Thread: SBC in 72 Nova problem ??

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Hello gents new user here. I bought a 72 nova show car that has a built 406 in it. It's been running great for 6 months and now I'm having problems with the engine and can't seem to find the problem. It runs great until it gets up to temp (180*) and then it dies, like someone has turned the key off. When I try to restart it it fires once in awhile but will not start or stay running.
I have the following ignition : MSD 6AL series box, MSD Blaster Coil, with a Mallory Dist. No points or vacuum advance.

The Fuel System : Elec. fuel pump and Elderbrock 650 carb.

I run the car up to temp and when it fails I check the spark at the plugs and it looks to be fine. The fuel pressure gauge at the carb shows a steady 6lbs of pressure. I take the breather off looked down into the carb and cracked the throttle and I saw fuel spray in. I moved the wiring around from the dist and 6al box while it was still running trying to find a bad connection or short, but no luck. I'm at a lost on what to look for now ?? Any Help or suggestions would be great.

Coil could be breaking down?? Do you have spark when it won't start??

Just my .02 but if the fuel is good then it is in the ignition. The miss match of parts MSD and Mallory would be where I would be looking. Mallory was big name in the 60s but MSD has passed them long ago. If heat related the distributor is the only part of a 3 part system that would most likely be effected.

I guess the question is how long does it take before it fires again ? How to test might be to run it up to temp, when it dies, pull the cap or put an ice bag on it, try to cool the distributor. Then go right back and see if it will run. Could do the ice bag thing on the coil also. I assume that the trigger in the distributor is replaceable, MSD is and that is all that's really in there.

It is going to be a bit of a crap shoot unless you are able to get a fix on the failing part. If you want to do back box troubleshooting, replace the coil or trigger take your pick, 50/50 chance of nailing it the first time. I seriously doubt it will be the ignition box, MSD web site has a step by step trouble shooting guide you could use as a reference btw.

Thanks for the fast reply. I changed the coil and the problem is still there. It's tough to say if spark is there when it fails at 180* cause sometimes it starts right back up after it dies and then dies again. Real Intermitten problem. I will check out the MSD troubleshooting web page before I change the dist. trigger.

Trying pulling a few plugs when it dies, see if they are wet with fuel. Choke is staying open right? I am interested in how long you must wait for the thing to run again. At that point make a note of the temp then try to repeat that same event. Run to 180 car quits, cools to whatever and runs again to 180 and quits. Odd for sure, with machines there are always new things to learn. MSD will also show how to check the trigger btw, their product of course but the operation should be similar.

Last time I had a similar problem, it was the pickup in the distributor

Do you have electric cooling fans? The fan may be worn and drawing more current than normal when the switch turns on (180°) dragging down the ignition.

Ok, here we go. Check this out. I was checking the wiring out on the dist that goes to the msd box and i had to move a clamp in order to look at it close. So I stuck my screw driver to move the wires over I touched the wires and the base of the dist and it killed the engine. I tried it on purpose with a screw driver again and it kill the motor every time. Don't know yet if its moving the wires in the base of the dist. or there is a bare spot somewhere. So I was thinking, I'm just going to pull the Dist out so I could get a good look at what is going on. Then I was shocked and confused what I saw. I brought what I believe to be the compression stroke on #1 to top dead center and made sure the timing mark was right. Well the rotor was pointing to number 2 spark plug but had #1 plug wire on it. So do people do this to make there plug wires lay or look better ? I'm thinking now, is this really the compression stroke. Will I have to pull a valve cover to make sure ? This thing has a roller cam in it and the rockers are all tied together. Will I be able to tell what position the valves are in when a pull the cover ? Or is there a better way to do this ? I'm old school where the rotor pointed to the #1 spark plug position, the piston is up, and the timing marks line up.

A lot of people move the wires on the cap to keep from having to re-stab the dist when they are one or two teeth off and that appears to be what you found. No big deal, #1 can be anyplace you want it.

FYI, we changed out the Mallory Unilite electronic Dist to a MSD dist and our problems went away.

Glad to hear it toasted Mallory, better to have system componentsmatched, happy motoring.