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Old 02-14-2006, 10:51 PM
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66 heads on 74 454?

I'm considering buying a '74 SS 454. The current owner tells me he has '66 heads on the stock '74 lower end. Says he has to run a mix of racing fuel and premium to keep detonation down due to the 10.5:1 compression...

Does this sound right to any of you BBC guys out here?
Maybe its a common mod, I dont know much about BBC's (yet)

I was really hoping for a stock '74 454 that I could wake up with intake, cam and exhaust and still run cheap pump gas.


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Old 02-14-2006, 11:18 PM
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They are probably closed chamber heads. Pull the valve cover and check the #s. They make high compression at the cost of poor flow.
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Old 02-14-2006, 11:58 PM
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The problem that you'll encounter with any of the motors from '72 up until EFI is that the compression ratios were dismal and squish was non-existant due to the excessive deck height. If you are going to add a little soup to one of these motors, you really should tear it down and correct the deck height / squish. You'll find if you do, that you'll have no trouble running pump gas at up to 11:1 with iron heads and a cam that matches the c.r. (squish at 0.035" to 0.040").
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Old 02-15-2006, 04:06 AM
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I'm a BBC fan and I don't mind telling you that BBC head's chambers are pathetic at best. The chamber shapes don't do a darn thing for swirl or quench compared to modern heads. 10.5 on 66 heads sounds like 100+ octane to me.

I'm running 8.6:1 on my 454 and I had to carefully tune my ignition curve to prevent detonation on cheap fuel. Modern aftermarket BBC heads have solved that issue, but old-school iron BBC heads don't cut it. Swap those old heads for some newer castings... even 049s and you'll get much better performance and octane tolerance.
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Old 02-15-2006, 04:55 AM
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Nothing can be figured till you know what heads and what pistons are being used... While all the mentioned info is good things have to be considered... What are you going to use this engine for...? If you want fuel economy forget it... If you want performace then use the higher compression and its advantages... But first find out exactly what you have...
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