2.4 Engine Build advice

[Phoenix65]

Phoenix

Hello All,
It‘s been quite a while since I‘ve been here to the point where I lost the login info and needed to reregister. Life has gotten in the way.

Some of you may recall I have an Oxford/ Dalmatian Blue 73 911t. A lot has been done to get the body and core mechanicals to as perfect as I can afford :-). There have also been a few „upgrades“ and personalized modifications along the way. Bronze bushings, stiffer torsion bars, drilled rotors, side vent windows, and a few other bits and bobs. Nothing which can’t be reversed. Automobile Associates in Canton, CT have been terrific partners in getting Phoenix to where she is today.

The two areas I either do not trust myself to do or frankly do not have the patience for are engine rebuilding and wiring. AA will be doing both.

The engine build goal is to cost effectively increase reliability and low to mid range torque for spirited driving. I would like to switch to PMO EFI with Clewett management.

Beyond that AA is recommending boring the case spigots and going with 93 mm JE p&c’s and 10.3 –1 compression ratio. This will require twin plug, which I‘m told will help with low speed response. The heads will also need to be modified for the twin plug, and the port sizes would be 36 intake and 35 exhaust with GE30 cams. Front mounted cooler will also be needed. They estimate this engine would produce roughly 190ftlbs of torque.

Alternatively, I am considering something along the lines of a period correct (sans EFI) ST motor.

The current engine will be used as the base and is configured as:
- [ ] PMO carbs 40
- [ ] Bore: 74mm OEM Mahle 911s piston and cylinder
- [ ] Stroke: 70.4mm
- [ ] Compression Ratio: 8.8:1
- [ ] Valve sizes: 46mm intake / 49mm exhaust
- [ ] Port sized: 32mm intake / 32mm exhaust
- [ ] Camshaft specs:
- [ ] intake duration 270/ exhaust duration 254
- [ ] Exhaust opens at 36ABC/ closes at 20ATC

I‘m hoping this board can give me some advice on these options vs the goal of reliability, strong usable torque, fuel efficiency and cost to build.

What do you think?

Many thanks in advance!!
... Oliver

[blucille]

Good to see you are back, Oliver...it was great to have you driving with us all those years ago. Hope you’ll be ready for a spring drive

[Phoenix65]

Thank you blucille.
I am hoping to get back into group runs. Phoenix has been sitting in a bubble for too long.

[csbush]

Going to twin plug seems like a lot of expense for the HP gain. You should be able to get over 200 hp from a 2.7 S modification with carbs. Sure you can do twin plug and EFI, but how much HP are you trying to get? Anything over 180 should be a lot of fun to drive in that car.

[gled49]

In 46, Ex 40. 84mm bore. In a low comp motor, twin plug will net u “0”.

[edmayo]

I think your goals of fuel economy and cost may pretty much limit you to what you already have. Just for grins check for full throttle, you'd be surprised how many cars don't have it.