hi chev guys.. Need some more info on a motor I just bought

Depending on what casting number head you have they could have different capacities in chamber in them and therefore different CR's.

1.94 heads are good heads and 2.02 heads are very rare and do not really do much more unless you get well above 6000 RPM a lot. A few words of caution here. First if those are pre 73 1.94 heads they have soft valves and seats and will not last long in a engine being run hard on today unleaded fuel. (they were designed for leaded fuel) Second and most importantly if you plan to turbo or supercharge it even 9.5 is too much. You really want 8 to 8.5 (even less if planning 10 PSI or more) if you plan to runs some boost with pump gas in that motor because of detenation concerns. Under boost when you hear serious knock it is ususally too late when you hear it and damage is done as you can melt a piston in a heart beat under boost if you get fuel knock. I would suggest that you look for some late model 1.94 heads with lower compression (bigger chamber) and with hardened valves and seat that were designed for unleaded fuel.

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Has it just had a valve job or have hardened valves AND seats been installed? Yes a overbore will increase CR and in your case about maybe .5. ALso it is not generally a good idea to bore .060 over on a

4 inch bore SB as it weakens cylinders and can have heating issues and also now that I think of it, I defenately would NOT turbo or super charge it with than amount of overbore as block/cylder walls could crack or fail under boost. Boring .030 is safe limit to over bore on that block if you plan to boost it.

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A turbo charged old 283 would be sweet. You cold use 307 heads on it to lower CR for boost. (you could even do a 307 too as they both have

3.875 bores and lots of meat in block and head for boost.

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Older 283's have forged steel cranks. Most without a drilled and tapped hole to retain the harmonic balancer. Easy to add.

Al

Good point, I remembered the forged crank but forgot about the pressed on only damper on earlier ones. I had a 67 283 I put in a 72 4x4 truck for a while (so I could keep using truck) about 30 years ago while I was rebulding and warming up the 350 for it and it had a tapped and drilled snout from factory. Not sure what year they started tapping them as I have seen them both ways.

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