4.3 LX Melting spark plugs

[Dsilvers112]

I have a 96 Cobia with a 4.3LX just rebuilt motor. After i put the motor back in took it out 2 times and it ran fine. Took it out the last time and took off from the ramp and it was running good stopped and took back off and went to open it up to full throttle and it was like it was bogging down and didnt want to open up. Changed the fuel water seperator filter on the water and tried it again and still same problem. Got it back home pulled the plugs and 3 of the plugs electrodes were melted off. Any suggestions? Also had an angle valve job and the heads ported and polished for more HP during Rebuild.

 

[tractoman]

Re: 4.3 LX Melting spark plugs

Is it running super lean? Are the melted plugs white?

 

[Dsilvers112]

Re: 4.3 LX Melting spark plugs

im really not sure if its running lean, the plugs are kinda dark

 

[Dsilvers112]

Re: 4.3 LX Melting spark plugs

not sure if that helps. im really stumped on this.

 

[180shabah]

Re: 4.3 LX Melting spark plugs

Sounds like a little pre-ignition

Pre-ignition damage is caused by excessive high
temperatures. Center electrode melts first, followed
by ground electrode. Normally, insulators are white
but may be dirty if plug has been misfiring.

could be lean mixture, over advanced timing, vacuum leak, pour fuel quality, incorrect plug(heat range)...

 

[Dsilvers112]

Re: 4.3 LX Melting spark plugs

i talked to a couple of people and they mentioned an incorrect plug or too cheap of plugs because of the work i had done on the heads i had done. Also if this helps put another set of plugs in it and ran it on the muffs will run fine for a couple mins then starts skipping again. if i cut it off and let it sit a little bit come bck out and run it again and it will do samething again run fine for a min the start skipping

 

[boat127]

Re: 4.3 LX Melting spark plugs

its not your spark plugs its your fuel.

what type of fuel are you using? you should be using high octane.
go to a colder plug and reduce the gap 0.010 and you will see a difference

 

[boat127]

Re: 4.3 LX Melting spark plugs

going to a colder plug and reducing the gap by 0.010 will keep the fuel in the combustion chamber longer, keeping it cooler and making more power and increasing fuel ecomony

you should phone NGK and see what plug they recommend with your set up

 

[vegasphotoman]

Re: 4.3 LX Melting spark plugs

lean for sho!

 

[180shabah]

Re: 4.3 LX Melting spark plugs

you should be using high octane.

Or you could run the 87 octane the engine was designed for and the manufacturer recomends.....

 

[Dsilvers112]

Re: 4.3 LX Melting spark plugs

ive never had a prob with the carb on this boat before. does anyone have an idea on a good plug to use and should a good plug and 93 octane solve my problem

 

[Dsilvers112]

Re: 4.3 LX Melting spark plugs

also does anyone know what gap i should use. Thanks for all the help everybody

 

[JustJason]

Re: 4.3 LX Melting spark plugs

You should be using AC MR43's (or the LTS if you have vortech heads).

Check your fuel for water, pull a sample of it, dump out your fuel water sep filter.

Change all your fuel filters, you may have 1 in the carb and 1 in the fuel pump, you'll have to go looking.

Double check your total advance timing.

If the filters come out looking like junk, a carb rebuild may be in your future.

 

[John_S]

Re: 4.3 LX Melting spark plugs

Also had an angle valve job and the heads ported and polished for more HP during Rebuild.

Anything else changed from stock?

 

[Dsilvers112]

Re: 4.3 LX Melting spark plugs

nothing other changed from stock besides the heads having angle valve job and being ported and polished its got the 4bbl carb. i kinda thinkin its got somthing to do with the spark plugs not being able to keep up with the heads but im not sure. just got off from work goin home to work on it today and see what i can figure out...

 

[[OBC]Patch]

Re: 4.3 LX Melting spark plugs

Spounds like like your using to hot of a plug. A cold plug will pass heat to the block better, reducing the plug temp. Having to large a gap will also draw more voltage from the coil making for a hoter spark. maybe platinum plugs would help?

 

[John_S]

Re: 4.3 LX Melting spark plugs

Most people won't mess with porting vortecs. Maybe a little port matching, but thats about it, unless you are making other major changes.

Ok, if you haven't changed compression, cam, or anything else, stock plugs and 87-89 octane should be fine.

Go thru Jasons list.

Is the 4brl new? If so, probably tuned out the box to sbc not V6.

 

[Silvertip]

Re: 4.3 LX Melting spark plugs

Did you actually time this engine after assembly? Are you sure you have the right head gaskets? Is the engine running hot? Vacuum leak was mentioned earlier -- have you checked for an open port in the manifold or incorrect installation of the manifold. Burned electrodes says "hot", "too much timing advance", "lean" and/or detonation.

 

[Dsilvers112]

Re: 4.3 LX Melting spark plugs

Head gaskets are right ones, manifolds are fine and the motor never ran hot even when it started acting up.

 

[Bondo]

Re: 4.3 LX Melting spark plugs

Got it back home pulled the plugs and 3 of the plugs electrodes were melted off. Any suggestions?

Ayuh,... That's Detonation,... No question....
Who set to timing,..?? to what ?s,..??
It could be bad fuel, or a Lean carb as well...

Your head job has no effect on sparkplug choice,... The ACs Jason stated are the Right plugs....

Are these to original heads,..?? or a different Casting #,..??
How thick is the head gasket,..??
What casting # heads are they,..??