SBC cam swap

[devonrommel]

Hey guys, I have an 83 K2500 suburban. Stock LT9 350/Sm465/3.73s.

I asked comp cams what RV type cam they recommend for my engine. They suggested this:

Grind Number:XE256H

Engine Family:Chevrolet 262-400 c.i. 8 Cylinder (1958-1998)

RPM Operating Range:1,000-5,200

Cam Type:Hydraulic Flat Tappet

Lifter Style:Hydraulic Flat Tappet

Camshaft Series:Xtreme Energy

Camshaft Gear Attachment:3-Bolt

Usage:Street/Performance

Valve Springs Required:Yes

Camshaft Material:Cast Iron

California Proposition 65:WARNING: Cancer and Reproductive Harm P65Warnings.ca.gov

Advertised Intake Duration:256

Advertised Exhaust Duration:268

Intake Duration at .050 Inch Lift:212

Exhaust Duration at .050 Inch Lift:218

Intake Valve Lift:0.447

Exhaust Valve Lift:0.454

Lobe Separation:110

Assembly Lubricant Included:Yes

Intake Centerline:106

Lobe Lift Intake:0.299

Lobe Lift Exhaust:0.304

My question is, what kind of gains can I expect from this? I'm trying to get more towing power on the cheap.

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[cstew47]

In my experience, I have never seen a cam swap alone make a big performance increase. The cam is part of the system consisting of the carb size, head flow, torque converter stall speed and gear ratio. I wouldn't get your expectations too high for just the cam swap, although, that spec seems right for your truck.

 

[75gmck25]

That 212/218 duration should work, although most references I've seen had a max of about 214 @ .050 duration with stock heads. If you use stock heads and a decent carburetor and intake manifold you should get a noticeable increase in power, but with this duration you are at about the best you can get with stock smog-era heads.

If you also swap to better flowing heads it will really help a lot. If you use aftermarket 64cc aluminum heads and thin head gaskets you can get the compression up about 1-1.2 points, and the aluminum heads will tolerate more ignition advance without pinging. Better flow, higher compression and more timing - it all adds up to quite a bit more power.