'67 Ignition Timing

[Dave Stafford]

What would be the acceptable timing today for 400HP motor with 92-93 octane available? Suggestions on gas additives also will be apreciated.

[Rob Brainard]

Re: '67 Ignition Timing

Dave, That is a good question!! Before anyone can answer that it is important to know how you got 400HP. By that I mean, what is the compression of your motor, cam used, aluminum heads, etc. Normally, I would start with 10 degrees advance and try it. If there is no ping go up about 2 degrees, if there is pinging go down 2 degrees.

[Joe L.]

Re: '67 Ignition Timing

Dave-----

Your 1967 L-68 engine uses 10.25:1 compression ratio and the GM #3883986 camshaft IF IT IS OF ORIGINAL, UNMODIFIED CONFIGURATION. My suggestion would be to start at the factory-recommended initial timing spec for this engine. If you experience no pre-ignition with this setting, that's where you probably need to be. If you experience pre-ignition at this setting, back off the setting 2 degrees at a time, and stop when you get to minimal pre-ignition. But, don't get the engine into a retard setting. I doubt that you'll need to.

[Dave Stafford]

Re: '67 Ignition Timing

Joe, do the tick marks represent 2 degrees each mark? I put a light on it this weekend and its now set at 8 degrees with 4 (I think) as original spec.

[Dave Stafford]

Re: '67 Ignition Timing

Here's what I know of this engine: '67 427 w/ tri-power induction L-36 converted to L-68, 10.25 compression ratio, standard 390 HP cam , standard heads (10.25-1), non-HEI ignition. I'm not hearing a "ping', but am having engine stall starting off; maybe carburator (s)?

[Joe L.]

Re: '67 Ignition Timing

Dave----

Yes, the "tick" marks do represent 2 degrees each. 4 degrees BTDC(advanced) sounds about right for a factory-recommended setting, but I'll confirm this later. If you're running 8 degrees without any significant pre-ignition, that should cause you no problems and might give you better fuel economy and power. I'm a little surprised, though, that you can run this much without pre-ignition. But, so much the better. Personally, though, I wouldn't advance the timing any more even if the engine will tolerate it.

[Joe L.]

Re: '67 Ignition Timing

Dave----

I did confirm that 4 degrees BTDC is the correct, factory-recommended initial timing setting for your 1967 L-68 engine.

[Jeff C.]

Re: '67 Ignition Timing

The factory timing for the L-36 (390 HP) and L-68 (400 HP) are the same; degree's BTDC. The engines are identical except for carb's, 1 4B vs 3 2B. My L-36 is rebuilt to factory specs and runs best with no pinging at 4 degree's on 92 nolead gas.

[Jeff C.]

Re: '67 Ignition Timing

Dave,

Sorry the 4 got dropped.

[Jerry Clark]

Re: '67 Ignition Timing

Hi Dave:

My 69 , 400 hp built to 475 with a camshaft change, some carburetor rework and port and polish runs well at 8 BTDC with no additives whatever.

Best of luck.

jerry

[motorman]

Re: '67 Ignition Timing

most chevy engines run best at 34-38 degrees total timing. the best bet is to mark of the damper with a pair of dividers for 34-38 degrees and set the timing at full advance with the vacuum disconnected. this means running the rpm up to about 4000 rpm and line up the scribed line with the 0 mark on the timming tab on the cam gear cover. then let the engine return to idle. if the static timing is way off at at idle that says there is someing wrong with your distributor.i have all the specs for marking off the damper for all diameters and if any one wants the numbers e mail me.