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I HAVE A 66 GTO WITH A (1973)400 (093 HEADS) 4 SPEED.I looked at a 389 (YC code 9778789):confused from a (wrecked) 65 Catalina, 094 heads mild cam, 4 barrel Edelbrock. The owner ran started the engine and it sounds good. Would you recommend this set up in my GTO. Also would the 093 heads make any difference on this block?
 

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If you're interested in performance, keep (and build) the 400 with some good heads. If you're interested in "restoring" the car, then you'll need to find a 389 that has the right data code and engine code to have been 'correct' for the GTO.

Bear
 

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Also would the 093 heads make any difference on this block?
The 094 heads have smaller valves (1.88/1.60) and were installed on the 326 in 1966, the CR was rated at 8.6 and produced 250 hp.

The 093 heads were used on a 389 with 1.92/1.66 valves, the CR was 10.5 with 68cc chambers. HP was rated @ 335 & 360 depending on the carb setup.

In my opinion the 093 heads would be the best choice for the Catalina 389.
 

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I'm using 91-93 octane fuel from my local gas station in my 66 GTO with the original factory 389 and the original factory 093 heads without any problems. I rebuilt the engine with the original pistons with a slight bore and milled the heads.
 

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i installed a (period correct) '65 389 YF 325 hp. out of a bonneville in my '65gto. it has 76 heads 1.92/1.66 valves. with forged pistons, 068 cam , stock carter afb, stock points dist. it runs beautiful with sunoco 93 octane pumpgas.
 

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The humidity and 2 octane points help a lot. In arrid California, with only 91 octane fuel, it's no-go. And has been that way for more than 20 years. I am basing my experience on mutiple early GTO's with stock compression, etc....that I've owned and driven. I wish we had better fuel here. If you can get away with stock CR on pump gas, more power to you! I can't make it happen here!
 

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The 094 heads have smaller valves (1.88/1.60) and were installed on the 326 in 1966, the CR was rated at 8.6 and produced 250 hp.

The 093 heads were used on a 389 with 1.92/1.66 valves, the CR was 10.5 with 68cc chambers. HP was rated @ 335 & 360 depending on the carb setup.

In my opinion the 093 heads would be the best choice for the Catalina 389.
in 1966 the valve size was 1.92 and the comp. was 9.2.1, the figures you stated are for 64 and 65. info from my phs papaers:cool
 
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