383 cam ideas

[rich67]

built a 383. put a 4x4 extreme cam in. the hottest one. 480/498 lift. thinking i might like to get up in the 500's. how hot can i go and not ruin drivability. have flat tops. 10.5-1. aluminum vette heads. very small chambers 58cc i think. 2.00/155 valves. think springs are good to 550 or 600. any feedback appreciated. know a little from reading but dont know alot. thanx rich

[79shortbed]

Well since this is going in a truck, I wouldn't get too crazy. Keep the duration low, lift numbers high in a perfect world. Strokers seem to take a bit larger cam than a standard stroke/bore small block, so there is a bit more leeway. The Comps XE274 or the Lunati Voodoo equivalent sounds like a good compromise between low end grunt and top end scream. Use 1.6 or 1.65 rockers to get the most lift from them. I am no expert, and I'm sure other people with more experiment will chime in.

[Fred T]

Contact the techies at the cam manufacturers. They will want all the engine and drivetrain specs from the carb to the tire size. They plug it all into their computer and do a good job of matching a cam to your vehicle and needs. The more info you can provide, the better the recommendation.

I just looked, Comp Cams also has a place to do this online.
http://www.compcams.com/Company/CC/C...amHelpNew.aspx

[Marv D]

I got a silly question. How do you know what your compression is if your not sure of the chamber CC?

I ran a 383 with flat tops with very large 6cc valve reliefs, a standard 0.025 deck clearance, a 0.040" head gasket, 58cc heads and that motor would have exactly 11.54:1 compression.

[rich67]

Originally Posted by Marv D

I got a silly question. How do you know what your compression is if your not sure of the chamber CC?

I ran a 383 with flat tops with very large 6cc valve reliefs, a standard 0.025 deck clearance, a 0.040" head gasket, 58cc heads and that motor would have exactly 11.54:1 compression.

sorry that was with 64 cc iron heads id planned on using so be higher your rite. not sure how much tho. 53 cc chambers on new heads. my bad. when i bought stroker kit it stated 10.5 -1 with 64 cc chambers. may not be able to run new heads and run decent on pump gas. not in truck yet. all can be changed. thanx for input everybody.

[rich67]

Originally Posted by Fred T

Contact the techies at the cam manufacturers. They will want all the engine and drivetrain specs from the carb to the tire size. They plug it all into their computer and do a good job of matching a cam to your vehicle and needs. The more info you can provide, the better the recommendation.

I just looked, Comp Cams also has a place to do this online.
http://www.compcams.com/Company/CC/C...amHelpNew.aspx

good advice dude.

[Marv D]

Thing is Rich, your cam duration needss to match the static compression. You can bandaid a bad combination with a late intake valve closing to bleed off cylinder pressure, at the expense of vacuum and drivability (not a good idea in a 4x4)

There is a few wise old engine builders 'rules' of thumb in engine building....

The fuel you plan to run dictates the compression you can have
The compression you have dictates the cam's valve timing
The cam's valve timing dictates the rpm operating range of the engine

NOTE: these are MOTOR OCTANE, not esearch, or R=M/2
85 octane for 8:1 to 9:1
90 octane for 9:1 to 10:1
95 octane for 10:1 to 11:1
100 octane for 11:1 to 12:1
105 for 12:1 to 12.5:1
110 for 12:5 to 13 (Methanol prefered above 13:1)

NOTE: this is the MINIMUM compression required to support the 0.050" cam timing listed
For 10:1 compression, use a cam with 250° @ 0.050"
for 11:1 use a cam with 260° @ 0.050"
12:1 use 270@ 0.050"
... etc


Remember these are very VERY general guidelines and not hard line choices. But.... See how it all kind of falls in place to be a combination from beginning to end. The cam is the brains of the motor,,,, Pick the fuel, compression, cam to fit the operating range of your intended use. You'll be much happier with the results.

Typical operating RPM ranges This varies by piston speed, bore, rod length, and too many details to even think about,,, but as a very general rule of thumb for small blocks (general rule of thumb is add 5° for >400 cubic inches, add 10° for >500 cubic inches)

<230° @ 0.050 idle to 5500rpm
230° - 245° @ 0.050 to 6500RPM
245° - 260° @ 0.050" to 7000 RPM
260° - 275° @ 0.050" to 7500 RPM
275° + 8000rpm and above