I started a thread this morning regarding my car starting to clatter and running rough. This evening I put it up on jack stands and popped off the valve covers, everything looks fine. Started the engine and removed the plug wires until I found one which made no difference when I pulled it. I took out the plug and it appears the metal tab was pushed down on the electrode. What the heck is causing this? Is the piston smacking it? I gapped the plug and it runs fine. Any idea of the cause?

valve dropped...clattering isnt good at all.

is wrong with these engines...its like five in three months??

b

let's see...the cars are 30 YEARS OLD and being bought and abused by people that think they are like Hondas?!?!?!?

Mueller is having a BBQ,.... roasted britt for dinner LOL

Maybe you just got lucky and ate a washer or something. And it passed out the exhaust. (happened to me a couple "O" times on V8s)

If you didn't eat a seat. You might have eaten something that was loose in the carbs or injection system. (check for loose induction stuff)

If the engine now runs fine. And doesn't make any nefarious noises.......

You are a very, very lucky man...... Indeed......

Twystd1

Over heating is the number one cause of dropped seats. I bet the cyl. fins and shrouding is just full of crap.

Do a valve adjustment before you run it again...one will be way out of whack....

Mike you havent met me, seen me or probably havent actually read into anything about me.

I drive a 1974 Porsche 914, with a 1.7L engine. I cruise, not race (why bother) and couldnt be happier.

If I wanted a Hondah, I woudl get one...

b

that was not an attack on you, I'm just stating my opinion, which is based on some facts, the cars are 30 years old, motor failures are going to happen more and more.....there is nothing "wrong" with the motors except for age and use and some abuse....expect to see more engine failures both with the /4's and the /6's as time goes on....

Initially I thought it was a general statement...

we're cool.

I see this now, I guess alot of people just run the crap out of these engines 20+ years ago and now the OE engines are starting to fail?

Global Warming maybe?

b

Thanks for the input, I'll do an adjustment and see what happens. Is there anyway to determine if the valve seat is the culprit without removing the heads?

you might be able to remove a valve cover and compare the height of the valves as you turn the motor over....

If one valve stem (valve adustment) is sitting way in (seat is out sitting crooked in it's bore) or is sitting way out (sunk into its bore) you have seat problems. Sometimes this doesn't work as the seat can be sitting in its bore but still be loose.
But the spark plug is a classic sign of seat problems.

There is prolly some ways:

1.) If the suspect valve is very loose, the seat could have cocked and is holding the valve open. This would case a misfire on that cylinder (won't build compression).

2.) If one valve is very tight, the seat is pulling into the head (under spring pressure). If it can be adjusted to tolerance, it should tighten up rather rapidly. Worst case scenerio is that you can't get any adjustment at all.

3.) I can't see with the configuration of the valves and combustion chamber how a valve could hit the spark plug. I could see the seat coming out and possibly hitting it, but then it would misfire on that cylinder.

4.) And what Muller said

Edit*** Are the electrodes bridged? 0.28 isn't all that much and a piece of carbon coming off the combustion chamber can bridge the electrode / possibly bend the tang.

Personally, I blame the insurgency..................bastards........

I think I might pull the intake runner off on that side, might be able to get a peek at what's going on in the cylinder.

Thanks again.

It's Al Gore's fault

Nope, it's Britt's fault.
I GOT PROOF.............

Could be a little piece of chop stick? Just a thought. Not necessarily a good one but a thought none the less.
Elliot (semi retired)

Britt, I'm with ya bud. I am a country cruiser myself. I'd love to vintage race, but who has the cash!!

I don't know how you guys do it.....

A compression test will tell you if you have a dropped seat. I had one that popped in and out of the head (while I was driving!!) so a check of the valve clearances didn't really tell me anything. A compression test showed total leak-down (0 PSI!) on that one cylinder. The starter-cranking pattern was also very uneven; it sounded like "RR-RR-RR-..-RR-RR-RR-.."

Try a compression test. If you get one cylinder reading very low, you'll know you need to pull the heads.

--DD

Well, not so lucky after all. I adjusted the valves and started it in the garage, ran real smooth. Took it for a gentle spin, after a few minutes the clatter returned along with the missing. Guess I'll pop the heads off this weekend.

LES,

I was hoping ya just got lucky...........

Let us know what ya find...

Giterdone..!!!

Cheers,
Twystd1

Here, let me say this one more time: COMPRESSION CHECK. That should tell you if you have a dropping valve seat.

Re-check the valve adjustment; at least inspect the valve train. Who knows, it could just be a valve adjusting lug that you didn't tighten correctly...

--DD

Will do, thanks Dave.

Or you could go to Harbor Freight Tools for a leakdown checker for $60. It should work at least once before taking a crap.

I was going to check out Northern tools, got one a few miles from home. Are they any good?