I've got my list of cams for the new 406 narrowed down to three top contenders and I thought I'd throw this out as a topic of discussion. Who would do what, and why?

The engine will be a forged 406. 10.5:1 compression. Dart Pro-1 215 c.c. heads. 2.05"/1.60" valves. Car is used primarily for bracket and recreational "hobby" drag racing. Two problems: 3.08 rear end gears and 1 5/8" primary tube headers.

All the cam choices are solids because that's what the heads are set up for. Bottom end ought to be good to 7K RPM. Single-plane intake, 800 D.P. Holley, headers, yadda, yadda. Here are my three top finalists--in no particular order--including specs and approximate (Desktop Dyno) peak h.p. and torque numbers:

No. 1: Iskendarian #201035. 288/288 advertised duration; 254/254 duration @ .050"; .525" lift with 1.52 rockers. Lobe center angle is 108 degrees; installed on a 104 degree intake center line. D-Top Dyno estimates 482 peak h.p. @ 6K RPM and 467 lb. peak TQ @ 5K RPM.

No. 2: Crane Powermax (F-280-2). 280/288 advertised uration; 244/252 duration @ .050"; .518"/.536" lift with 1.52 rockers. Lobe center angle is 112 degrees; installed on a 108 degree intake center line. D-Top Dyno estimates 485 peak h.p. @ 5,500 RPM and 485 lb. peak TQ @ 4,500 RPM.

No. 3: Schneider 12003. 284/284 advertised duration; 240/240 duration @ .050"; .510"/.510" lift with 1.52 rockers. Lobe center angle is 110 degrees; installed on a 106 degree intake center line. D-Top Dyno estimates 475 peak h.p. @ 5,500 RPM and 494 lb. peak TQ @ 4,500 RPM.

I ran each combo through the program again with large tube headers to see which one picks up the most power:

Isky gets 11 h.p. and 5 lb. TQ. (H.P. Peak moves up 500 RPM)

Crane gets 9 h.p. and 4 lb. TQ. (Power band stays the same.)

Schneider gets 7 h.p. and 3 lb. TQ (Power band stays the same.)

What to do?

 

#2. If not only for the 112 LSA. I think the wider torque curve would better suit your application, especially with the 3.08 rear gears.

 

run this one through your dyno...Oh, I already did that for you...Oh...I already ran the cam too...

look here:

http://www.corvetteforum.cc/ubb/Foru...ML/010766.html

 

I suggest #2 as well. The added duration on the exhaust lobe plus the extra lift should help, considering your header size. With more gear I would have chosen the Isky, but the crane will compliment your gearing offering a broader torque curve.

 

Thanks, guys. I was tending to lean toward the Crane Powermax myself. My reasoning was that the .536" lift on the exhaust side would be something the Dart heads would like. The 112 LCA is rather appealing, too. This cam may even like the addition of 3.55 or 3.70 gears down the road. (One of these years.)

 

Are you spring limited to a low lift? I went with something like the crane SR 236/350-2s grind only it's a custom for more lift.

 

Spring-limited by the Darts' out-of-the-box configuration to .620" lift and solid lifters.

That and flat-top pistons with a .040"-.045" quench (including the .039" head gasket.)

 

Jack - George said I should talk to you. I have the one step lower cam in my street driven 355. I'm using 1.6 cc roller tips. Your cam choice should be fairly radical even in a 406. Mine is listed as fair idle and yours as rough. I think you find good power out to 7000 rpm.

I installed my cam straight up and have about 10.5 c/r. I take it that your also going to run 1.6 or so rockers? DD charts higher hp with higher lifts.

 

I'm not too worried about idle characteristics any more. I'm THIS CLOSE to giving up on trying to comply with the envirolaws here in Kalifornia. The 406 ought to smooth out the idle of the bigger cam a little because of its larger displacement. Your "one step lower" cam (I don't know the spec. offhand) in a 355 is probably a little on the noticeably rumpety side. Where does Crane advise setting the idle--about 800-850?

 

I'm running a lightweight aluminum flywheel internally balanced and ATI 6 1/4 damper. So if you have the extra mass of external balancing your idle could be lower. I guess what I'm saying is Crane didn't recommend an idle speed. I have 238/248 .490/.510 114 lc with 1.5's I have 1.6. I also set hot lash to .018/.022 and I think that these last set of springs are 125# closed 1.46 dia duals good for upto .600 lift. I have never had valve float even at 7000. Solid cams make a Vette run like it should. If you have not run a solid cam before you will find that by altering lash by as little as .004 you can notice a change in idle quality. So if I went to .022 intake you actually gain a couple of inches of vac. For smog time!

When you first fire it up you will be impressed. My idle is in the 800's range

 

Cool.
I'll have a little knowedge curve to work through on the solid cam vs. the hydraulics I'm used to. Now if I can just get the Slowest Machinist on Earth to get busy ordering up my pistons, life will be good...