Folks,

I'm building a 383 motor, and CamMotion has given me some specs on a cam that they suggest. Custom grind with base circle for rod clearance. I was going to go flat tappet, but found out I had some nice springs for a solid roller setup so will likely be going that route. The cam they suggested is:

254I/264E @ 0.050, 0.643"I/0.621"E @ 1.5 ratio
0.023" lash, 108 sep, 104 installed

That seemed a bit outrageous, but I wanted some additional feedback from you guys on what to expect and whether I might want to go smaller. While the initial purpose of the engine will be drag racing a 2800# car /w/ 4000 stall and 4.88 gears shifting at 6500, I might want to migrate it over later. Maybe there's a happy medium? Maybe I just plan to swap cams later. Also, going this much on the cam, what can I expect problem-wise and where should I beef up? Also, what would be the advantage to such a large cam with relatively low RPM and no extensive port work? I'm guessing none, just looking for some useful discussion.

Here's the run-down on the motor:

Chevy 383:
-Scat 9000 crank
-2-pc seal 350 block .030 over
-Powerforged SpeedPro pistons
-Sealed power plasma moly rings, hand-gapped to 0.018 upper, 0.022 second
-Scat 4340 I-beam rods
-Fluid dampener
-Race balance (+/- 1 gm)
-Hooker SuperComp open headers
-Sportsman 2 200cc heads, 2.05int, 1.65exh, 64cc chamber
-Brodix hi-rise HVH manifold, port-matched to heads
-Carter AFB 850
-Valve springs: 250# at seat, 500# at 0.500 lift, 1.9" installed height, 1.55" dia

Thanks,
Craig

 

You'll probably have to get the spring seats in the heads cut for the springs that cam will need. You'll also need to get the valve guide cut down for that much lift. You'll need to check valve to piston clearance .100" minimum.

I don't think those heads will flow enough for that much lift.

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Follow my racing progress on Stephen's racing page
and check out the race car

87 IROC-Z SuperPro ET Bracket Race Car
461 naturally aspirated Big Block

Best ET on a time slip: 11.242 altitude corrected to 10.89
Best MPH on a time slip: 121.52 altitude corrected to 125.89
Altitude corrected rear wheel HP: 497.9
Best 60 foot: 1.546

Racing at 3500 feet elevation but most race days it's over 5000 feet density altitude!
Member of the Calgary Drag Racing Association

87 IROC bracket car, 91 454SS daily driver, 95 Homebuilt Harley

 

That cam seems too large to be shifting at 6500 rpm. I picked a 242/248 .608/.612" solid roller for my 377 and the rpm range was 2500 - 6800. You should definately have some port work on those heads. I chose Brodix heads which are 215cc but they flow 302 cfm at .500" and 312 cfm at .650". You need some good flowing heads to be turning those kind of rpms at that much lift.

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87 IROC-Z 305 TPI gears, exhaust, converter
14.70 at 94.1 mph
Solid Roller Minirammed 377 waiting to be installed