2.4L CIS Upgrade
 

I just bought a 73.5 911T, 2.4L w/ CIS induction. Having read through Waynes two books and 911 Engine Performance rebuilding I am quite perplexed. As everyone else does, I want to improve the performance at the least cost. I understand my options are 2.2S pistons and 964 cam, or 2.7L pistons and cylinders and I assume 964 cam. I read in the Performance Rebuilding book that there was a race version of the 2.4 that used a 86.7 instead of 84 mm cylinder bore. As of yet I don't know which cylinders I have on the car (Biral, Nikasil, or Alusil). Can any of these be bored out and replated? It seems like this might be less expensive than new cylinders (2.7) and possibly stress the engine less. By the way, I was planning on using the Bursch header and exhaust with Jet-Hot coating to reduce temperatures. I don't need heat in Texas! Looking forward to all the wise comments.

Thanks guys, my first 911 (my 3 yr old calls it my junk car because it is pretty rough).

Hi there. I'm not sure how this question slipped by...

There are two different types of 2.4 engines - you have the CIS version. You can upgrade to 2.7, or you can simply buy a 2.7 and go from there, without damaging your relatively rare engine case (2.4L 7R). The 2.2S pistons option won't work with your CIS engine - it has to be an MFI or carb'ed engine to work.

What is it that you are looking to do?

-Wayne

If your '73.5 T 2.4 liter is stock, it has cast iron cylinders. They are not plated. Jim

I am looking for good power for fun drives into work and some back road blasting. I have a much more comfortable and probably faster daily driver (Acura CL). Considering all the other money I have to put into the car I don't want to spend $7k on a new motor. Based on the engine building wizard it would cost me ~$4500 for parts and some tools. Pistons and cylinders would run about $1300 (bore and compression).Then I still need to get machine work done and put it all together myself. I have talked to Motormeister but his bad rep in here scares me. I have also talked to EBS and Supertec. Supertec said he would bore and compression increase my motor then use intake system from a 2.7 CIS (move injectors from heads to runners) and I would use a header. He would build this motor for $7500. He also suggested a 3.0 motor for $9000. It is hard for me to justify building the motor myself if his numbers are so close to what it would cost me. I assume his experience would be better than all the books I have read. I have both of your books Wayne. Good references but still begs the question if a professional can build the engine for close to the same price then why should I do it. Satisfaction is one aspect. I am also concerned about doing business with a company that is not down the street.

Hi,

It is your call.

But, the way I see it, you keep it stock, or you do a 3.0/3.2 transplant to build a modest hot rod or a 3.6 for a hot hot rod. Dollar wise, this seems to be the way to get the most bang for your buck. As Wayne notes, the 2.4 CIS case is prized by racers for it's lightness.

If your motor is healthy and your just looking for a performance increase then you might look at spending some money on suspension upgrades instead.

Just a thought.

Hmm, do some more research. I can suggest some very reputable rebuilders if you'd like...

-Wayne

Yes Wayne I would appreciate the advice on some reputable rebuilders. After doing some quick calculation I am starting to convince myself to rebuild my engine with an overbore and compression increase and add PMO carbs. Sort of like a high performance 2.4 S engine. I assume the case wouldn't be too stressed due to boring the spigots like on a 2.7. Wayne you have suggested buying a 2.7 as a starter. Well in California it might be easy to come by engines but here in Texas it is not so. I like the idea of a unique engine and my quick calculation tells me that it would only be about $500 more than re-doing a 2.7 engine. Besides I am weary about buying something that I don't truly know it's condition and then to have to rebuild it anyway...


Wayne, would you update us on your restoration of your 73.5 911T. I am anxiously awaiting to see what your plans are and how it is going. I am going to have to put a new drivers floorpan in mine but most everything else seems solid (I hope)... I only heard the engine start but could smell gas so I shut it off. I may just try to get it running, after I do all the body work and repaint it that is.

Mark Jo now has that 1973 1/2 T car, check the main forum for some posts on it - just saw one yesterday...

The 2.4 7R case is valuable because it's a 7R case that can accept the 2.4 spigots. I would not bore this case out if I were you, as you would be tossing $$$ away and ruining the case. Simply buy a 2.7 case on eBay ($100-$200) instead...

-Wayne

I haven't seen to many 2.4T 7R cases up for sale, how much are
they going for? I got one I may eventually sell.

F.

Whereas a normal 2.2, 2.4, or 2.7 case might be worth about $100 or so, I would think that the 2.4 7R cases would be worth about $500-$800 to the right buyer...

-Wayne