Who has hot-rodded their 3.6--what did you do and was it worth it?

[JonT]

I'm guessing my 3.6 transplant will be needing a top end rebuild in the next year or two and while I'm in there I might beef it up. I'm trying to get some ideas as to what other folks have done, ballpark costs, and I'm not sure where to start so I'm trying to get some recommendations.

[ja78911sc]

Sell it & buy a 964 Turbo

[JonT]

It may come to that

[RWebb]

try a 3.8 RS motor

also you need to distinguish OBD I vs. II

[Bill Verburg]

Originally Posted by JonT

I'm guessing my 3.6 transplant will be needing a top end rebuild in the next year or two and while I'm in there I might beef it up. I'm trying to get some ideas as to what other folks have done, ballpark costs, and I'm not sure where to start so I'm trying to get some recommendations.

First thing to realize is that the 915 will limit what you can do, a full 3.8RS is not areal good companion for a 915.

second, street use and track use will point you in different directions as will local laws.

third, 964 based engines and 993 based engines do have different paramaters to work with.

For most street use w/ ocasional track days I'd limit mods to cams, valves, heads, chip and exhaust. But if you are going into the bottom end anyway........other possibilities present themselves

You can easily spend $30 -50K(or more) building what is the current state of the art 964/993

[Bill Verburg]

Originally Posted by Noah

Check out 9M, the British tuner.

again, 915 limited as to what can be done

[Steve@Rennsport]

While a G50 is preferred, a late 915 can be suitably modified to work very well with a 3.8RS motor. We have quite a few of these out there being used for DE's and competition.

[Bill Verburg]

Originally Posted by Steve@Rennsport

While a G50 is preferred, a late 915 can be suitably modified to work very well with a 3.8RS motor. We have quite a few of these out there being used for DE and competition.

Again I'll have to disagree, I suppose you can spend a lot of money to beef them up some but they are way over their design limits w/ a 3.8RS, I'm perfectly comfortable w/ a stockish 3.6/915 but when I had a 3.8RS /915 I could literally make the trans cry w/ injudicious use of the throttle. Depends on how you want to use it too, for normal around town use no problem, but it's when you push it that the issues will develop

[Buckterrier]

Not to hijack but what kind of ponies & torque could one expect from a 3.8RS 'upgrade'?

[JonT]

Thanks Bill

"For most street use w/ ocasional track days I'd limit mods to cams, valves, heads, chip and exhaust."

What kind of output/power curve do these types of changes represent?

[ja78911sc]

Originally Posted by Bill Verburg

Again I'll have to disagree, I suppose you can spend a lot of money to beef them up some but they are way over their design limits w/ a 3.8RS, I'm perfectly comfortable w/ a stockish 3.6/915 but when I had a 3.8RS /915 I could literally make the trans cry w/ injudicious use of the throttle. Depends on how you want to use it too, for normal around town use no problem, but it's when you push it that the issues will develop

Jon, you know how week the 915 is--been there done it--twice in one year.

Drop the mod thoughts and step up into a new ride. Sounds similar to a discussion you had with me.

[Mahler9th]

Not sure I full understand the question, but...

My current car started out as a 1950 pound 911 with a 3.8 liter engine. Haltech FI tuned on the street/track (not a dyno). Schrick cams, a 993 intake manifold (with a custom set up for flapper control). Very torquey and probably with ~330 bhp output. Now I have some aggressive cams, same intake but with a 80mm Ford Throttle body and maybe 370 or so output. There are a lot of things you can do to increase performance... I'd consult an engine buildewr with a known reputation.

Been running a 915 for 8 years of racing and testing, and no output related failures. We have many high output 911 cars with 3.4 to 3.8 engines and 300 - 400 bhp running 915's and they seem to be okay. One of these cars is owned and raced by Peter Smith.

Saying that 915s cannot under any circumstances handle these outputs is not accurate. Nor is saying that Redline oil is no good in these transmissions. There are trade-offs for sure, but absolutes.... no.

There are some great experts here on the internet. There are even more that never visit these forums.

[ischmitz]

Getting us back oo topic,.... the first thing you need to tell us is what type of 3.6 you have. This will determine what needs/should be done. Next, let us know what your goal is (just reliability, peak performance, etc.)

For example I have a '92 964 with the early-style heads and when it came to rebuilding time I replaced the rod bolts, a known weak link on the 964 with ARP. I also had fire ring seats cut into the heads and cylinders and finally I decided on a super S cam. Of course I added a chip and I must say I am extremely happy with my choices. The engine is great fun and very reliable. And yes, I do run it behind an improved mag-case 915 with no issues for 35,000 miles so far. The 915 is 7:31 and has the single-piece bearing retainer and the ribbed differential cover plate.

Ingo

[ErVikingo]

It depends on what your intended use and budget is. Also on what your maintenance intervals are (thinking especially of the 915). As Bill says, you can beef up a 915 but it will still be limited.

IMHO, you must not only think of upgrading the engine without upgrading the rest (including the brakes ).

[JonT]

My intended use is for street and several DE's per year. I'm not building a race car, just throwing money at this car I've had for 14 years and can't let go of because I'm too attached. Would 330-350 hp be a reasonable goal? I'm looking for reliability, not a super-high strung bomb. My 3.6 is from an '89 964 so its an early one. My transmission has been rebuilt with new shorter 3rd, 4th and 5th gears so its in good shape. I agree that I may need more brakes at that point but I have Carrera brakes on it now and they are outstanding for the tracks I run on locally. Budget? Good question. I'm probably looking at what's possible, the estimated cost, then work backwards on the cost/benefit. I realize these upgrades are not cheap and frankly stupid to do on an '80 Targa but its a toy so I don't care. Thanks for all the help.

[Bill Verburg]

I'd be a lot more comfortable w/ a track only 915 that has a cooler and reinforced sideplates and 930 bearings etc. than a stock 3.8RS hooked up to a 915 for street use where 1st and 2nd can get abused w/ regularity. It's no so much the hp as the torque especially when multipied by the lower 2 gears

a stock 915 gear cluster is rated for 181 lb/ft for normal street use and maintainance, for racing w/ reinforcments and weekly maintainance ala Wevo 275 lb/ft.

a 964 is 228 lb/ft and a stock 993 243 lb/ft and a stock 3.8RS 265 lb/ft using factory #s.

Now it was my experience w/ my 3.8RS hooked up to a 915/67 w/ cooler that in first or second gear abuse the side plates would distort enough to weep trans fluid all over the place. The fix would be to send it to Wevo for some fairly expensive reinforcement. Fortunately I found a more appropriate environment for the engine.

just form cams/valves/exhaust and chip you can get upwards of 300reliable hp w/o the fairly large torque increases from bigger p/c

a really nice 964 combo is ss cams, 993heads(maybe w/ SRS or ss undercut valves) a nice 1.75" header type exhaust for close to 300 hp you would want to do more w/ the bottom end for more track use

[ischmitz]

Jon,

I don't think there are any reasonable way ecconomically to get a 964 significantly above 300 HP. What Bill describes is pretty much what I got w/o the heads: A 964 with SS cams, 993 heat exchangers, free exhaust and a chip. And I am close to the 300 HP mark. The ARP rod bolts were additional safety since the stock bolts are a known weak link. My next logical steps would be to increase valve sizes and beef up the valve train so I can bump RPM. After that there is a sort of plateau since everything else involves radical changes and mucho dinero.

To add another 50 HP I think I'd have use one or more of the following options:

- bump displacement to 3.8 or 4.0 ($$$$)
- put a mild supercharger on it ($$$$)
- put a mild turbo on it ($$$$)
- carb it with engine management system
- user aftermarket EFI/engine management system
- use aftermarket heads

That being said you'd be way better off selling your engine and pick up a varioram 993. And even then it will be tough to get signitficantly beyond the 300 HP mark. You might want to look into a 964 turbo or even a 993 twinturbo.

Ingo

[JonT]

Thanks Ingo--how do you like your engine after the changes? How does it behave I imagine those changes would make it a little more peaky on the torque curve. I need to dyno my engine to see where its sitting at now.

[RWebb]

how do you feel about turbo chargers?

either beefing up a 915 or getting a G50 will still entail "throwing money"

brakes were also mentioned above

so, how is your pitching arm?
will it hold up to the throwing you will have to do?

[ischmitz]

I couldn't be more happy with mine - it runs awesome and I really like it a lot. In combination with the 7:31 tranny it has truckloads of torque. Also, the price tag was not too bad since I didn't have to replace major components.

Ingo