2.0 aluminum 901/06 rebuild options

super9064 · 07:38 AM

I have a 68L that I am converting to a lightweight café racer.
It has a 901/06 engine, aluminum case Weber IDAs. Parts I have laying around, 71E cams, 71S crank, 73.5 CSI rebuilt heads (small ports). I would like to get the boards input of my options. I plan on using the car mostly just blasting around town, and an occasional DE event. Since this car needs everything I need to put a cap on how much I spend on the engine. I am looking for a fun drivable package. I want to spend enough to get into the 160hp range, but don’t want to spend to little that, for a bit more I could get a lot more. The other factor that I think should be addressed is the very likely probability that we will all be faced with is poor quality fuel in the future. I am concerned that our high compression hot rods will have real problems some day soon.
The options are many, on the low end I could build the 901/30 Rally engine, basically S pistons and S cam for 150bhp. Or go for larger displacement. The basic problem with going bigger is the expense of lots of machine shop time on the case, and heads. I’d like to get some opinions on what would be the best options, under the circumstances. Thanks

kenikh · 12-14-2007, 07:41 AM

You won't get to 160HP on CIS head ports and E cams w/ a 66mm crank. Your best bet would be to get a 70.4mm crank for additional dispalcement. You should get to 160 HP at 2.4L.

super9064 · 12-14-2007, 07:53 AM

Quote:

Originally Posted by kenikh

You won't get to 160HP on CIS head ports and E cams w/ a 66mm crank. Your best bet would be to get a 70.4mm crank for additional dispalcement. You should get to 160 HP at 2.4L.

Those are just parts that I have on hand, If I can use them in some combination great, if not thats fine too. For a 70.4 mm crank to bring me up to 2.4l don't I need 2.2 (84mm)P&Cs as well?

kenikh · 12-14-2007, 08:28 AM

Quote:

Originally Posted by super9064

Those are just parts that I have on hand, If I can use them in some combination great, if not thats fine too. For a 70.4 mm crank to bring me up to 2.4l don't I need 2.2 (84mm)P&Cs as well?

Yes. Should have mentioned that, too.

They are pretty abundant.

304065 · 12-14-2007, 09:00 AM

You are in exactly the position I was a couple years ago.

One thought at the beginning: a '68L would be worth much more in restored condition than converted to cafe-racer. Most of the SWB cars suffer from RUST, which makes them difficult platforms to build a performance car from-- just look at Speedo's extensive surgery on his own 911R project to get a sense of how badly these cars have deteriorated over the years.

It bears thinking about whether it makes more sense to restore the '68 to original or close to that-- keeping the slab-sided fenders and skinny tires, finding all of the '68 one-year-only interior bits and generally enhancing the value. Remember, people who buy '68Ls don't do it because of the wide tires and huge horsepower, they do it because the car is a time machine, a throwback to Butzi's original design that is the direct descendant of the 356 before the car became a German hotrod and the fenders started flaring.

That said, my own saga of considering the rebuild options is well documented here. Here's a link to the thread, perhaps you have already seen it. Suggestions for warmed over 2.0 901/05?.

What I ultimately concluded, after taking into consideration originality, complexity, my own skill and experience level and budget was to do the following:

Bore cylinders to 81mm for 81x66 (2040cc)
Rebuild stock heads with 39/35 valves and 32mm ports
JE 9,5:1 pistons
DR Camshafts Supercup on 102 (basically, a modern lobe design on a 911E cam)

I then have refreshed, rebuilt, replaced every nut, bolt and part number in the engine, making invisible improvements along the way, replacing the wear items like all the sprockets, chain tensioners, etc. I'm going to go only slightly out on a limb and say that ALL 911 engines from the 1960's are basically worn out if they haven't been rebuilt, so you will end up replacing a lot of parts because the old ones are just shot.

Budget? Stock, about $10,000. If you want to go bigger, plan for half again as much, and if you're going to venture into 911ST or 906 territory, triple that amount.

If originality is not an issue, build the engine to 2,2E specs. You will end up with slightly different looking cylinders, but only the cognoscenti can tell. The crank from the 71 is the same as the '68 crank I think, so you should have a choice of a good one to use.

zoopboing · 12-27-2007, 10:24 AM

John, I read with interest your threads talking about boring out cylinders to
81mm for 81x66 (2040cc). I have a 1969 911E 1991cc engine (80x66) that I am stripping down and rebuilding (slowly!). I'm in the UK, and am trying to find 81mmx66mm stroke pistons, as I have to bore out the scratched/corroded
cylinders. Any help on finding some 81mm pistons would be great.
Thanks, Ade

daepp · daepp's Garage

With respect to poor gas in the future, don't we have the option of adding an octane booster after each fill up?

304065 · 12-29-2007, 09:53 AM

Zoopboing,

My 81mm pistons were made by JE. The other option for a twin-plug engine with high octane fuel is the Mahle 906 pistons. These were available new via Andial and I believe Tom1394Racing can help in the used department.

Of course there are other options. Dr. Steve Weiner has a supplier based in UK that he deals with for something more exotic. . .

super9064 · 01-22-2008, 01:10 PM

Well I've given it a lot of thought. I think I am going to send it out to Supertec and have Henry build me 2.2S spec motor. Any thoughts?

shbop · 01-23-2008, 03:21 PM

Quote:

Originally Posted by super9064

Well I've given it a lot of thought. I think I am going to send it out to Supertec and have Henry build me 2.2S spec motor. Any thoughts?

Yes. You'll have one beautiful motor! Be sure to post pictures.

JCF · 01-31-2008, 03:01 PM

Quote:

Originally Posted by super9064

Well I've given it a lot of thought. I think I am going to send it out to Supertec and have Henry build me 2.2S spec motor. Any thoughts?

I've seen one of his 2.2S's.
A work of art !

jluetjen · jluetjen's Garage

Quote:

Originally Posted by zoopboing

John, I read with interest your threads talking about boring out cylinders to
81mm for 81x66 (2040cc). I have a 1969 911E 1991cc engine (80x66) that I am stripping down and rebuilding (slowly!). I'm in the UK, and am trying to find 81mmx66mm stroke pistons, as I have to bore out the scratched/corroded
cylinders. Any help on finding some 81mm pistons would be great.
Thanks, Ade

Zoopboing, I've got a 2.0E which runs fine with the current 10% Ethanol/Gas mixture used here in New Englan. It's got S pistons and I run with 93 octane since 94 is no longer available here. I had to retard the timing slightly, which brought the temperatures up a few degrees, but other then that I've had no issues. I don't expect that 81 mm P&C's will be a big issue as far as engine combustion performance.

super9064 · 02-27-2008, 12:40 PM

Quote:

Originally Posted by super9064

Well I've given it a lot of thought. I think I am going to send it out to Supertec and have Henry build me 2.2S spec motor. Any thoughts?

Up date, Just got off the phone with Henry, He thinks I should just go for it and and build a 2.7RS spec motor. So..........now I'm thinking...

again

304065 · 02-27-2008, 02:06 PM

Hmm, 210 HP with MFI in a narrow-body 68L with unvented brakes?

So now you're into machine the spigots, nikasil P&C, 70.4mm crank and rods, S cams, port the heads. . . along with all the other mods, e.g. external oil cooling, uprated suspension and brakes to handle the additional power. . . what do you want to do with the car?

kenikh · 02-27-2008, 03:57 PM

Build an 66mm x 85mm on Biral bores w/ Mod-S cams and 9.5:1 CR. Then you don't have to overbore your spigots. Dollars to doughnuts that motor makes only 10HP less than that 2.7; that's combo is more than enough to scare you.