After a week long differential rebuild I took it out for a couple quick test drives. Second drive was about 15 miles and I stopped to grab a drink. Came out, car started and made it a couple blocks before it started to misfire. Pulled into another store parking lot. Opened the hood, fuel was in sight bowls, so not fuel problem. Then touched the brand new coil and it almost burnt me. Unbolted off the manifold and hung if off the wiper door actuator. Bought a bag of ice and cooled it down in about 10 minutes. Started up ran fine and drove back 10 or so miles home with no problem. I'm assuming when I stopped for a drink all the heat built up under the hood enough to overheat the coil. My engine runs nice and cool all the time. stays at 180 and goes close to 190 in the heat of the day in heavy traffic in town. Cools back to 180 within a minute of rolling again. Second time now I've broken down in a month. Same issue first time but didn't know it. That time involved a tow truck. Went down a crazy rabbit hole changing and replacing everything. So obviously not mounting the coil back on the intake. I'm running a MSD distributor with a Blaster 2 coil and MSD 8.5 wires. Where are you guys mounting your coils? I read that it can up to 3' but could have issue at higher RPM's depending on your setup. Looking for mounting place ideas.

Thanks

 

I mounted my coil on the firewall next to the wiper motor just to get it away from the engine heat...every little change helps.
Question: Did you replace the OEM 12V wire that exits the fuse block and attaches to the coil System. If you upgraded to a "modern" 12V coil you must put a new non-resistor wire from the fuse box to the coil +Terminal to prevent melting the coil windings.

Also...a coil will get too hot if the ignition key is left in the ON position while you are doing other things to the engine. It wold be better to install an OFF-ON switch under the dash easily reachable. Then you can turn off power to the coil while leaving the key in the ON position while working on other electrical problems.

There also is the problem of defective cols...I bought a Mallory 12V round coil which lasted 2 weeks. The Auot store manager told me Mallory had a batch of coils with defective windings.

Check your coil while it is cold for prper resistance readings....check the coil again after it is hot from the car being driven to see if bad windings might be the problem...it's worth the effort.

 

Maybe its hooked up wrong. I'm running an MSD distributor, MSD 6A ignition box and a blaster coil. Per the wiring chart I used, which was how it was when i got the car except i installed a new wiring harness but hooked it up the same way, it has the yellow wire and I can't quite tell but maybe white with red or black tracers? My camera and eyes are pretty bad. I do see on the chart that the white with tracer colors goes through a fusible link. So that needs to be replaced with a wire straight from the fuse block but leave the yellow? As you can see in the attached picture they are tied together just before feeding the MSD box. Which is the red wire that turns the box on and off. I usually unplug that when doing anything and i need to leave the key on so the ignition is not live. I do have three coils now and I'm pretty sure they are all good. Again been chasing a rabbit down a hole. Your suggestions are greatly appreciated!

 

Get rid of the Blaster coil. Their junk. In a previous thread of yours I mentioned the problems I had with MSD and Accel ignition coils. You won't have those problems with a Delco or Standard Motor Products coil.

 

Here's my post from 2017 regarding the MSD and Acell ignition coils:https://www.corvetteforum.com/forums...ion-coils.html

 

FYI, GM sold millions of cars and trucks between 1958 and 1974 and they all had intake manifold mounted coils and no problems with ignition coils overheating. IMHO, you don't need to reinvent the wheel. As I said earlier, MSD and Acell coils are junk.

 

Wow. This is nuts. I started reading through that post, just want to clarify the wires. The white wire with tracers that attaches with the yellow from the started that turns my MSD box on and off, do I need to eliminate the fusible link? Does my MSD 6A box need that or just a straight wire to the fuse box?

Ordering a new Delco U505 now!

I literally had the thoughts on the side of the road yesterday, I wonder what someone will give me for it! I was having a bad moment!

 

Received a new AC Delco U55 coil. I now have 4 coils. Ran it for about 10 miles and it did not cut out. So.... Maybe that fixed it? I probably need more run time to see for sure to see if it overheats still. I still had this annoying light throttle hesitation it's had for a year though. Found the jets in the carb were way to big. Forgot I installed those last year when I was at my wits end trying to run down the hesitation issue. Swapped those back to stock jets and it's the smoothest its run so far. Of course we have weather here today so not sure I can get it out for some real testing. I also moved my coil off the engine and removed the fusible link. Hoping to do some fine adjustments to the carb and timing today to get it dialed in. Fingers crossed.

Thanks for the suggestions and help so far. Hopefully I can move on to other projects on it that are a little easier. Not sure there are any.

 

So, you are reinventing the wheel.

 

No but until it stabilizes and doesn't leave me stranded with an overheated coil, then I will move it back to the intake and see how it goes. I am a firm believer it has been there and should be. I believe I had a multitude of issues that all came together and left me stranded. Was it a fuel pump issue? New fuel pump, nope. Was it a timing issue? Checked 100 times and changed springs way to much. fix it nope. Was it a over jetted carb? Not really sure but sure helped with light throttle stumble. Was it a overheated cheapo coil? I do know that left me stranded. Iced it down and got back home. Installed a New AC Delco U55 coil. Jury is out if that fixed it or not. I sure hope so. Drove it about another 10 miles today and so far so good. I never found any good information about the original coil wire from the ignition if it was ok to use or not being it has a fusible link. I have a complete MSD setup so that wire is just used to turn the unit on and off not powering the coil. Confused if the white with tracer wire is ok or not with the MSD. Do you have any knowledge you can share on that?
Thanks

 

Ever have a coil leak oil down onto the intake manifold? My TI system has a 207 (GM replacement coil) that has leaked oil. Coil still runs just fine but I replaced it with. New 207 coil just in case.

 

Retarded ignition timing can greatly increase under hood temperatures. What is yours set to?

 

I'm using Lars timing instructions and right now it's running at 16 initial and 32 total. I've moved that around within a couple of degrees but seems as though it works well there. I never did do the research to figure out what my compression ratio is. Assuming that comes into play along with spark plugs when it comes to heat under the hood. I have old Trick Flow heads, cylinders bored .060 over and compress is between 190 and 200 on all cylinders. During my run yesterday I did notice that it had a slight popping in the exhaust after letting off the throttle at higher speeds. I'm assuming that might possibly be too hot of a spark plug. I have at least six sets I've was playing around with last summing so thinking I should try maybe a cooler set. I'll probably take them out today and look at color on them.
With this setup and possibly having too much heat under the hood that could be killing coils, I'm not clear where the timing really needs to be. I have the large radiator, new aluminum and it seems to keep the internal temp where it should be according to my gauge. Has a 180 thermostat and fluctuates between 180-190 depending on running down a road or stopped in traffic. After running for a bit and turn it off i see it heats up to 200-205 for 15-20 minutes before falling back to 180 and lower.
sorry for all the information. Just hopping to get this thing dialed in.
Thanks for any and all input.

 

Not yet but I bet not far from that last weekend.

 

Put the stock plugs that are recommended for your engine. I would stop changing so many variables.

Re-read the post by Doorgunner and he I believe is accurate in his assessment of your problem. That is a common mistake in wiring. I always run my MSD equipment to a battery connection as I do my EFI system. I don't like adding circuits to a 59 year old wiring system so I have an aux Fuse block under my passengers dash panel. It is supplied with a #6 wire from the battery directly and powers my ignition, EFI and electric fuel pump.

There is NO WAY that your coil suffered from "Heat Soaking" in that amount of time. It is likely as mentioned to you before a bad coil. I have a 1968 C3 with a 427 built like an L88 engine. For the past twenty five years I have been running a complete MSD ignition on my Corvette. I have the mechanical tach drive MSD billet distributor, MSD 6AL, MSD Superconductor wires and a Holley Sniper E-Coil.

In the past ten years alone I have had several coils fail of different brands. The MSD Blaster 2's are not very robust. I now have a E-Coil made for the Holley Sniper EFI systems. It was twice the price but the guys at MSD all swear it will be worth it. I mounted this coil on my firewall as did our friend Doorgunner and it is farther from heat.

Vibration is a killer of the oil filled coils like the Blaster 2. The solution according to MSD was to spend more and buy a better grade ignition coil. Leaving the ignition on will heat up a coil but it also burns up your ignition points. You do not want power going to the ignition all the time as per MSD.

Another point about our Ignition coils. I have been using the Compression of the L88's (12.25-1) and I was taught to open up the plug gap for a high compression engine. Well, that is incorrect. By using a smaller gap the coils will also last longer as you are not stressing them out on top of a HOT engine block. My car suffers serious heat soaking after shutdown so I frequently open the hood to dump it out. I have never had a coil fail just because of the heat soaking , when they failed they did so gradually from a higher RPM slowly down lower RPM and were misfiring like crazy by the time they gave up.

Best regards,
Chris

 

Thanks a lot for your assessment. I replaced both wiring harnesses under the hood last year. Had splices and all kinds of crazy stuff going on so I did a reset. I have bare bones in this car. No radio, ac, EFI or electric fuel pump. The wire in question is just a one that gives the MSD 6A unit the signal to turn on when ignition is on. I have a connector on that wire that I unplug anytime my key is on for any amount of time when I'm messing with stuff. I have a switch I'm going to put in for that instead. The larger red power wire for the MSD box is connected on starter where the battery cable is connected. Is that ok to have it there? The wires going to the coil come straight from the MSD 6A. So, it doesn't use any wires from the cars harness. I have an old school billet MSD distributor as well. Cable driven tach. The MSD 6A unit is also brand new. I have two now and nothing was wrong apparently with the one from around 80's. The guy I got the car from showed me a receipt from some shop in the 80's where he had modifications done to the engine. Top end, intake, 750 Holley, MSD set up, headers.... I've had a hard time nailing down which are the correct spark plugs. MSD says a really wide gap of .060 or something. I been running anywhere between .035 -.045. Its at .035 right now and will probably leave it there.
Thanks again

 

On your hesitation I also have a 1970 LT-1 and I was getting a little stumble just off idle and found that if my idle mixture jets not correct, I adjusted to 1.5 turns out and it made a difference. I run Sunoco 110 Supreme and my timing is 15 degrees before TDC w/ vacuum disconnected and it runs strong

 

Your car looks great. If it wasn't a complete monsoon here this weekend, I'd be out putting some miles on mine to see if it's really fixed or not. I put the original size jets back in my Holley and it seems to have possibly taken care of the light throttle hesitation. It was very annoying.

 

I have another car with an MSD blaster coil - i had overheating issues that turned out to be due to high resistance in a couple wires - start with the basics and confirm voltage to the coil and resistance on all the plug wires and coil wire. Sometimes the problem is an easy fix.

 

I need to pull my plugs and I will check the wires when I do. They are new MSD 8.8 wires but that doesn't mean much.