Fouled spark plugs?

[crj1968]

found this:

150 at sea level = 125 PSI at 6000 ft.

I think you are probably OK for compression... 

[XH29N0G]

Looks like my altitude is 4692 feet. I think the gauge bumped up at about 1 Mississippi. The driver side was closer to 97 consistently while the passenger side was closer to 93 consistently. How do I check the gauge for accuracy?

I am still not 100% clear if you saw the gauge bump right up to 97 and the stay there through later bumps, bump to lower levels like 65, 80, 90, and ultimately level off at 97 after the engine turns over 5 or more times? 

Let me ask another question, does  the gauge have a valve that works so it stays at 97, or does it just bump up and the drop back down.

For what it is worth, the pressures you measure should convert to about 110-115 psi at sea level which is low, but consistent cylinder to cylinder.  This suggests to me that the oil you see and the compression are not related.  It is still low, so it might deserve some more checking. Someone on here will know if that is an issue.

I would just see if you can borrow another gauge and if you get the same reading.  I checked my gauge for accuracy using tubing and hose clamps to connect it to a bicycle pump that also had a gauge and checked to see if they matched.  If there is a source of compressed air and another gauge you could use that too, but the simplest might be to borrow or buy another gauge.
   
 


 

[rikubot]

Sorry about that, I replied this morning in a hurry and realized that I forgot to answer that part of the question. It was on the 4th or 5th jump of the gauge and it would hold until I hit the release valve. Any clue why my compression would be low-ish? She's pretty low miles.

[c00nhunterjoe]

What cam is in it? If its bone stock, then you probably have a 7:1 motor which sounds way off. Redo the test with a small spray of oil in the hole and see if the numbers jump up 15 or 20 psi.

[rikubot]

I'm actually not sure what cam is in it. I can't find all my paperwork from the rebuild, and I don't remember what they put in it. I want to say that it's bone stock besides the edelbrock. You mean way off as in way too low?

[firefighter3931]

What plugs are you running in this 440 ?  The dynamic (cranking) compression is low(er) than expected due to the mile high elevation. For every 1000ft of elevation you loose approx. 3.5% cylinder pressure. 

This is why cars that race at elevation are slower ; they're making less cylinder pressure and consequently...less power than at sea level. 

I'm not a fan of PCV valves....they will put oil vapor into the combustion chamber. I prefer to run a breather on each valvecover.

I would try a set of NGK XR4 plugs gapped at .035 and try running it with two breathers. Get the idle mixture as lean as the engine will tolerate and set the total timing to 40*.

You should have a nice blue/white spark....dull orange/yellow indicates resistance in the ignition system and a weak spark.

As for the low cranking compression ; it could be low static compression, a cam that's too big or a cam that was installed retarded.



Ron

[XH29N0G]

I just decided to try a check using one of the online calculators
I ran the settings in the image below through the dynamic compression calculator at Wallace racing:  http://www.wallaceracing.com/dynamic-cr.php
The cam specs are from http://victorylibrary.com/mopar/mpcam-tech-c.htm


It looks like it the stock cam (image) at 4500 ft with 9.0:1 compression would give 112 psi.  At a static compression ratio of 8.5:1 the calculator gives 103 psi for the stock cam. If your static compression is 9:1 or 8.5:1 then your numbers may not be that crazy.  A later closing intake like the 484 or 509 will drop the compression by by 5 to 10 PSI at these conditions.  Other variables could reduce the dynamic compression ratio.


So after thinking about it some more, you might be fine and the gauge may be fine too.  I would assume the gauge has a few psi uncertainty.

I am at sea level so am used to seeing higher dynamic compression numbers.  See if C00nhunter and Ron think this makes sense b/c they know more than me.  

[c00nhunterjoe]

Wow, i completely bombed that one... i thought i read "692" feet.... 
100 psi at nearly 5000 feet is about right for tye typical low cost, low comp pistons so since they are all within reason of each other, the bottom end is ok. Had the cylinders that had oil on them been considerably lower then the others, you would have had a probable answer for the oil, so now it is pointing more towards pcv or intake gasket sucking oil.

[rikubot]

Thank you all so much for helping me to pretty much eliminate the rings as the culprit. I'm really not worried about the oil much at all anymore. I have learned more about motors in this thread than anywhere else. Timing, compression, oiling processes, and more. Your extensive knowledge is highly impressive and I appreciate the time you all spent finding data and posting it. I learned a little more last night about heads and Pistons, so now I have a REAL question: should I get new Pistons, rods, and a cam???  

[c00nhunterjoe]

You shouldnt give up just yet. Definatly should pinpoint the plug problem. Oil Fouled plugs is never good. Are your valve covers baffled? Try as ron suggested and run with open bresthers for a few cruises and recheck the plugs to see if they stay clean.

[rikubot]

Yeah they are baffled. I think I have a spare breather to use as well. Should I disconnect the driver side to the filter?

[c00nhunterjoe]

Just for the test, yeah, run 1 breather in each cover, fresh plugs, drive, then recheck plugs. This will confirm or clear the pcv system as the culprit.

[rikubot]

I should mention that I was running M/T aluminum valve covers that had a very little baffles on them. I'm now running the original stamped steel covers. Think that would make a difference? And just today I finally got them to seal up! Lol

[rikubot]

I can post a pic of the bottom of that valve cover if needed.

[c00nhunterjoe]

I ran the mt fovers for years with pcv and never had oil problems. You might be sucking oil past the valley gasket.