20/21 or 993SS cams for stock 3.2

[drsimonwong]

Hi,

I'm about to undergo a full rebuild on my 120k 3.2. It's a Euro engine putting out 235hp and not using much oil but has become a regular on the track and is starting to leak oil.

I'm hoping to reuse the existing P+C's and will keep everything pretty much stock but will upgrade the known weak zones.

Rod bolt upgrade to Raceware , steel headstuds and phospherbronze valve guides.

Am considering more aggressive cams and it appears many on this board are using the Webcam 20/21s. A few are using the 993SS/Supercups.

I would also assume with this change I'd be smart to upgrade to race valve springs and Ti retainers?

Already have SW's chip and SSI's with M+K muffler.

It's a dual purpose car but being progressively setup as a "drive it to the track" car.

What can I expect to gain/loose from the changeover from the stock cams? How will everyday driverbility suffer? Where will the power and more importantly the torque changes occur?

The 20/21 I suspect will have most torque in the midrange and the 993SS's up top?

I'll upgrade to 3.4 if I find I can't reuse the existing P+C's but that'll be really bad to my budget so I've got my fingers crossed for the teardown.

Thanks in advance.

Richard 9113-2 your input in particular would be great as i'm kinda building your car....:-)

Simon

[88-diamondblue]

Email John at Dougherty Racing Camshafts www.drcamshafts.com He posts here as Camgrinder. I used his DC22 grind on my Carrera rebuild and Jeremy has used his 993SS cam. He is great to work with and will recommend based on what you want from the engine. Prices are very resonable and service is top notch.

The only thing I notice on drivablity for me is idle is cammy, you can tell by listening to it there is a different cam. It take a little more throttle to start out after that the power comes on at around 3800 and goes strong to 6500. Also consider talking with SteveW about any changes needed to the chip if you change the cam. I did the custom chip with Steve which I need to get to the dyno so we can finish tuning the chip.

[drsimonwong]

Michael,

Thanks for the response and the heads up, I email John.

Do you have any drop off/stalling issues that Steve couldn't fix?

Did you loose any mid/low end torque compared to before? I guess it'll be hard to tell as you did a capacity bump.

Simon

[Carrera3.5L]

If budget is a concern than I would consider sticking with stock steel retainers. The ti versions are nice but in a street motor that doesn't have the capability to rev over 7,000 (or make power at that rpm) it is more an esoteric upgrade...

The 20/21 grind has pretty good mid-range while the 993SS will be better in the upper rpm ranges. If you have any type of emissions testing that you have to go through you may also wish to pose that question to John so he can factor that into his recommendation...

I am happy with the 20/21 profile due to my particular constraints but would have liked to use something a bit more...Steve did raise the idle to 880 rpm due to the slight lope of the cam grind which is pretty smooth now.

No drop-off or stalling issues here either, as Michael alluded to having Steve dyno optimize the chip for the cams and your other mods is good advice. Chances are he will find you some additional drivability and power with optimizing the air-fuel ratio for your particular engine.

I know you don't want to do it and it will put a significant dent in your wallet, but I would strongly consider changing the pistons/cylinders at 120K. What is your goal for this newly rebuilt motor with tired pistons/cylinders to last? They don't last forever and they may have taken a beating with 120K on them...Whether you purchase new euro 95mm units or upgrade to 98mm's is up to you.

Good luck with the project and be sure to post pics of the rebuild...

Ralph

[drsimonwong]

Ralph,

Good thoughts. Mid range torque is what I really need I guess considering I've only really had one season of tracktime. Plus on the street it'll be heaps better than topend power.

No emissions issues here.

Should I stick with stock springs rather than the race ones people tend to pair with the Ti retainers?

With regards to the P+C's I guess budget is the main force driving the decision. I don't have the knowhow or time or equipment or space to do my own rebuild. Here in Oz anything Porsche is $$$$$. I've got to allow US$8K for a bog standard rebuild with existing P+C's.

Plus I'm having the transmission rebuilt too so that's $2-3K.

My car is a daily runabout and it racks up about 8-12K miles a year with 8 track events a year. I'm hoping to do more time on the track next year and in the future too.

I suspect 2-3 years of this and I'll need another top end rebuild and I'll know then wheither this will become a pure track car and warrant new P+C's or it'll be sold on for something else.

Simon

[Carrera3.5L]

Simon,

Unfortunately, Porsche parts are expensive, no matter what region you are from...

I would replace the valve springs no matter what during the course of the rebuild, and if it were my decision would use sport versions even though you won't have a high rpm motor. They may accelerate wear a bit faster than normal and maybe take a horsepower or two but they may help in the event that something bad happens and you slightly overrev the motor. All just my personal opinion so take it fwiw and ask a variety of people about their experiences before making a decision...

There are a variety of manufacturers/resellers out there, I have used both Andial's (whom I think is being made for them by Eibach but just a guess) and AASCO's in the past without problems. Since you may be getting your cams/rockers/etc from John, you may also wish to purchase the sport valve springs from him at the same time and save on the shipping costs...

Another thing I just thought of with respect to the 993 SS camshaft profile is whether you will have suitable piston-to-valve clearance if using with the stock pistons. I believe the guys here on the board that are using this profile (the ones I know about anyway) have changed the pistons as well, getting rid of the swirl dome of the stock CIS/DME units in favor of the high-dome versions with deeper valve reliefs that allow for use of greater lift camshafts. Just a thought but another question to ask of John...

I'm fairly certain he'll find this thread and perhaps make his recommendations to you public so other people searching in the future will benefit from his knowledge...

Ralph

[Carrera3.5L]

Originally posted by drsimonwong
I'm about to undergo a full rebuild on my 120k 3.2. It's a Euro engine putting out 235hp and not using much oil but has become a regular on the track and is starting to leak oil.

Just caught the last part of this from your original inquiry. You mention that the motor isn't using oil but simply has some leaks, why are you certain you even need a rebuild? If the origin of the leaks are something simple, such as oil return tubes, valve covers, cam lines, etc, you may be better off just fixing those. Even if you have to temporarily drop the motor to fix the "big 3" up top, fixing the leaks rather than completely rebuilding it will save you thousands in the short-term and allow you to budget for a full performance rebuild in future years when you decide what direction to go with the car...

Does the motor have a dead cylinder? Are compression and leak down numbers consistent?

Ralph

[drsimonwong]

Ralph,

Had a minor service done at 210000km and no oil leaks anywhere, smooth running, dynoed at 235hp.

After 5 track days and 8000kms the brake fluid was getting low and I'd knocked off one of my brake cooling scoops so I took it in to my shop to have it replaced.

My mechanic listened to my car and up the values clearances needed to be done. He seemed suprised as he'd done them at the minor service.

On the host we noticed a fair amount of oil weeping from the cylinder and case joins of the 2 end cylinders at the back of the car(1 and 4 is it?). This had never happened before in the history of my ownership.

On closer inspection the little shim that sits between the cylinder and case seemed to be partially slipped out of the join area.

We discussed what this meant and decided that if I was planning to continue to run my car hard regularly (montly) on the track it may only be a matter of time before something lets go and gets destroyed.

Thoughts as to wheither our decision to pull everything apart is necessary?

Simon

[Carrera3.5L]

Simon,

I certainly defer to your mechanic, who has seen, driven and maintained the car so I'm sure he would be your best source of information...

I don't believe it is particularly uncommon to see some weepage from the cylinder/case seal as the motors gain mileage, my personal motor had some at 80K and I have seen others with a slight leak as well. Other than being annoying...

But if the copper cylinder base shim is loose enough where you can actually move it around and it is out of position, that sounds like the end result of something else...is the whole head/cylinder/ assembly coming loose due to a head stud issue or perhaps something else?

Maybe some of the guys with more experience than me can weigh in, it's hard to play doctor on the internet and I'm not very good at it anyway...

Ralph

[drsimonwong]

Ralph,

We're not 100% sure, but the base shim is visiblely out now, and it wasn't before so somethings come loose.

I do remember missing a shift at one point in a recent track day so it could be overreving related.

We're both nervous enough about the whole thing to accept that given this new symptom, the car's milage and it's intended usage as more of a track car means better safe than sorry.

I don't want to break my engine down if I don't have to, but neither do I want something to let go the next time I redline it.....

Thanks for your input. I'll let you know how it goes.

Simon

[911-32]

Hi Simon,

Its a nice motor to build that is for sure. Its pulls really well and holds on to its power right up to near 7000 rpm. You may have seen the dyno chart:



It makes good torque but you need to keep it up above 5000rpm to really move along - which with the std gear ratios is not always so easy. Losing a little weight from the car mades a lot of difference. As a benchmark, I can just about hold on the back of a 996 on the long uphill straight at Spa. I just lose a couple of car lengths.

I just had the car dynoed again after remapping and the torque curve is flatter and better in the midrange but the peak hp came out at 258.5hp - so no improvement there. I think with SSIs and the std intake, 260hp is as good as I am going to get. I also dynoed with one outlet capped on my M&K and it made 7/8hp less.

I did the race springs and Ti retainers but you could certainly save a few pennies on steel retainers and heavy duty springs - I think Camgrinder can supply.

The SS cams are a little obnoxious as they have a pretty chunky/throbbing idle. I idle at 1000rpm to smooth it out a bit. I have described it as a little like a big outboard boat motor when out of the water. With this exhaust muffler combo it drones somewhat at 2200-2800rpm but capping an outlet fixes that. Uncapped it screams. Its a unique sounding 911 with a really metallic wail at the top end. It sounds more like a GT3RS on the dyno than a 3.2, though the RS kicks on for another 1000rpm or so.

You are welcome to PM me with any questions.

Richard

[JeremyD]

I also have the 993 ss cams on a 3.4 = extrude honed, my car also has a lopey idle. Cold, it acts like it's going to stall, but catches nicely.

To me it is the perfect choice. More "S" like than anything else. From 1000-4000 it acts just like a normal carrera. Above 4000 and it has the kick of a turbo. It will take some practice driving fast on the track - as to get the most, I really need to keep the car between 4500-6000 rpms - but that's kind of the fun of it...

[911-32]

Looking at the peak power, you really need to keep it over 5000rpm on the track. The beauty is that it holds its power to nearly 7000rpm. I think the next sensible mod for a track car is close gears - unfortunately, I keep getting distracted with things that are much sexier to look at like ITBs.....

Assuming my engine and Jeremy's were built to equal tolerances, you can see he is getting about 10hp more than the extra capacity would suggest (assuming equal dynos as well), which sounds about right to me, given the extrude hone and bigger diameter extractors.

BTW, I kept the std flywheel but added a light pressure plate and 930S clutch. Its slightly more prone to stalling but 9 out 10 times the engine catches itself. My clutch is probably 50% heavier than stock so if I don't pay some attention I occasionally stall. I think the std flywheel is a smart choice though I would have been happier to go for lighter one for my use. If I do the g'box, I may yet do the flywheel.

RB

[drsimonwong]

Thanks for the input guys.

Going the 993SS rather than the milder 20/21 makes it a "S" vs "E" from longhood speak I gather.

Ultimately I've got to figure out if I'm designing the engine for the street or the track. I suspect my best choice will be either stock or 993SS rather than the halfway 20/21.

My M+K is the 2in1out so it'll be quiter and will hopefully run to 250hp. Wonder what I'll get with the stock cam?

I'm going to chat with my mechanic but I'll PM you Richard when I have more questions if you don't mind .

Hey, do you guys know what's the best option for maximizing torque in the midrange?

Simon

[drsimonwong]

Ooophs, Ralph answered the last question about the 20/21 having better midrange.
Simon

[911-32]

Camgrinder can also do a Super C2 grind. One of our guys used this on a 3.0 SC (search for Bruboy on Pelican where he posted results) and is very pleased. Seems to have acheived most of what Supercup cams acheives but without any of the lumpy idle etc.

IMHO rebuilding std is a waste of a good opportunity. You are paying for all the labour etc to have a rebuild, why not gain a few hp and gain a stronger upper rev range. Its a no brainer, no?

[drsimonwong]

On one hand I've got to weigh up wheither I'm going to continue to run in "stock" class or go to modified in my series.

My stock class we have 3.2's, 964's, 968Clubsports and Boxters. The front runners in the class are the 964's and the 968's. We have one very fast 3.2 who runs 2nd all the time, but mostly its the younger cars that are fastest.

The modified class that a cam change would bring puts me in with the 3.0RS replicas and fully stripped lightweight club cars.

On the other hand I'm not particularly competitive in either class so I might as well build the car I want.

So I guess you are right :-)

What I really need is to learn how to drive properly......

Simon

[JeremyD]

Or buy a C2 -

[drsimonwong]

Believe me I've thought long and hard about it.