Hot rod Engine choice...2.7 or 3.0???

[cnielsen]

I'm restoring a 67S and I have the original engine but I want to keep it on the shelf and build a hot rod motor for the car. I want to build something special and not just plug something in to get it running. As a matter of fact, the car is in bare metal so I have time on my side.

I already have a built set of webers, new SSI's and a sport muffler.

I have two core motors...

The first one is a 77 2.7 that was previously rebuilt although poorly. It has RS Mahle pistons and cylinders and an updated oil pump and the rest of the internals are good. It does need a full rebuild though and the case will require all the typical machine work..line bore, shuffle pin but it does already have time certs for the cylinder head studs. I think the cam towers would need rebuilding and my cams are not good. rocker arms also need rebuilding. The plan would be to sell the RS pistons and get some higher compression J&E pistons in combination with Solex cams. The heads have already been mildly ported but not yet sure of the condition of the valve guides, and I have a matched set of intake manifolds.

The second choice is a seemingly low mileage big port 3.0L. I don't think the bottom end of this motor needs anything done to it so I would save massive $$$$ on machine work and ultimately end up with a much stronger case. I would do valve guides but i have no reason to believe that the rest of the heads, cam towers etc would need any significant ($$) work done to them. I would go the same route of higher compression pistons and Solex cams and use the same webers and SSI's.

The 2.7 seems a more appropriate motor to put in the car but with the money I could save on building the 3.0L, I could do a twin plug distributor, amber shroud etc. Furthermore, once it is installed, who is really going to know a significant visual difference between the 2.7 and the 3.0? The 3.0 is heavier and that may not be good for a SWB car.

Is there any problems mating a 901 trans to a 3.0L?

Thoughts, suggestions for a cool motor???

[rfuerst911sc]

From what you have stated I would go with the 3.0, but to be honest I am 3.0 biased. In my opinion the best bang for the buck that Porsche has produced.

[Steve@Rennsport]

3.0 for me, too.

Both engines need a good front oil cooler, regardless, and the 3.0 is more durable as well as $2K less expensive to build, all things being equal.

I like 2.7's (have one in my own car) but wouldn't do it again, based on what I've seen lately with these engines. 2.7 "S" engines are more susceptible to case cracking now as all these things are getting pretty old and have been used hard over the years.

JMHO, given the investment required to do a proper mag-cased engine now, its foolish to spend that kind of money unless its a restoration and its imperative to retain the original engine.

[al lkosmal]

Chris,
I like 2.7's too. One of the best engines I ever had was a 2.7 w/9.5:1 JE's, E-cams, 40mm Webers, SSI's, Dansk 2in-1out sport muffler. It was a hoot,...... but the 3.0 sounds like the way to go here. With some 10;1 JE's, and all the rest of the goodies you've mentioned above it should be have some serious grunt, make all the right noises.... and be reliable.

As far as living with a SWB with a 3.0 in it, you might want to talk to Don (haycait911) who went down this road a couple of years ago. If I remember correctly his 3.0, modded in a similar fashion to your plans, made some serious power. He installed a 915 as well.

regards,
al

[Fishcop]

I'm also running a factory spec 2.7RS build and love the character of the engine. But in hind sight I would have built a 3.0 engine for the cost savings and general longevity of aluminum over magnesium. I'm sitting off a local 3.0 turbo case as I reckon it will provide the best of both worlds for me...

[Reiver]

The 3.0 turbo and the 3.0 non T are the same case...both marked 930. Could explain the longevity of the normally aspirated car.

[shbop]

Now that we've solved the motor end; what trans. issues, if any, does the 3.0 bring to the table going into a SWB?

[Steve@Rennsport]

Originally Posted by shbop

Now that we've solved the motor end; what trans. issues, if any, does the 3.0 bring to the table going into a SWB?

Jon,...Thats an excellent question,...

IF one is very gentle, a properly prepared and built 901 will work, however its not generally reliable for engines of this displacement, given the 7:31 & overhung 1st gear. Even with a billet intermediate plate and side cover, its not a beefy enough transmission for a healthy 3.0 (unless driven by your Mom).

I'd be using a re-geared '76 or '77 915 in there as in the long run, its going to be far cheaper.

Naturally, JMHO.

[cnielsen]

Thanks everyone for the advice...it's making my decision much easier!

Lets discuss transmission issues, fitment into SWB chassis, axles etc... Obviously, the rear seats need a bump in the sheet metal.

I have several transmissions to choose from but I have to say, I'd like to stick with the dog leg shift pattern in this car. So that narrows it down to the original aluminum 901 or a nice mag case 901 I have from a '69.

Suggestions?

[LakeCleElum]

I have this engine in my 73.5:

http://forums.pelicanparts.com/porsche-911-used-parts-sale-wanted/586102-fs-engine-transmission.html

LUV It.........

[cnielsen]

That's a great deal!

[rfuerst911sc]

Is there a difference in the 901 in a 911 vs. the 901 in a 914 ? The reason I ask is I have a 914/6 GT clone with a 1978 big port 3.0 and original 914 901 transmission. Been using it for almost 3 years now and the tranny still lives. I do take it easy on 1st gear but 2nd -5th is full power and lot's of fun. The transmission is stock with no modifications for the extra power. Maybe it's a time bomb waiting to go off ?

[racer_X]

What is the difference in weight between the 2.7 and the 3.0?

Also, does the 2.7 from the RS last longer than the 2.7 in the 911S? Or are they prone to the same failures?

What is the difference in terms of cooling, stud failures and valve seat failures?

[Steve@Rennsport]

Originally Posted by rfuerst911sc

Is there a difference in the 901 in a 911 vs. the 901 in a 914 ? The reason I ask is I have a 914/6 GT clone with a 1978 big port 3.0 and original 914 901 transmission. Been using it for almost 3 years now and the tranny still lives. I do take it easy on 1st gear but 2nd -5th is full power and lot's of fun. The transmission is stock with no modifications for the extra power. Maybe it's a time bomb waiting to go off ?

Its no time bomb, however a 3.0 engine places loads on those old gears (depending on ratio) that they oftentimes will no longer handle. We see more failures due to fatigue now. Without an LSD, wheelspin reduces stresses on the gears, too.

If you have the stock, magnesium intermediate plate, the chances of an expensive failure really do go up.

Its really all about how the car is driven,....

[Steve@Rennsport]

Originally Posted by racer_X

What is the difference in weight between the 2.7 and the 3.0?

Also, does the 2.7 from the RS last longer than the 2.7 in the 911S? Or are they prone to the same failures?

What is the difference in terms of cooling, stud failures and valve seat failures?

Weight differences are about 20 lbs.

MFI engines tend to run significantly cooler than CIS ones due to differences in fuel mixtures, however a 210BHP motor makes more heat than a 175BHP one does.

Both engines cool the same; its all about how the engine is configured and having a front oil cooler system.

Magnesium-cased engines had steel studs which never broke; 3.0 ones had the 1st generation Dilavars which were problematic.

Neither engine had valve seat failures; both engines suffered from soft valve guides and that's easily resolved with a good aftermarket guide.

[cnielsen]

I suspect it is all how it is driven. As long as you don't drive it like an American hot rod off the line, I suspect the life span will be significantly improved.

So, which is better... The original 67 trans or the mag case out of the 69? I like the idea of the 69 trans due to the traditional clutch linkage and not that goofy ear that comes off the side cover. Any issues fitting the 69 transmission of should it bolt right in?

[Steve@Rennsport]

Use the mag transmission, but install the billet intermediate plate and side cover.

Its a bolt-in as long as you have Lobro CV's.

[cnielsen]

While we are formulating an engine plan...

If I was to build this into a 3.2 short stroke motor with 98mm pistons, is there any benefit to a twin plug system or is it just eye candy? Also, what is going to be the real world difference between the 9.5:1 and the 10.5:1 JE pistons?

What is the general consensus on LSD brands for the early transmissions?

[Steve@Rennsport]

Originally Posted by cnielsen

While we are formulating an engine plan...

If I was to build this into a 3.2 short stroke motor with 98mm pistons, is there any benefit to a twin plug system or is it just eye candy? Also, what is going to be the real world difference between the 9.5:1 and the 10.5:1 JE pistons?

Its all about CR & available octane. At 10.5:1, you must have twin-ignition to run on pump gas, however its unnecessary at the lower CR. Now,......there are other benefits to twin-ignition (especially using carbs or MFI) such as better overall drivability, improved throttle response and cleaner running. Engines so equipped are better behaved, all things being equal.

What is the general consensus on LSD brands for the early transmissions?

Guard, hands down! Nothing is as durable or as adjustable.

[cnielsen]

So the next question is naturally...is it worth going for the higher compression? What is going to be the seat of the pants difference and real world driveability?