Hot Rods Sparkplug wire keeps popping off from distributor

Hi; on the 1927 Phaeton we have with a Big Block, lately, one of the sparkplug wires keeps coming off the distributor cap after driving for 15-20 minutes. Seems to be cylinder #3. It fits snuggly when put in yet if pops completely off. At first I thought maybe the wires were too tight and vibration was making it come off so I loosened the wires (they are tied together) but it happened anyway. The wires are not on a loom on that side, just lose but tied together. The connector part in the boot has some whitish scale on it which I tried sanding off. I added some of that dialectric connector stuff but nothing.

From what I read, it could be:
a) Vibration tugs off the cable. Odd that is the same one everytime.
b) Some kind of gas is kicking it off? From combustion?
c) Wires need to be replaced. Take these to be about 10 years old, probably under 10K miles in them
d) It's my fault for not knowing much about cars

 

Good wires and caps have "click" in feel them. Do the rest of them and not this one? Some times you need to pull the wire out of the protective boot and push in the cap, then put on the boot.

 

Thanks! Will check and try that tonight.

 

Push the wire through the rubber cap a little more. HRP

 

If all else fails put a small Zip Tie on that one.

 

How close are you to the firewall? Hard to tell from the picture, but is the boot for #3 wire rubbing on the firewall and working it's way off?

 

Yep, should be able to see if there s a smudge on the firewall. If so, maybe a smaller boot might be enough to give it clearance.

 

It's touching the firewall basically. So it may be the vibration. Last year I drove the car twice for over 2 hours and no issues, but I guess that'd how things start.

 

If it used to be OK, maybe something else has changed and allowed the engine to move, now causing the rub. Check to see if the motor mounts or the trans mount are still good. Maybe they cracked, or collapsed?

 

If you raised the tail shaft of the transmission up just 1/4" it would move the distributor away from the firewall enough so the boot would not rub. As the engine torques on the motor mounts it rubs the boot off of the distributor cap against the firewall.

 

Back in 1964 I had a 62 Chevyll with an Rochester fuel injection. Since the distributor was higher I could hit the firewall when you hit it hard from a start. It would break off one of the tabs holding the pointer on the rotor and turn it. The first time it was a bitch to find. The first time I didn't have a spare and I just moved it back. Lesson learned...Damn that car was fun...

 

I think B J R nailed it!!

 

From your pictures it looks like that plug wire is coming in over the top of the others. That probably means that it is not able to be pushed all the way down in tower which is causing arcing which could be the source of the corrosion. maybe a straight or 45* boot may solve the problem.
If all the mounts are good you could try to loosen them and push the body back to the rear limit of tolerances and push the engine to its forward limits.

 

OK, thanks for all the ideas. The boot in question is completely against the firewall, touching it. Looking at old photos, it seems that's just how it was setup. This is again a BBC 454 wedge onto a 32 frame of a 27 Ford, so barely fits. The front engine mounts are solid, no cracks and rubber in good shape. I cannot tell how the transmission and the rear of the engine are held up, again not a car guy. It seems they just 'sit' on cross members and there seems to be some rubber setup under the transmission. This car is channeled so the transmission goes into the cabin of the car, so you can hardly see it from underneath. Needless to say, I am not going to be messing with this because I can't even understand it.

The boot does go all the way down and snap hard, but I agree that it could be some engine jostling and rubbing against the firewall that makes it come off. I have put a trusty zip tie on the boot, since it's the easiest thing to try. The gap is non existent between boot and firewall that it was hard to even fit the zip tie. Will drive it this weekend and test it.

Was also thinking a solution would be to remove the distributor cap, put a dent into the firewall, and that would make a gap between boot and firewall. Not the classiest solution.

Thanks!

 

USE...wire separators..!
Light to heavy cross fire WILL occur with the wires tied together like they are.
This is a definite no-no... to all that use high tension plug wires. Unless you use those high dollar fiberglass wire sleeves.
Wow, I thought everyone knew this..!?

Mike

 

Put a tiny drop of dielectric grease on the firewall where the boot is, that should take friction out of the equation.
See what it does, how long it lasts.

 

Just put a 1/4" spacer under the transmission mount and you will have your clearance. Otherwise you may end up breaking the distributor cap. Except for denting the firewall, everything else is a bandaid approach to fixing the clearance problem.

 

A big hammer should fix it....

 

I've had that dialectric grease spit the boot right off the cap a few times. I like the grease, but it needs to be on the post (hei) and not the boot. Try cleaning the inside of the rubber boot and see what happens.

 

Dented (clearanced) firewall is as traditional as it gets.

 

Who ever built that car should have indented the firewall for the distributor though. You still might have to take the BFH to it for a little extra clearance. That might mean the "traditional" put a dent in it for clearance for now and figure to have the body man put a proper indent in it if and when it ever gets redone for fresh paint.

Going back and looking at the carb already running slightly down hill to the front I think that they already raised the back up for clearance in the past. raising the back up a quarter inch would be the easy way but that would throw the carb off more yet.

 

Went to a trig website. Assuming a 36" length between front and rear motor mounts and raising the rear mount 1/4" it said the angle change would be .001*. Thought it would be more. Easy check to see if that would be enough is just loosen the trans mount bolts, jack up the trans and slide whatever you have for 1/4" spacer in and lower jack. Observe clearance.

 

But the farther you get from the centerline of the engine mounts the more the distributor moves away from the firewall. The distributor cap is at least a foot above the centerline of the mounts.

 

That’s a problem.
Maybe not the only problem but that’s a problem. Dent that fire wall for some clearance...
Unless your engine angle is off and your drive line angles are for shit in an attempt to get transmission clearance on the floor pan.
Seen it before

 

I keep looking at the dist pic/wires....... Is it me, or is # 1 on the pass side of things instead of the drivers/left side? I can see the firing order on the cap, but if routed a lil goofy, it'll have interference issues..... Run- yes, but...... Just seeing if I'm SEEING sans my cheaters....... And hard to find you glasses when you don't have your glasses on to find them!

 

You're absolutely right. I was addressing Mr48chev's concern about the change in the angle of the carb mounting surface and suggesting a quickie way to see if a 1/4" spacer would do the job. Looking at the ratios involved it should gain about 1/8", probably a tad less. Also need to check clearances around trans/shift linkage, etc. and frame and body

 

If you jack up the transmission and the carb angle is too far off, you can get a wedge shaped carb spacer to level the carb back out. Or at least you used to be able to, I haven't looked for one in a long time.

 

As much as I hate to say it, a ball pien hammer is the easiest solution. You could also try going one tooth counter clockwise with the distributor. Might be worth a try...

 

I put a zip tie on the troublesome distributor wire and drove it for a couple hours and that fixed it for now. If it happens again, i think denting the firewall is a pretty easy fix.


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