Best engine build for lightweight mid-year backdate?

[Maxhouse97]

Doing some research on a long-term project to build a lightweight, longhood 911. See nearby thread on picking the body/shell (leaning towards a low optioned mid-year to backdate vs original longhood, I’m coming from a ‘87 3.2). However I am thinking about buying an engine first to rebuild and use to swap in once I buy the car (in 2-3 years). Which engine would you recommend? I know there are a lot of threads on this, but the market has moved around quite a bit (SC/3.2 up and longhoods flat/down) so I’d like to see what folks think now. Gratuitous pic below of the target.

Here are my priorities in trying to acquire something that is the epitome of a zingy, responsive motor to align with the ethos of a lightweight longhood:

- Character/revability/sound
- Good mix of torque/redline (shooting for linear power to 7k)
- Robust/reliable/low maintenance once set up
- Bang for buck (used engine price + required machining + parts)

I do not care about hp, power, or originality. I am shooting for a fun to drive, go-kart like experience. I intend to perform as much of my own labor as possible, perhaps sending out the case/heads for machine work, etc. I am not in a rush.

Here are my current candidates in order of priority (attempting to maintain similar cost between choices):
- 3.2 SS w/ EFI, single plug
- 3.0 w/ ITB, maybe dual plug (maintaining similar cost to above)
- Stock 3.2 with euro pistons and aftermarket EFI
- 2.7 or 2.4 with mechanical fuel injection

To be honest I lean away from anything smaller than 3.0, as I have experience with AL case engines and am scared off by the issues/cost of a 2.7 that could come with the car. I am also wary of the cost of anything in the 2.0-2.4 range. I think there are a lot more SC/3.2 engines out there so would like to take advantage of that.

I’ve heard so much about the 3.2SS, makes me feel it provides the best bore/stroke combo for my application at relative affordability (with a high mileage rebuild I think you will be buying new pistons anyways). That being said if I can get the character I’m looking for out of a 3.0 that works for me. However I also acknowledge that there may be something about the 2.2-2.4 range engines that has the “ Je ne sais quoi” of good longhood cars. Thoughts? Appreciate the input, half the fun is doing the research and dreaming up the combo … like a kid building a Lego car.

[Bill Verburg]

Originally Posted by Maxhouse97

Doing some research on a long-term project to build a lightweight, longhood 911. See nearby thread on picking the body/shell (leaning towards a low optioned mid-year to backdate vs original longhood, I’m coming from a ‘87 3.2). However I am thinking about buying an engine first to rebuild and use to swap in once I buy the car (in 2-3 years). Which engine would you recommend? I know there are a lot of threads on this, but the market has moved around quite a bit (SC/3.2 up and longhoods flat/down) so I’d like to see what folks think now. Gratuitous pic below of the target.

Here are my priorities in trying to acquire something that is the epitome of a zingy, responsive motor to align with the ethos of a lightweight longhood:

- Character/revability/sound
- Good mix of torque/redline (shooting for linear power to 7k)
- Robust/reliable/low maintenance once set up
- Bang for buck (used engine price + required machining + parts)

I do not care about hp, power, or originality. I am shooting for a fun to drive, go-kart like experience. I intend to perform as much of my own labor as possible, perhaps sending out the case/heads for machine work, etc. I am not in a rush.

Here are my current candidates in order of priority (attempting to maintain similar cost between choices):
- 3.2 SS w/ EFI, single plug
- 3.0 w/ ITB, maybe dual plug (maintaining similar cost to above)
- Stock 3.2 with euro pistons and aftermarket EFI
- 2.7 or 2.4 with mechanical fuel injection

To be honest I lean away from anything smaller than 3.0, as I have experience with AL case engines and am scared off by the issues/cost of a 2.7 that could come with the car. I am also wary of the cost of anything in the 2.0-2.4 range. I think there are a lot more SC/3.2 engines out there so would like to take advantage of that.

I’ve heard so much about the 3.2SS, makes me feel it provides the best bore/stroke combo for my application at relative affordability (with a high mileage rebuild I think you will be buying new pistons anyways). That being said if I can get the character I’m looking for out of a 3.0 that works for me. However I also acknowledge that there may be something about the 2.2-2.4 range engines that has the “ Je ne sais quoi” of good longhood cars. Thoughts? Appreciate the input, half the fun is doing the research and dreaming up the combo … like a kid building a Lego car.

for any street car the torque curve is going to be the signature characteristic, followed by gearing and weight, these will be further tweaked by the type of intake, clutch, suspension, wheels and tires

here are typical torque curves for potential engines, any of them will be made more responsive by the use of ITBs, lighter clutch, select transmission , select wheels and tires


The 3 middle curves would probably be the most fun in a l/w street car w/ appropriate wheels and tires

the 993nvr graphed has 993RS cams and 1.75" OD headers, the 3.4 mod has 993ss cams and 1.75"OD headers

a 3.2ss will lie between a stock 3.2 and the modified 3.4

[Jeff Higgins]

I was pondering this very same question darn near 20 years ago. My '72 T had a fresh, but stock, 2.4 T motor. Knowing was I was just going to pull that motor and put it aside, I had the proverbial "blank slate" before me. I had no motor to start with, which allowed me great flexibility in my choices going forward.

I wanted something that felt like an early "E" motor, rev happy but not as peaky as a 2.0 liter "S" motor. I wanted mid range torque for street drivability, but a fun "snap" on top. "Character" was a big, big concern.

Back in those days, some of my buddies in R Gruppe up here in the Pac West were already putting 3.6's into early cars. Enough so that we earned the moniker "the big block boys" within the club.

Well, fortunately, I had the chance to drive a few of those cars before I had to make my decision. They all felt like they had small block Chevy motors in them - no character, no free-revving "early car feel". Fast, yes, but not what I was after. As a side note, many of those 3.6's have since been replaced by smaller, freer revving motors by their owners. We all kind of reached the same conclusion.

Others had found kind of a "middle ground" and were putting 3.2's in their cars. These all had that same lack of "character", especially with the relatively lower rev limit of that motor, driven by its compromised rod bolts. Just not what I was looking for.

I finally settled on a 3.0 liter. Not just a stock SC motor, but using one as a starting point. I liked its reputation for robust reliability, and I liked the potential to build a nicely revving motor. In the end, I now have a 3.0 liter converted to MFI, running custom cams that John Dougherty and I worked out together, almost 11:1 compression, twin plugs, etc.

It's everything I hoped for. Plenty of torque to get my 2,200 pound car around without having to wring its neck, but rev happy as can be all the way up to its 7,200 rpm redline when we want to play. Not the most powerful option (about 250 hp and 240 ft lbs of torque), but it's been plenty for this light little car. Reliable and robust as well - we celebrated 100,000 miles together this last summer.

So, yeah - I cannot overstate how happy I am with this motor. "Enough" power, fantastic durability, and just the right "character". Worth considering...

[gled49]

Jeff, are u able to run pump gas? U saw my Yellow outlaw, it’s 11.2 and I’m running 98 unled non alcohol, afraid to run pump gas. Gordon

[Jeff Higgins]

I remember you telling me that, Gordon. I think I've got half a point, maybe a bit more than half a point less compression than you have. While I run it on street gas (93 ethanol blend) I do have to say, though, I'm right on that ragged edge. I have total timing backed way off, down to 25 degrees, which helps. I have to be careful on really hot days east of the mountains, often backing the main rack adjustment out a couple of clicks just to put a little more fuel into it. For the most part, though, in my Puget Sound area weather, it does just fine.

I did not intend to build it with that much compression. I'm using the JE nominal 10.5:1's (which are apparently a bit less in many motors) and would have been just fine with that. Unfortunately, the 3.0 I started with must have had only two studs left on each side that had not broken. As a result, the heads had been fretting on the tops of the cylinders, and had to be machined quite a bit to get past the damage.

So, yeah, while I get by, I think less would be better. A cleaner set of heads as a starting point would really help.

[Maxhouse97]

Thanks for the response Bill - great input. I assume you mean the optimum is a flat curve as revs rise, signaling linear power to redline. That plus a decent starting torque.

And thank you Jeff - your response was exactly the dialogue I was looking for!
To your point, the question is how much of the character is dictated by breathing/heads/cams (which I am considering are easier to change) vs the bore and stroke combo? I feel like this is the biggest decision I am making up front, vs the other things that I can change after the fact.

For example see below for values from different engines. The 3.2SS is notable for being the most oversquare of the choices.

Bore and stroke combo, ratio:
- 3.6: 100 x 76.4 … 1.308
- 3.4: 98 x 74.4 … 1.317
- 3.2: 95 x 74.4 … 1.276
- 3.2SS: 98 x 70.4 … 1.392
- 3.0: 95 x 70.4 … 1.349
- 2.7: 90 x 70.4 … 1.278
- 2.4: 84 x 70.4 … 1.193
- 2.2: 84 x 66 … 1.272
- 2.0: 80 x 66 … 1.212

I am going by the common belief that long stroke is optimal for torque, where short stroke is good for revs. Interesting that the 3.0 is known for being torquey but it’s the most oversquare of any of the stock engines.

Jeff this supports your choice of the 3.0. You make a pretty convincing case for sticking with this motor. Probably also a bit cheaper than a 3.2SS.

[Bill Verburg]

Originally Posted by Jeff Higgins

I was pondering this very same question darn near 20 years ago. My '72 T had a fresh, but stock, 2.4 T motor. Knowing was I was just going to pull that motor and put it aside, I had the proverbial "blank slate" before me. I had no motor to start with, which allowed me great flexibility in my choices going forward.

I wanted something that felt like an early "E" motor, rev happy but not as peaky as a 2.0 liter "S" motor. I wanted mid range torque for street drivability, but a fun "snap" on top. "Character" was a big, big concern.

Back in those days, some of my buddies in R Gruppe up here in the Pac West were already putting 3.6's into early cars. Enough so that we earned the moniker "the big block boys" within the club.

Well, fortunately, I had the chance to drive a few of those cars before I had to make my decision. They all felt like they had small block Chevy motors in them - no character, no free-revving "early car feel". Fast, yes, but not what I was after. As a side note, many of those 3.6's have since been replaced by smaller, freer revving motors by their owners. We all kind of reached the same conclusion.

Others had found kind of a "middle ground" and were putting 3.2's in their cars. These all had that same lack of "character", especially with the relatively lower rev limit of that motor, driven by its compromised rod bolts. Just not what I was looking for.

I finally settled on a 3.0 liter. Not just a stock SC motor, but using one as a starting point. I liked its reputation for robust reliability, and I liked the potential to build a nicely revving motor. In the end, I now have a 3.0 liter converted to MFI, running custom cams that John Dougherty and I worked out together, almost 11:1 compression, twin plugs, etc.

It's everything I hoped for. Plenty of torque to get my 2,200 pound car around without having to wring its neck, but rev happy as can be all the way up to its 7,200 rpm redline when we want to play. Not the most powerful option (about 250 hp and 240 ft lbs of torque), but it's been plenty for this light little car. Reliable and robust as well - we celebrated 100,000 miles together this last summer.

So, yeah - I cannot overstate how happy I am with this motor. "Enough" power, fantastic durability, and just the right "character". Worth considering...

you drove the wrong cars

but in a way I see what you are saying, compare the 3.8Vram torque curve(aka 'The Buffalo") w/ the 3.6nvr( aka 'the Pouncing Puma'), When I had a 3.8RS in my '76 it was not as sporty feeling(aka fun) as the 3.6 w/ cams

the Pouncing Puma is what what makes for a fun sporty drive. w/ the right gearing

not ot the same scale as the above but just compare the gross character of these

Note the Pouncing piuma in the 2.4S and the 2.7RS, which surprize the engines most prized for sporting behavior, I owned a 2.4S and while it was a ball on the track it was not so much fun for around town use.


here's another look, the 3.6Rs and 3.6stock nvr are 993 non vram motors the Rs w/ RS cams has a more pronounced Puma shape, the Dashed red is a well built 3.2 ss the main thing to like there is the extended rev range which is much more able to take adavatage of gearring

[winders]

The displacement has very little to do with the character of these Porsche engines. It's all about the cams and the rev range. Put the right cams in a 3.6L and it will be as fun to drive as any 3.0L and provide a bunch more power in the process.

[skinnerd]

I think a 3 liter might be the sweet spot IMHO.
When you get an engine with too much power such as the larger displacement engines, it's not so easy to use or enjoy all that power on the street.
The car accelerates too quickly if that makes any sense.
The track is a different matter of course.

[Jeff Higgins]

Bill and Scott raise excellent points - "character" is determined far more by induction and cams than by displacement. It's entirely possible to build a 3.8 "RSR" spec motor that has all of the "character" we would ever want. Absolutely.

And, in a different car, it would be an absolute blast to drive. Like Scott's race car. But, and this is important - he has a lot more tire, downforce, brakes than a narrow bodied (or even RS flared) lightweight street hot-rod has available. Beyond that, he has a myriad of other modifications that one may or may not wish to perform on such a lightweight street hot-rod.

One of the more frustrating experiences for me has been to drive significantly "over powered" cars. I know Mark Donahue once said "I'll have enough power when I can leave two black stripes from the exit of one corner to the entrance of the next", but I believe he was being somewhat facetious. There is such a thing as "too much power" in the kind of platform it sounds like you want to build. It will serve to overwhelm the platform, and become the dominant trait of the car. Think Mustangs leaving cars and coffees...

I'm all about "balance", or "synergy". To me, a 3.6/3.8, even a happy free revving example (and yes, some of those I have driven absolutely were, with RSR cams, EFI or PMO's, etc), just feels "wrong". If I wanted that kind of over powered muscle car, I would buy that Mustang, or Corvette, or Viper. But I don't. To me, there is a "sweet spot", the "Goldilocks" car. And, well, I believe a rev happy 3.0 (or 2.7, 2.8) lands right in the middle of it.

[Maxhouse97]

That’s a great point Jeff, my intended build would likely have 205 mm rear tires (225 max). 22-2300 curb weight target.

[bavaria911]

What are your thoughts of a 1973 MFI 2.4 that was bore-lined and shuffle pinned at Olies, with original Mahle 2.2S pistons , S cams and a 013 S-MFI system?
Can anyone tell me the stats on that kind of build.
TIA,
Scott

[Bill Verburg]

What displacement gives you is torque everywhere, very nice at the top w/ cams, but also available when just tooling around

most of us aren't running to redline all the time, that was what i didn't like about my 2.4S

inductions like ITBs gives you the ability to run more cam, if that is what is desired, and also instant throttle response

headers are great fro flow and when opened up can give a really nice boost up at he top

I did mention wheels and tires, theses are really important design elements too, an inch of tire height in back makes he tire harder to fi and costs ~12lb-ft of torque, that's roughly the difference in engine displacement of 200cc, ie the difference between a stock cam 3.0 and a stock cam 3.2 or 3.2 and 3.4 or 3.4 and 3.6 etc and the gamut of usual rear tire ODs runs from 23 to 25.3"

~100lb of chassis weight is worth an equivalence of 8lb-ft, and particularly significant in the front bumper area and secondarily in the rear bumper area

if limited to ~205/225 tires on 7 & 8, maybe a lesser displacement w/ more cam is desirable but I have never felt that a 993 engine w/ 225/45 x15 or x16 was dangerous, certainly not as dangerous as rain is w/ a DoT R tire

[Bill Douglas]

If you can get your hands on a Euro 930/10 engine you are half way there already.

9.8:1 compression ratio, big ports and runners, the distributor already has the right curve. Doesn't need any special gas. Rev's well with SSIs.

[Bill Verburg]

Originally Posted by Bill Douglas

If you can get your hands on a Euro 930/10 engine you are half way there already.

9.8:1 compression ratio, big ports and runners, the distributor already has the right curve. Doesn't need any special gas. Rev's well with SSIs.

and responds well to cams + chip+ exhaust

[OSC911]

I posted this in another thread but pretty relevant here:
I have a ‘76 non sunroof coupe - no a/c, no power windows, no radio, no brake booster. It is a very fun car to drive - like go cart handling as previously stated. It is about as close to a long hood as I can get without the expense. I have had an SC and a 3.2 Carrera and I would rate the fun factor higher than both of these cars. In saying that, I never tried to shed weight from either but I am sure the less weight equals more fun. I am currently converting to a 3 litre with ITB so I hope I don’t spoil the feel of the car. I am fairly confident it won’t. My advice is to keep your ‘87 and loose some weight from it. You might not get the exact long hood experience but might get close.

I have now completed the 3.0 litre EFI/PMO ITB/Motec conversion now. The car is absolutely great. Revs like a two stoke motor bike and throttle response and sound is amazing. Had a tune/dyno completed and made 207hp at the wheels with CIS cams and pistons. It has really transformed the car.

[usera]

My 3.2 SS seems perfect, 240 HP, great sound and revs like a motorcycle. I purchased a 964 Turbo this year and sold it weeks later because I didn't like driving it nearly as much as my 3.2 SS.

[Cairo94507]

I recently had the pleasure of driving a very nice 3.2 SS motor with Webers and a nice SS exhaust. That car screamed and pulled hard all the way to 7,200 RPM - that was where I let off. It just loved to rev and pulled like a small-block Chevy motor. Good luck with your project.

[rumlyne]

I'm with Mr. Verburg and Winders
My V-Ram 3.6 is in a 2300# SC
My muscle car buddies say it feels
like an electric car with a good sound track.
I think that "feel" comes with a motor
that comes on the cam like a 2-stroke dirt bike comes
on the pipe.
I built a DE car. I wanted a car that I could just
get in and drive.
Look where the torque comes on with a V-RAM on
Bill's graphs. By 4k rpm it's all there and stays there
until you run out of stones.
I have a gutted Miata track car as well. If you let it get
below 5K you want to get out and see what's wrong.
They are both so much fun they should be illegal.

Merry Christmas Pelicans

[RSTarga]

The best Porsche I ever drove was the limited edition 3.0 RS with MFI.
Revvy with enough torque on cn36 tires 8" and 9" wheels.
I think only 60 or so were built, even the street versions,(like the one I borrowed) were very light.
Very flexible engine that was good even on the street, 917 brakes.
If I ever own a mid year, that is what I would replicate.