Max torque from a 3.0l rebuild
 

Apologize if this has been asked elsewhere but search didnt give me much. I have an 83 ROW and I like to auto-x. Recently made the switch to a megasquirt setup (Bitz) with the intent of a bigger, better engine in the future. Engine has no know issues with about 100K on it but underwhelming in an auto-x environment and ho hum in street driving. I have not had much seat/tuning time since installing the MS but do notice a lot more throttle response. Assuming I reuse my case, what can I put together to give me the most torque? I have a lead on a 3.6 crank and rods as well as all the existing 3.0 bits. Local 911 wrecker has older parts so newer stuff, if needed, will need to be sourced. Reasonable budget on this with the expectation that once done its my "forever car"

Hi, are you sure your engine is in fine health? Normally the ROW 3.0 SC engine is quite peppy...
If it's not leaking oil,and has good leakdown, I'd look into cams, good tune on the efi kit, and shorter gearing plus an LSD if you don't have one.

As I mentioned Im into the tune phase so am optimistic it will be more responsive. My CIS had several issues which I was aware of.

My build question is for a replacement engine that I would like to build. Its not an immediate need but I know what I like to feel in the seat of the pants so it will be sooner rather than later.

Here is what is generally available
bore stroke & displacement
95 70.4 2994
97 70.4 3121
98 70.4 3186
95 74.4 3164
98 74.4 3367
100 74.4 3506
102 76.4 3746
104 76.4 3894
100 76.4 3600
99 76.4 3529
100 80.4 3789
102.7 80.4 3996
104 80.4 4098

here are the stud spacings, which limit bore
964/993 90mm
3.0-3.2-3.3 86mm
2.0-2.7 83mm

I suppose that you could build a 98mm bore x 76.4mm stroke(993/or 964crank) 3458cc motor which would likely be pretty torquey w/ the right tuning

the issue w/ 100mm bore on a 3.0 block is cylinder stability, similar to the 3.8 conversions on 964/993 w/ 102mm bores and 107mm spigots as opposed to 109mm spigots

JMHO, but for torque on a budget start w/ a 964 or better a 993

Al- I also have an '83 ROW SC, and echo Arlo's comment: Properly set up, that car will GET UP AND GO!! Mine had been acting a bit lazy a couple years ago, and my mechanic realized the injectors were a bit off. He cleaned 4 and replaced 2, and this car hasn't run this well in 20 years!

Mind you, it starts coming on strong at 3800 and keeps building to 5500. If you are seeking 'torque' at lower revs for autocross, that powerband may be less than ideal- I don't know that style well. Just my 2c from a distance.

In general torque output is proportional to displacement for normally aspirated engines. So bigger engine will have more torque.

john

Its that 3800 power band Im trying to get down. Being a cab, track days are done for me but never miss an auto-x. My last 2 cars were a lotus 7 clone and a miata. 911 is no comparison for power to weight which I accept but that off the line push into the seat is what I want.

The get out of the hole TQ from a 3.0 can be very impressive .
Here is a link to a dyno sheet and drag slip from my 3.0
This drag time is with a traffic light start , just letting the clutch out smoothly,
full out at 1,200rpm. I blew the Civic Type R away at the start, 3 car lengths ahead
at the finish line , 3" ahead, enough for the win, @ 101 mph.
This engine is all stock except for the cams, and warm up regulator .
With the right parts a 3.0 can make 260 hp and 235 TQ

Have fun, http://forums.pelicanparts.com/porsche-911-technical-forum/1073886-3-0-rebuild-performance-advice-2.html#post11082047

Thanks. Thats the kind of info Im looking for. My engine isnt broken so Im not looking to fix it, just planning for a future build to get the most out of it to make this my "forever car". I will always be upgrading something or else the car becomes boring to me.

For an auto x car, I would concentrate on reducing the weight of the car as much a reasonably possible, at your comfort level.

I regularly AX my car. It has an SC motor with carbs, backdated exhaust, midrange cams, and JE pistons and weights in a 2200lbs. It starts to pull around 3K rpm, and with my low geared trans it is perfect for AX.

I have known several guys with SC motors running CIS that were quick at AX, btw.

You may find this thread interesting. http://forums.pelicanparts.com/911-engine-rebuilding-forum/1114059-preferred-cam-timing-adjustment.html?msclkid=e97be9e1cfd011ec895678afa4 a29d54

Already well down the path to "enlightenment". Floor & engine sound deadening removed, bumper shocks for euro tubes, rear seats, backdated heat etc.. We run classes and my RWD 3.0l puts me with other 3.0l and its quite a spread in HP.

What did you decide upon?

I havent yet. Still looking at options. Id like to build this as a second engine so what I find as a core will dictate most of it. If no core, then Ill play with what I have over the winter. Currently a torquier cam will be the first step.

I had two broken head studs on my 3.0 so I was planning on rebuilding it into a 3.2SS. I did the same thing - bought megasquirt, installed ITBS, and worked out some bugs before I took the engine apart.

I was very familiar with the impact of cubic inches in dealing with VW engines (built a 2332cc with ports/valves/induction/cams geared toward torque). There is no substitute for cubic inches.

I started calling around to find shops in my area and stumbled upon William Knight. After a conversation with him I went down the cubic inch route. I ended up building a 3.55 with ITBs and MS3X and love it. The power from low RPM is just nuts and there is no need to ream at high RPM all day long - it just pulls, and to me, for street driving, this is where the fun is. Anyway, I'd recommend giving him a call. He's a good friend and a great resource for nearly everything in the air-cooled performance space.

Spoken with William. We talked back and forth and he threw me some ideas and then life got busy. Have to reconnect with him again.

What is this 3.55 you speak of?

If it were me, After weight (as some have noted), I would first look at "gearing"...a 915 with the 7:31 ratio (or similar) and 15 inch wheels is a winning combination at speeds under 70...

It starts with the 3.0 case, custom crank, rods, and pistons (98mm), open the '81 heads to 39mm intake (CNC), 964 oil pump, etc. William selected the cams based on my preferences (I like torque for street driving). It's a mild mannered street engine with loads of low/mid range torque.

Is that custom crank around 80mm stroke?

I think Joes crank was 78.4 mm. we made it from a 3.2 crank.. It gives better rod journal size and higher piston speed. WK