Can I run super unleaded 92 octane gas in a 427/425 engine or do I need additives? Thinking of a rebuild, could drop compression or any other suggestions?
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Re: 66 427/425, Regular Gas w/ additive?
Bill----
Yes, you can. However, if you experience significant pre-ignition, then you'll need to use an octane booster or retard the ignition timing or both. If neither works, then your best bet is to reduce compression ratio.
If, using 92 octane pump gas, you experience no significant pre-igintion, then you know that the gas is just fine. It all depends upon whether you experience pre-ignition, or not.
My guess would be that you won't be able to run on 92 octane fuel without significant pre-ignition.In Appreciation of John Hinckley -
Re: 66 427/425, Regular Gas w/ additive?
Bill
When I rebuilt my 65 396 I went with 10 to one pistons, stainless steel valves and hardened valve seats. The 396 ran fine on 93 octain but realy woke up with a 50/50 mix of Cam 2.
good LuckComment
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depends upon the cam
The stock cam had a long duration and a late closing intake valve which lowered the dynamic compression ratio. I would shoot for 10:1 with the stock cam. If you go with an aftermarket cam with a shorter duration, you may need to go for 9.5:1.
For more info, go to the Keith Black web site www.KB-silvolite.com and check what your dynamic compression ratio will be with your chosen cam and heads. I used to just take someone else's word on it but I found out that I kept getting burned - too low and it runs like a dog, too high and you're buying a lot of avgas at 8MPG!
Good luck,
MarkComment
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