help w/ 2.4L engine project

[ty901]

guys;
looking for help and opinions. the patient is a stock 2.4L CIS T engine. 7R case ~ 100,000 miles. looking to build something up for warm to hot street use & DE events (SWB car). i don't want to split the case. i was encouraged to start with a set of 2.2E P&C & webers. carbs i have and i'm more comfortable with them than MFI. there must be something to the P&C idea as they're tough to come by. (what IS IT about these anyway ??) can i keep the cast iron cylinders and replace the CIS pistons ? i understand new rod bolts are a must. any other "gotchas" ? i presume these cams are not worth reusing in this application. comments ? sorry, for the litany of newbie questions. all help greatly appreciated.
cheers
jerry

[Jay Auskin]

Do a search on user "Tyson Schmidt" and his car "scruffy". There's alot of good info on 2.4L T upgrades. 2.4E P/C's are a good upgrade, but there are other things that should go along with this to tap the potential.

[Grady Clay]

Jerry,

A great deal of this has to do with the history and condition of the engine. If it has been well maintained with clean oil, never overheated (broken fan belt), and is truly original only then would I be comfortable with rod bearings without splitting the case. Of course you can do this and find you must split the case if the rod bearings show abuse.
The advantage is that this doesn’t relieve the mag case and require machining the main bearing bores and no cost of main bearings.
The disadvantage is you won’t be able to add the oil system mods or inspect the main bearings. Carefully inspect the chain sprockets and jack-shaft gear for ware or damage.

You will still need to have the case mod for cylinder stud inserts.

Rebuilding the heads with new valves and guides is pretty straightforward stuff. Don’t let anyone sell you stiffer valve springs.

Changing from CIS to carbs will require decision on cams and consequently rocker arm refinishing.

Yes, you will have to pay attention to the cam lift and timing and the piston valve cut-out to insure proper clearance. The cam and piston vendors can help you there.

The P&Cs you choose are very subjective and are determined by your intended use. Higher compression makes more power but requires higher octane fuel. These days twin plugs are a very viable (and desirable) option, particularly when you already have the heads out for repair.
You don’t want to use the iron “T” cylinders. Try and find Nikasil cylinders with OE Mahle pistons, new are preferable but expensive. Of course there are a lot of other options, each with pros and cons.

If you have to split the case, I would go to 90 mm RS P&Cs or, for extreme fun, 92 mm RSR P&Cs but only with twin plug.

If you can find a ’69-’73 911S MFI setup, don’t be afraid of it. That can produce the most spectacular performance and normal humans can successfully deal with it. There is a lot to this conversion.

You will need to reconfigure your fuel system depending on what you decide.

Your 901 transmission should work OK so long as you don’t try and light up the tires in 1st gear. You should do a maintenance overhaul on the transmission, replace the two intermediate plate ball bearings, and see if it has the up-dated differential parts.

At least you should clean, inspect, re-grease the CVs and replace the bolts, Schnorr lock washers, and rubber boots. When Porsche went to LWB in ’69, they went to the huge (Turbo size) CVs.

Best,
Grady