LS swap 500HP might be lighter, and half the cost. ;)

Did my 78 SC a couple years ago and just hit 20k. Stock CIS, 95mm 9.5/1 JE's, Elgin 'Super SC' grind (middle ground between stock and 964) and SSI's. Overall, I like the combo but if I had to do it again, would go 98mm Max Moritz style pistons. Reason being it wants to detonate at the top of the RPM range on 91 octane when timed to spec. Have really cold plugs which helps. Sometimes I mix in a bit of 100 unleaded netting about 93. MM would have cost about double of JE + replated barrels but in hindsight, totally worth it..

There’s a 3.6 posted now for what seems a very good price. IIRC $14,500 but even if you get a decent 3.6 for $15-$20,000 you’re taking a gamble installing it without freshening it up. And, you’re a long ways from being done financially. It costs a lot of $ to do a proper 3.6 swap.
Personally, I’d way rather have a lightened 911 with a hot 3.0
Another option would be to get a 3.2 and turbo it. If done correctly they can make huge power reliably.

I have a engine in my 73.5 with these mods and running CIS:

1) Max Moritz 3.2 liter pistons and cylinders, 2) 964 cams, 3) Raceware hardware, balanced rods, Carrera oil pump. New parts included: intake valve sleeves, rod bearings and rods balanced, and rocker arms. Transmission clutch disk, pilot bearing and fork were replaced. Early Exhaust.

HP is 209 at rear wheels. Maybe 235-240 at Crank? I think 300 hp is a reach as Bob K said...

Sorry, to get my $17,800 for anything you are going to have to do better than a single handwritten sheet with vague descriptions and round numbers. I'd want part numbers, specs, labor rates, estimated time to completion, etc, etc, etc. Plus, I don't see 300hp coming out of that engine. What 3.0 do you have? If you want 300hp just slap on a turbo, keep turning up the boost until you get to 300, when it blows up then worry about whether to rebuild or swap a 3.6.

ixxified,

Seems they ran away with your thread?

In the US, the 3.0 CIS engines were crippled making a first attempt at smog control.

First things first. Replace the exhaust. It was all channeled over to one side. Either get tuned headers or if you still want a heater get SSIs. You'll get 17-20 hp immediately. If you don't fix the exhaust first, then it will prevent any other upgrades from producing the desired improvement they should.

Secondly, replace the CIS. The CIS is sensitive to blow-back from aggressive cams. So your choice of better cams is limited by the CIS. I've found the CIS to be very dependable but it cannot be re-mapped. You can't change the carbs jets or the fuel injection's map. Simplest, wonderful solution is to replace the CIS with 6 PMOs. Put your foot into it and you'll hear Banchees wailing at you from behind! I chose to go the EFI route instead (Bitz kit). I'm happy, but I feel it was a lot harder to learn all the new stuff.

Thirdly, pick a new set of cams. At least something more aggressive than the CIS would have allowed. At this point you'll have the engine that the SC should have come with from the factory.

Each of those could have been done as individual projects or you could do them all at once. Of course there is a lot more that could be done, but it's a start.

Borrow a copy of Bruce Anderson's 911 Performance Handbook and read the section on SCs.

Michael S. Jackson
'78 SC w/Bitz

3.6 is extra weight as well.


Don't neglect the poor 915 on your road to 300hp.

Hope you are able to share some dyno results in the future, I'm sure many would be interested. Should be 300hp if it's a streetable setup, maybe more if it's on the racier side?

Apologies to to OP. Didn’t mean to hijack your thread. Seems like we are considering similar ideas. Just sharing what I have learned.
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QueWhy: Yes I agree, the handwritten vague estimate gives me no confidence.

Define your budget and your goals...

For 300hp I think you're looking a budget at least the value of your car... maybe more.

Think of it this way, Porsche didn't ever try to make NA power from their engines... they gave up and slapped a turbo on them.

The 3.6L swaps used to be worth while... but with engines going for 14-18K used, with another 10-12K+ in freshening costs you have a huge bill for what is really a small jump in power.

From my research being in a similar place I think a fresh build with hot cams and carbs or ITB headers and good ignition you'll have a fun very responsive engine... get the car down to 2200lbs and your power to weight will be very good and give your faster than stock 3.3 turbo acceleration

Whoops I thought plexiform was the OP.

Ixxifield, absolutely do the SSI/header and exhaust(provided you don't live in CA ) first. I just installed SSIs and an M&K muffler on my 3.0 SC. Results are way better than I expected. I think the 17-20hp figure in the post I quoted is based on an assumption and actual gains may be less. Personally I don't care if I gained 1hp or 100, the car is way more fun to drive and listen to, I saved some weight from rear of the car and it looks much better. For about $2000 including heat backdate my only regret is not doing it sooner.

I think the key to 3L power is getting a nice loud exhaust and enjoying the sound, while accepting you will not get HP out of a 3L without a HUGE amount of cash.

I'm beginning to accept that my Porsche is a very expensive Miata from Germany. :)

Couple thoughts on 300HP 3.0L SC engine.
First what RPM does it take?
Since Torque in a normally aspirated engine is very tightly tied to displacement to get more HP requires more RPM. lets assume our well tuned 3.0 L that has around 200Ft/lb of torque you need that at about 8000 RPM ((RPM * T) / 5252=HP) not very streetable as the cams to get you 8000 RPM will not make much low end torque. So if we want to increase torque we make the engine bigger, say 3.5L , we don't need as much RPM. So we get a 74.4MM stroke crank and 100MM P&C and assuming the torque increase from displacement gets us to 233FT/LB we now only need that at 6900RPM which is a little more streetable but still a big jump from the 4500K torque peak on a stock SC.

john

There are a couple of books out there that detail many options. Bruce Anderson's Porsche 911 Performance Handbook and Wayne's How to Rebuild and Modify Porsche 911 engines. Good reading and informative.

There also have been many build threads here over the years. Maybe some here can offer some links.

An exhaust backdate, SSI, and a re-tuning of the CIS can make for a fun car, if you reduce your weight. Then add carbs for a little more umph. The next step is different pistons and cams. That is the best bang for the buck, IMO. After that the sky is the limit.

As far as light flywheels go, that also comes in degrees. The stock SC flywheel is already very light. If you have one of the aluminum pressure plates you will have all the response you want. I doubt you would notice the difference with a pound or two removed from the stock SC flywheel. On the other hand if you go with an aluminum flywheel, you may not be happy with the way it drives.

Just thinking out loud here as it addresses the question at hand...

So say you have SSI, Carbs, weight down under 2300#, added cams, ... whats the next logical step... twin plug heads? 10:1 comp? swap to large port heads or port work?

I think the sweet spot is SSI, Carbs, Cams, and maybe a comp bump... get the car under 2300#

Wondering where the smart money is.... I think spending 25-35K on a 250HP motor is just plain stupid, unless your a doctor or a lawyer and 35K is chump change. ;)

Maybe i'm in the minority here under a quarter million a year. :D

I don't think it has to do with the amount of money one makes, I believe it is more about how one wants to enjoy whatever that amount is. Priorities are different for everyone, that fact doesn't make some people stupid.

I get that, but it's from my perspective. If 35K was a monthly income I might not care about dropping that on an engine... alas I am neither smart nor talented so my means are limited.

The fact that I was able to get a 911 at all is amazing to me.

I still think 35K for a Porsche engine is insane, I mean they haven't change in 40 years the tools should be more than paid for right, same goes for pistons right.... I would love to understand the price structure of a 6K set of P&C's But it is what it is, so if you want to play you have to pay and if I was wealthy I would,I might grimace but i'd still pay it. LOL

But back to topic, I think if money is an object, a smart build might be carbs/ITB, SSI, Cams, and maybe a compression bump with ignition, then drop that weight... the rest spend on suspension bits.

If my mechanic gave me that list purporting to get 300hp on street gas from a 3.0, I would find a new mechanic. 250 would be a stretch. That last 50-75 hp are the hardest.

For what it is worth, this is what Supertec put into the 3.0 in my '74 targa (with S options: gauges, brakes, and shocks/struts, etc.). Execution is as important in a rebuild as much as great parts...and Supertec was considered the best builder the game by many (I hauled my car crosscountry on a trailer to ensure that some local dumbass didn't have to learn on my car). I told them that I wanted a 3.0 engine for the street that would give me 10 years and 100k miles (minimum) on street gas. Very drivable, but one that sounded and felt kill my '74 2.7 (just faster and with more torque). This is what we came up with (and the kind of detail that your mechanic should be giving you before you make any decisions):

From the build sheet:
Engine, new JE Pistons/Mahle cyl.,9.5
WebCams 20/21
clutch
resurfaced flywheel
rebuilt distributor
New permatune
rebuilt alternator
high torque starter
Oil Pump, modified for increased flow
mag, polish, balance crank
bal rods, pistons,pulley
new valve guides/valves
49 in, 41 exhaust ports 39 in, 38 exhaust
turbo valve covers
carrera tensioners
new chains
SSIs, early SS muffler
rings
bearings
Supertec head studs
Carerra Oil Cooler and Fan
No smog, oxygen sensor, etc.

The shop was pretty surprised at how fast the car was...likely because it had 15 inch wheels and 7:31 gearing. They estimated close to 250 hp...but I never dynoed. They used a '78 top end for bigger manifold runners and increased the size of the valves...and an '82 bottom for increased compression. The car is very fast and revs very well, pulling hard to redline. It is the fastest 3.0 that i have driven...by far (including carbed models)....I did eventually go back and update my suspension to match the added hp...but nothing crazy.

I opted to skip carbs and probably left about 25 hp on the table (as i wanted the reliability and economy of CIS...and wanted the car to ultimately look and feel like it was factory, but a bit more reliable and more horsepower/torque). I could have done a used 3.6 for about the same money.

If I were building another, I would do exactly the same (for a street car). For what it is worth, it is much faster and more drivable than my 3.2/G50 carrera up to abut 85 mph (due to gearing) Lots of torque and rev happy. You do have to shift a lot (due to the 7:31)...but I like that.

I would love to drive a 7:31 car, I know in the past changing the gearing can make a huge difference in the joy of driving dept.