Any one has installe 993ss cams on a SC 3.0 204 ?

[nicorun_974]

Hello,

I would like to upgrade my engine for my 73 rs backdate (base is 3.0 sc 1982 204 hp)
I have already 39 mm rsr manifold with race exhaust.

I would like to keep my CIS as it is.


Does anyone has installed 993SS cams (from dougherty racing cams) and can tell me how it works on a standard 3.0 euro SC with only my upgraded exhaust ?

How does it drive. Is is still drivable between 1 000rpm and 3000 rpm in the street. What is the torque and power increase.

Thank you very much to you all for your answer and excuse my English (I am from Reunion Island and normally speak French.

Nicolas

PS : I may change Pistons and cylinders but not sure if I will order stock euro 204 or uprgraded pistons. Any advice on this too.

[Spenny_b]

Hi Nicholas, unfortunately I don't know the answers to your questions, but if it were me, I'd really wanting to speak to John Dougherty and seek his guidance. I don't know him, but from what I read, he's the man, if he doesn't know, then unlikely that anyone will!

Also, it could be that if they aren't compatible straight away, then *perhaps* they could be re-profiled to change the lift/duration characteristics, and that would certainly be a job for Dougherty.

Cheers
Spencer.

[Flat6Heaven]

Hi Nicolas. Do you have to keep CIS? If so, you will be limited in your choice of camshafts as anything too agressive will upset CIS. Higher rpms will be ok but idle quality and low-rpm driveability will suffer.

CIS pistons have very little room for high-lift camshafts, which is another limiting factor.

If you must retain CIS for racing class rules, it can be somewhat modified to match more agressive cams.

Finally, as Spenny_b said, Dougherty is an amazing resource.

Good luck and watch out for the sharks in La Réunion's waters ;-)

[nicorun_974]

Thank you flat6heaven
Yes i have to keep cis.
I know that it limits thé use of agressive camshats and that s why i want to be sure that 993 ss cams are ok with cis. John recommended them to me but i would like other advices about drivability.

[Flat6Heaven]

Oh, ok. Maybe someone with direct experience will chime in...

[kenikh]

Old thread, but I talked to Dougherty about this. 993SS is a nice cam for a car with Euro compression only (9.8:1 or higher). Will actually work fine with both small and large port motors, so long as the compression is up. I'll be installing these cams in my small port SC.

[nicorun_974]

Thank you.
I installed these cams on my 3.0 with 10.5 Je pistons and PMO carbs two years ago.
Works fine
Nicolas

[kenikh]

How did the car perform compared to stock in terms of power delivery? Where in the power band does the power fall off?

On CIS, John says the car will make power to about 7000 RPM.

[nicorun_974]

Sorry
I Didn't measure

[safe]

I installed them in my 3.2 with ITBs and headers.
Lost 10 hp on top and torque all over the line...
Worst money I ever spent on the car.

[kenikh]

^ what compression ratio? If 8.5:1 that's to be expected. They need high compression. If you are running 9.8:1 euro compression, then this is interesting, for sure.

[KTL]

Referring to safe's comments on poor performance, I thought these cams are best suited to single plenum engines that work well with the wider lobe separation angle, in the range of 112 to 113 degrees similar to factory SC/Carrera cams? One of the benefits in using ITB induction is to be able to use a cam with more overlap (narrower lobe separation angle), which is not one of the 993SS features.

[kenikh]

^ correct

[safe]

Originally Posted by kenikh

^ what compression ratio? If 8.5:1 that's to be expected. They need high compression. If you are running 9.8:1 euro compression, then this is interesting, for sure.

Stock euro 10.3:1.

[safe]

Originally Posted by KTL

Referring to safe's comments on poor performance, I thought these cams are best suited to single plenum engines that work well with the wider lobe separation angle, in the range of 112 to 113 degrees similar to factory SC/Carrera cams? One of the benefits in using ITB induction is to be able to use a cam with more overlap (narrower lobe separation angle), which is not one of the 993SS features.

ITBs can work really good with 112 degrees.
John D, recommended these cams. He says it's not properly tuned, my tuner says the stock cams let the engine breed better.... Both cams pulls all the way to 7000.

[kenikh]

ITBs should not be an issue. This is either a tuning or a cam mismatch issue...John gave me the same advice. In turbo applications, these cams get rave reviews and I loved them in my buddys otherwise stock 3.6 964.

[fred cook]

I don't know what year your car is, but if you can find a CIS airbox and intake runners from a 1978 or 1979 car that would help. The early SC CIS system used larger intake runners than the 1980 and later cars. When I built the 3.3SS engine for my SC I did this conversion along with some other mods. Even with the extra displacement to feed, my engine will pull very well on the top end (7500 rpm redline) and makes good torque on the bottom end and midrange. I installed an Innovate air/fuel gauge to help with the system tuning. Now, it starts easily, runs well and still gets pretty good fuel mileage. Something to remember is that if you want more torque, add displacement, for more power improve the heads/breathing.

Big port Carrera twin plug heads


100mm Mahle pistons w/LN Engineering cylinders w/10.1:1 compression


Modified early CIS unit


Completed engine ready to install. Notice that there is no distributor. Engine uses
an XDi twin plug direct fire ignition.

[KTL]

Not trying to imply wider LSA doesn't work with ITB induction. Just saying that ITB is more tolerant of narrower LSA than is a single plenum with an airflow meter. The reversion effect can futz with the sensor plate or air flow meter.

At higher rpm the narrower LSA can often generate more peak power. But the wider LSA can produce better overall/average power. Narrower LSA has poor low RPM characteristics and is generally lopey/choppy there. Wider LSA is smoother operation at low RPM.

I doubt the stock SC/Carrera cams let the engine breathe better. They are a compromised cam that has to balance economy, emissions regulations and driveability. The 993SS is biased toward performance first & shouldn't be out-breathed by a stock cam. Especially when you consider a SC/Carrera cam is intended to operate at 6200 or below (Carrera 3.2 rev limit), whereas a 993 or 964 has a factory 6800 rpm limit. Both engines pull nicely to just below their rev limit. I can't believe a 993SS cam would undercut that.

[kenikh]

Tell us about how you modded the airbox. I was planning on opening up my small port airbox for large port runners.

[fred cook]

Originally Posted by kenikh

Tell us about how you modded the airbox. I was planning on opening up my small port airbox for large port runners.

I'm afraid that won't work. The tubes moulded into the airbox do not have enough "meat" to allow them to be opened up that much. You will have to source an early airbox.

As to the mods I made, I started with the early airbox and runners. I used all of the hardware off of a 1980 airbox (fuel distributor, wur, etc.) but backdated it to approximate the 1973 1/2 system. Then, I mounted a push switch on the throttle linkage bracket and wired it to activate the Cold Start Valve at full throttle. This puts a bit more fuel into the mix when the hammer is down to avoid a lean running condition. Once the completed engine was reinstalled, I used an air/fuel meter to adjust the a/f mix so that it runs at idle and "normal" speeds near 14.7:1 but at full chat the a/f mix changes to about 13:1. Since the switch only activates at full throttle, it does not affect fuel mileage much. Also, the CSV system has a small set of distribution tubes so that all cylinders get about the same amount of fuel, a better system than just dumping more fuel in the airbox. As I said earlier, it starts easily, even after sitting for several days, runs well, makes very good midrange torque and top end power and still gets decent fuel mileage. I also used a set of Carrera heads that had been prepped for a track car w/nice big clean ports and a slightly modified SSI exhaust system with a two in, one out muffler. All this was done just to see what level of performance could be achieved using the CIS intake system. If I ever decide to change over to ITBs, the work will all be outside the engine, not requiring another teardown. However, I am quite happy with what it is now!

Switch added for CSV activation.


CSV manifold tubes in airbox.


Intake runners ported to match cylinder head intake.