Technical newbie taking the leap...

[Phoenix]

I'm know you've hear all this before...

I’m still sifting through all the relevant posts and am ordering Wayne’s engine book today. As with all posts though, each situation is a little different and I was hoping to get your initial thoughts.

I purchased a 73.5 2.4t several years ago and immediately started its restoration. The engine was extremely poorly done by “those who shall not be named” (see my past posts on the 911 tech board)). After a second “top end” rebuild, the end result is a 2.4 case (or so I think: engine # 622 1267) with 2.4 t pistons, PMO’s an Eletromotive Ignition and the chain tensioner upgrade. Overall the engine runs well and is very driveable though it is a hard starter and does smoke a bit at initial start up (embarrassing actually) and seems to run extremely rich (very black exhaust pipe and 11-13 mpg). It was dyno’d last year with 135 bhp at the hubs.

Given the rebuilding fiasco, the fact the case which I now have is still from “those who shall not be named”, its very smoky start up and the fact that I’d love to have a bit more power, I’m starting to look into building a new engine.

My objective is to have a reliable motor which puts down somewhere between 180 – 200 bhp at the hub with oodles of low end torque. I will be using the car aprox. 80% street / 30% PCA driver education and possibly do a bit of Autocrossing. Given the amount of time effort and money which has gone into restoring the body, exterior and brakes keeping everything as period correct as is reasonable, I’d like to keep the powerplant period correct as well. Also, I want to keep driving the car while I build the “new” engine.

My initial question is what options do you see are best for me to:

a) keep the motor period correct / correct for the ’73 model year (production or racing)
b) net 180-200 hp at the hub
c) have strong low-end torque
d) have good reliablility and relatively “easy” start-up
e) better my fuel mileage (a long shot I know)

I know I want to start with a “fresh” case as I’m not comfortable with what I have; likely a 7R case.

I’m guessing it will take me 3-4 months to figure out what I want to do and another 6 months or so to get all the parts together. Once I have everything, I’m guessing another 3-5 months to put it all together (I don’t have a lot of time and still have a very long “honey-do” list). I’ve never done this before and really want to make sure I do it right and enjoy the process. This will be my stress relief, get away from my daily routine project. Knowing a board such as this exists will be an immense comfort as I tackle this.

Many thanks in advance for you support and guidance!!!

… Oliver


__________________
...Oliver

'73 911T: 2.4/ PMOs/ Electromotive Ignition
'03 Audi A4 Quattro Wagon

[img]http://www.pelicanparts.com/cgi-bin/pmpre/pm.cgi?login=Phoenix&action=display&[img]

[Doug Steinel]

Any objection to buying a 3.0L? They are reliable and will give you your 180 horses right off the bat. They are out there for $5k.

[Jim Sims]

Your list has too many mutually exclusive specifications. Forget gas mileage and emissions control (if you want to drive it one the road) if you want 180-200 rear wheel hp with period correct technology. Jim

[afterburn 549]

my 2 cents ...cis is hard to beat for that hp and neat simple and reliable .180 t.t.g. is no problem and a mag case (check thread history) is my way to go with all the new updates it will serve you well.

[Phoenix]

Thanks fo rthe quick responses.
Doug/ afterburn 549 - I really want to do what I can to keep the car period correct so that knocks out a 3.o ltr - though it is the fiscally better option. It also knocks out CIS. It came with that originally and put out a total 130 hp (if memory serves me correctly). I've been told that you can't get 180 at the hub with teh original 73.5 CIS no matter what mods you do.

Jim: In NY any car over 25 years old does not have to pass a sniff test. I've registerd it Historical which also helps it legal. I knew gas mileage was a long shot but want to think this through as well. I'd be happy keeping what I have (11-13 mpg) with the added power.

I was thinking something along the lines of a 2.7 in RS or RSR spec.

[ChrisBennet]

Originally posted by Phoenix
I will be using the car aprox. 80% street / 30% PCA driver education

Excellent. It's good to see someone who drives their car at 110% like Porsche intended.
-Chris

[Grady Clay]

Oliver,
Try this idea:

A ’72-’73 2.8E MFI 10.3:1CR twin plug (hidden) built on a new 7R case with all the mods.

Advantages:
Neck snapping performance.
Very street drivable.
Good for DE and auto-X.
Reliable ~230 HP.
Period correct.
When properly set you can get 15-25+ MPG depending on your driving.


Disadvantages:
High octane requirement.
Complex and expensive.


Whatever you do you will need a front oil cooler.
See if you can find a good original 2.4E engine to start with. With a fuel pressure regulator, your carbureted T can be directly interchangeable.

Do some Pelican searches on “2.7RS, 2.8S, MFI.”
Tell us more about your 911; coupe/Targa? Suspension? Do you intend to use A/C?
There are several on this Forum that have this engine configuration. You can have much help and proper advice from experienced Pelicans.

Best,
Grady
gradyclay@hotmail.com

[Phoenix]

Chris - I was wondering how long it would take before someone caught and flamed that. I'm assuming 10% overlapping driver ed with street. We have many fun to drive roads in our neck of the woods.

Grady - I am thinking through a high CR motor but am a bit concerned about the availability of high octain fuel. The best I can regularly get is 93 now that Sunoco has stopped offering their higher rated fuel.

The more I read, the more a 2.7RS w/ MFI sounds like the direction I'd like to take.

Many thanks... Oliver

[Grady Clay]

Oliver,
Is your “Phoenix” screen name an indication of the 911 project? It sounds like it is very alive and flying.

You should also get Wayne’s other (101 Projects) book and Bruce Anderson’s book.
I recommend you get a Factory Workshop Manual ('66-'83 - expensive but worth it) and the several commercial books; Haynes, etc. You will want a copy of PET (PorscheErsatzTeile) spare parts CD. See if you can find a paper copy of the ’72-’73 parts catalogue.

Start yourself a MFI manual with all the info available on this Forum. With some study you can educate yourself if MFI is the way you want to go. Once you understand how it works it is OK to deal with, it is not rocket science. MFI has the best throttle response and great performance compared to any Porsche fuel system.

Now is the time to collect and organize technical information so you can make the best decision for you. There is a lot of fun in the chase.

Best,
Grady

[Grady Clay]

Oliver,
There are several possible solutions to the high compression – octane issues.

First, define how you want to use the 911; where and how much. If you want to use it near home, you can order personal drums of 100+ octane fuel. If you want to go to events all over North America will you trailer it or have to deal with fuel availability?

With a planned trip, high octane is available in most big metro areas. Install a big Factory fuel tank and/or an auxiliary fuel cell. Here in the Denver metro area there are several sources of 114+ octane where you just drive up and pump it yourself. A little research can find these octane “oasis.”

Twin plugs help reduce the octane requirement in almost all situations.

Keeping the heads cool reduces the propensity for detonation. The 1.8:1 engine fan arrangement works great for this.

Knock sensors and the ability to back off the ignition advance can help.

For short trips (2-4 tanks) you can carry some leaded race fuel to add to pump premium. Big effect.

With your knowledge of adjusting mixture, you can set the mixture rich in an extraordinary situation.


Soooo; Yes, you can use high compression.

Best,
Grady

[Wayne 962]

Originally posted by ChrisBennet
Excellent. It's good to see someone who drives their car at 110% like Porsche intended.
-Chris

Well, it could be that 10% of your street driving is also driver's ed! (although it shouldn't be)...

-Wayne

[fintstone]

Oliver
I would build the High perf 2.4 discussed on this thread:
72 911 Engine Debate
That is a great choice for horsepower and is period correct.

You may well have a lot of reusable parts. A good builder or machine shop will be able to test/evaluate your parts and determine which are ok.

[Phoenix]

Ouch! Posting that thread hurt!! The wound has just barely healed with scars aplenty.

This time around I will not make the same mistake! (Though I'm sure I'll make a few new ones ;-). With the help of this board and a trusted local mechanic, this next motor will be something I can be comfotable with and even proud of. It's time to pay the piper.

[Phoenix]

After reading tons of posts here and Wayne’s book, here’s what I’m thinking. It's pretty much the RS spec listed in Wayne's book with E or Solex cams and an E MFI system in hopes of keeping the torque in the lower RPM range.

• 7R case
• ’76-’83.5 oil pump
• Oil bypass update
• 2.7 crank
• Carrera Pressure-fed Chain Tensioners (currently have)
• Updated idler arms (930.105.509.00 = L / 930.105.509.00 = R )
• Case savers on cylinder head studs
• 911 turbo oil squirters
• 2.7 RS Euro pistons & cylinders
• 2.7 heads - not sure if I can use my current 2.4 heads?
• E or Solex cams - Which is best to help keep the torque in the lower bandwidth?
• Camshaft housing oil pressure restrictor upgraded (901.105.361.01)
• 11 blade cooling fan (currently have)
• Air baffles modified (between cylinder baffles narrowed 1” )
• Turbo valve covers (currently have)
• E MFI system
• High pressure fuel pump
• SSI (2 in 1 out)
• Front oil cooler (does this have to be in the front bumper or can I use this with an “S” spoiler
• All the replacement parts listed Wayne’s book

To help keep the costs down, I’m hoping I can salvage many of the parts in my current motor and sell off its PMO carburetors and Electromotive Ignition.

Or I could sell my curent motor and buy a 2.E with a 7R case and rebuild that.

What do the experts think?

[jgparker]

Wow, sounds like a great combination. Since you are asking for opinions, here is mine. Keep the PMO carbs, unless you already have the MFI (Save $, similar power, looks great). In a smaller engine Solex cams are a great choice but in a 2.7 S-cams may be a good choice as well. They have plenty of low-end torque in the larger displacements, and have a lot more personality. SSI with 2 in 2 out exhaust would be even better. Did you say what head studs your going to? Sticking with stock steel? I hope the real experts chime in on your choices too.

Good luck,

JP

[Wayne 962]

Hmm, if I were you, I would go with a 3.0 and put some carbs on it. Good power, reliable, and period-correct looking. When the engine is tired, replace the pistons and cams with something more aggressive...

-Wayne