Don't know, though piston compression would change ohm resistance at the spark plug, confusing the Box....You may want to ask MSD.

What procedure did you follow to diagnose the original ignition box "failure"?

Is it possible the procedure did not take into account a failure somewhere else, like the timing chain?

That's what I'm thinking. I would be willing to bet the original box is good. I would recheck it.
As for the chain, if I don't use a Jesel belt, then it gets a Rollmaster. I have NEVER had a problem with one...and I have used a ton of them. Good luck with it.
Eddie

Thanks to all on the well wishes!

Yes, the first thing we did was to retest the original box. No spark. (we had tried it on the other engine before ordering the new one as well) The MSD procedure is pretty straightforward. With the unit unplugged from the engine, you tap a jumper between two leads 5-6 times and it will fire. It you have good power and ground, this jumper test will result in a spark at the coil if the unit is good.

Old unit, no spark, new unit, sparks like a s.o.b. (using the MSD jumper test)


And as most folks predicted, it took out some valves and a guide to boot. No piston damage luckily. The guy doing the valve job noticed the non-bent valves wouldn't create a good seal with just vacuum, so he reseated them. They did fine with spring pressure, but not so much with vacuum. And the spring pressure was a little inconsistent as well. So, I'm going to replace the chain on the other side and pull the heads and have those valves reworked as well.

And I figure with the exhaust manifolds out of the way, the installation of the swim platform will be a snap! Trying to find SOMETHING positive here! :lolhit:

Ya gotta make the best of it. If not, you'll just cry.

The MSD procedure is pretty straightforward. You have the wiring harness disconnected from the motor, so the only thing it sees is power and the leads to the coil.

http://www.msdignition.com/page.aspx?id=3206

Just went thru this issue and below is something you should look out for....

Your engine builder may not have checked to make sure the timing gears were lined up... Also, camshaft run-out.... Both of these factors will contribute to your chain wearing out prematurely and/or breaking the chain and/or timing gear.

The one that I just did had numerous teeth missing from the cam sprocket. It turns out the cam sprocket was .020 further out than the crank spocket, which thankfully I was able to catch before failure!! My machine shop had to machine the back of the camshaft sprocket so I could get perfect alignment.. Then the end-play was at 40 thou so I had to adjust the timing cover to get that within spec as well.

Thus an FYI of what to look for.

Thanks Panther, we'll double check that