1968 Engine Vibration

[franklinair]

A while back I wrote about an engine vibration at a specific RPM. I had installed a stock overhauled 302 engine, using the original Harmonic Balancer & Flexplate. Installed a new Pertronix unit in the distributor. Adjusted/tuned the engine: Idle RPM 700, 15" vacuum, Timing @ 10 degrees BTDC. Everything was looking good, except at 1100 RPM the engine developed a strong vibration. RPM's above & below that point, the engine was smooth. Installed a new Harmonic balancer= no help.
Disconnected all rotating units (water pump, alternator, P/S pump)=no help.
I was preparing to drop the transmission in order to replace the Flex Plate, when I remembered that the only NEW rotating part I had installed was the Pertronix ignition unit. Being inherently lazy, I thought I'd switch back to the points & condensor set up first. BINGO. Smooth as silk @ all RPM's. The only thing I can figure was at that specific 1100 RPM, the rotating device on the distributor shaft was not talking nice to the solid state unit, causing a breakdown for the ignition which caused the apparent vibration.
Thought I'd pass this on, in case anyone ever runs into a similar situation.

Neil

 

[robert campbell]

Neil,
NO WAY!!! Boy, is that alot easier fix! You would never convince me that this could happen. I need to wrap my feeble brain around this one!

Rob

 

[Ruppstang]

Wow! I would have never guessed that given how many Pertronix units I have used. That one is allways the killer when it is the new part. Thank goodness you had not pulled the transmission yet. Thanks for the tip. Marty

 

[our special]

Wow! I would have never guessed that given how many Pertronix units I have used. That one is allways the killer when it is the new part. Thank goodness you had not pulled the transmission yet. Thanks for the tip. Marty

Let me give you another tip. When installing your pertronix unit, make sure that you leave just enough of the wires inside of the distributor as needed.

If the rotor button comes in contact with the red wire while the engine is running, and the brass end of the rotor button removes the caseing from the wire, you're in for a rough ride.

Ask me how I know!! Dave

 

[aemoo28]

You got me thinking. My car's been spitting off #5 spark plug ever since we put in the pertronix. Twice while driving yesterday she spit it off.

Not like I run over pot holes, speed bumps, no way. I'll just be driving along and bam! Suddenly the idle is all bouncy and erratic so I pull over and squeeze the hose/tube back on. Smooth sailing until bam! Off again!

 

[franklinair]

Do you mean the spark plug wire is coming off the spark plug?

Neil

 

[aemoo28]

Black wire is coming off porcelain, maybe too shiny/slippery? Wasn't a problem before, but ya know this car...I've used tools to tighten this connection...

I'll post a picture next time I drive her. Interesting where the black wire usually ends up... what more can I say? It cracks me up cuz she'll start jumping around when it comes off, and we'll have "this conversation", me and this car. It begins with "Haven't you learned who's the boss here" and "You're not in California any more".

 

[robert campbell]

Amy,
It’s the number 5 spark plug wire. Pull it off and look in the end. Way up inside is a round contact that should snap around the shiny metal end of the spark plug you pulled it off. Take a pair of pliers and gently squeeze the outside of the rubber boot that goes onto the spark plug wire in the area of it that surrounds the contact. It is to big/loose to grab the contact on the spark plug. A good fitting spark plug wire when pushed on will “snap” onto the spark plug when connected. Not a loud snap or anything, but you will feel a snap on so to speak.

Or stop buy sometime for yet one more hug!!! Val and Rob think Amy is the bomb!!

Rob

 

[aemoo28]

Now that I've discovered the upside down Pony on the steering wheel, I'm a little scared (again) of this beast. Ok stand by... doing the spark plug thing...

 

[robert campbell]

Amy,
Yes, your steering wheel is not centered. Do not fuss with it until you rebuild your front end!! We will get your pony off its back....

Rob