351 Burned plug tip.

[elpaso]

1980 Ford 351 Windsor - engine idles fair, <br />big miss at 1500 rpm or higher.<br /><br />Pulled spark plugs, 7 looked normal - on #2 <br />the plug tip was almost melded.<br />Ran a compression test - 7 clyinders have 145.<br />#2 has 90.<br />Put in new plugs -ran 15 minutes - checked #2<br />tip was almost burned off.<br />What is going on.

 

[scamper]

Re: 351 Burned plug tip.

Could it be, with 90# in 2 the gas is burning more rather than exploding properly? Or maybe #2 is not getting the right mixture, valve or something?

 

[akriverrat]

Re: 351 Burned plug tip.

http://marinemechanic.com/site/page164.html

 

[llerrad]

Re: 351 Burned plug tip.

With low comp. in cyl. and burnt plug could be burnt valve.

 

[Jdeagro]

Re: 351 Burned plug tip.

Sounds like a burnt Exhaust valve. Before pulling the heads off, get some gumout or other liquid combustion chamber / valve / fuel injector cleaner that is normally added to the gas. Run the engine up to temp, and then drip the liquid cleaner into the carb slowly. The engine will smoke and want to stall out, don't drip in more than it will take to keep the motor running. You will need to continuosly ork the throttle. When you are done, most or all of the carbon in the chambers and arround the valves will have been cleaned out. If carbon was built up arround the valve, keeping it open, it should now be cleared and seated properly.<br /><br />If this cleaning does not work, pull the heads and get a valve job. Also make sure the engoine is not running too hot or too lean after the valve job as this problem can return.

 

[loadnet]

Re: 351 Burned plug tip.

I agree with nautiJOHN,<br /><br />Once you conclude it's a bad exhaust or intake valve, and get it all fixed up, you'll need to do further testing to make sure the problem doesn't duplicate itself.<br /><br />Have you done any vacuum tests?<br />Sounds like you have an EXTREME LEAN condition happening with that hole.<br /><br />Does your engine intake have a vacum line connected to the port that goes to No 2 cylinder? If so, take a peak around and see if you have a cracked rubber line or fitting.<br /><br />Also... to test the burnt valve theory a step further..you can squirt some oil in No 2 and pull another compression test on it.<br /><br />If the compression DOES NOT INCREASE close to the other cylinders, I agree with the above person's reply and would say you have a burnt valve or one that is so carboned up it won't close completely. <br /><br />Are you hearing a loud popping sound under load?<br />If at the same instant you hear the skip you are currently hearing, you are also hearing a loud popping sound out of the carb - the culprit will most likely be a messed up 'intake valve'<br /><br />You may not hear the popping sound unless you really spike the engine under a heavy load but if it's an intake valve you will hear the steady loud popping for sure.<br /><br />Hope this helps some.