Swallowtail

Hey guys,

I’m starting the process of disassembling the 2.4 engine of my ’73 Euro-Spec 911t (Zenith carbs).

Of course I read the Dempsey book and the recommended upgrades. One of the first decisions I have to make will be about the oil bypass modification. As I understand it’s easy to do but entails a whole lot of other expensive mods (new oilpump, new pistons).

For reference - regarding the rest of the engine (crank, pistons, cams, carbs) I’m considering one of two options:
1. Keep everything stock
2. Keep everything stock with upgraded pistons (e.g. 2.2T)

What are your opinions on the bypass mod with a near stock 2.4t engine?


PS: I kept the threat title open since I might ask other related questions here

myflat6

I am also rebuilding/upgrading a 2.4. Keep in mind that once you split your Mag case, it will need to be examined by an experienced machine shop. When these cases are split it relaxes the Mag and almost all of them will need an align bore. The mains end up in an oblong shape. Since the case will be at a machine shop, the oil bypass can be done very cheaply by them and it will include the correct pressure relief spring/parts.

Nickies make a great 2.5 slip in option. Going the 2.2 piston option is also a good option.

Good luck with your build!

Swallowtail

Hi Bill,

thanks for your input. You are correct about the case having to go to the machine shop. I'm not worried about the cost of the machining.
What I want to know is if it's recommended to do this without changing the oilpump for the later style 4 rib AL version. I should have probably been clearer about that in my initial post.

myflat6

Got it. I did a bunch of research on this very question. There are many mixed opinions but I ended up sticking with my stock pump and sending it to Glenn Yee Motorsports for a rebuild and port/polish. A couple reputable shops recommended this so it was enough for me. I am also not building a high revving high performance motor.

r911

how will the car be driven?

why not a 2.7L?

Swallowtail

Car will be driven on the street only. Building a 2.7 would nice but will probably add $10k on the rebuild (New Cylinders, New Cams, New Carbs, etc.).
I do not want to build a hotrod but if a little bit more power can be had at more or less the same money why not...

Swallowtail

I contacted LN Engineering about that. They say that I have to buy new cylinders as well if I want to use their pistons. Is that true for all popular aftermarket pistons?

myflat6

Yes, this is true since the cylinder bore is increased from 85mm to 87.5mm. They sell a kit that has JE Pistons.

Charles Navarro

The pistons we stock only work with our Nickies cylinders. The piston to cylinder clearance is different for an aluminum cylinder versus a cast iron or biral type. The factory cylinders often do not use nominal bore sizes, so the bores have to be measured to properly size the piston as well. Many discover the cylinders will be out of round or excessively tapered - the factory tolerance is .002' ovality or taper. This is why our off the shelf piston is not a fit for you.

jon@ebsracing.com

Jon from EBS Racing here. In case your interested we offer a JE piston set 85mm 9.5:1CR with reconditioned bored & fine honed 85mm cast iron cylinder set for both 911 2.2 and 2.4 applications. Price is $1475 piston & cylinder set (w/exchange cylinders). If you have Biral cylinders you can send them in and we'll recondition your cylinders. Also can supply EBS Racing Engine Rebuild Kit for $795.00. Kit contents are with upgrades is attached below. Will need to know if you have carbs or MFI for gasket set. Items can be added or deleted to kit and price adjusted accordingly. If you have any questions or require more information please call or email jon@ebsracing.com

Swallowtail

Hi Jon, that sounds like an interesting offer. I will shoot you an e-mail later.