help me pick a cam!

Jeff Alton · 08-11-2005, 12:18 PM

Help me out and pick me a camshaft!
Here are the details of the car and motor being built. There are still some variables.....

Car: 84 911, full coilovers, 935 suspension front and rear. huge brakes, sway bars, monoballs, light weight interior, roll bar......
Weighs about 2490lbs. STOCK gearing in a 915 with LSD.

I use it on mostly on just two tracks and for fun on the street. Problem is, the tracks are quite different. One is our local track Mission, which is tight and has a couple of slower 2nd gear corners. Never gonna see 5th on this track but a few more revs to play with would help..... The other track is Seattle which is quite a bit faster and only has one really hard pull in second gear comming out of 3b. I don't really want to change the gearing and realise that this will of course be a compromise.

The motor. 3.4 base on a 3.2.
10.5:1
twin plugged
46mm PMO
ARP rod bolts
Now, I have a set of 1.5 SSI's, and a set of 1 5/8 993 HE that I can use as well. Should I get 1.75 B+B? I do need heat, I think.

I need this motor to have a decent bottom end BUT I would like to spin it to atleast 7K? Can this be done? I don't need 8k but I want some power there at 6800+ .

Let me know what you think, I am all over the map from 993rs to a web 120/104 to a ge60/80 (dc60/80 from camgrinder)

Thanks, Jeff

Bill Verburg · Bill Verburg's Garage

You need to be concerned w/ ID and pipe length and collector layout and size.

ssi are 1 3/8" ID w/ a splayed collector
I will need to go measure the 993s
B&B comes in either 1 1/2"or 1 5/8" ID all w/ a tripod collector

heat or no?

emissions inspection or no?

7k isn't really spinning that much more than stock, my 3.8 w/ RS hyd cams is still making very good power there.

Jeff Alton · 08-11-2005, 12:55 PM

I need heat, I think the 993 is about 1.5 ID or almost anyways. I can also measure when I get home. My current 3.2 never even sees 7k. Hmm, nice to hear that your 993RS cam motor is making power at 7k, that is one of the cams I am interested in as it should still give me pretty good bottom end. Emissions testing will not be required.

I read your recent reply about tube length and diameter, but that just maybe confused things for me a bit more!!

What collecter is better? Flat or Tripod? I guess the 993 collector is not that great....

Jeff

Tyson Schmidt · 08-11-2005, 12:55 PM

SSI's are 35mm I.D. No good at all for 3.2 heads.

993 HE's are 38mm I.D. Perfect for 3.2 heads.

What pistons are you using?

If you've got valve clearane, I'd go Mod-S. Lots of power up high all the way to 7K, excellent mid-range, and still some bottom end torque and throttle response. The widened lobe-centers really broaden the torque curve nicely, which is what you need from your description.

kenikh · 12:58 PM

Can your pistons clear a high lift cam? At 10.5:1 I assume they are JEs or equivalent. I seem to recall early 'S' cams are a blast in larger motors that can clear them. They are supposedly very linear in 3.2L and bigger, but make awesome power to ~7300 RPM. The 46 PMOs are a great choice because you won't run out of air and fuel at high revs, too. I think camgrinder makes a modified S profile that would be perfect.

(edit) Looks like Tyson and I posted at the same time!

Bill Verburg · Bill Verburg's Garage

You would actually use the SS cams which are the mechacical version of the RS, As long as intake and emissions allow I think I would want something w/ a little more overlap and a little lumpier

Jeff Alton · 08-11-2005, 01:10 PM

Pistons are 10.5 JE so valve clearance should not be an issue. Mod-s sounds like fun, power up to 7300.......hmmmmm that would be nice! How much will I be killing the top end with the 993 HE or will I? John has been doing all of my cams, so I would like to use one of his grinds if possible.

Tyson, if I understand you correctly, the 993 HE will work well on this combo? What muffler would you run with them. Triad, custom flowmaster....?

Thanks guys,

Jeff

JeremyD · JeremyD's Garage

Find a set of 964 B & B with heat - then go with the 993 ss cams.

kenikh · 08-11-2005, 01:23 PM

Why not run an early Sport muffler? It'll sound wicked and make good power.

Jeff Alton · 08-11-2005, 02:11 PM

Mating up an early sport muffer to anything other than early HE or SSI's can be a bit of a challenge. I love the look and sound of them though!

Jeff

JeremyD · JeremyD's Garage

Quote:

Originally posted by catca
Pistons are 10.5 JE so valve clearance should not be an issue. Mod-s sounds like fun, power up to 7300.......hmmmmm that would be nice! How much will I be killing the top end with the 993 HE or will I? John has been doing all of my cams, so I would like to use one of his grinds if possible.

Tyson, if I understand you correctly, the 993 HE will work well on this combo? What muffler would you run with them. Triad, custom flowmaster....?

Thanks guys,

Jeff

Jeff Alton · 08-11-2005, 03:41 PM

Is that the "happy crab". Looks nice but isn't it kinda pricey for a muffler?

Jeff

JeremyD · JeremyD's Garage

true

Jeff Alton · 08-11-2005, 04:01 PM

Maybe Ben can make me one up? I should call him about that.....

Jeff

JeremyD · JeremyD's Garage

That's why he's working one up for me - I'd think that would be the next one for him - based on the 993 heat exchangers!

camgrinder · 08-12-2005, 08:20 AM

The Dc40 (mod s) on 108 lobe centers will give you a 3500 to 7000 rpm powerband. Depending on your valve springs, I have a custom grind which make more power in the same powerband.

Jeff Alton · 08-12-2005, 09:12 AM

Thanks John, the custom grind sounds like the way to go! Will your "mild" spring upgrade do it, or do I need the race ones?

Thanks, Jeff

JeremyD · JeremyD's Garage

and how would the custom compare to the 993 ss that you did for me John? BTW - your cams fit like butter!

Tyson Schmidt · 08-12-2005, 09:26 AM

Quote:

Originally posted by catca
Pistons are 10.5 JE so valve clearance should not be an issue. Mod-s sounds like fun, power up to 7300.......hmmmmm that would be nice! How much will I be killing the top end with the 993 HE or will I? John has been doing all of my cams, so I would like to use one of his grinds if possible.

Tyson, if I understand you correctly, the 993 HE will work well on this combo? What muffler would you run with them. Triad, custom flowmaster....?

Thanks guys,

Jeff

Actually the 993 HE's are the best bang for the buck, but if you are running the high overlap cams I suggested, then some B&B or GHL headers would be the best. (With the high overlap, the equal length tuning effect of the headers will take better advantage of the overlap on the cams.) But use a custom muffler like a Flowmaster or a Magnaflow, since the B&B and GHL mufflers aren't holding uo well.

Others have suggested 993SS cams. I disagree with this. They are great cams, and are the most aggressive cam you can use with Factory EFI. But you really should take advantage of the fact that you've got carbs and JE pistons, and run the higher overlap cams.

Camgrinder's better version of the Mod-S sounds pretty fun!

camgrinder · 02:29 PM

Here are the specs compared to the DC40(Mod-S) cams
Using the 46mm PMO carbs I like to widen the lobe centers to 108 degrees. I would not run 108 with a set of Weber 46mm's.
To run a set like this without carbs would take a fully programable EFI like motec etc.
I would run the racing springs. These cams will pull past 7000 rpms, and if you miss a shift you will be glad you have them.http://www.drcamshafts.com/profiles/DC42.htm