2.4S engine rebuild & mods - keeping the character

[james]

looks like I might be rebuilding my 2.4S motor.

My car is an all stock, matching numbers, 1973 2.4S. Pre-rebuild it's been kicking out around 200bhp. Mainly use for touring + fast cross country blasts on the twisties

What I would like to achieve is a bit more power, but keep the character of my S engine .. eg that fantastic feeling / kick up the backside when coming on cam at around 4500 rpm 8)

My thoughts were to increase the compression ( we run 95 & 98 octance fuel here in the UK) but keep it single plugged.

If new barrels & pistons are needed, then there is always the option of a displacement increase ( 2.5)

Anyone running a high comp 2.4S motor ? Does it still have that special S feeling ?

Of course, maybe the sensible & possibly the cheapest way would be to keep the engine stock.

Any other suggestions / opinions ?

Thanks

[execmalibu]

To get a very good increase in performance and to keep from having to modify anything all you need to do is to install stock 2.2 911S pistons. They are the same 84mm but are 2 points higher compression.

The engine will run Great and the car will have exactly the same feel only a bit more of everything!

2.5mm Pistons if you can find them work great also!

[FL-Frank]

[QUOTE=execmalibu;262237]To get a very good increase in performance and to keep from having to modify anything all you need to do is to install stock 2.2 911S pistons. They are the same 84mm but are 2 points higher compression.

The engine will run Great and the car will have exactly the same feel only a bit more of everything!QUOTE]

We treated our '72 T's 2.4 engine to this modification when we rebuilt it 5 years and 30K miles ago, and agree whole heartedly with execmalibu's advice. It pulls hard throughout the rpm range now.

All the best,

Frank

[jameshtaylor]

How far do you want to go? A 2.7 gives you 12% more power and torque without changing much of anything. Port it a bit, raise compression, do the oil pump while you're in there and you'll have a real hot rod.

[cscrogham]

If you do this modification, be very careful to note the clearance from the piston skirt to the case on the piston downstroke. The 2.2 skirt is longer than the 2.4 and in many cases will need to be clearanced slightly.
This does make a very nice running engine however...

[james]

thanks all

I'm not wanting to machine the case, so any displacement increase would be a 'slip-in' option.

What's the measured compression ratio you're all running with the 2.2S pistons ?

Anyone modified the valve train, rod bolts etc in search of some extra revs too ?

[execmalibu]

The increase in compression from 8.5 to around 10.2 also increases your reving ability! The stock 911S engine can easily handle 8,000+RPM...

A Lighter aluminum RSR type flywheel is a great (and cheap) mod to reduce weight!

Lightening the valve train/rods etc is very expensive and only helps a little unless you are racing...

[Allen Henderson]

IMHO, the best mod by far would be to make your engine a 2.7 RS one. It will be identical in appearance and you'll get great increase in performance. Many feel there was something magical about the 2.7 engine, all things work together perfectly and you have a very "happy motor."

-Allen-

[MarkS]

I prefer the 2.2 S piston and cyl route for your application, reason nothing like a zippy small bore which I consider up to 2.5. I have had RS spec 2.7's and various configurations up to 3.8. Sure they make more HP and torque but the delivery can't compare and that's where it's at for me.

[Cliff]

http://cgi.ebay.com/ebaymotors/ws/eB...2#ht_1843wt_94 Here is a set of nos on ebay