepared for another round - hopefully equally as satisfying.

I must extend a big thankyou to Rich Walton for taking the time and effort to put this motor up on the dyno at Jerry Woods.

Regards

Hayden

Thanks for taking the time Hayden and Rich..

This is a good sample to add to the archives!

It's always nice to see a 911 motor coming out voluntarily, instead of by necessity. Although a mis-shift by the Wevo-meister would have made a good 'man bites dog' story. Sort of like Jim Fixx's heart attack.

What are the plans for the new version of the motor?

Hayden,

Very sensible approach and well worth the effort.
What are the cylinder leak numbers and cranking compression?
As you disassemble it, let us know the components and specs you find.

How is the new ’72 2.4S configured? Are you planning to restore the “T” engine to original or leave it improved?

Someone should compile a summery of all the engines that have been on Jerry’s dyno over the past (30?) years. Rich and Jerry are too busy to do something that mundane.

Best,
Grady

The summary would be a great idea. Bruce Anderson has taken some of JW's info on past motors and used it in his books, but it would be great to have a compilation of what can be expected from the various combinations. The caveat, of course, is variations in altitude, humidity, temperatures, and other factors (e.g.-my dyno's better than your's sort of thing) but it could serve as a valuable guide when one is choosing which route to take when building a motor.
Novices new to this should take note that it is not all about maximum horsepower and torque either, but flexibility ,range, and how the motor is to be used.

Jack,

In a somewhat pre-empted ironic twist, I do have to admit that an over-rev is one of the many accumulated indiscretions that mean the motor is coming out.

Having said that, it was back in early 2001 (pre WEVO shifter design) and although we could not even get a leakdown on the RH cylinder bank, some careful trickery by the JWE tech's and a careful recovery period gave us enough compression to keep it alive. Once the valve seats had assumed their new angles and wear patterns, it was not too bad - as can be seen on the dyno. That in itself was a risk, so I am pleased we made it this far and it has come out in one piece.

The interim motor is 2.4S pistons, Elgin "SMod" cams, the same 911E pump from the existing motor is going on it. We will run 1.5" headers and phase 9's and the intake manifolds are getting opened up to 38mm from the 34mm current size. It made 200 on carburettors apparently, I assume we willbe about there on MFI too, perhaps a little more from the exhaust. I am told to expect a decent torque fill on the lower rpm scale from the SMod cam.

The old motor will be refreshed in the same config (as above - assuming we like it) except with 85mm bores (up from 84mm) and reunited with the parts loaned to the interim motor - then placed back in the orange car.

The interim motor will then go in my '72 street car, with heat, Abarth muffler and suitable MFI pump, probably 911E throttle bodies and stacks as I only have one set of "S" stacks.

Grady,

We didnt take any numbers, there were so many other reasons to pull the motor that it was not critical - although it would have been interesting.

When we get inside it, I will update the spec. 180 hp is stout for an "E"+ spec motor, so I will be keen to know what makes it work so nicely.

The original "T" motor will never make it back to a "T", the car is far from original, being quite the small bore early hot rod. Owners before me made good choices and spent quite a bit of money, we are still enjoying that. I am a small bore fan and have been collecting enough parts to stick to the 2.4 liter format well into the future.

I agree a record of all the motors run on Jerry's dyno would make an interesting read. I am sure they have some pretty good records, but like many they are busy with their immediate future. It would take an archivast like Bruce Anderson to catalogue it in a presentable format.

Regards

Hayden

Dave,

That's a good point regarding the quest for peak power. One reason my E+ spec motor has been so much fun and so competitive is the driveability. It was making 152 hp and 160 lb/ft at 5000 rpm, this makes it very easy to drive.
I believe it is critical to accurately identify how you want to use your car, what you can afford and what specification will offer the best balance of compromises. I am sure in your position you have this conversation several times a month.
For the way we use our car, I was reluctant to go to a full "S" spec cam and intake, I am hoping the "SMod" cam finds some middle ground.
The effect of the stock aircleaner was pretty significant. Perhaps we will try some individual filter elements on the set-up dyno work for the interim motor.

Regards

Hayden

Great thread. I would love to find out what's possible w/ a T motor.

An enjoyable read:)

Another data point for a 2.4T motor (posted this before).

145 rwhp - http://members.rennlist.com/jpinkert/pepe%20dyno%20run.jpg

The config is a mystery to me...just as yours is. Based on the timing, I have a T cam. I also rebuilt the MFI pump years ago to T specs. My guess is it has 2.2S pistons, bumping the compression.

Its ironic because I was just reading Bruce's performance book this morning. He supports Hayden's comment about making sure to build the engine to the specific use you plan because a street engine will spend 90+% of its time at 1/3 load. Tyson and I have been talking about this a bunch too and he echoed that. Good luck Hayden. Those are damn good numbers for a tired engine.

My stock 2.4 “T” motor pulled 129hp and 129lb/ft at the rear wheels in my 914 last year, with no air cleaners and open headers.

nein14-6,

Was that a "T" with MFI or Carbs? I know of another 914-6 (stock 2 liter) that showed a large drop in max HP with the stock air cleaner on - somehting like 10hp and would not really pull beyond 6500. The 12 hp my motor was down at 7000 is very signifincant, especially when we do track work and run so long at WOT, typical of a small motor.

Regards

Hayden

2.4t
 

Hayden,
After reading this I have hope that the "T" engine can make some great Hp. Do you know what else beside the pistons were changed?
And please forgive the question (I am learning) but do you have to change the cyliders when you but the "S" pistons in?
Thanks for any info, there are very very few Porsche down here so I am on my own for info and projects .

Derek

Derek,

I am not really the person to ask about engine specs, power potential etc.

My 911T motor definitely has 911E cams, 911E MFI pump (by serial # at least) 911E intake port Ø, 911E Throttle bodies & 911S trumpets.

Beyond that, is speculation at this point. The idea that it has 911E or 911S compression ratio is speculation, folio paperwork shows E pistons later date than S pistons on a previous rebuild.... we will open it up soon enough and try to find out.

It is possible to change pistons without changing cylinders, but seek an expert opinion on whether your combination of parts are compatible, both as components (not all are) and wear condition of all the parts.

Regards

Hayden

Not so much typical of a small motor but rather of an E, especially a 2.4 running the stock 32 mm intake ports. Basically it was getting choked off by the intake tracts and the cam.

Dyno Results
 

As a point for comparison, I just had my 73 911S dynoed at an Alfa Club event. It is stock but was bumped up to 2.7 when it was rebuilt 30,000 miles ago.
180 first run
170 second run with air filter set up removed.
This was done at Magna Flow the exhaust people. They said that the fan used to keep the engine cool may have effected the air flow without the airbox.

John,

I think you may have misunderstood, see the initial post again.

The 12hp delta is at 7000 rpm with and without the stock air cleaner assembly.

Power at 6250 was the same with and without the air cleaner assembly.

I agree, the general loss of power above 6250 rpm is a function of the elements you mentioned.

Is 32mm stock for 2.4 "E" ? My 2.4 911T made to E+ spec are 34mm. I do have 3 spare sets of throttle bodies, 29mm, 32mm and 35.7mm. One set was definitely from a 911E motor I bought complete some years ago, but they have all been mixed together.

It's starting to look like I have a bit of a hybrid built to a unique spec?

Regards

Hayden