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I have a 1972 240z. It was rebuilt ( not by me) using an L 28 engine block and head. I noticed that the spark plug gapping is different for 240/260/280 with the 280 having the largest gap. Does anyone know what gap I would use for this engine as described? Thanks.
 

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It very much depends on the ignition you are using.

To go wider you need a stronger spark and electronic ignition. If you widen the gap and you are running points, you will burn your points out. The FSM says 0.8-0.9mm for a car on points.



If it helps: With a 1.5ohm flamethrower coil (claimed output of 40kV) and electronic ignition on a modified L28 I run 1.2mm gaps without issue.

The gap thing is a bit irrelevant really (if you have electronic ign) unless you are after ultimate performance and every half an HP matters. To be frank, on the road I don’t notice the difference between .2mm changes in the gap or a even a lower powered coil.

What really matters and would be good to know is how much compression you have and what cam duration, lift, LAS. Setting the ignition timing and AFR on a rolling road, under load at different conditions to get the optimum timing with headroom for knock / hot days / poor fuel quality etc is where it’s at.

Hope that rant helps!
 

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Discussion Starter #3
It very much depends on the ignition you are using.

To go wider you need a stronger spark and electronic ignition. If you widen the gap and you are running points, you will burn your points out. The FSM says 0.8-0.9mm for a car on points.



If it helps: With a 1.5ohm flamethrower coil (claimed output of 40kV) and electronic ignition on a modified L28 I run 1.2mm gaps without issue.

The gap thing is a bit irrelevant really (if you have electronic ign) unless you are after ultimate performance and every half an HP matters. To be frank, on the road I don’t notice the difference between .2mm changes in the gap or a even a lower powered coil.

What really matters and would be good to know is how much compression you have and what cam duration, lift, LAS. Setting the ignition timing and AFR on a rolling road, under load at different conditions to get the optimum timing with headroom for knock / hot days / poor fuel quality etc is where it’s at.

Hope that rant helps!
Thanks. I have electronic ignition with the flamethrower coil you mentioned.
 

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Thanks. I have electronic ignition with the flamethrower coil you mentioned.
You’re most welcome. Gap them over 1mm and see how you get on - the wider the gap the more stress it puts on your cap as the spark has to jump further. So don’t go over 1.2.
 
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