crane HI-6S & boost

[mustangcobra93]

Is anyone running a crane HI-6S ignition box with any luck on a higher compression car or a supercharged application. I've having some troubles in the upper rpm range and have been told it might be the box..that I need a HI-6 instead of the S. Just wondering if anyone else had the same ordeal.

[fanglemeister]

edit: yes I am running a 6S with no problems on one of my cars, in fact it fixed a top end miss I was having, app is 9.5cr, n/a 330hp at the crank, redline 6k rpm.

What rpms are you calling "upper" rpms?

The 6 and 6S vary only slightly in their operation:
6S does multi-strike up to 2k rpm; above that, one long spark,
6 does multi-strike up to 3k rpm; above that, also one long spark.

The 6S will fire reliably and accurately up to 8000 rpm, the 6 fires correctly up to 12000 rpm. This is due to recharge time required, not the actual output capacity of each.

Both boxes use the same PS91 coil to create the fire across the gap, so ultimately, the current across the plug gaps is essentially the same out of both ignitions.

I would try the cheapest solutions first:

if running plug gaps over .040, back the gaps down to .035, maybe slightly less,

richen up the mixture on the top end; plugs misfire most easily when trying to spark across a lean a/f mixture,

check for leaking plug wires, use good wire loom separators,

check and clean all grounds - at the engine block, at the battery, everywhere in-between. Feel free to add an extra ground strap to each cylinder head.

borrow a replacement coil

borrow a replacement TFI module

sometimes when we own a hammer our problems all look like nails. Is it possible the engine is getting oil into the intake somewhere, or has bad ring seal or valve seals? An engine will knock or detonate if it consumes any significant amount of oil.

Hard to say more without any details, but that gives you something to think about anyway.