Chasing down a miss, 1968 Polara 383

[GOLDMYN]

Hi, as the title indicates, I'm chasing down a miss, 1968 Dodge 383/330hp, I had a standard valve job performed and most of the other components are new. The miss has been there before and after the valves were done. SO, I decided to perform compression test. pulled the plugs, #8 had oil on it and #6, the tip was bent. onto the test. thought I would ask for comments as I continue. mike

 

[CBODY67]

To me, NONE of those spark plugs looks very good. Other than the two noted plugs, when was the last time that car has been on the highway for an hour or so? On the two flaky plugs, what do the piston crowns look like?

Oil "from the bottom" will wash clean the edge of the piston crown, usually. I'm presuming you looked for "witness marks" from the plug gap being closed?

Just some thoughts,
CBODY67

 

[Big_John]

and #6, the tip was bent

I'd say that's the cause of your miss.

 

[71Polara383]

I'd say that's the cause of your miss.

What's more concerning to me, it wasn't bent when I put it in...

 

[Big_John]

What's more concerning to me, it wasn't bent when I put it in...

I was gonna say that someone dropped or banged the plug installing it, but this is concerning.

In a stock 383, I can't think of any reason other than something rattling around in the combustion chamber that would do cause a bent strap.

 

[71Polara383]

I was gonna say that someone dropped or banged the plug installing it, but this is concerning.

In a stock 383, I can't think of any reason other than something rattling around in the combustion chamber that would do cause a bent strap.

Yeah absolutely. I actually installed the plugs while the engine was out on the stand. Thats the easy way. I will say we should have gotten all new tune up stuff for the car, but I reused the plugs/wires it had when it came to me as I was under the impression those items were recent. I am certain I gapped all the plugs before putting them in, is it possible I missed one? Maybe. I don't think so...but maybe.

Id roll the starter over a few times to be sure nothing is in the cylinder. Put new plugs in - and go from there.

John We also advanced the camshaft 4° on this engine as well... Doubtful that's the issue but seeing a smashed plug makes me wonder

 

[Big_John]

Id roll the starter over a few times to be sure nothing is in the cylinder. Put new plugs in - and go from there.

That's the logical thing to do. Maybe a look inside with an endoscope.

John We also advanced the camshaft 4° on this engine as well... Doubtful that's the issue but seeing a smashed plug makes me wonder

I can't see how that would do it. The plugs are too far away from the valves. Same for pistons. The plugs aren't close enough to hit with a flat top piston.

 

[GOLDMYN]

drum roll for the suspense, I completed the compression test with my trusted helped (wife) having 2 trips to the bathroom, a quest stop by and the dogs feeding time, we were able to march on, 2nd try on# 4 was dry. I'm only a shade tree mechanic, the numbers could be higher but not lower LOL. The engine has 84K miles on it. maybe 30 since work Hey Wyatt, DON'T take anything personal. I just want a direction to go forward. I send for a rebuilt distribritor from (halif) mike.

 

[71Polara383]

Hey Wyatt, DON'T take anything personal. I just want a direction to go forward.

I understand and I'm not. Just offering what information I have so we can conclude this and you can get to enjoying that vert.

That's the logical thing to do. Maybe a look inside with an endoscope.

I can't see how that would do it. The plugs are too far away from the valves. Same for pistons. The plugs aren't close enough to hit with a flat top piston.

And that's what I thought too but I figured having all the information is necessary for your professional analysis.

 

[GOLDMYN]

Thinking about taking the valve cover off and look for what? The other issue is #8 wet, I could actually see a drop of oil on the tip of the spark plug, where's that coming from, cause a misfire also.

 

[CBODY67]

And what did #8 plug smell like?? Oil, gas, or both? Ref post #2 above.

CBODY67

 

[GOLDMYN]

sorry, I don't recall, I've got a shop in town who will scope the cylinder

 

[stain]

Gap the plugs, re-install and see if the miss is still there. Easiest course of action right now. If the tip gets hit again, then continue down that path.

 

[GOLDMYN]

will do, thanks for the support

 

[GOLDMYN]

YAHOO, changed plugs, #85, runs sweet, down and got 15 gallons fresh gas I hope it stays this way. New top the end of the month, sanded some of the primer off the passenger-side rear qttr.

 

[71Polara383]

Excellent!!!

 

[Jakter]

Couple years ago I had 3 Autolites stop firing on two different cars.
Changed to NGK'S and haven't had a problem yet.
On the one car, found one plug not firing, changed it, drove great again, thought the problem was fixed.
Week or so later started running rough again.
Pulled the plugs found a different plug not firing. These plugs were only a few months old and were not oil fouled or carboned up.