Increasing performance of 1978sc!

[rdane]

Noah's article is where everyone starts. Good stuff.

911s are made to run at high rpms. The race cars need something like 7 to 9K!

My build list and some earlier comments that hopefiully will help to put it all into perspective.

Originally posted by rdane
Here is what I used. Costs can go past 15K$ or be less than 10K depending on what you are starting with for a 3.0.

Great engine as is...amazing really. I would not do it again on a CIS 3.0, unless I was starting with a decent 3.0 with SSIs and hopefully a good performance cam.

What most forget is all the street flat 6s will cost the same to build basically, if new cranks, P&Cs and rods are part of your needs. At that point look around for options. IMO having done it and beat the 3.6 transplant costs by a good deal with similar performance I would look for a 3.2 Motronic and start there for a 3.4 or bigger engine.

Also the Max Moritz P&C is specifically designed for single plug and 93 octane gas.

The cost of case work, P&Cs, rods and cranks become trivial in the long run for a street engine that will last well over 100K miles, so plan well.

My '79 CIS 3.0 to 3.4 has the following at 258hp and 251# of torque.

3.2 crank
Puater rods and bolts
Mahle 98 P&Cs @ 9.8 for a 3.364
SFL Piston skirts, Ceramic coat on the Pistons
EBS valve spring
TI retainers
APR case studs
New injectors
new exhaust valves (which is why I tore the engine down)
boat tail the crank cases and half moon the cylinders
Bored throttle body
match and polish the intakes
20/21 webcams
SSI
sport muffler
light flywheel
sachs power clutch
(I used Jon @ EBS for the majority of Mahle and other engine parts)

Twin plugs? I didn't do them but I did the machining so they could be added at a later date. I also live at sea level and in a mild climate with 93 octane gas available. (At 8K miles I can say I am not disappointed in a single plug)

Skip the older dual plug stuff and do Electromotive twin plugs. It is good insurance on bad gas and cheaper to install. Twin plus are insurance to keep your engine in one piece. Problem you'll have is deciding where to stop with case work, twin plugs, induction, cams, compression ect. My budget was $15K and I beat that by $1500 even with extras like the coatings, case work, injectors and throttle body and got a great engine.

My start point was big as it gets, street gas, single plug and no case work. That defined the 98 P&Cs, 74.4 crank for 3.4, and 9.8:1 compression.

But I also had a great engine going into it with a new clutch, flywheel, cams and SSIs which is not part of that budget number.
If I had not already done all those I would not have started my 3.4 CIS project. I could do a better (read 3.4 or bigger) Motronic for less.

[nostatic]

Originally posted by crashmy911
You are the reason I went with the modifications that I have made to this car. I had broken studs and had to do something and cams and valve springs were two areas that where cheap to do. After doing this the car is fun and fast butI would just like to make faster and perform better lower in the rpm range. Hell to pull away from suv's and mini vans in this thing you have to really run it. Don't get me wrong either it is still a fast car I just wish you could get some level of performance with out hammering it.

Like I said, get a Mustang.

If you want to win streetlight drag races and don't want to live in high revs (I can't understand either of those, but to each their own), there is no replacement for displacement.

As for me, I love running these cars in the 4-6K range. Who cares about the first hundred feet or so....once you get up there and keep it there, there is plenty of fun. But, to each their own...

[rdane]

I have an '83 SC engine with '74 heat exchangers, and it has good torque from as low as 2,500.

From an earlier thread.
Reseda Dyno Day - Results

(DD74) has a stock SC motor in his 1974 911. His only mods so far are early (74) exhaust and a Triad dual-in-dual-out muffler. With a car as light as he's made his, the slightly-better-than-SC numbers are going to make it really scoot:

Do a search under Tom's screen name emcon5. He has done a bunch of really good comparison graphs for cams and the 3.0/3.2s.
try Best Cam Profile For A Stock SC?
and
http://forums.pelicanparts.com/911-engine-rebuilding-forum/168088-cis-964-cams.html?perpage=10&highlight=20/21

Originally posted by emcon5
Updated.



What I would really like to have is a graph for an otherwise stock early SC with backdated exhaust.

Tom
edit: fix chart

[dd74]

Yes, it's a beautiful thing.

[rdane]

Worth noting the better torque curves aren't really a matter of CIS adaptable cams in 3.0s it is the different valve sizes in the early and late SC heads. That is shown in the torque curve comparison chart. (trust the torque curve shapes more than the numbers)

More HP can be found in the bigger ports of the early heads, more torque in the later, smaller heads.

That trend was followed through to the Carrera's 3.2.

As many have mentioned 4000 to 6000 rpm is where the 3.0s come alive. Nothing is going to change that short of ditching the CIS and the CIS appropriate cams. You can get more power with a hot cam and carbs but your rev range will be higher and power in an even more narrow band.

If you really want torque talk to the guys on board who have the 3.6s or the guy who owns a Z06.

[dd74]

RDane - In an Excellence magazine from this summer, Bruce Anderson finally seemed to conclude that the 2R runners (smaller) were more appropriate for the 3.0 engine in stock form than the larger 4R runners which were on the 78-79 3.0s.

[rdane]

David, guess it depends on what you find "appropriate". Porsche thought the hp was a good idea over low end torque in the race cars. When the American market kept complaining about the high reving engines Porsches shipped with, first they enlarged the engines from 2.2 to a 3.0. Then when even that didn't make folks happy they made the ports smaller to get more low end torque out of the 3.0. Americans were still looking for a V8's torque....more displacement and smaller ports again on the 3.2...which gave more torque.

Torque has always been behind building a bigger flat 6. HP is just a measure of torque, right?

[crashmy911]

I will try thing with the throttle body and see if it is opening fully tommorrow. If my car is in say third gear and I'm driving along at 2500 rpms should I be able to stand on it and go like mad or would it be better to down shift it and floor it. I have found that If I'm not running the car fast it doesn't like when I stand on the gas unless the rpms are already high say 3700 or up. the car dosn't even like to go up hills unless the rpms are above say 3000. With other sports cars I have had. You could drive along at 2500 rpms and not have a problem going over inclines. With this car it will complain alittle bit and even lug if I try and do this.

[nostatic]

Originally posted by crashmy911
With other sports cars I have had. You could drive along at 2500 rpms and not have a problem going over inclines. With this car it will complain alittle bit and even lug if I try and do this.

A 911 is not "another sports car". But you sure you're not talking about a muscle car as opposed to a sports car? For instance a Honda S2000 doesn't really get cranking until well over 6 or 7K.

Try keeping your revs between 4-6K. Shift to keep it there. If it means 3rd gear on the freeway, so be it. If you stomp on it, it will go. But it will never feel like low-rev-torque-happy 'merkun iron.

[anthony]

At 2500 rpms in third, if you want to it to go, you better downshift to second.

>>You could drive along at 2500 rpms and not have a problem going >>over inclines.

Were those V8s? 2500 rpms is barely a blip off idle for these cars.

[H20911]

After skimming this thread and reading the same advice that is given all the time it seems (all good advice though)
I have to say.

1) gear it lower and stay in the upper rpm range
2) 3.6 conversion with Mods
3) get a mustang (good advice already given)
4) get a big block GTO, Chevelle, GS, Cuda ......etc.
5) ride in a V8 converted 911 and see what you think.

because as the advice given might imply your can't get there (Torque) from here with a N/A 6 with out $$$$$$. then you will have a high strung engine that will push (but not pin) you back in the seat.

I'd go 3.6 with mods and the diet if you want to stay with in the p family.

[dd74]

Originally posted by crashmy911
...With other sports cars I have had. You could drive along at 2500 rpms and not have a problem going over inclines. With this car it will complain alittle bit and even lug if I try and do this.

This, I think, is the reason so many people swap in larger engines, such as 3.6s, when the real nature of the 911 engine is not necessarily low-end torque, but high-revs.

This could also be, on a more technical level, why Webers have been said to only be good with 911 motors if they are track cars. CIS and Motronic are much better suited for all-around driving.

[crashmy911]

Don't get me wrong about the car. I love it and I love how it revs and comes on the cam. neat stuff. Just wanted to see if I could make it better down low. Maybe as I become a better driver I will push it harder and not be afraid to be carrying so much speed into corners and out. So it could be me. I wish or maybe would be wiser to drive at slower speeds accelerating out of corners waiting to see if it slides at slower speeds and still be able to correct. I'm just scared to be at the speeds I'm at when diving spiritedly. Second just wish I could do them at lower speeds and allow the sliding and mistakes to happen at much slower speeds to learn how to correct. When ever I'm at the slower speeds I would need to be in first to get the power I need and we all know that first isn't somewhere you want to be when downshifting and pushing the car the way I want to.

[fintstone]

Sounds to me that what you really need is a little DE.

[asphaltgambler]

Rdane: was that reading in rear wheel HP /TQ??

[nostatic]

Originally posted by fintstone
Sounds to me that what you really need is a little DE.

what flint said. Sounds like the last thing you need is more hp/torque. Instead, get to know your car in a proper environment. You'd be amazed what a stock SC can do...

[masraum]

Originally posted by crashmy911
Don't get me wrong about the car. I love it and I love how it revs and comes on the cam. neat stuff. Just wanted to see if I could make it better down low. Maybe as I become a better driver I will push it harder and not be afraid to be carrying so much speed into corners and out. So it could be me. I wish or maybe would be wiser to drive at slower speeds accelerating out of corners waiting to see if it slides at slower speeds and still be able to correct. I'm just scared to be at the speeds I'm at when diving spiritedly. Second just wish I could do them at lower speeds and allow the sliding and mistakes to happen at much slower speeds to learn how to correct. When ever I'm at the slower speeds I would need to be in first to get the power I need and we all know that first isn't somewhere you want to be when downshifting and pushing the car the way I want to.

You need a DE and or some AutoX experience. If you want to experience things at lower speeds then find a deserted parking lot the next time it rains and experiment there.

You don't need more power, you need more experience and confidence or if the drive for more low end torque is that important then you need a different car. These cars/engines are built more like a highly strung racing engine than a regular car engine, and so they need to be revved. The more you do in the way of cams, free flowing exhaust, free flowing intakes, you are just making the engine build more power at higher RPMs. The odds of you building a 911 engine that will put you back in your seat at 1500 rpm and hold you there until 7 or 8000 rpm are not very good.

It sounds like you aren't in the right gear when you are coming out of a corner. Try downshifting. You probably want to have the engine at 3500-4000 or even 4000-5000 when coming out of a corner to feel the pull.

[crashmy911]

I guess where I get to drive the car spiritedly is on back country roads that you wouldn't be going all that fast. What happens I want to down shift inot first and that scares me with the 915. So what happens I'm in second and that isn't low enough. So maybe I just need lower gears in third forth and fifth. Hell I never use fifth unless i'm going over 100 miles an hour!

[masraum]

Hmm, must be some really tight twisties to not be going at least 35 or so. You wait for 100 to go to 5th? Wow, I was in 5th at 70 if I was cruising on the highway.

[rdane]

No big deal, we all have had steep learning curves with these cars. Best bet is a PCA DE. That will answer a wealth of questions very quickly.