"Hot" cam choice for small port 3.0 with SSIs.

[917_Langheck]

And the greater missing variable not accounted for in that graph is the afr trace.

One cannot throw 5 variables into the mix and claim that a particular one is the issue without isolating the other 4.

As to the Henry's claim, that was conditioned as across the range, and not at a particular rpm. Do a pull without the m&k and one with, all with an afr readout, then we'll all know where the issue lays.

[70Ripper]

my 3.0 w/ carbs, 9.5:1 comp. sing plug, SSi w/ a Bursch exhaust - running a 906 set of cams and on thru 7000 still has me asking, are you sure ? Everyone said S cams but man 80Kmiles w/ these 906's and you can't get the smile off my face - until I pull up to the pump.

[Emo993]

Not a 3.2, mine is a 2.2 E engine with S pistons, John's Mod-Solex DC30 cams, 40 PMO's and Ben's header and sport muffler. Feels like the earlier graph, pulls great from 5 to 7,000. Great sound with some drone around 3.500. Mark

[Gordo2]

Originally Posted by icarp

... I have 230hp at the crank and I can smoke just about any other similar displacement car, including a 2018 civic type r and a wrx sti 2018 in the 1/4 mile . 14.02 sec. Theses specs with stock cis pistons and 34 mm ports

I do not like the Gt2 102 grind from DRC, it is a cam for your grandmother.
Mike I don't think you liked it either .

Ian

If you want to kick-a$$ in the 1/4 mile - buy a Mustang

If you want your 911 to have more torque at 2,750k RPM - buy the GT2 102 // and Grandma will greatly appreciate your headrests when you stomp 3rd gear at 2.5k RPM

Call DRC - he's a great resource to talk to. I called him over a year out of starting into my rebuild and he really helped me narrow in on achieving the kind of performance I was looking for.

Good luck, Gordo

--------------------------------

Side note: I agree with 917 regarding RSstop's graph showing 5k RPM performance dip. Install a wide band / Air Fuel Ratio (AFR) reader and you will know exactly what's going on.

Lacking AFR readings, it appears your idle circuits are providing primary fuel up to ~ 5k when your carbs transition to main circuits.

Idle to main circuit transition is difficult to smooth out on carbs. If you currently like how your engine runs and accelerates, I suggest you leave things alone. Otherwise - study up, experiment and enjoy the the learning curve.

[icarp]

The OP asked for a hot cam , The GT evo 102 or 108 is a came based on an emission based cam .
I am working with a very fun 3.2 with the gt2 108 cams in the car now , yes it is lots of fun and smooth pulls to 7200 rpm, making about 230 hp at the crank. I do not consider this a hot street cam
It is a better street cam than stock . There is no question this is better than stock . 50 hp better
It is just that I would trust my grandmother with my car if it had this cam in it
A stock 911 s 1973 2.4 is much more of hot street cam, wow , tuned well this cam rips ! and lots of low end torque , as I said , tuned well.
Just my thoughts, as for my 911 drag car , I drove that car 65,000 miles in three years,
getting 28 mpg and it rips , 146 mph, It also has 10 track days of playing, all on my fav mini van tires!!! wink wink
It's an Opinion
I like having FUN !
Ian

[snbush67]

Ian, I think it’s possible that you’re getting hung up on the words “Hot Cam”. I know what KY asked 4, but I think he clarified in his post that he wanted “the hottest” cam that would work with his current set up.

It’s like the lady that went through the MD drive through and ordered “hot coffee” then got scalded, she really meant “the hottest coffee” that she could drink safely.

Given the small ports and Weber 40’s a hot cam for KY would be a GT EVO cam.

And OBTW you get 28 mpg because you have a cheater knob.

[Jeff Alton]

Enlarging small ports to bigger ports is not a really involved operation.... If the OP is interested.

[camgrinder]

Like Henry said the DC40 is a good choice for this engine. For a 4000+ RPM powerband.

[Henry Schmidt]

Originally Posted by G450X

Henry,

Not to hijack the thread, but what exhaust do you recommend for a SC 3.0 mild mod short stroke (Max Moritz 9:8:1) with a slight cam bump (M1) with SSI’s and early (‘79) CIS?

I assume a 15 hp exhaust bump should benefit the original post question since that 3.0 has carbs and he’s looking for cam recommendations.

The worst part of my ‘82 SC is that it “dies” at a little over 5k RPM - heck, my high mile Benz W210 OM606 diesel revs higher!

Back in the 70s, a cam guru [Harry Weber] took on the task of making a cam that would fit in a CIS engine [back then, a 2.7] that would offer performance and the clearance needed to work with the squish chamber piston. He came up with a Web 2021.
The interesting thing about the cam is that it offers a stable vacuum for idle but increases vacuum on light throttle acting very much like an accelerator pump. The cam has good performance into the low 6000 rpm. John at DRC has his version of this iconic cam I believe he calls it the DC21
This cam is even a great choice if carburetors are fitted to a stock SC or 3.2 Carrera engine.
On a side note: the CIS air flow meter has a tendency to run lean on light throttle cruise. This phenomenon is caused by a transition from turbulent air flowing across the metering plate to a laminar [high volume/low pressure] flow at cruise. This reduction of plate lifting force/pressure causes the lean running condition. Clean exhaust flow helps but it is always a concern when considering compression increases..
Lean running at cruise makes acceleration through max torque [high cylinder pressures] a detonation nightmare.

As for exhaust: there are a plethora of muffler choices but we like the Dansk Sport muffler for performance and reasonable decibel levels.