Yukon Jack
1/2 ton status
My engine with a fresh cam, lifters, springs and rocker arms bent a pushrod and broke numerous teflon valve seals. When I went to try to pull the valve springs I could not get the cylinders to hold pressure so I was told I needed to pull the heads to see if I had bent valves. I got the passenger side head off last night and just got back from a machine shop with good news and information on what happened.
To start off, I was told the valve springs needed to be shimmed up as presently they were at about 70 lbs when closed and the cam specs required 90 lbs. The machinist said he would actually like to see a little higher than 90 lbs.
The whole problem surrounds the teflon valve seals. When the problem occurred a number of people pointed their fingers at them and they were 100% correct. I reviewed alot of information when buying all the components and I sure thought I read that those valve seals could be used without machining but I was obviously wrong on that I now learn.
When the spring compressed the valve seal was not seated properly resulting in contact strong enough to bend 1 pushrod and destroy numerous valve seals.
While the heads are off the machinist will do a valve job even though he said they were not too bad - the heads are off so now is the time to do that and start fresh.
He will also machine the studs to accept the proper valve seals and then he will have the heads prepped for reinstall with new guideplates that I have that will be used in connection with 3/8" pushrods.
The total price for the head work will be in the neighborhood of $240 which sounds awfully fair to me.
Now I have to figure out how in the world I can put the heads back on without messing up the new head gaskets. It was a bear getting the head lifted off and I don't know how I will set the heads back on the installed engine without screwing up the head gaskets. Maybe I can install some all-thread rods to use as guides so the heads drop down cleanly.
Then I need to figure out how I am going to get the torque wrench on a couple bolts at the back of the heads. Clearance is minimal and as it is now a torque wrench will not get back there. Probably gonna have to lift the cab up one side at a time to gain enough clearance - oh the joy
Definitely a relief to know what caused the problem and that it's not going to be too expensive to fix. The extra time that will be involved sucks but oh well, what else do I have to do in the late evenings 
As a side note he said I should stay with the peanut port heads as I am after low end torque with this very heavy truck (about 6,000 lbs) - really didn't want to finance different heads so that is good.
To start off, I was told the valve springs needed to be shimmed up as presently they were at about 70 lbs when closed and the cam specs required 90 lbs. The machinist said he would actually like to see a little higher than 90 lbs.
The whole problem surrounds the teflon valve seals. When the problem occurred a number of people pointed their fingers at them and they were 100% correct. I reviewed alot of information when buying all the components and I sure thought I read that those valve seals could be used without machining but I was obviously wrong on that I now learn.
When the spring compressed the valve seal was not seated properly resulting in contact strong enough to bend 1 pushrod and destroy numerous valve seals.
While the heads are off the machinist will do a valve job even though he said they were not too bad - the heads are off so now is the time to do that and start fresh.
He will also machine the studs to accept the proper valve seals and then he will have the heads prepped for reinstall with new guideplates that I have that will be used in connection with 3/8" pushrods.
The total price for the head work will be in the neighborhood of $240 which sounds awfully fair to me.
Now I have to figure out how in the world I can put the heads back on without messing up the new head gaskets. It was a bear getting the head lifted off and I don't know how I will set the heads back on the installed engine without screwing up the head gaskets. Maybe I can install some all-thread rods to use as guides so the heads drop down cleanly.
Then I need to figure out how I am going to get the torque wrench on a couple bolts at the back of the heads. Clearance is minimal and as it is now a torque wrench will not get back there. Probably gonna have to lift the cab up one side at a time to gain enough clearance - oh the joy
Definitely a relief to know what caused the problem and that it's not going to be too expensive to fix. The extra time that will be involved sucks but oh well, what else do I have to do in the late evenings
As a side note he said I should stay with the peanut port heads as I am after low end torque with this very heavy truck (about 6,000 lbs) - really didn't want to finance different heads so that is good.
