MGB Crane Cams XR700 Fireball - wet conditions?

[RickB]

I got my 1980 MGB with this Crane Cams XR700 Fireball electronic ignition already installed.
Coincidentally the head has the infamous crack back around cylinder #3 just above the distributor.
I have a new head and dual carbs and early exhaust and plan to change it all out next month, just running as is for now.

When the engine is warm and it leaks back at the cracked area it's coolant that escapes, when hot this can take the form of steam.
In direct line on the inside fender is where the Crane XR700 is mounted.

Yesterday I could not get the car to start, it's like it just wasn't getting enough spark.
I have a spark tool I connect inline with the spark plug wire and it was showing a very weak spark.
The car simply wouldn't start, the starter (newly replaced) was working great, the battery was fully charged and the carburetor was getting gas.

It was very wet outside, it was in fact raining on me while doing the troubleshooting.
Eventually I gave up and went inside to get dry.

This beautiful morning the air had cleared, there was a light breeze, and the crescent moon was up above shining brightly.
Everything had dried out.
I thought I'd go ahead and give it a try, I said to my wife: I'm going to see if by some miracle it just starts this morning."
I put the key in and turned and the engine immediately came to life.

Thanks for sticking with the story so far, I know I've posted a few times already about these problems and I think I may be closing in on the actual cause.

If the XR700 gets wet and stays damp maybe it doesn't work until it drys out?
I know this is true with most electronics.
It can't dry out until the relative humidity allows that to happen.

The last time this occurred badly was also a very rainy night and after the engine had heated to the point that the crack had let out coolant and steam.
Eventually I got it to run and made it home, but it wasn't fun.

IF - and that's a big "if" because this has been a lot of guesswork so far, but IF this is the problem then replacing the head is the obvious solution.
For the short term, until I get a week off in March to do the work, I plan to figure out some way to protect the ignition components from the wet.
Hopefully I'll see a big difference (like it will start up and run all the time) and that will confirm I have the right solution.
There's also no grommet where the wires enter the distributor, I need to make sure that's sealed so coolant vapor doesn't enter there.

 

[Joe Reed]

I would think the Crane unit would be sealed enough to not be the problem. I think the distributor is the more likely suspect. Maybe a crack in the cap or in a vacuum advance line?

A half century ago I had a Dodge slant 6 that started running like crap any time the weather was damp. I bought some clear plastic waterproofing spray and hosed down the distributor with it to no avail. Finally, even though it looked brand new, I removed the vacuum advance hose that ran across the valve cover from the carb to the distributor. It was cracked underneath right where it made the bend to go down to the distributor. A new hose and the car never sputtered again.

Since you're going to change the head soon anyway, why not use some JB Weld to seal the crack and see if that stops the leak....at least temporarily.

 

[RickB]

Thanks Joe,
I will look at that, there's also a hole where the wires enter the distributor that has no grommet and it's directly under the leaking area.
I'll get a new cap and see about sealing up the hole and also replace the vacuum line and see if any of that helps.
Haven't had much luck with JB welding things in the past so I think I'll try the other things first.

 

[Sarastro]

I had one of the Crane XR700 units on my Bugeye Sprite for several years. It is completely sealed, so some water on it shouldn't cause trouble. It's possible for moisture on the low-voltage connections to be a problem, but still unlikely. The most likely culprit is water on the high-voltage lines, cap, coil, or something like that. A crack in the cap, for example, can cause no trouble when everything is dry but cause a lot of trouble when it's wet. If you are emitting steam all the time, it seems impossible to avoid some wetting of the high-voltage bits.

I guess you could examine the cap for cracks, maybe try a new one. but the ultimate solution is probably to prevent things from getting wet, which means fix the head or at least create some kind of deflector for the leak.

 

[RickB]

I'm taking a week vacation next month to work on the car.
I'll get the head replaced, convert to 74 exhaust and intake and do a couple more things.
I think you're right about the cap & rotor side of things, that area is getting soaked.

 

[Joe Reed]

If the distributor is getting soaked it doesn't really matter if the cap is cracked or not - it's gonna cause problems...

 

[RickB]

So here's what I've done since we last visited this subject.

In an attempt to isolate the source of the leak I fashioned a barrier out of cardboard that fit around the top of the vacuum advance nipple to block leakage from around the heater control valve and the distributor.
I observed the cardboard getting wet on a daily basis.
I received from Mr. Schlemmer at Advanced Distributors a new cap & rotor which I installed one morning when the car would not start at all after a night of hard rain, after installing the new cap & rotor the engine came right to life.
On the day I ordered the new cap & rotor I also ordered a new heater control valve and heater hose figuring they hadn't been replaced in a long time and may be the source of the leak.
Last Friday after work I replaced the heater control valve and hose and put a new cardboard block in place to see if there would be more leaking after replacing the valve.
So far the car has not had difficulty starting even on very wet days and I have not noticed any new leaking of coolant.
I still need to replace that head but at least for the moment things are better, the main incentive of my planned week of working on the MG has shifted now to installing the head, dual carbs and older style exhaust for performance and personal enjoyment of the car.

 

[Joe Reed]

Glad you got it sorted out!

When I installed my stock early exhaust manifold (to replace a broken, cheap tube header) the one I got was missing some of the studs...and the holes were too buggered to simply install new studs. That left two options: drill/tap to a larger size, or use bolts. I chose the latter.

I dropped allen head cap screws in from the top...seated in a puddle of JB Weld. The JB Weld held them in place during installation, and I didn't care if it didn't withstand the heat later on since they weren't going anywhere once they were torqued.