Spark Plug Contacting Piston/Valve? 5.7

I just pulled and replaced all 8 plugs. 2 came out perfect (not rich or lean.) 5 looked rich (black.) 1 looked rich and the ground electrode was bent almost to the point of touching the center electrode. This was the #8 plug (back left from inside the boat.)

I ran the engine for 30 seconds between doing the right and left plugs. After I finished with the left plugs the engine wouldn't turn over. I pulled the new #8 plug out and the engine turned over. Assuming it was just flooded I replaced the plug and tried again. Again it wouldn't turn over, just a very quick ert sound before nothing.

Can the piston or a valve actually be hitting the plug? If so, I'm afraid to ask, what does this mean for me?

Am I just flooded and turning it over without the plug in didn't clear it?

The engine is the pre-vortec 350 (thunderbolt.) New plugs are NGK BR6FS. Old plugs are NGK UR5. From what I could find the UR5's are exactly the same size, just an older or automotive only plug.

Re: 5.7 Tune-up - Spark Plug with Bent Ground - Won't turn over with new plug

Re: 5.7 Tune-up - Spark Plug with Bent Ground - Won't turn over with new plug

I got it started by taking the plug part way out, starting, turning off, turn once, start, stop repeat until tight. It may be making some tick or clack, but my ear isn't trained. After starting and running successfully multiple times, it again won't turn over. I'm thinking something must be hitting, but it only makes the engine stick when it isn't already moving. So, if the engine is able to turn over it powers right though the contact.

Engine Serial: 0C540638

Do I need a rebuild? Please no.

Re: 5.7 Tune-up - Spark Plug with Bent Ground - Won't turn over with new plug

Re: 5.7 Tune-up - Spark Plug with Bent Ground - Won't turn over with new plug

Well, if you install the plug and the motor stops, when you remove the plug the motor turns ,that tells me the plug threads are too long.

Re: Spark Plug Contacting Piston/Valve? 5.7

Hows the starter?

Re: Spark Plug Contacting Piston/Valve? 5.7

This seems really odd.

When you take the plug out that's been in all the way, and the motor fails to turn over. What shape is the plug? Is the tip bent and touching the electrode? is the electrode broken? does it appear a very large, heavy, piece of metal knocked the sh*t out of it?(Equivelant to you taking a hammer to it and hiting it dead on).

A battle of a piston hitting the end of a spark plug. The piston will win by a long shot.

Is the battery fully charged? any chance the starter is binding?

Re: Spark Plug Contacting Piston/Valve? 5.7

Can the piston or a valve actually be hitting the plug?

Click to expand...

No. If something hit the plug, you would be able to see the damage on the plugs. Plus, the plugs you used are the same length.

Again it wouldn't turn over, just a very quick ert sound before nothing.

Click to expand...

Try this, remove the coil wire out of the distributor cap and ground it to the block and see if the engine will turn over with all new plugs in it.

Re: Spark Plug Contacting Piston/Valve? 5.7

Starter seems fine. From all I have read I have the correct plugs. I'm 99% sure I have the correct plugs, but I would be happy if the experts would tell me I am wrong.

I compared the new and old plugs, and if anything the new ones would be a slight bit shorter from where the seat contacts the block to the electrode tip.

The reason I was changing the plugs was due to really poor performance and running at low RPM under load. I thought this was being caused by a need for a tuneup and the battery being drained and causing low power to the ignition. On the last trip back to the dock it was missing badly and would only run up to about 1800 RPM (under load) and between 5-10 MPH.

What internal damage would allow the piston to slap/tap the spark plug? Is there any test I can do to confirm there is internal damage?

Re: Spark Plug Contacting Piston/Valve? 5.7

I will try grounding the coil. I'm afraid of those things, lol, always get the $*@# shocked out of me.

The new plugs show no visible sign of a major collision. The old one was bent to nearly touching the ground electrode to the center electrode.

Re: Spark Plug Contacting Piston/Valve? 5.7

With the engine off and the key off, just pull the center wire out of the distributor cap and put it up against a ground. Then hit the key and see if the engine turns over. you don't have to hold anything.

Re: Spark Plug Contacting Piston/Valve? 5.7

Grounding the coil didn't do anything. I stuck a bolt in the boot and placed it againts a bolt head going directly into the block.

As soon as I backed out the plug it turned right over. You can hear a distinct slap or twak sound while it is running. I think I'm screwed.

Re: Spark Plug Contacting Piston/Valve? 5.7

Do a compression test.