Modifying a 2.4E with webers-suggestions?

[6771911esses]

I have a 2.4E with Webers that I am getting ready to freshen up. I am also interested in squeezing more power out of the engine (as much as possible w/o major machine work). My goal is a bit more that a 2.4S which is 190hp. Let's shoot for 190-200hp.

I have been considering the following modifications (feel free to comment on these individual points):

1. 2.2 S pistons, original if I can find a set. If I go with JE pistons what compression ratio and mm size can I go to w/o having to modify the combustion chamber? How deep should the piston tops be cut out for the valves to clear (I suppose JE may have this information)?

2. "S" cams. Webcam, Elgin, or original? BTW. I am looking for a set. I am going to use Webers so I don't need MFI cams, but I will consider them if someone has a set for sale.

3. Porting the heads to 2.4S spec or 2.7S spec. Any suggestions on the porting?

4. What jets, chokes, emulsion tube sizes would I need for the Weber 40 IDAs, or will I require 46s?

5. Turbo valve covers.

6. Carrera chain tensioner upgrade.

7. Any other suggestions are welcome. I do not want to change cylinders unless mine are too worn.

8. Any suggestions on the ignition. I have used Pertronix in non-Porsche applications and like it. How has it worked for 911 owners?

This engine will go into my 71 911s that has a fresh stock 2.2s MFI (not for sale!). I am converting it to look like the "RS" (ducktail, et. al. already have front spoiler), and would like the hp in the 190-200 range .

BTW. I have never rebuilt a 911 engine though I have read plenty on the subject. I have decent experience building tuned BMW and Jaguar engines so this stuff is not totally out of my reach. I also have a very experienced Porsche engine builder in town whom I can always get involved. The fun is to do this myself.

Looking forward to constructive input!

Mike Nahar
67 911s
71 911s
non-Porsche: 65 Lotus Cortina (for sale), 79 Morgan Plus 8, 75 BMW 2002 turbo, 1972 BMW 2000tii Touring (for sale).

[surfdwn]

Are you still looking for 2.2 P's anc C's? I was going to do the same exact build and bought all of the parts. I sold the body last week and am now ready to sell off the engine and the "goodies". I have Mahle 2.2s pistons and two 1973 911s cams. Interested? I'm keeping the webers and possible the '93 911S distributor for my 3.0 project.

[TimT]

WOW i like this thread

1. 2.2 S pistons, original if I can find a set. If I go with JE pistons what compression ratio and mm size can I go to w/o having to modify the combustion chamber?

get JE 10.5:1 they work in the 2.4 head, you will still have to check clearances depending on cam choices

2. "S" cams. Webcam, Elgin, or original? BTW. I am looking for a set. I am going to use Webers so I don't need MFI cams, but I will consider them if someone has a set for sale.

get the GE-60 cam

3. Porting the heads to 2.4S spec or 2.7S spec. Any suggestions on the porting?

open the ports to 36mm, have the machinist just plunge the mill, do the handwork yourself.

4. What jets, chokes, emulsion tube sizes would I need

I have to open my carbs to get the info.... bit o brain fade now

5. Turbo valve covers.
6. Carrera chain tensioner upgrade.

YES!!

While you having work done on the heads..... have them modified for twin plugs..

then get some sort of twin plug ignition.... electromotive works... but there are other options

[jluetjen]

6771911esses;

You will definitely need to port the heads to 2.4S/2.7RS spec (they're the same at 36mm's) since the 2.4E's were port restricted compared to most 911 motors. BTW - What are the dimensions of your existing intake ports at the manifold face? How about at .5 inch in, 1 inch and 1.5 inch in? Depending on the shape of your existing ports you may need to do more then just plunge from the manifold face and match the existing shape. This is why I was asking about your existing shape since I have seen conflicting information about the ports on the 2.4 liter motors.

With 2.4 liters, S cams and 40mm webers I doubt that you'll be able to get more HP then a stock 2.4S, even with the bump in CR. Compared to carb's, MFI generally will get 10HP more because the intake breathes easier without the carb venturi in the way - this is true on almost every MFI'd engine I've seen spec's for. 911 and otherwise. So you will most likely wind up at 180 HP. The way to get more then 190 HP is to do all of this AND bump the capacity up to 2.7 with larger pistons and cylinders. If you were to go down that route I'd even open the intake ports out to 38mm.

If you twin plug, bump the CR, use GE60 cams, and port the heads as described with a 2.4, you will most likely wind up with an engine that pulls better then a 2.4S at low to mid revs and still gets the 180 HP at higher rev's.

[TimT]

John what ever gave me the idea that you would chime in too?

[6771911esses]

I have yet to tear apart the engine, therefore I would not know what size the ports are. I am assuming the engine is a stock 2.4E unless previous owners got into some mods. I understand that even the 2.4s livens up with 2.2S pistons. I may have access to MFI and have not yet decided if I will stick with the Webers. So, realistically w/o MFI I will not see 180+ hp. If I elect to go to 2.7 don't I have to machine the case and heads? Who do you recommend and what are the usual machining costs? Aren't I better off buying a 2.7 case then? I like the idea of tweaking the 2.4.
Keep the toughts coming.......

[jluetjen]

TimT; Fancy meeting you here!

[Phoenix]

6771911esses:

I'm wondering where you ended up here? I'm starting to work through ideas on how to increase power, searched the threads and like your approach.

Will this or a similar approach work with a non 7R case (what are teh pros/ cons?). Since my MM fiasco I have and older case (6221267).

Current = 2.4 p/c, L cams, pmo's and an electromitove ignition putting out 133 hp at the hub (dyno'd).

Looking for 190-200 as you are.

Any thoughts?

[6771911esses]

The T engine is not the ideal basis to build up. The crank I reckon is not counterbalanced. Do not quote me on this but I believe that is what I have been told.

As for my 2.4E: I will use 2.2S pistons and stick to the E cams for more low end torque rather than building a high revving S like engine. I think that I should end up with close to the 2.4S performance which is 190 hp.

To put things in perspective, this 2.4E will eventually make room for a 3L transplant with Webers, etc. for 240-250 hp.

Get Wayne's new book on 911 engines. It is fabulous!

Good luck!

Mike N

67 911s
71 T/ RS
71 911s