289 Timing...What determines the Differences?

[Bill Wells]

I have a modified K code in my 65 Stang, bored .040 over (now 294.3 cid) , balanced, solid lifters, aluminum roller rockers, pertronix electronic ignition (in distributor only), stock coil, high rise Shelby intake manifold (dual plane) , 715 Holley carb w/stock jets and some other minor engine tweaks. mated to a tremec 5 speed and ford 9" rear end, , 3.89 gear ratio.

my plugs are gapped at .035 and are just fine, and have been fine as well with previous plugs (I have been using Autolite 45's). I use 93 octane fuel, no problems.

the 65 Mustang owners manual says for a 289 to gap plugs between .032 and .036 (my copy does not say specifically if the K code is different as it lumps the 289s together) . the 66 shelby gt 350 owners manual says to use BF32 plugs and gap them between .028 and .032. the NAPA guide book today says gap them at .035.

timing, I can't recall what it was set at , my notes are missing from my file. I do plan on taking it to a dyno shop though to maximize the settings once I get it going this spring (real soon) as have never felt it was optimized by my seat of pants adjusting. chassis dyno shops here typically get $125 for first hour and $100 thereafter for 'fine tuning' of air/fuel mixture for carb tuning/jet changes and timing adjustments plus the printouts. I don't really care what the true rear wheel hp is (there is so much variation it seems between one chassis dyno and another) but am real interested in the DIRECTIONAL changes due to tweaking the carb and timing.

the 66 GT 350 shelby owners manual says initial timing should be 12 degrees BTDC . my 65 mustang owners manual says initial timing at 8 degrees, but again, my book does not indicate K code specifics, just generic '289's, so perhaps a specific Ford K code reference would recommend different plug gaps and timing. I follow the 66 GT 350 book however, except for the plugs gapped at .035 and since they have worked fine at that gappig thru several plug changes, I will leave it there.

good luck. bill wells.