Sparkplugs

« **on:** July 20, 2014, 10:53:39 AM »

Anyone ever have any problems with spark plugs? This last time I took my boat out after I redid the head gaskets and put new sparkplugs in, I was having trouble with my timing. I couldn't get it to run good. Kept missing a lot and come to find out I think one my spark plug wires was disconnected the whole time while I was messing with distributor. I didn't find that out tho till I gave it one more lap around the lake and that's when my sparkplug blew apart from the other bank side. So yesterday I took all plugs out to regap em and that's when I found out that all my sparkplugs had closed up on me and one of them was pretty shut bad. Can it be possible my piston is hitting them? Second picture is the one that blew off apart

« **Reply #1 on:** July 20, 2014, 03:31:49 PM »

More details on motor and parts being used. What spark plugs Are you using in what cylinder head? Compression ratio and piston style?

Sent from my iPhone using SoCalJetBoats mobile app

« **Reply #2 on:** July 20, 2014, 04:24:51 PM »

Not too sure to be honest. It's bbc 454. Oval port heads. I think I bought auto lites a6..

« **Reply #3 on:** July 20, 2014, 05:43:47 PM »

I don’t see any marks on your pistons and I would doubt that those small domes would really come near the plugs. Take a look at your valves for a witness mark where they might have hit the plugs. I forget which valve (intake or exhaust) will smack a TDC tool, but if you have the long reach plugs installed when you need the short, the valves could hit the plugs. I can’t tell which heads you have, but I run Autolite 26 plugs which have a short thread (.460). It appears that the Autolite A6 plugs have a long thread (.750) and will protrude into the combustion chamber. Even though both of these plugs have the same 14mm thread, the 26 has a tapered seal and the A6 has a gasket.

You might also check your valves for straightness and seal if they did hit. With the heads assembled, position the combustion chamber surface level, with plugs installed, and the valves closed. Then pour some rubbing alcohol into the chambers. Monitor the intake and exhaust ports for any leakage.

If you have the heads disassembled, roll the valve stem on a flat surface with your hand while watching the valve head for runout. You could also chuck them in a drill press to watch for runout.

Good luck,

Joe

« **Reply #4 on:** July 20, 2014, 05:47:42 PM »

Detonation killed those plugs..

JMHO.

GT

« **Reply #5 on:** July 20, 2014, 05:51:34 PM »

Quote from: Flusher on July 20, 2014, 05:43:47 PM

I can’t tell which heads you have, but I run Autolite 26 plugs which have a short thread (.460). It appears that the Autolite A6 plugs have a long thread (.750) and will protrude into the combustion chamber. Even though both of these plugs have the same 14mm thread, the 26 has a tapered seal and the A6 has a gasket.

Oops, I missed the first pictures

« **Reply #6 on:** July 20, 2014, 07:13:37 PM »

Quote from: Flusher on July 20, 2014, 05:43:47 PM

I don’t see any marks on your pistons and I would doubt that those small domes would really come near the plugs. Take a look at your valves for a witness mark where they might have hit the plugs. I forget which valve (intake or exhaust) will smack a TDC tool, but if you have the long reach plugs installed when you need the short, the valves could hit the plugs. I can’t tell which heads you have, but I run Autolite 26 plugs which have a short thread (.460). It appears that the Autolite A6 plugs have a long thread (.750) and will protrude into the combustion chamber. Even though both of these plugs have the same 14mm thread, the 26 has a tapered seal and the A6 has a gasket.

You might also check your valves for straightness and seal if they did hit. With the heads assembled, position the combustion chamber surface level, with plugs installed, and the valves closed. Then pour some rubbing alcohol into the chambers. Monitor the intake and exhaust ports for any leakage.

If you have the heads disassembled, roll the valve stem on a flat surface with your hand while watching the valve head for runout. You could also chuck them in a drill press to watch for runout.

Good luck,

Joe

My heads are still intact with motor. These pictures where before I assembled the motor back together. I was doing a head gasket changed and new valve seals along with pressure test.

Quote from: GT Jets on July 20, 2014, 05:47:42 PM

Detonation killed those plugs..

JMHO.

GT

Detonation? I was messing with the distributor a lot to try and get it to run good but either way I turned it, it still wouldn't sound/run right. Like I mentioned earlier, I messed with dizzy and got it as best as I could (still sounded not good) said fuck it and drove it like and that's when it blew a sparkplug porcelain out of its thread. Later the next day I noticed that on the other side of motor, one of sparkplug wires wasn't on. So I'm not sure if it was like that the whole time when I was messing with the timing.

« **Reply #7 on:** July 20, 2014, 07:15:10 PM »

But I'll check my sparkplugs when I get home and see which ones I actually have. But I've ran these b4 with no issues

« **Reply #8 on:** July 20, 2014, 07:31:13 PM »

Spark plug looks like it was dropped. The broken section of the porcelain is white in color.

« **Reply #9 on:** July 20, 2014, 07:37:15 PM »

They all looked like that pretty much when I took them out to re-gap them

« **Reply #10 on:** July 20, 2014, 10:01:42 PM »

First off, detonation will not bend the ground strap....the only thing that can alter the ground strap gap or position is a mechanical interferance with the piston dome or debris in the cylinder. It does not look like you have a large dome on the top of the piston, looks like a closed chamber dome in an open chamber head and looks like you are using the correct short reach tapered plug. As far as ignition timing, set base around 15-18 and total 35-38 deg. and that should be fine. With those pistons and an open chamber head I don't see your compression being more than 10.4:1 or there about. As we know boat engines run on the cool side and with that compression and timing set correctly and runing at least 91 octane, you should have no detonation issues. How far in the hole is the piston at TDC?, Block been decked a large ammount? also have the heads been milled a large amount?...has anything else been recently changed?...It's going to wind up being something stupid.

« **Reply #11 on:** July 20, 2014, 10:24:53 PM »

Quote from: 86caribbean on July 20, 2014, 10:01:42 PM

First off, detonation will not bend the ground strap....the only thing that can alter the ground strap gap or position is a mechanical interferance with the piston dome or debris in the cylinder. It does not look like you have a large dome on the top of the piston, looks like a closed chamber dome in an open chamber head and looks like you are using the correct short reach tapered plug. As far as ignition timing, set base around 15-18 and total 35-38 deg. and that should be fine. With those pistons and an open chamber head I don't see your compression being more than 10.4:1 or there about. As we know boat engines run on the cool side and with that compression and timing set correctly and runing at least 91 octane, you should have no detonation issues. How far in the hole is the piston at TDC?, Block been decked a large ammount? also have the heads been milled a large amount?...has anything else been recently changed?...It's going to wind up being something stupid.

WTF are you talking about?

I have seen aggressive tunes with too much timing cause detonation literally dozens of times... Detonation will ABSOLUTELY cause physical damage to the spark plug extremely similar to what the OP has pictured.

He already stated in as many words that the timing was NOT adjusted right and was all over the place and he drove it while running like crap.

Betting a set of new plugs gapped to .035" and a max timing of 36 degrees makes it purr like a mountain lion. JMHO

Would be willing to also bet the timing was running 40+ degrees advanced when it ran the best because of the dead hole due to the disconnected plug wire.

GT

« **Reply #12 on:** July 20, 2014, 10:32:22 PM »

Quote from: GT Jets on July 20, 2014, 10:24:53 PM

WTF are you talking about?

I have seen aggressive tunes with too much timing cause detonation literally dozens of times... Detonation will ABSOLUTELY cause physical damage to the spark plug extremely similar to what the OP has pictured.

He already stated in as many words that the timing was NOT adjusted right and was all over the place and he drove it while running like crap.

Betting a set of new plugs gapped to .035" and a max timing of 36 degrees makes it purr like a mountain lion. JMHO

Would be willing to also bet the timing was running 40+ degrees advanced when it ran the best because of the dead hole due to the disconnected plug wire.

GT

Hopefully your right haha.. what's the sparkplug you guys recommend? The short ones?

« **Reply #13 on:** July 20, 2014, 10:34:15 PM »

The picture of the plug you showed is NOT an A6 Autolite.... $:-\$

GT

« **Reply #14 on:** July 20, 2014, 10:54:48 PM »

Quote from: dat1dsm on July 20, 2014, 10:32:22 PM

Hopefully your right haha.. what's the sparkplug you guys recommend? The short ones?

Start with Autolite 25 plugs.

« **Reply #15 on:** July 20, 2014, 11:00:26 PM »

Quote from: Flusher on July 20, 2014, 10:54:48 PM

Start with Autolite 25 plugs.

If you indeed do have tapered seat heads, I concur...

GT

« **Reply #16 on:** July 20, 2014, 11:02:13 PM »

Whoops. I have ap26

« **Reply #17 on:** July 20, 2014, 11:06:04 PM »

« **Reply #18 on:** July 20, 2014, 11:18:03 PM »

I would think you would be OK running that plug. What ignition system are you running?

GT

« **Reply #19 on:** July 20, 2014, 11:39:04 PM »

Quote from: GT Jets on July 20, 2014, 11:18:03 PM

I would think you would be OK running that plug. What ignition system are you running?

GT

Mallory distributor and mallory coil. No resistor box. I ran it direct cus I was having problems with it last time out. Before I replaced head gaskets, other than milky oil and shot out jet pump, motor responded real quick and sounded good

« **Reply #20 on:** July 20, 2014, 11:43:46 PM »

Quote from: dat1dsm on July 20, 2014, 11:39:04 PM

Mallory distributor and mallory coil. No resistor box. I ran it direct cus I was having problems with it last time out. Before I replaced head gaskets, other than milky oil and shot out jet pump, motor responded real quick and sounded good

Ok, what do you mean "no resistor box" I hope this means you are running an internally resisted coil?

The ballast resistor is there to keep the coil from catching fire if the key is left on.... Not trying to scare, but make sure that is correct. If not an internally resisted coil, it needs to have the resistor...

Gap those new plugs at .035" and run it...

« **Reply #21 on:** July 20, 2014, 11:47:30 PM »

Quote from: GT Jets on July 20, 2014, 11:43:46 PM

Ok, what do you mean "no resistor box" I hope this means you are running an internally resisted coil?

The ballast resistor is there to keep the coil from catching fire if the key is left on.... Not trying to scare, but make sure that is correct. If not an internally resisted coil, it needs to have the resistor...

Gap those new plugs at .035" and run it...

I ment a ballast resistor. I was having problems with it. so I ran it direct.

« **Reply #22 on:** July 20, 2014, 11:58:21 PM »

Quote from: dat1dsm on July 20, 2014, 11:47:30 PM

I ment a ballast resistor. I was having problems with it. so I ran it direct.

Buy another one...... $:-\$

Read the warning on the MSD cut sheet...

You may have an internally resisted coil, but it will say it right on the body of the coil somewhere...

http://www.jegs.com/InstallationInstructions/100/121/121-8202.pdf

GT

« **Reply #23 on:** July 21, 2014, 12:00:59 AM »

Ok. Ima get some new plugs and gap em .35 and set my idle at about 15deg. And see how she runs. Pull plugs out and see how they look? What plugs again? Ap26 or 25

« **Reply #24 on:** July 21, 2014, 12:06:31 AM »

Quote from: dat1dsm on July 21, 2014, 12:00:59 AM

Ok. Ima get some new plugs and gap em .35 and set my idle at about 15deg. And see how she runs. Pull plugs out and see how they look? What plugs again? Ap26 or 25

Idle timing is pretty much irrelevant if you do not know how much timing is built into the distributor... Find a way to get the timing at >2,500 RPM to approx 36BTDC.

As for the plugs, either will work, they are 1 heat range away from each other. I run MR43T AC Delco, good enough for the factory, good enough for me... The "M" denotes a marine plug, just nickle plated is all..

GT

dat1dsm

bbfsouthwind

dat1dsm

Flusher

GT Jets

Flusher

dat1dsm

dat1dsm

Hoofy

dat1dsm

86caribbean

GT Jets

dat1dsm

GT Jets

Flusher

GT Jets

dat1dsm

dat1dsm

GT Jets

dat1dsm

GT Jets

dat1dsm

GT Jets

dat1dsm

GT Jets