It's BAAAAACK!!!

[Power Wagon]

Finally got the heads rebuilt, the correct head gaskets installed, and the PW runs great!



For those of you who mess with such things... Can anyone explain to me why heads with hardened seats installed will end up with the valves beating the seats out? In 15K miles or less, it totally shredded the hardened seats, with some of them recessing more than . 050 in that short time.



The valves showed they'd been very hot, but were undamaged, and replaced for wear in the keeper area.



It's a mystery to me and to the guy who built the heads...

 

[Gary - K7GLD]

HMMmm - I would suspect the seat wear issue would be related to:



1. Poor materials.

2. Poor fuel lubricity.

3. Poor valve lash/operation.



I would sorta reject the poor materials issue, seeing how the REST of the Cummins is build - so wonder about the other 2. The fact that the valve faces themselves were still OK would seem to suggest poor heat transfer between the hardened seats and the block?

 

[Andy Perreault]

Could the truck be running too lean, creating way too much heat? How did the spark plugs look? They may show if this is the case or not.

It sounds like a fun project truck. How about posting some pictures?

Andy

 

[Max340]

If the valves showed visible heat effects, they were damaged. Even if physically in correct form, the metal is changed in temper etc. That much heat indicates why the hardened seats got pounded out. My guess is that the seats were not transferring heat to the head and were unable to disperse the heat from the valve and combustion effectively.



The two questions I would ask are:



1) Is there excessive heat? Cause?



2) Are the seats properly installed so that they have full contact with the head and are able to fully disperse the heat?

 

[Power Wagon]

The original seats were installed properly, tight, and seemed to be of normal quality.



This engine runs a bit on the lean side, but not so much it doesn't run good. I towed a trailer with it, but it did the valve seat damage doing normal driving around.



I did set the valves correctly the first time, and but they stayed only a short period of time. One normally does not expect to have to reset the valves in less than 6 months, repeatedly. After setting them about 2 months after rebuilding it, I didn't set them again until it started to have problems.



I did have a pinging problem anytime this engine was worked hard - which tends to mean excess heat. However, I took the excess heat problem to be caused by the valve-seat / leakage problem, not the other way around, since it didn't ping at all when I first rebuilt it. As for it running too lean, it seemed to ping worse if I richened it up.



Well, anyway, it has new exhaust seats and new valves, doesn't ping when run at reasonable timing settings now...

 

[BCFAST]

Sounds like you've arrived at the resolution I would have suggested... . timing. Some engines seem to really, really love timing! and then you keep getting the carb jets fatter, and fatter... and then the exhaust valves check out! LOL Motors run their very best JUST before they blow up. Get the timing in the middle-range, fatten the jets a tad from 'normal' and find a plug that burns about right. How about cam timing? If it's way advanced or retarded you may be burning back into the seats...

 

[Power Wagon]

Actually, I tend to set the timing by where the engine runs best. To work it real hard, you have to retard it slightly from there to avoid pinging, but it doesn't seem to perform much, if any, less.



I have re-curved the ignition to get less centrifugal advance than it used to, topping out roughly 38 degrees. It has an adjustable vacuum advance can, that gets about 20 -24 degrees and if memory serves, it's all in at about 8 inches or so.



As for the cam timing, it doesn't seem to be excessively advanced, and it certainly isn't retarded, as the engine has good grunt power from 1200 and up.



I thrash the daylights out of it towing... I've driven it flat to the floor in 3rd for 15 minutes or more at a stretch, and I've had to buck a headwind that kept it flat to the floor in 4th for 30 to 40 miles. But, it is a 318 after all, and it should NOT have problems no matter what.

 

[rich m]

Hey Gary, PW's got a 318 in an old PW

Originally posted by Gary - KJ6Q

HMMmm - I would suspect the seat wear issue would be related to:



1. Poor materials.

2. Poor fuel lubricity.

3. Poor valve lash/operation.



I would sorta reject the poor materials issue, seeing how the REST of the Cummins is build -



---just preventing unnecessary headscratching---rm

 

[Gary - K7GLD]

YUP - I gathered as much after reading a few later posts...



Same principles still apply...