yes, i'm planing to change the heads on my 305 carb, it has 60cc and the small 1.72/1.5 valves wich gives me a misserable 8 compression. i can buy a set of 416 heads (58cc 1.84/1.5), maths shown a compression of 9.5 aprox. the question is:
should i keep using ordinary unleaded or go to SUPER unleaded?
thank you very much...fern.

 

unless you have a typo in there 2cc isn't going to get you 1.5 more points of compression. if you don't have a typo run the same fuel you've been useing and see how it works.

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1st & 3rd

 

FSG,

By comparison, flat-top pistons with four valve reliefs and 58cc chambers on a 305 at standard deck height and ring locations yields about 9.5:1 static compression. If your piston volumes are altered, deck height changed, gasket different, etc, you'll have to calculate the differences. Stock components and 60cc heads should get you about 8.9:1. Double check your stock castings. I think you'll find a different volume than 60cc.

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Later,
Vader
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