Curious as to where you are getting power for your msd box??  And is it getting full 12v to the MSD??  just a thought!

I've seen some Fords shear the roll pin that holds the gear to the distributor shaft.  It will drive you insane trying to figure it out.  I'll throw that out there because its as likely a scenario as any. 

Are you still running points?

I'm with Sal on this!   I'm still a little confused about mixing the MSD and a points type of Dizzy.  I would think you would go ane way or another.  I guess I need a bit of education on mixing the two!  I don't claim to know everything about anything!!

Wow, so many replies so quickly!  There's a reason why I think this is the best board out there!  

So on the topic of ignitions - I should have specified, I am running a high voltage coil with it.  The reason for points..  well, I was running a Pertronix, but had it go bad on me.  2nd one I had randomly quit - no short or high voltage conditon or anything I could have done to it either time.  Just quit.  I read many others have had same experiences, so I'm done.  I stayed with points since the MSD box just uses the breaking to ground as a electronic signal to fire, so while a bit old school it gives the signal it needs so I didn't put it high on the upgrade list.  

The dizzy isn't roated or sheared, I checked the timing while cranking with a light and to make sure also checked against the valves themselves with the covers pulled.   Although, I didn't check to make sure the crank is timed right to the valves.  Probably should do that, althoguh compression checked out so I havn't yet.  

MSD has its own dedicated heaveir gauge wire going stright to + for main power, so it's getting 12.  Keyed ignition to MSD has its own dedicated lighter gauge (matching gauge coming out of the box) to the terminal on the starter solenoid.

I'm going to order up one of those new-fangled dizzy's and set of plug wires, I'm not so sure that's the answer due to the binary nature of the fault and behaivor of the plugs on manual triggering, but it was on the short list of upgrades and I just need this problem to go away for more reasons than I can describe here, so if it has a chance of working it's worth it! 

I'll keep posted of what the results are, but if any other thoughts come up while the parts are in transit, I'm all ears!



 

Just saw the addtional post from SteveinNC - thanks for doing the back checking on my previous posts!  Wow, what a good member of the board.  

To answer those questions, what is reused and not and more of a history of the build:

First it was a 302 from a '71 Ford Torino.  I put in a more ild edlebrock cam, intake and carb.  Ran ok for a long time.  Then I got all uppity and got a set of Edelbrock heads with larger valves.  Machined down the heads and the intake to match to bump up compression, pulled the pistons to re-ring them and then ended up replacing them with higher compression ones while I was at it (~10.5:1 all in at this point, so not that much).  Put in the newer more agressive cam as well.  Got it started up..... and 30 seconds in the rough running engine made some metallic clanking for a few seconds, started running rough enough to shake the tools off the fender, and spitting white smoke.  I pulled the coil to cut the engine and just pushed it back into the garage to sit for a few months.  I just couldn't even look at it.  A few months later, I pulled the head hoping for, against all odds, a blown gasket.  Well, one of the pistons was rotated.  Dropped the pan and it looked like a grenade went off in there.  Turns out it looks like a connecting rod bolt broke and things went to hell from there.  So out comes block, in goes an early '90s one fresh from the machine shop with a brand new 331 stroker.  I checked everything while assembling andf it all checked out dimesnionally.  After some effort got that one started up, and that ran great.  Sat for two weeks, wouldn't start.  Suspected washed cylinders, so put oil in the plugs and cranked for a while.  No start.  Pulled the plugs, cleaned them off, manually fired them, then it ran fanstastic.  Started repeatedly and reliably.  Sat for a while, then no start and that's where I'm at. 


Summary:  Re-used parts that hark back to the pre-blown buildl: Distributor, MSD, plug wires, intake, carb
                 Re-used from the blown rebuild: Distributor (with lighter springs now), coil, MSD, plug wires, cam, carb, intake, heads (redid the valving on the bad cyl.) 

 

Last edited by Big Tag (12/28/2014 8:20 PM)

Replace the condenser, sounds to me like it is shorting out and killing the signal to the MSD box. 

Lil' Hoss wrote:

Replace the condenser, sounds to me like it is shorting out and killing the signal to the MSD box. 

 
I agree, if you have no known mechanical problems with the distributor replaced the condenser.

Well, new dizzy is on the way.  Should have it in the car on Wednesday, or at the end of the weekend.   I'll let you all know how it turns out!

How was TDC determined?  I've had issues like this where the timing marks on the balancer were not right.  A piston stop and a timign tape fixed that pertty easily. 

disconnect the hot wire to the coil.

tun a jumper wire from the battery to the coil . . you can leave it connected for 5 minutes with no problem.

check wires with lite

spray flammable brake cleaner or starting fluid into carb.

try to start . . if ot pops you have spark but your timing is off.

set timing to 10 dehrees btdc and spray again.

if it still pops your distributor is 180 degrees off.

if it does nothing try another coil.



.

I'll fab up a piston stop today to double check, but the irregularioty of the spark is really digging at me.  Even if timing was off, the plugs should still be firing all the time.  

It seems like the plugs are not firing under compression.  They test fire on the bench no issue, and I was getting it to hit but not catch when timing was 20+ deg ATDC.  So, assuming timing marks are correct which will be better verified, it is hitting because the plugs are firing, but not generating enough power to catch since it's so late.  Advancing the timing it transistions to no plugs firing at all.  Not even just not hitting - the timing light shows intermittent or no firing at all.  The only difference here is the ammount of compression when the plugs fire. 

Anyone ever hear of this?  Or have I just talked myself into a conclusion while grasping at straws here?  I have a new coil coming in today or tomorrow, I don't really want to bother trying with my low-voltage coil backup.  So either my current coil is weak (surprising, since as I mentioned it doesn't have many hours on it) and it fixes it, or nothing changes and I wind up with a proper high-voltage back-up coil for the roadside parts kit.
 

Again, are you sure the coil is connected properly?  Wired backwards you will still get a spark, but it will be very weak.  Maybe so weak it can't overcome positive environmental pressure.  Did you check resistance through the coil?