November 2011 Chevy High Performance Q&A

Kevin McClelland Sep 22, 2011 0 Comment(s)
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Life goes on

I haven’t had any project cars in about 15 years; I have been busy with life, raising kids, and working. I was just wondering what would the effect be if I were to change the rocker arm ratios from 1.5:1 to 1.6:1 on a stock small-block Chevy? I don’t know what year the engine is but I’m pretty sure that it is pre-’80s and it has the dipstick on the driver side.

Also, I rebuilt a 350 out of a ‘69 Camaro about 15 years ago. It was never installed in a car and I tore it down to check it out. It looks clean and in good shape. Problem is, I forgot what cam I put in it and I have lost the paperwork for it. I am pretty sure it is a 0.480-inch lift cam. Is there a way to figure out what I have? Lastly, it had a three-speed manual trans on it. I want to put it in my ’83 Z28, which has a four-speed auto. Are there any balance issues or problems involved in that?

Tim Ferris
Mason, MI

At some point in our life our car projects get put on hold. We’re glad that you’re at a point in your life to pick up your car hobby where you left off 15 years ago. For the rocker swap, if the small-block in question is completely stock you will have enough additional valvespring to accommodate 0.030-inch max lift. This is what you usually pick up on average with stock-type camshafts lift. Along with the increased lift, you will see a couple of degrees of duration at the valve based on the increased rocker ratio. Increasing the rocker ratio is an easy way to pick up some power gains.

Identifying the camshaft in your small-block can be as easy as removing the camshaft plug in the rear of the block. Most aftermarket cams have the part number or some type of identification number stamped into the face of the rear journal. If you’re lucky enough to find ID numbers, you should be able to search on the Internet and find the specs. If there aren’t any markings on the camshaft, you could profile it with a degree wheel and a dial indicator. This isn’t that tough if you have the equipment. You can check on the COMP Cams, Crane Cams, or Lunati’s websites for profiling instructions. You can find duration at any tappet lift, separation angle, max lift, and camshaft installation point. It’s very straightforward with the proper instructions and, again, the tools to do so.

The ’69 350 small-block is what is called neutral balanced. This means that all balancing is done with the crankshaft and rotating assembly. An externally balanced engine means that either or both the harmonic damper and flywheel have balance weights designed into them to complete the balanced rotating assembly. You can install your ’69 engine with an ’85-and-earlier, 350-cid-or-smaller displacement flexplate and have no worries on balancing. All these engines are neutral balanced.

Sources: compcams.com, cranecams.com, lunatipower.com

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