SC cams upgrade
 

I apologize for posting this, but not easy to decide based on older posts. New cams are in the cards. The car is a stock ex California 1980SC with aftermarket EFI, EDIS, SSIs and Dansk Sport 2-1. The engine appears to be untouched at 84 000 miles and is running good.
Lately I have taken myself thinking it is a bit too docile though. I enjoy being able to pull away from 1500 rpm and I use the 1500 - 2000 rpm range a lot in town. On the open road however when I am out breaking the law I wish it had a bit more oomph on the top. Just a little bit of that nice getting on the cam feeling. Is there a concensus on the next step in cams ? Is it the 964 cams, 20/21 grind or whatever.. I would rather not give up much at the bottom and don't need a lot more in the top end. Just slightly more temperament would be more in line with how I use the car. I did see a very interesting thread here on the forum comparing different cams on the dyno


Thanks for any advice

Regards

Contact John Doughtery, Doughtery Racing Cams (camgrinder). I run DC-15 in my SC, but I also have a turbo in it. The DC-15 run good at low end. You may want DC-20 on an n/a car.
Pat

Anyone out there with experience with the DC13 cam in an SC ? My understanding is I can expect it to come on early with a medium increase in torque, and then hold on slightly longer than the SC cam. Is this correct ? Anyone out there who has run it ? Car is 9:3CR, small runners and EFI

Trond,

I think you should check out the 964 or 20/21 grind. These should still clear the CIS pistons and give you the upper rpm boost you are looking for.

If you look at cam specs you want to increase the exhaust duration. This will shift the rpm range a bit higher.

Do you have emissions requirements? I suspect not. There are some custom grinds that should clear your pistons while giving you more GO than the 964 grind. John D. is the man to talk to about this.

Contact John Doughtery. Tell him what you want, what you have, and he will make a recommendation. there are a million opinions on this board...

an answer depends on how the question is understood.

Looking at dyno curves and various posts I believe I want a profile more oriented towards low end than the 964 cam. For my usage mid range and even low range torque is preferrable to top end. I need a strong engine between 1500 and 2000 rpm where I spend most time. Under normal driving I rarely go above 4000 and almost never above 5500. The backroads simply don't allow for it and the consequence of being pulled in at those speeds on the few good roads are 2 months in jail and 3 year ban on the licence. There are no tracks within 2 days of travelling and I need to focus on what happens between 1500 and 5000 rpm. I looked at various dyno printouts and the Elgin SC330, 20/21 and DC15 cams all look more suitable to my driving style. The next step will be I expect 3.2SS conversion but only if I cant control myself.

And no, no emissions for cars older than 30 years

Btw I have an appointment tonight for a rolling road session ! been waiting for a long time for capacity

Trond,

JMHO, but your small-port heads (and intake) were optimized for low end throttle response and torque so the gains from a 964 cams change will be less than the equivalent large-port engine gets.

Another alternative may to be to simply retime the SC cams for a little more upper end pull.

For the record, a 3.2 conversion along with a set of big-port heads and 964 cams makes a very potent combination that had both great low-end performance as well as a hard pull to 6K. :) :)

probably greater than 90% of the aftermarket cams provided for the 911 (for the DIY at least) come from Dougherty, Jerry Woods, or WebCam. best bet is to call John and someone at Jerry Woods directly. No need to reinvent the wheel. They have done this many times...

Thanks for advice everyone. I was pointed towards the DC13 by Dougherty based on my description of what i want from the engine and I believe I will most likely follow his advice. I was just curious if others had tried the cam and how they liked it.

Just came back from the dyno. We found 12 HP more, mostly caused by too much ignition timing. Very pleased with how it drives now and engine character suits my driving very well so will see if I can live with it as it is.

Here is the plot; before and after; http://forums.pelicanparts.com/uploa...1295995716.jpg

Sounds Great. Congrats!

DC13 cams ordered. More torque but similar delivery as stock cams. After dyno tweaking my current setup I like it better, nice torque delivery for my driving style on the local roads. I no longer want more punch at the top, but rather a bit more of the same !

Is that 171.7 hp at the rear wheels?

I have been looking at the tbitz EFI conversion for mine and I think you have helped me make up my mind. I'm in the same situation - low compression USA ex Califoria spec engine from 1983.

Just out of interest, with the tbitz unit you do away with the air flow plate, so does that allow you to go more agressive with the CAM? The old CIS system was quite sensitive and didn't like any of th wild CAM grinds.

Tim

Yes, correct it's rear wheel power. I removed the air flow plate, it is not used with MAP based EFI and using a more aggressive cam is OK. I don't want an aggressive cam (I did but changed my mind after the dyno session) but instead went with a cam that emphasises what the engine is already is good at, ie strong midrange. According to the good (cam)doctor I can expect a slightly wider and taller torque curve and thats perfect for me.

Thanks

Its amazing what you can get out of these engines without cracking the case open. Like you, I have a 3.2SS in my future but am happy working my way up to it and staying at 3.0 for now.

Tim