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Old June 10th, 2023, 08:24 PM
Prowbar Prowbar is offline
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Join Date: Dec 2020
Location: Friesland, the Netherlands
Truck: 1965 GMC 1500, 478 V6, SM420
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Default Re: '65 GMC 1500 project. From the Netherlands

Been working on a cam design.

I've added Pete Chronis custom cam specs. Note these specs close the intake much later, to up the dynamic compression ratio. Note the shorter duration figures (advertised) These specs also have a little improved lift.

Stock lift figures as measured by me, with the current camshaft, without any valve lash, are .415" for both intake and exhaust.

I also added the cam I want to have ground for my build. I have to decide on the lift, but the rest is pretty much final. Unless you have groundbreaking suggestions

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It is a compromise between the stock camshaft and Pete's design.

Compared to stock, earlier valve intake closing to improve dynamic compression. A little less duration as a result. The exhaust is about the same as stock. I was concerned with cylinder filling at first, but don't think it matters as much due to the improved valve job and slight porting in the heads.

I've also decreased the valve overlap compared to stock, but not as much as Pete's design. The lobe separation angle comes out to 109 vs the stock cams 110.

Let me know what you think.
Attached Images
File Type: jpg Custom cam specs 478 David.jpg (3.23 MB, Multiple views, 2 clicks)
File Type: jpg Cam specs Peter Chronis 1.jpg (149.2 KB, Multiple views, 3 clicks)
File Type: jpg Cam specs Peter Chronis.jpg (76.3 KB, Multiple views, 2 clicks)
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