Build a 3.0 or upgrade to 3.6?

Jack, 911T (Beautiful P), and others who have upgraded to more cc's I'm particularily interested in your opinion on this topic. Especially if any one replaced a 3.0 with a 3.2 or 3.6.

I recently asked an engine rebuilder if they would accept by 3.0 in exchange for a 3.6 rebuild. While they would, I was puzzled when asked "Why would you get rid of the 3.0?" Are there advantages to putting in 4K plus into a 3.0 to get 80 - 100 horses, or is it better to just install a 3.6? I am interested in reliability as well as power since my 78SC is a daily driver? I am just at that point of beginning to build my 3.0 and want to be sure the money wouldn't be put to a better use by a bigger engine. Any thoughts?

My first question is how do you plan on achieving 100 more HP for only 4K?

Well, it kind of depends on what you define as drivability ... have you ever driven an early 'S'??? Certainly, for $4K-$6K in parts, some used, like Webers, and all of the labor done by your self, a more powerful engine in the 3.4-3.5 liter range can be built that would be what I call more responsive, higher-revving than the 964 engine, assuming you are talking of a 'stock' DME-controlled engine like Jack put in his Black Bea uty! But, I feel a 915 transaxle in the 'improved' category would be needed with 7:31 r&p, and that adds to the cost, maybe up into the $8-10K range, since a ZF limited slip can run $1500 alone!

Personally, I prefer the idea of a higher-revving, 'S'-cammed engine over a bigger, lower-revving, later, 964 DME engine ... but your 'drivability' ( or flexibility ... if I read between the lines correctly) issue may mean you don't really want an 'S' engine that 'prefers' to be kept above 4000 rpm to deliver instant response.

After driving and testing the entire lineup of 900-series cars in 1969, Mark Donohue stated that the 911T was the most 'fun' to drive ... as it was geared perfectly for the torque curve of the 'T'! He further stated that the 'E' and 'S' cars needed shorter gearing to trade off some of the top speed capability for better pulling power at lower speeds and suggested that 90% of 911S drivers didn't use the top speed very often, if ever, and that the better pulling power of closer-ratio gearing would be appreciated fully in daily driving. Paraphrased from memory, but you get the gist of what he was getting at, I think. Your SC gearing is even further away from ideal than the 'stock' '69 models had, and would need a ring & pinion change, at the minimum, to benefit from an 'S'-cammed engine! But, it would be worth the cost and trouble, to go along with your rebuilt, more powerful, engine!

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Warren Hall
1973 911S Targa

Wait, did someone mention my 911?



I think the intended use for the car should guide you. If you're putting together a track-purpose car, then a 3.6 conversion is probably stupid. It knocks you out of all but the modified classes for most racing groups, where you're suddenly competing with guys with too much displacement and too many dollars -- and you may even face weight penalties for driving such a light car!

I have to admit that I'm not very familiar with the upgrade paths for a 3.6. Weber conversions, cam changes, cylinder and piston work, etc. are probably much more expensive for this engine than the same work for more common (and more-often-modified) engines that only have 6 spark plugs to change.

I think for racing a Porsche, it makes more sense to go where there are more guys who are doing the same thing. A 3.0 or 3.2 might have more to offer, viewed this way, and it's a simpler upgrade for any pre-89 car.

All that said, my car was upgraded exactly how I wanted, which was as a great weekend car that I would occasionally take out on the track. For that, it's really, really great. The 1993 engine is reliable as all get-out -- especially since mine only had 17,000 miles on it when I got it, and didn't have the cylinder head problems, and has had the power steering unit removed. I also added the dual distributor vent kit, and got rid of the tricky dual-mass flywheel. This engine also has a torque curve so generous that I can drive like a little old lady if I choose to, keeping the rpms south of 3000 and still have a perky car (although why I would do that is beyond me).

And when the driver of this car, say, chooses to put it to the floor in second, and take it from 2500 rpms to 6500 rpms in a few blistering heartbeats, well... that larger-displacement torque curve takes you from 25 mph to 60 mph like you've been shot out of a cannon. Having the 7:31 ring and pinion gearing helps, as does having 600 or so fewer pounds on board than a 964. And amenities like the additional rubber and the limited slip only add to the fun.

It's a $10,000 upgrade, which is a lot. Coming from a 125-hp 2.2 liter engine, I can say that -- for me -- it was definitely worth it. I more than doubled the power of the car. But if I already had 217 hp, then the 50-hp or so increase (performance chip included) might seem a little bit pricey.

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Jack Olsen
1973 911 T (3.6) sunroof coupe

[This message has been edited by JackOlsen (edited 11-16-2000).]

I have only a small faction of the Porsche experience of the above gentlemen, but here is my belief. Among major upgrades to achieve better acceleration for an SC, I believe they go in this order:

1. SSI exhaust
2. 7:31 ring and pinion
3. pistons and cylinders

At least, I think this is what Bruce says. He says the 7:31 r&p feels like fifty horsepower and I believe him. The SSI system is maybe 25 horsepower. I truly believe these first two upgrades would make an SC decidedly fun to drive. Decidedly. But this is just what I think I hear. I have not applied my reasoning to my car. Yet.

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'83 SC

Thanks for your imput Warren and Jack. Between the both of you its like having an angel on one shoulder and the little temptress on the other. Do I want a high rev'in race type motor (which would be an absolute blast to drive) or a low reving machine with more muscle and the "reliability" of a newer designed motor (probably a blast to drive on a daily basis). It will take some thinking. But you guys have pcertainly providing me with the first step in my analysis - which road do I want to venture down.

There is one key factor here that should not be overlooked: the light weight of your car.
Power to weight ratio is the key to high performance and reliability. Witness any vintage race with a Lotus Élan in the running. As much as my friends and I adore Porsche's, we DREAD the lightweight, low power Élans.
Light weight means reduced stress on your motor and other components; superior handling and braking; and less of a need for a high power motor. Mr. Chapman said it best: There is more free horsepower in a chassis than the competition thinks...
I believe a well-built 3.0 would be a GREAT motor for your car. You could use some of the awesome upgrades mentioned above, have a very reliable motor, and probably get all the power that you can "use" out of the car.
Keep in mind that this input is coming from a fellow with a 612 HP Turbo Buick.
I do believe that a 3.6 weighs more than a 3.0, which will not only affect weight bias, but to some degree, counteract the extra power it provides. Don’t get me wrong, the more power the better, but I think for the prescription you laid out for us, a well thought out 3.0 will provide miles of reliable and fun smiles. (It’s late...)

Just to muddy up the waters a little more I'll add this: for the price of an installed converted 3.6 you can have a 3.3 turbo. Almost no limit to the power that can be added as you get used to current levels.
"Speed costs, how fast do you wanna go?". Seriously, you must also consider maintenance and repair costs. These are much lower on the modified 3.0 than any other option. Only you know your pocketbook and how hard you wish to abuse it.

As far as the 50 hp 'gain' by re-gearing, I don't really know, but it just makes using a particular engine a lot easier, and there had to be a reason why the reknowned engineer/driver Mark Donohue mentioned the factory gearing in his 1969 test ...

One outfit that does quote the 50 hp figure with regaards to gearing is the following:
http://www.rennsportsystems.com/~porsche/1-d.html

As far as Lotus Elans go, building fast, reliable ones is not cheap ... there was an article a few years back about one that the owner spent $40K -- just to get it 'right' and he said he didn't regret any of the dollars spent! But, even 30 years ago, 280 hp was available in an engine transplant ... the Cosworth BDA engine, 180 hp in street trim, 280 hp in racing form, though not cheap! A stock, 96 hp Elan was fun, but, 1400 lbs + 280 hp equals a blast ... if you relace the LUCAS electrics with something reliable!
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Warren Hall
1973 911S Targa

[This message has been edited by Early_S_Man (edited 11-17-2000).]

"Why would you get rid of the 3.0?" >??hmmmm wonder who would ask such a question .

I have a second question for you and probably the most important in answering your question of what to install or build for power for your Porsche.

What is the Porsche to be used for
Autocross?
Drivers Ed/Time Trials?
Open road driving?
0-60?
Road Racing?
or?

and DONT tell me, "Roy I want all the above", hahahaa , like everyone says be more specific.

So what are you wanting this motor to do for you?

and what is your budget for building your motor?

Roy at http://www.motormeister.com

Ya Roy, I wonder . . .
OK more specifics. I plan on using the car as a daily driver. (I only drive about 4 miles to work, unless I have to go fromn OC to LA, then traffic) I am really looking for the car to be a lot of fun on the twists and turns of rural roads, accelleration that pins you to the seat, and also a fun and fast car on the track. I'm not necessarily looking to go 150MPH, and not looking to win Daytona, but zero to eighty really, really fast would be great.

Warren, I was looking into the 7:31 R&P but the information on the Rennsport site seems to say the benefit is changing the transmissions gears (1st - 5th) and the 7:31 R&P is actually a weak(er) set up. Is this your understanding. If I could gain accelletation benefits by a this change it is probaly a must do.

I have a friend with an Elan (a plus 2, actually, but close enough). Great fun to drive but certainly lacking in that Porsche "quality" feel (probably because it is plastic...)

He and I looked into options for repowering it. I was astounded to find that the BDA is MORE expensive to buy and rebuild than a 911 engine!!!! So serious performance (and lots of forged steel bits) is expensive.

I wondered (those with sensitive ears (eyes?) cover them) if a modern Japanese equivalent could be put in, such as a Toyota 3sge (2 litre twincam, easy cheap 180hp on carbs and hot cam). Would not cost you more than US$1500 to do this in NZ, which is cheaaaap.

Of course it is butchery though... There, I said it in a public forum - it is almost like sticking a V8 in the thing.

Would be fun though.

I should probably go off and ask this on an Elan board. I am a bit worried they will tear me a new ******* though.


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Cameron Baudinet
1975 911S

the 7:31 R&P represents lower gearing and quicker acceleration. I wish I had it. Even just cruising the freeway without straining the engine, while 4th is the best at 60mph, my car likes third better than fifth at that speed. The very beginning of the power band (3500 rpm) is 85 mph in fifth. The car will go almost 100 mph in third!

So, the 7:31 R&P, alone without a gear change, would produce quicker acceleration and more gear options at the speeds I drive. As a track car it's probably just right. maybe. You still have two gears to choose from at 120.

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'83 SC

I tend to agree with Rarly8 - I think the most bang for the buck can be had from swapping the 3.0 for a 3.3 Turbo engine. I investigated this when I saw an 82 turbo Euro motor for sale recently. If you sell your 3.0 and buy a 3.3 and add brake and suspension upgrades, I think your final cost comes out at around $6000 or so. Given the price differential between the turbo and the regular SC, I think this is the only performance mod an owner can make that will actually see the car appreciate in value even beyond what you've put into it. And because of similar vintages of the cars, it's much more of a bolt-on operation than most engine swaps (read Jack's experience modifying the 3.6 to go into his 2.2 car). From there, you can tweak the engine to your heart's desire for even more horsepower.

Emanuel

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Emanuel Brown
1983 911 SC Targa
http://home.att.net/~epbrown01/91183.jpg

If you decide to rebuild the 3.0 don't forget that you can get P+C to increase dissplacement to 3.2.

Bobby