US Spec 911 SC Targa Tuning options

[jehinboltonuk]

Hi All
I recently imported a standard but high mileage (220k miles) 911 SC Targa Sport (Bilsteins and 16" Fuchs) from the US to the UK. It runs well and feels surprisingly strong for just 180hp but it is a bit smokey on start-up and the gearbox feels tired. It also pops and bangs a lot on decel even with 98 ron fuel. The interior carpets are also pretty worn but I haven't found any rust anywhere yet and the paint is pretty good.
Anyhow, long story short, I'm just in the process of stripping the car down - removing the aircon, cruise control, etc - and thinking about what to do with the car to give it a bit more pep without going crazy. In terms of the engine and gearbox I was thinking as follows as follows:
* PMO 40 carbs,
* 9.8:1 JE pistons,
* 964 profile cams,
* Ported head (its a USA car with the small ports),
* 1 5/8" European Race Headers (losing the heat and fitting an electric heated front screen) or early SSIs (and keeping the heat),
* A 2 in, 1 out Dansk muffler for a stock look, and
* Recurred distributor (will always run 98 Ron fuel)
In terms of the gearbox, I was thinking:
* Strengthened cover plates,
* A Quaife 40% LSD, and
* An gearbox oil cooler, but
* Perhaps shortening the ratios to reflect the real world.
If really like the character of the current engine so, although more power would be nice, I really want to keep the power delivery broad and also keep the cost reasonable. Would be interested what everyone thinks and any views on what I might gain from the set-up described?

[Steve]

[jehinboltonuk]

Hi Steve
Thanks for the congrats and for the good advice - I always wanted a 1980s 911 and I think I finally got mine just in time. Now I just have to make it into the car I always wanted!
The point is well made about the small port head, I guess one option would be to try and find a set of Euro heads. However, that probably isn't realistic or affordable, so I guess it is a question of making the most of what I have and making a nice driver.
In terms of the exhaust, presumably, with the PMOs, I'd fit the SSIs for the pre-76 2.7L, rather than those for the MFI SC (mine's a 1982 model) with the connection for the oxygen sensor?
On the piston front I thought about the JEs because they have deep valve pockets and I thought that with the carbs I could use a more aggressive cam, such as the S cam or the 964 one I mentioned. re the Mahle pistons just as accommodating?
The other thing I wondered about, if I'm buying Mahle pistons anyway, is the Mahle 3.0 to 3.2 conversion for the SC. This retains the short stroke characteristic of the existing engine but gives a 10:1 compression. Would that still be OK (with 98 Ron fuel(at low UK altitudes and mile UK weather) for a single plug set-up and do you know if this is a good conversion?
On the transmission, no I don't intend to do a lot of track days, but I did think about doing some occasional speed events (sprints and hill climbs) just for fun. These are relatively short events but I don't know how the transmission would stand up? Either way, I think the box definitely needs rebuilding now. I'd be interested to know how much it might cost for you to rebuild the transmission as per your video. (There is no import duty either way if I ship something for repair and then it is shipped back.)
I think you can also do the distributor as well? The PMOs don't seem to be a hugely popular conversion here (mine are on their way) and, of course, most people here have a ROW car.
So, the recipe now sounds like:
PMO 40s,
SSIs with a sport muffler, and
Mahler pistons, possibly the 3.2 conversion, and
A new cam, as yet unspecified, but perhaps sticking with stock just retimed?
Best regards
John

[jehinboltonuk]

PS I should have said that part of the reason for buying a 1982 911 and going for the PMOs is about not having any real electronics or complex plumbing on the car and being able to work on it using good old fashioned tools without a laptop. I wanted a good old mechanical car!!

[Steve]

Hi,

Unless you decide to install the big-port heads (or have your's CNC'ed to suit), adding 964 cams is a waste of money.

With your stock heads, tune the engine for maximum torque & low-end throttle response. More displacement adds more to your power curves and thats a very good thing. Don't go crazy on CR otherwise you'll have to compromise on ignition timing. The distributor should be recurved for best performance, but thats factored by CR and octane. There is a special set of 98mm Mahle P/C's made specifically for single-ignition and pump gas so thats the best choice.

Close-ratio gears make a huge difference and this is the place to spend money. It runs $3500-$5500 to rebuild a 915 now and add $$$$ for gears to that.

[jehinboltonuk]

http://www.fvd.de/us/en/Porsche-0/-/-/- ... 3.0_L.html

http://www.patrickmotorsports.com/part/ ... torsports/

Hi Steve
Thanks for the additional advice. However, finding the right piston and cylinders doesn't seem to be straightforward. I believe that Mahle make a 98mm piston with the right 22mm wrist pin and offset with a 9.8:1 CR which would be ideal but I can only find people supplying 10.3:1 or 10:1 CRs (see links), which are probably too high for a single plug head. Do you know the right Mahle part numbers, or can you supply the right Ps & Cs? Presumably, if I'm using carbs, I"m not limited to the peaked Max Moritz style piston crowns?
In terms of the engine, the emphasis is on low and mid-range drivability with:
* PMO 40s,
* 3.2 Ps & Cs with less than 10:1 CR (if I can find the right parts),
* Standard but (possibly machined heads?),
* Standard cams (perhaps advance as per 3.2?),
* SSIs, &
* recurved distributor.
Then to put the emphasis on the rebuilding the box with lower ratios and an LSD (I'm thinking Quaife geared rather than the traditional ZF clutch design, though I wonder if the latter is better at taming lift-off overseer?)
The car is intended to be a long-term keeper, so the aim is to get it right whatever it takes.
Best regards
John

[Steve]

Hi John,

Mahle does make that wedge-dome (MM) piston in a 22mm pin size that usually comes in at 9.8:1 and I can get you a set of P/C's if you wish. These are specifically designed for single-ignition and mild cams so an SC or 964 cam will have sufficient piston-to-valve clearance.

Naturally, the engine builder needs to measure & confirm CR and clearance as an integral part of building ANY motor.

[Steve]

Almost forgot,... a Quaife is a TBD and does nothing to help trailing throttle oversteer; this is why I think they are best used for FWD cars.

We use a Guard LSD which is FAR better than the OEM ZF units since these are both adjustable (40/60 or 50/80) and the preload is tuneable for the type of use the car will get.

[jehinboltonuk]

Car isn't finished yet but thought I'd share an update.
Engine spec vs the original US spec SC is from top down: '66 cams, large port 3.0C heads - twin plugged, 46 PMO carbs, carrillo HC pistons and nickie cylinders, JD Racing distributor, Classic Retrofit CDI+, High Performance coils, boat-tailed cranckcase, arp rods and bolts, 964 oil pump, RS flywheel, Sachs Performance Clutch, SSI heat exchangers, Danske 2:1 sport muffler. Gearbox spec is: rebuilt 915 with standard ratios, reinforced sideplates and OS Giken plate LSD.
Body isn't finished yet, but has been stripped out (no carpets or sound deadening and all redundant electrics removed) and resprayed black, with chrome detailing, an EB Motorport ducktail, FIA rain light, Safety Devices 6 point bolt in roll cage and 6 point harnesses and will have Sparco Grid 2 seats (nice and wide for my lardy arse!), a fire extinguisher and homemade RS style door cards. Electrical and fule cut offs, placards and tow hooks will also be fitted - I plan to use the car for occassional hillclimbs, sprints and autotests.
I will work out what to do with the suspension once all the above is finished and the car has been weighed, etc.
Hope you like it so far.

PS Fueling is better now than on the first run.
PPS Will worry about the final cosmetic detailing once the whole car is finished - so I know there are some little bits that need redoing.

[Steve]

Nicely done!!