[smurfbus]

79 930 with MSD 6A and blaster coil. Rotor 1.2Kohm no_name with a bit longer contact area. IIRC plug wire resistance 1.4Kohm, BB headers, tial 46, 0.8bar.

This is hard to figure out. Im going to check the header bolts tomorrow but it sounds like it's not running 6 cyl. Plugging out different cylinders won't stop the backfire or even affect the idle much. Spark seems very strong at the plugs and it seems I have always had a lot of advance at idle. I tried different timing but no help. It does not backfire when cold.

This started when I figured my distributor rotor had melted (engine still ran fine) and at the same time I did an oil change and valve adjustment plus installed a new no_name 1.2 Kohm rotor. I first tried original 930 rotor but it did not idle under 2000rpm.

firing order 1 6 2 4 3 5, ccw distributor, closer to distributor vacuum port plugged. boost side connected.

I have removed all the helper devices (only wur left) so there should not be any vacuum leaks and a hand torch (butane?) did not affect idle when I pointed it at several hose connections and IC connections (tried starter help too).

I tried to adjust plug gap (and different plugs too) and I have tried 0.03-0.04 with no help.

Tried different idle COs and rpms, no help. AFR initially goes lean when it starts to act up and richening it won't help. This leads me to beleive its ignition related. Misfires show as lean.

I saw one plug wire at the distributor arch with the turbo oil line (to intake filter) fastener but removing the fastener did not help idle backfire but stopped arching.



1. Does bigger gap help idle?
2. Should I have same resistance at the plug wires as in the rotor?
3. Is a bad rotor different resistance?
4. is the plug wire trash if it arches agains metal?
5. Can I buy american muscle car wires 8.5mm or 7.5mm, should they be resistor ones? And how long?


Almost all the backfire cases on the forum archives are when on decel but my car does not backfire too bad on decel. Only the normal burble unless really hammering it and loooong decel afterwords.

I wan't my smoothness back. And again this started when I changed the melted rotor! I can't order the NAPAonline rotor so I have to use whatever I find. I have one spare 1 Kohm rotor I will try too (maybe even new distributor hat).

TIA