Cam for a 3.2SS
 

I'm selecting a cam for my 3.2SS. It has EFI with individual throttle bodies, twin-plug heads, and a 9.5:1 CR (I may bump this to 10.5:1 with new pistons). It runs on 91 octane pump gas. Its primarily for autocross use, so I'd like a wide torque band - starting no higher than 4,000 and good top-end power at 8,000.

Any advice on which cam to use? I'm leaning toward something with a 300 intake, 270 exhaust, 102 phase centers and at least 0.45 lift.

i'm building almost the same engine. i asked john dougherty (camgrinder on thi board) and he recommended the DC-62 108 degree cam. i was going to go all out and get ge-80 cams but unless the engine is run to 8000rpm you will only be limiting when the power starts in the rev range. the dc-62 cams will have peak power about 500-700rpm lower than the ge-80 but will have broader torque and hp. i don't have the car done yet so i can't give a real recommendation yet but i would prefer useable hp over peak hp.

I'm not familiar with the DC-62. What is its input and exhaust durations? Is it like a GE-60?

What CR are you using for your engine?

intake: 274, .502 lift
exhaust: 254, .490 lift
108 deg

it is basically half way between a ge60 and 80.
my CR is 9.5:1 and i'm running individual throttle bodies, ported heads, 98mm pistons and 1 5/8 headers.

Our engines are very close.

What type of porting did you do to your heads? I've left my ports at 39mm.

I assume those duration numbers are at 0.05 lift. Right?

My engine is 9.5:1 right now, but I'm debating buying new pistons to bring it to 10.5:1 or 11:1.

yup, .05 lift - check out camgrinders web site for more info. www.drcamshafts.com. the porting is only slightly enlarging and smoothing - really just port matching to the intake. stock early sc heads flow great already. i went with 9.5:1 because i found a set of mahle cylinders/pistons for reasonable money. going with JE pistons and having a set of 95mm cylinders modified/re-plated is'nt a bad option. The 73 rs only had 8.5:1 cr. i also like the fact i don't have to worry about detonation even if i get low octane gas.

Hey Guys,

I'm planning on building almost exactly the same motor as you both too, but with 10.5:1 CR as we have 98 octane gas in Australia.

What sort of power are you both expecting ? Anyone dyno'd ?

What diameter Throttle bodies are you running ?

Craig.

My SS 3.2 is going on the Dyno this Tuesday. It has just been built, with new 98mm B&P. 10.5:1 CR. Andial S cams, 78SC heads, Crank fire ignition (Xdi), SSIs, Boat tailed and mooned cylinders, 46 PMOs.

It pulls straight away and keeps going. I have still only done 500 miles in it and as yet it has not been really pushed.

http://img.photobucket.com/albums/v2.../motor32ss.jpg

Alan.UK

Is the octance calculation in Australia the same as the USA? We use (RON+MON)/2. This results in a US octane rating of 92 equalling over 95 octane in Europe. Just make sure you aren't mixing apples and oranges as most folks on this board are quoting US calculations.

We actually now have a 100 RON Octane fuel available at petrol stations around Australia - Shell Optimax Extreme.

I'm not sure how RON and MON numbers compare, but I'm guessing we have pretty good fuel available compared to you guys in the USA.

Craig.

Mod S or Std S cams will work very well in this motor, with good low-end torque, and good high-end power as well.

-Wayne

EarlySport,


kenikh is correct. In Australia we specify RON at the bowser.

(RON + MON)/2 or Anti Knock Index is not used as a spec in Australia, although there was talk of it being introduced.

BP Ultimate (RON 98) actually equates to about 92.5 AKI (average 87 MON) when you are talking the same language as the Northern Americans.

I'm not sure what the comparison is when ethanol is blended, but I will look into it at some point.

Hope this helps.

Just got the dyno results for my SS3.2. A nice strong 260bhp. I will post the full results when I can scan them in. The S cams give a nice flat power curve. Its a scream to drive espically as its in a light 1971 car.

Alan