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Discussion Starter #1
I have a set of heads from a '70 351 that would flow much better than my stock 289 heads. The question is, would this hurt performance because the combustion chambers are roughly 60cc's
where as the 289's are smaller (I beleive I've read somewhere around 58cc's)?? Or will the improved flow make up the difference? Same ? would go for GT-40 heads since they also have 60cc chabmers..
Thanks for any info...
Andy
 

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Andy,

The early heads are better in all ways except the exhaust port is smaller. The drop in compression would kill any gain you might get from the slightly larger exhaust port on the '70 heads. In fact your car would be really doggy.

Best bet if you want real improvements on a 289 is to get a set of Edelbrock Performer RPM heads with the small combustion chamber and 1.94 / 1.60 valve sizes. You will feel a huge gain.

There are other brands of aluminum and cast iron aftermarket heads (like the old GT40's) too, all offer significantly better gains than can be had from the stock heads. I recommend you save up and go for the aluminum ones which also take a lot of weight off the front of the car, something all Cougars desperately need.

A set of tubular exhaust headers will give you decent performance gains too and are mandatory to see the maximum benefits from a new set of heads.
 

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Discussion Starter #3
Thanks Royce...

I will putt around with the stock heads until I can save enough
for aluminum. Looks like a good project for this fall/winter.

Andy
 
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