Is installing a 70.4mm crankshaft into a 1969 crankcase just plug n play?
 

Hello

I want much more power from my 110HP 1969 2.0 911T.

I will go for the following upgrades:
- 2.2S P/C
- E-cams
- 2.2/2.4 T/E heads

I have however not decided if I should keep the 66mm non counterbalanced crank or go for a 70.4mm crank.......any thoughts on that?

Thanks

Mikael

The 69 heads are not going to match the 2.2 cylinders. 2.7S heads a better choice.
2.2S on a 70.4 crank comes out to about 10.3 Cr. you need to clearance the pistons.
Find a 2.4 and you ll come out with a better combination to build with.
Bruce

Hi Bruce

Thanks for the quick reply :)

I know that the 69 heads don't fit. That's why I have found a new set of heads from a 2.2/2.4 T/E. They should have same size combustion chamber and valve size as the 2.7 heads You mention.

Piston to valve clearance shouldn't be a problem when using S-pistons together with E-cams. But are You thinking of clearance between the 70,4mm crank and the 2.2 S-piston skirts...? Any other clearance issues?

I know that a 2.4 would make a better starting point. But all I got is this old 69T and I would really like to keep it, so my question remains the same:

Is installing a 70.4mm crankshaft into a 1969 crankcase just plug n play or should I keep the 66mm non counterbalanced crank?

Thanks
Mikael

get your hands on any good repair book like Haynes (Ch 1) that lists all the components spec sizes, and compare everything

also get a copy of Wayne's book here on Pelican

and read Bruce Anderson's book before you get to deep into this moneywise - Ch 4 in Vol 1 or Ch 5 in Vol 2 - (Vol 1 is actually more helpful for our old engines - find it on eBay or Amazon)

your new 2.4 crank has larger big-end rod size (57 vs 52) so you also need the 2.4 rods - and they are different, so now you'll need different pistons

you have to measure and compare-fit everything in that parts jumble
CC the piston-cyl head when loosely together on bench for your CR before you even think about bolting it all together
you may have to cut the piston slipper skirt to clear the crank cw's
you should boattail the case
you should have the case timeserted
you should upgrade the oil pump - more case work

imho - if you are on limited budget - keep the stock bottom end parts and just look for more ompression and a E cam - or buy a decent used 2.4 or 2.7 COMPLETE - you can get one for 1/2 what it would cost to build

- otherwise you are in for a $10,000 ride between the parts bin and the machine shop

.

Mikail: the 70.4 2.4/2.7 crank will plug and play in the 69 case-- -the first time I did this I used the early aluminum case with no problems. You will need the 2.4/2.7 rods.
Bruce is right---if you use the 2.2S pistons/cylinders you will have a little over 10/1 compression because of the longer stroke. The 2.2/2.4 heads do not have the chamfer on the outside edge and you will have to cut the chamfer to get adequate piston to head clearance. The wrist pin size is 22mm, same as the 2.0 rods so the pistons will work. Check the clearance between the case and the piston skirt at bottom dead center---If there is a problem relieve the case--not the piston. (I do not think there is a problem there---but check it to be sure) There is no problem with the skirt to crank counterweights. I installed oil squirters when I did this with a early aluminum case but I think with the Biral 2.2S pistons/cylinders you can get away without it----- the factory did not install squirter's until late 1971---so they ran those pistons without them originally. If it were mine I would install them.
Good luck---I remember the engine I built as being a lot of fun---S cams, 36mm ports, 46 webers, it surprised a lot of people.
aws

Thanks for all the valuable input :)

There is only 1 thing I don't understand:

AWS: "The 2.2/2.4 heads do not have the chamfer on the outside edge and you will have to cut the chamfer to get adequate piston to head clearance."

How can that be? The 2.2/2.4 heads are all the same (except port size), so I thought they would fit perfectly with my 2.2S P/C's :confused:

The heads fit without work but the ports are small compared to 2 7 S
Bruce

Yes, the ports on the 2.2/2.4 heads are only I 32mm & E 32mm compared to the I 35mm & E 35mm of the 2.7S heads.

I chose the small ported 2.2/2.4 heads because of two things:

1. I am afraid that to big intake ports could hurt low RPM power (this will be a street engine on E-cams).
2. I wanted the heads to be plug n play (without visiting the machine shop, which is quite expensive here in Denmark).

Now, this might be a stupid question, but will 2.7 heads (which are made for 90mm cylinders) fit my 84mm cylinders without going to the machine shop?

you may want to consider this:
from

Steven M. Stomski
STOMSKI RACING
Jstomski@aol.com

T cams, are very good cam, specifically for lower (lower
compared to E and S cams) end torque. By combining T cams with E P/Cs
or even S P/Cs, yes, you will get an improvement over a straight T motor as far
as power is concerned, merely because the compression ratio is increased in
either case. Moroever, the combination of T cams with S or E P/Cs will
give a more "driveable" motor that will not be as "peaky" as an E or an S.
With T cams on S or E P/Cs, you will be on the power at lower RPM, but will not
have as much top end power or overall horsepower.

Review of T motors, and T cam specifications in general, reveals some very interesting facts. Surprisingly enough, the T motor and T cam outperforms the E and the S cams and motors on some performane standards. While many people that build up "custom" motors do not use the T cam probably merely because it does not have the E or the S designation (and therefore can not be as fast or as good), depending upon your application (autocross, some shorter tracks, or street driving), T cams with higher compression P/Cs will produce
excellent results.

.................................................. .................................................. ....
From: Rennsport Systems <porsche@rennsportsystems.com>

The 2.7 heads sit right on the cylinder top, they are all the same size sealing surfaces.
Bruce

Mikael: Bruce is right--the heads will work without modification--- I built that engine over 35 years ago and forgot I used 1969 911S 2.0 heads that I modified to fit the 2.2 84mm cylinders---The combustion chamber configuration is different on the 2.0 and I had to chamfer it to get the desired piston to head clearance. If you have the 2.4T heads I would just go ahead and enlarge the ports to 36mm by hand and use them---32mm is way too small, even with e cams.--- You haven't mentioned venturi sizes---if you are not going to enlarge the choke size the port diameter won't matter.
aws

Interesting thoughts about the T-cams.

The 2.4E ran with I 32mm & E 32mm port sizes, that's why I figured that it would also be a nice setup for my new engine. Any thoughts on that?

I was planning on using Weber 40 IDTP carbs together with the 901.108.321 intake manifolds. I am not sure about what venturi size they have, but Haynes repair book states that they should be 27mm. I guess I will need to change to a venturi size of 30mm or even 32mm - and some of the other internals of the Webers probably needs to be changed too (main jets, air correctos, idles and emulsion tubes).

we still don't know what kind of budget you are working with on this engine, nor how long you are willing to have it on the bench and have a non-running car,

, so some of the advice you get here is highly $$$$ dependent - if you do everything yourself it's less $$ but a lot more time

you should read all this - http://rennsportsystems.com/letstalk-2/5-how-to-make-your-porsche-faster-na-engines-1/ - Steve is a regular here

27mm venturi was for 2.0 T motors with small valves - your hot & larger displacement motor will need bigger venturis

yes you'll want to increase the venturis and along with that and the cam change comes a host of trial & error jetting once you get the engine running - Anderson's book does give a jetting & venturi start-point as i recall, and a phone call to Mike Pierce of Pierce Manifolds will be wise once you get to the carb rebuild stage - great guy - he will spec & sell you all you need for the application you finally determine

get the Weber Tech Manual by Bob Tomlinson - it will walk you thru the calculations you need to consider based on your displacement and airflow

another factor to consider - inlet port sizes - if you go to 2.7 heads they have larger inlets - so now you need to buy a set of PMO manifolds - or - try to grind your own to match (which can easily screw up flow and make things worse if you don't have a model to duplicate or a friend with a flow bench)

Weber IDTP's are OK, but they have different internal porting - designed for emissions control so they are said to tend to go lean at a certain point- I just chatted with Martin Baker about that 2 days ago - you will want to search "webers" in general here - and on general 911 & 914-6 Pelican sites - it's been discussed to death -

- i think i have some added notes on all that scribbled in my weber books & will have a look - but you are stilll a long way from needing to know that - i sold a nice set of IDTP's with manifolds & linkage on eBay last year for $1500, so that tells you what you can expect to recoup if you decide to buy IDA's

for sure, you need to modify them for anti-percolation (PMO tool) and be sure to get the base insulators, and to relieve the well-bottom for better fuel feed under hard cornering - that's all in the books

- in my case, i installed a Halmeter with dual 02 sensors in the exhaust and then tuned for stoichometric band at cruise and RICH on accel

- i once had about $1000 worth of various jets in my box as i went thru the drill - i still have the meter but removed it from the car awhile back since i had finally gotten the jetting right, and later sold the jets as one lot - 'way cheap - (i needed the $$) - so it goes

one other item - you should install new chains, ramps & tensioners - the latest carrera style are best - but costalotta, and so long as you install any new set they'll probably never wear out in your lifetime

Sounds like a slippery slope. In your situation a cheap(relative) alternative is use your stock bottom end. hopefully you didnt split the case yet($$$ ) use your 2.2s pistons ,with solex cams. and later heads. that would be a lot of improvement and would pull an S out of a corner.S

Hi Mikael,
where are you located?
I have done a lot of such mods and could probably be of help in details.
And: Sprichst Du deutsch? Wheras english is not a problem.
Greets Robert (Lübeck and Küsten)