AWAUDIO

FWIW, have you checked your dwell and timing advance? My 1972 240Z was doing something similar when I got it... dwell and timing were way off. Put in new points, set the dwell, set the timing (was off by 5 degrees) and backfire went away. Didn't touch the carbs till later (after buying Bruce's video BTW). Also, when my engine was rebuilt, valves were set "loose" to avoid burning, then they were adjusted to spec after 1500 miles or so. They were just clicking a little and after adjustment were nice and quiet. Still are. Hope this helps. Andy 1972 240Z

Everything you need to know about this is located on the Hybrid Z site (sorry if this is a no no) authored by John Cofey from BetaMotorsports. I'm replacing my springs and struts on my 1972 240Z with the following: Tokico 280Z springs front and rear (8 coils front/9 coils rear) and Tokico Illumina 5 way adjustable shocks. This morning I went to a shop which does racing suspensions to confirm the compression spring rates for both the front and rear. Using the info from John and the FSM, we confirmed the following: Right front spring @ 604 lbs- no coils need to be removed; Left front spring @ 562 lbs. needs 1/4 coil removed; Rear springs measured at 703 lbs (FSM says they should be 635 lbs@8.4") so we're looking at removing .5 of a coil. Before installing I will run the compression tests again to verify. So to give credit where it's due, I got all this from John and I'm just verifying his calculations. Please read his post as it contains much valuable information. Andy