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DETONATION AND FUEL ADDITIVES

G Guest
I have a '71 with the high compression 351C (180 - 190 lbs. in all 8 cyl.), stock except Edelbrock aluminum intake, 600 Holley (vacuum secondaries & electric choke), and electronic ignition (Ford dist. with Accel coil). Had to back the timing off to 1 degree BTDC to get rid of pinging on Sunoco 94 octane, which is the best stuff we can get in Canada.

Not happy with the power characteristics with so little timing advance - feels lazy. Will octane boost or other fuel additives help, i.e. will they allow more advance without detonation? If so, which should I use and how much more advance can I dial in (I know 6 degrees nominal is stock)? Do additives separate from the gas? Any side effects from using octane boost or other additives? I currently use a lead substitute - can I continue to use it with octane boost and is it necessary? Will it mix with octane boost?

Do you have any other suggestions which might help me deal with this detonation issue (e.g. will colder plugs help - I use the stock recommended heat range/plug for '71 351C - ASF42C Ford/Motorcraft). I don't really want to lower the actual compression ratio or mess with the internals too much.

Thanks very much in advance for any help you may be able to provide.
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DS doug s (Guest)
do you still run the stock cam? a hotter cam, w/more duration, may help - the longer valve opening period may ackshully reduce running compression enuff to eliminate the detonation... a positive side-effect to better performance.

scott at cam research in colorado may be able to help w/specifics for cam specs. i'm sure there are other knowledgeable cam guys that could also help...
bosswrenchbosswrenchMember
I suggest that you drop the compression ratio by pulling the heads and adding thick composite gaskets that should drop the ratio at least half a point. 9-1/2: 1 with a stock cam & iron heads is all that current gas will comfortably allow. Your early may be around 11:1. The gasket change plus a radical cam should drop the cylinder pressure enough to make the engine live. Sure its a chore but gasoline is not getting better, and the future seems not to hold much promise for 100 octane at affordable prices, so do it before you detonate the ring lands out of the pistons and maybe destroy another 351C.
P PanteraOrBust (Guest)
Thanks for your advice. I will give octane boost a try though before lowering compression and/or changing to a hotter cam. I'd like to keep the engine as original as possible. Plus, I don't drive the car much so the added expense of octane boost shouldn't put a huge dent in the pocket book. If it doesn't work well I'll go the mechanical route. Thanks again.
C ckw@voyager.co.nz (Guest)
we have the same s**t fuel in New zealand , one answer if you can get your hands on it is to use av gas as it is 100 octane, can be mixed with the 94 unleaded to raise the oct and protect your valve seats .cheers cj
OTE]Originally posted by PanteraOrBust:
Thanks for your advice. I will give octane boost a try though before lowering compression and/or changing to a hotter cam. I'd like to keep the engine as original as possible. Plus, I don't drive the car much so the added expense of octane boost shouldn't put a huge dent in the pocket book. If it doesn't work well I'll go the mechanical route. Thanks again.[/QUOTE]
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