1960 283/270

[Mike M.]

What is the factory compression ratio for a 283/270hp engine?

Thanks in advance

[Joe L.]

Re: 1960 283/270

What is the factory compression ratio for a 283/270hp engine?

Thanks in advance

Mike------


9.5:1

[Mike M.]

Re: 1960 283/270

Joe,

Thank you, that's what I thought!!
I saw two other specs as well but I always thought they were 9.5:1 myself!

Thanks again
Mike

[Frank D.]

Re: 1960 283/270

Yes, relatively tame compression and they will run on 87 octane all day long if properly tuned.
My 270hp has used nothing else for 9 years...

[Stephen C.]

Re: 1960 283/270

Mike:all 283cu had 9.5:1 compression except for the 275hp fuel injection & the 315hp fuel injection with high lift cam had 11:1 compression.

[Duke W.]

Re: 1960 283/270

All '57 to '60 engines except the mechanical lifter FI engines had an advertised CR of 9.5:1, but depending on deck height the actual may be as low as 9:1. As stated, most of these engines will operate detonation-free on 87 PON regular unleaded, especially with the lazy centrifugal OE spark advance map, and may operate okay with a more aggressive centrifugal curve that will make more torque/power in the low to mid range.

When rebuilding these engines, my recommendation is to increase the true measured CR to 10:1 on base cam engines and 10.25:1 on Duntov Cam engines along with an aggressive spark advance map. Premium fuel will be required, but you get more torque and power, and the increase in fuel economy will negate the increased fuel price, so the extra torque and power is basically free.

Duke

[Duke W.]

Re: 1960 283/270

Mike:all 283cu had 9.5:1 compression except for the 275hp fuel injection & the 315hp fuel injection with high lift cam had 11:1 compression.

The '57 to '60 mechanical lifter cam FI engines were advertised at 10.5:1.

Duke

[Mike M.]

Re: 1960 283/270

Thanks guys!