911 2.4L engine rebuild question

[refugee]

Oh, I now understand about raising the compression with the 2.2 pistons.

If I do the 2.2 pistons and thus raising the compression, can the car run on
93 octane? I think that you or Peter Morgan said in your book that the 2.4
lowered the compression by lowering the placement of the piston rings and
thus lowering the compression to run lower octane...

I guess that I must also swap the camshafts with the 2.2 pistons. Do I have
to bring the rpm up high in order to take advantage of this change?

The 911T has Zenith carbs. I was really hoping they were Weber after
reading your book. Anyway, it sounds strange that they weren't cis or mfi,
but I think this vehicle came down from Canada or something. It might not
be US made.

2.7 pistons an option?

[Tim Walsh]

refugee,
First of all, what are you starting with as your base? I'm in the middle of a 2.4L rebuild right now out my old 2.4T. The 2.2 pistons will raise the compression ratio with the 2.4L crankshaft about a full point(I think) over the 2.2 compression.If you keep your Compression ratio under 10-9.8 you should be fine with 93 octane. I'm planning on using 2.2E pistons in my engine which should be about 9.5:1 CR, just fine for 93 octane.

The camshafts that you chose depend on what pistons your running. T pistons can only have T cams, E's can have T or E's. etc.

2.7 Pistons are something to consiter but they will require machining of your case and your case may or may not be strong enough for it.

The zeniths are ok carbs but the parts avilible for them aren't as pentiful as webers. If you can locate larger venturi's then you have a good chance of using them on your upgraded engine

[refugee]

l33t9eek,

Thanks for the compression question.

My starting base is a 2.4T engine with Zenith carbs. I think the engine is original and came from outside of the US b/c of the carb.

As for the Zenith, I just learned from Lee Marks (Motor Meister) that these carb are a bit better than Webers in some aspect. The first is that the standard factory comes with individual diaphrams for each throat(3 to each carb) compare to the standard Webers. You only get individual diaphrams to Weber for their top end model. The significant of the individual dia is that they produce more torque... There are a few other adv as well. The bad news is that there weren't lots of technical writings on em...

I am surpise to learn from you that I must change my case if I opt for 2.7. How come?

Can you please tell me where you are at with your current 2.4 rebuild? I would love to hear your ideas and especially things to watch out for...

refugee

[Tim Walsh]

Refugee,
I have a US spec 72T motor that I'm currently trying to locate parts for. My P&C's were in a car accident which ruined them, and my case is way out of spec and I need either lots of machine work or a new case.

About the Zenith carbs and MM. I would do a search here on MM before you put too much stock in their advice BUT I've heard that with a little ingenuity you can machine your venturies to a larger size or put in weber venturies. That's the limiting factor it seems for zeniths, the small 27mm venturies. I'm not a carb person but I would think from looking at port sizes and gas speeds you would want at least 32mm venturies, others would know more than I.

There are people on this board who have machined their 3R case (check the bottom side of your case for this part #) for 2.7 P&C's but I was leary about this myself as these cases aren't very strong. If you have a 5R case or a 7R case, you can machine your case to accept the larger P&C's. Even if you have a weaker case 2.7 7R cases are a dime a dozen.

Since I'm a student and on a budget I decided to upgrade my T to highcompression E specs. I'm planning on using 2.2E pistons and cylinders with an E MFI setup, ported heads and throttle bodies (34mm from 29mm) and E cams. I think it should make around 180 when tuned correctly and cost me a little bit over 4K for parts and machining.

I'm helping a friend out who's doing something similar to my engine. His will be a 2.4 engine with solex cams and E mfi induction. So far we've learned:
1. plastigauge ALL your rod bearings.
2. clean ALL the thru bolt holes and perimeter bolt holes or you'll end up with crud on your mating surface.
3. Install exhaust studs BEFORE you assemble your engine (don't ask)

Hopes this helps.

[Wayne 962]

Post Corrected:

Hi there refugee. Unfortunately, your 2.2T engine (if that is what you have) is not a good starting point for a higher performance engine. I discuss this somewhere in the Engine Rebuild Book, but I can't find it in there right now.

In short, the 911T 2.2 has:

- Zenith Carbs (I don't agree with Roy's assessment, as there aren't too many jet sizes available for these)
- Non-counterweighted crank
- Small valves in heads
- T-cams
- T-pistons
- Weaker magnesium case

In general, the only things you can reuse for a higher performance engine are the rods and the other outside equipment (alternator, fan, cam towers).

The more economical approach is to leave your T-motor intact and purchase a core 2.7 to work on. Guaranteed, it's the more economical way of doing things. I wouldn't worry about serial number matching - just keep the original engine...

-Wayne

[Scott Clarke]

I hate to disagree with our host, but 2.4 Ts, unlike earlier versions, did have counterweighted cranks. In addtion, some had 7R cases. While not as strong as aluminum, a 7R or 5R should do the job, while saving a considerable amount of weight. Also, 2.4Ts (and 2.2Ts, for that matter) had the same size valves as 2.2 and 2.4 Es, Ss, and even the 2.7 RS. The ports are, however, smaller.
-Scott

[Tim Walsh]

I'm going to have to disagree with Wayne as well for the same reasons as Scott says. My 2.4T had a couterweighted crank, same size valves as the 2.7RS (46,40) but smaller ports. The 2.2's and 2.0's had the bad crank and the 2.0's had the smaller valves

[Tyson Schmidt]

Not to mention the fact that the 2.4T had MFI, and not Zeniths.

[Tim Walsh]

Tyson,
Not all 72-73T's had MFI. I belive the euro spec T's had zenith carbs and 32mm ports instead of 29mm.

[Tyson Schmidt]

Yep.

[Roger 911]

I would like to reiterate the caution regarding Motor Meister.

I just did a little upgrading on my '72T MFI motor, basically a cam swap and Webers. I did a lot of research beforehand and deduced that I could probably put E cams in, given the 2.4T's lower 7.5:1 CR. When I called Motor Meister, Roy recommended Solex cams. I reminded him that I had 2.4T pistons, but both he and Lee assured me they had done this before on 2.4T motors and there would be plenty of clearance. Well, after waiting 6 weeks for the cams, I installed them and checked clearances...less than 0.8 mm, some as low as 0.5 mm (depending whose book you read, you should be looking for at least 1.5 mm). Great. So I have to pull the cams back out and send them back for Es, which had enough clearance when installed. If you've done the cam timing clearance check before, you know how much fun this is.

I won't even get into the frustration of dealing with MM day to day. The moral of the story; do a little reading and you will probably know as much, or more, than Motor Meister.

Good luck!

[rw7810]

i've seen several posts on this thread and others to include Wayne's book that trashes the 2.2 crank as being inferior because of being non-counter weighted. I know i've also read in a few places to include guru Bruce A. writings that these cranks were saught after by racers because they could spin-up faster. Just another data point.

[Wayne 962]

Typo - Whoops I meant to say "2.2T", not 2.4T. I also wasn't too sure which engine refugee was starting with. The 2.4T is a little better, but the case is weaker still (unless it's a 1973 1/2T which has the rare 2.4L 7R case)...

-Wayne

[Wayne 962]

Originally posted by rw7810
i've seen several posts on this thread and others to include Wayne's book that trashes the 2.2 crank as being inferior because of being non-counter weighted. I know i've also read in a few places to include guru Bruce A. writings that these cranks were saught after by racers because they could spin-up faster. Just another data point.

For 99% of the people rebuilding their engines, they are looking for a counter-weighted crank. Yes, the non-counterweighted crank can be used in conjunction with a lightened flywheel to reduce rotational mass and increase track performance. However, by far, these applications are rare, and many people don't feel comfortable building a high-reving engine with a non-counterweighted crank.

Despite the weight penalty, I believe that most of Porsche's (if not all) racing engines used counter-weighted cranks...

-Wayne

[Wayne 962]

Okay, let me ask the question - what engine do you have right now? Serial number please? When you mentioned the Zeniths, I thought you might have a 2.2. The serial number is located on the lower right side of the engine near the fan...

-Wayne

[refugee]

Guys, thank you very much for you input so far (Tim, Wayne, Clarke, Schmidt, Roger 911, rw7810).

Host, the following are the specifications:

Engine serial number from the fan housing: 901 106 101 5R

Engine serial number from rt on top of the valve covers(left and rt): 901 105 111 0R

Transmision serial number: 915 301 1020R

Oil cooler by BEHR: F8 then 901 107 041 02

Carb: Zenith 40 TIN 911 108 123 00
DEUTSCHE VERGASER GMBH & CO KG MADE IN GERMANY

I tried to cross reference the engine serial number with Peter Morgan's spec chart and came up with nothing.

I decided that the serial number from the fan housing could have came from anything. So I made the laborious task of taking the carb/engine shroud and fan apart b/c I have read somewhere that the serial number might be behind the fan somewhere. Well, I took the fan out but couldn't find the number.

Back to square one. I then saw from the body/engine restoration book that the serial number might be underneath the engine case next to the round engine drain cap. However, the heat exchanger are in the way right now.

I am currently at a lost. Any help/recommendation will be greatly appreciated.

Overall, from what I have read from all of you. I am tempted to leave the 2.4 Piston and Cylinder and try to take it into an S rather than taking the 2.7 conversion. Please let me know your thoughts on this.

As for some of your comments on Motor Meister, thank you. I originally planned to ship it out to them to do the work. Now I am guessing and having second thoughts.

Wayne, I read somewhere that you are also writing a book on the three series. Can I please ask you to also cover a 1998 M3 sedan. I just picked this up a couple of months agos and am very happy with it but can't find any good engine book on it. As for a compare between the m3 vs 911, my opinion is that they shouldn't be compared. Each is great in their own way.

[Wayne 962]

Hi there. The 1998 M3 *will* be covered in my new book. I think that you will like it...

Take your hand and put it on the top of the fan. Then drag it down the side of the fan towards the right, keeping your palm facing the fan. Aw, heck, I'll just go find the picture...

[Wayne 962]

The serial number can be seen in the left side of the picture...

The number begins with a 6...

-Wayne

[refugee]

Thank you,

Mine is painted over with silver paint. The previous owner must have tried to look it up b/c I see it being dulled. He must have tried to file/scrape the silver paint to see the number. I will try some very fine sand paper and colored solution to bring the number back.

[refugee]

Well, after some light wire brushing and fine sanding, the engine number is nowhere to be found. Is possible that the engine was stolen and the number was removed? I bought the car from Bethlehem, PA from an old guy who does lots of restorations. Anyway, back to square one.

I might have to take the piston and cylinder out to measure...

Host et al., please tell me if it is possible to make this into an 2.4 S specification. If so, do I need new camshaft? Can I still use the piston and cylinder? Can I also use the current Zenith Carb?

refugee