got some info on a '70 six for sale here in Austria
the owner told me, that it got a 2.5 engine installed in 1971 by the Porsche factory - now there's a 2.7 in

well, I've never heard about a 2.5
the seller told me, that is was a very special/rare engine, but it's gone for more than 20 yrs

now I wonder about that engine
does anyone know such an engine? what could you tell me about?
carbs or FI, power, torque, rpm bandwith ...
just try to describe this engine, please

many thanks in advance,
Gustl

i assume its just a short stroke 2.7...

Yep there were 2 versions of the 2.5 engine. Porsche only did it for racing classes, not for production. One was based off the short stroke 66mm crank (2.0, 2.2) with bigger pistons and cylinders, the latter was a larger bore 2.4. I think they put out around 250HP, not sure about induction but I think it was carbs. Short stroke 2.5's are supposed to be real screamers.

QUOTE (Aaron Cox @ Apr 9 2005, 07:20 AM)

i assume its just a short stroke 2.7...

but in 1971 there were no 2.7 available - as far as I know, thea came up in 1973

would be more likely, that it's a modified 2.4 - maybe for any rac car

As I recall one of the 916 had a 2.5 in it.
Joe

The 911 handbook has references to that engine and power output. There is a couple hurdles when making them as I think you use 2.7 P/C's (someone correct me if i am wrong) and the compression can be a little low, so you have to machine just a hair of the heads, but leave enough meat for the cam chains

QUOTE (Gustl B @ Apr 9 2005, 01:29 AM)

but in 1971 there were no 2.7 available - as far as I know, thea came up in 1973

the production Carrera RS 2,7 was a '73 model year car.

but the factory had access to interesting stuff back then... you do the math:
5,4-liter 70,4mm stroke 12-cyl 917 with 90mm Nikasil cylinders...
2,7-liter 70,4mm stroke 6-cyl 911 with 90mm Nikasil cylinders ...

Frère talks about the E/F Series 2,5 on p 246, 7th Edition. the first were overbored 70,4mm 2,4's but there were serious issues with crankshaft vibration. the 2,4 was produced for the '72 model year for which production typically begins August the prior year - 1971. development parts would have been available to the race shop even earlier than that.

the second series used the 90mm Nikasil 917 cylinders and the 66mm crank.

both produced about 275 HP with MFI.

okay - re-read your original request for technical detail...

stroker: 86,7mm bore, 70,4mm stroke. Bosch MFI only. 275HP @ 7.900rpm 27mkg torque(196 lbs-ft) at 6.200

flywheels came loose and cranks broke due to weaker crank and mag case distorsion.

big-bore: 90mm bore, 66mm stroke, MFI, 'similar' output.

I have seen a couple of 2.5 six cylinder engines. Paul Bernardo former POCer had one in the mid 90's. They are short strokes that scream like weed wackers if they are sorted, ported and cammed right!

There were 2.5's run in the 911ST, which was made in '70 to '72, but
I don't know when which engines were used.

I run the short stroke 2.0 liter version with 2.7 jugs, lots of fun....

There are a few iterations of 2.5's

the factory specials, and the 2.7 jugs on short stroke cranks.. ( low CR) either variation is a nice engine.

I once had (and J. Fort in Ohio now has) a 2.5, early 911 aluminum case, stock 2.0 crank with 2.7 P&C's, E cams. Very quick. Way better than my current stock 2.0 six.

I bought a 2.4 T MFI engine about 1 yaer ago. I was told it hadn't run in 10 years. I cleaned a lot of blanket fuz and animal dung off the top of the cylinders. Took the MFI off and installed some carbs ( don't know anything about FI but know I can get carbs to run). My son installed all the plumbing and a motor mount in a 914 and it fired up. On the DYNO it pulled 160 HP at 6oooRPM at the rear wheels......not a 2.4 T !!. We tore it down anyway and found 86.7MM pistons and nicasil barrels on a 70.4MM crank. The problem is when they bored out the 84MM 2.4 cylinders to 86 + the thickness of the metal on the inside of the "O" ring gasket slot was so thin that two of the cylinders had about 1" slivers broken out. NOW what do we do? Go 2.4 high compression; 2.7 high compression and have the case machined ; or go to L&N and have a set of "nickeys" made for the pistons we have. We are going to go with the L&N CNC barrels and keep this a 2.5 L . We are shooting for 200 HP with some torque for autoX.

go 2.5 with torque, long stroke, replace only what you have to and then look at gearing. Possibly a shorter 3rd for autocross?? Dyno it and build the gear box to use. HP is nice but I eat up bigger 911's with stock 4th gear at the track.

Someone here also had the second cut off and replaced with a custom gear??? Taller second???? lots of torque 7 k red line might be the only shift you need depending on the autcross course. Around here they tend to be tight...???

QUOTE (d914 @ Apr 10 2005, 09:46 AM)

Someone here also had the second cut off and replaced with a custom gear??? Taller second???? lots of torque 7 k red line might be the only shift you need...

the 914.6 standard 2nd mainshaft is GA (1,778:1) while a /4's is F (1,889:1)

that with a 7300-ish redline was just about all i ever needed.

there is always the 904 mainshaft... there was talk about remachining the stock shaft but after further investigation it was discovered (again) to be a sub-viable option...

I'm building a 2.5 liter.

Yup... if you check out Victory by Design, word has it that Redman's driving a 2.5 loaded six as a factory "pratice" car for Targa.

The two versions mentioned were years apart. The only 2.5's produced by the factory were race engines. The early one is simple (if you can find the special 89mm Mahles). They had 906 cams and 41mm intake ports (if'n I recall). They "were" around 250hp and the 911ST (as mentioned previously) competed with a 2.5.

Mine is going to be built off my 2.2 block with 90mm Euro RS (Nikasil) pistons. Rod ends will be rebushed to bring the CR back up to 9.5:1. I'll be using S-Cams and Webers for my race car. That's the "plan" anyway. It will be an autocrosser and sometime DE car that won't see "hours" of spanking time.

Back when I was trying to figure out WTF to do with my 2.4 T for MO POWER I did a lot of research on your basic early 911 mag case motors. Some conclusions....feel free to disagree:

Only 2 cases are worth fooling with (for a hot rodder), the 5R & 7R. of the 2, the 76 & later are best....followed closely by the 73.5 7R.

Odd ball displacements are a waste of money unless you're building for a specific class.

Nikisal cylinders are THE way to go.

The compression ratios for stock pistons for the 2.4 & 2.7
are too low and all the "tricks" for raising the compression....suck.

All the post 70 heads have the same size valves, but the ports vary widely.

S cams and Webers are a poor combo for a street motor.

Shopping for "pre owned" parts can be a boon or a bust.

Given enuff money, none of the above means squat.


BTW: Otto's makes (or converts) the 901 mainshaft to a replacable 2nd gear item. I *think* it's around 600 bucks.

QUOTE (J P Stein @ Apr 10 2005, 11:20 AM)

Only 2 cases are worth fooling with (for a hot rodder), the 5R & 7R. of the 2, the 76 & later are best....followed closely by the 73.5 7R. S cams and Webers are a poor combo for a street motor.

there are some who actually prefer the 5R on the basis that they have not been subjected to as much thermal stress in street service.

i'm working a deal for a 49-state 7R 2,7 that i think will work out nicely.

the bigger the displacement, the happier the S cams are in street service. at least, that's what my research has indicated, and which i'm hoping to demonstrate IRL, because the Webers are paid for, and rebuilding the MFI to 2,7RS specs isn't ...

the rest, no argument at all.

The least stressed case would be the 7R from 73.5 T.....logically. The 5R has the big spigots but not the bracing.
Pre7 7Rs don't have the oil mods....but any that are straight & true (or easily straightened) are gud.

My 7R needed a line hone. I had one arrogant dickhead tell me it must have been a shitty job cause I didn't get charged enuff to suit him. I think he is the PCA 930 tech guru.

QUOTE (J P Stein @ Apr 10 2005, 02:39 PM)

The least stressed case would be the 7R from 73.5 T...

i have just such a case waiting in my garage for the 2,2's rebuild :-)

QUOTE (ArtechnikA @ Apr 10 2005, 11:52 AM)

i have just such a case waiting in my garage for the 2,2's rebuild :-)

Nice. If I see one, I'll buy it just for the hell of it.

The S cams work great with MFI as the fuel reversion problems
don't happen as they do with carbs, but as I said, feel free.....
I learned some time back to neither over cam nor over carb an engine for it's intended use....the hard way, of course

i think that at first, i'll be running the 40mm Webers from the /6 on the 2,7/2,8 since they're paid for, and a set of RSR throttle bodies aren't :-)

since this engine is destined for the 911 (first) i have the additional option of running the tall manifolds, which will give me a little more room for match-porting too. that should help a bit.

I really like the 2.5 in my car. It is the for Jim Chambers car. shorter gears. lots of torque. strong shifts in all 5 gears, but not a highway cruiser.

Put some biga$$ balloon tires on it. It'll do great on the highway

Eric, now you know where I learned my lesson. A few years ago I bought the six shown below in San Jose, CA. Had a sport muffler (J. Fort has it now) and even shorter gears than his car. Drove it home in one day, 750 miles, required 4400 rpm to make 80 mph. Wish I had thought to stop and buy ear plugs!
Ida in fifth drives like a Lincoln Town Car (maybe not quite). Hand throttle at max is a fine cruise control, stays right at 70. WCC here I come.

However, if I can find a set of Mahle gas burners at a reasonbable price, I may have an optional set of lower profile tires so as not to be subject to ridicule by you young'uns.
A set of Boxster 7x16's might also be nice.

Soo... Jim . Whos car is that and what spacers did they use?
Joe

Car belongs to "jim912928" from South Bend, IN.
There is a thread in the classified parts for sale "16 Boxster Wheels", near the bottom of first page. He talks about them there.

He started with 6's in rear and 7's in front but has changed to all 7's.
No spacers, stock fenders. Not even rolled if I recall. Best looking big-bumpered car I've seen.

***Official Thread Hijack***

Jim's my hero. It seems as though he's got Ida's oil issues sorted out. My friend, you are truly the next rightful owner. Thanks for taking good care of this car

You can put whatever tires on her you want.

Also, the other Jim in South Bend has one hell of a nice looking car. I met both (the car and the owner) at last years MWC.

Back on subject... I'm still gonna build my carb starv'n 2.5 and it will probably be sitting on that good for nothing, rickety, shitty-ass, balsa wood block. I promise to write the board when it scatters crank bearings all over the county and pulls all the head studs. You all can say "I told you so" then.

Aren't the 7R cases magnesium?..and more flexible? Wouldn't you want an earlier aluminum case? I had a 7R case align bored and couldn't find the oversize main bearings for less than $800.

I redid a 2.7 a couple years ago and used an early (69 I think) aluminum case that I got from Bruce Jennings, with all the appropriate machining, the 2.7RS pistons, S heads C/R around 11.5:1 if I remember correctly, E-cam grind that is a little milder than the RSR grind, webers. I use this motor for endurance racing a 911.

QUOTE (HotRod @ Apr 11 2005, 12:04 PM)

Aren't the 7R cases magnesium?..and more flexible?

yes.

QUOTE

Wouldn't you want an earlier aluminum case?

tradeoff. by the time you've done everything you need to prep an aluminum case you might as well have started off with a 7R. if you have an aluminum case, it's not a bad place to start.

QUOTE

I had a 7R case align bored and couldn't find the oversize main bearings for less than $800.

i won't ask where; it's not important. donno why you'd spend money for machine work and expensive bearings when a low-time 7R could be had for a fraction of that. but it's your call, do what you want.

*next* time, tho, consider sending the case to Competition Engineering, where they can resize the case (just like resizing a rod...) and you'll wind up with a case that takes standard bearings and a '0' intermediate shaft gear. there's a limit to the magic they can work, because there are a few reasons you can't make a 911 case too narrow. buit new(er) cases are not hard to find...

QUOTE

I redid a 2.7 a couple years ago and used an early (69 I think) aluminum case that I got from Bruce Jennings, with all the appropriate machining, the 2.7RS pistons, S heads C/R around 11.5:1 if I remember correctly

did you use the standard or the Turbo piston squirters ?

QUOTE

E-cam grind that is a little milder than the RSR grind

an E cam is a LOT milder than an RSR!

QUOTE

I use this motor for endurance racing a 911.

24 hours? 12? where are there endurance race events for early 911's? love to get involved with that but i don't know of any events in my area...

QUOTE

I redid a 2.7 a couple years ago and used an early (69 I think) aluminum case that I got from Bruce Jennings, with all the appropriate machining, the 2.7RS pistons, S heads C/R around 11.5:1 if I remember correctly, E-cam grind that is a little milder than the RSR grind, webers. I use this motor for endurance racing a 911.

Sounds like a cool engine. From what I understand the big difference with the 7R vs. the Die-cast Aluminium would be the spigot base. 7R's had nice beefy spigot bases pressure cast into them. Makes for good increase mods. But hey, I'm just parroting what I've read in Bruce's book, like everyone else

"all the appropraite machining" is the key phrase here......to parrot Rich, who is parroting Anderson. Since some folks can't or won't read or don't believe what they read, someone has to do it.

And who better to parrot? I've spent a bit of time rootin' around in a few 9eleben motors and haven't found his info to be wrong....in stark contrast to the internet.

I didn't mention any names...

"baawwwwwk"

It's been 10 years or so since I had this engine done, but yes I believe that it was the Turbo Piston squirters...

I don't mean the 911E cam, E-Cam is a company that had their own grinds for 911s, don't know if they're even still around.

6 hours, 12 hours, I usually do the SCCA endurances, there's a 12 hour at Summit Point, WV in June.

I didn't spend much on the aluminum case, it kinda fell in my lap already machined and ready to go. I'll look back in the paperwork and see what all's in this thing.

Yeah, I knew I could get a 7R cheap, but thought that the aluminum would be better for racing, just an assumption...just was wondering if anyone else had had the issue with bearing prices after getting align bored?

QUOTE (HotRod @ Apr 12 2005, 09:19 AM)

...just was wondering if anyone else had had the issue with bearing prices after getting align bored?

first, thanks for the information !

we just had this discussion over on RennList's 911 List. MOST of the time, the #8 main bearing (the expensive one) is just fine and can be re-used. even if the bearing is worn beyond service limits (which may mean it's opened up to the clearance you'd want in a race engine :-) ...) the bore in the case is probably just fine.

so - even if the case can use an align hone on the shell bearings (#1 through #7) it should be carefully miked to determine if anything needs to be done to #8. if not, leave it alone and save a lot of money. or - send the case to CE and have them resize it.

i recall a case (long time ago, so i won't mention the shop since i've heard the situation is different now...) of a well-known VW machine shop that was famous for line-boring cases to an oversize that just happened to match the bearings that they'd bought up all of a manufacturer's production. you do have to shop around and be an informed consumer...

.25mm overbore main bearings with standard crank. are from 200-400 from the dealer depends on how the parts dept. reads it , They come in halves 2 to a box , So some Porsche dealers sell them for twice as much as others. The Ones that I know are redily available are for the late 2.7 Cases. The retaining tab is in a different location(more centered) earlier cases can be updated if need be.
The above does not include #8 bearing.

I know an old timer that has 200 sets of 1st over case ,1st under crank. ,said he got a good deal on them.
He still wants 250.00 a set, He will probably leave them to his Son.

2.7 based 2.5 is the most economical way to go.

QUOTE

got some info on a '70 six for sale here in Austria the owner told me, that it got a 2.5 engine installed in 1971 by the Porsche factory - now there's a 2.7 in

Is it green? Maybe it's the car in the video...

QUOTE (Eric_Shea @ Apr 12 2005, 09:46 PM)

QUOTE got some info on a '70 six for sale here in Austria the owner told me, that it got a 2.5 engine installed in 1971 by the Porsche factory - now there's a 2.7 in Is it green? Maybe it's the car in the video...

what video are you talking about

about the last 20 yrs it looked this way:



last fall a friend of mine bought it and did "a little work" on it (roll cage, steel flares, new paint, completely engine rebuild) and just sold it to spain
first I was really interested, but it was "a little" too expensive for me (more than 38k EUR )

one more

The first 911 engine I ever rebuilt was a 2.3L

QUOTE

what video are you talking about

Victory by Design. Redman driving a test run of the Targa.