Engine running problems (New Push Rods)

[myersdp85]

So im beating my head into the wal over this. Here is the situation. I had a push rod wear down to where it began to make the rocker arm make a loud clicking noise. The push rod began to deteriorate due to wear and a lack of oil. So i pulled the push rod and decided to replace all the rods with brand new ones. I replaced all the push rods and readjusted all the valves according to my manual. I did not adjust the timing of the distributor at all. Now when i start the truck it runs very rough. It was running just fine with a broken push rod before i replaced all of them. any ideas? If i didnt explain something well enough let me know so i can clear it up.

[454Man]

Try setting the timing

[jaredts]

Are you sure it was a pushrod and not a cam lobe?

[Fairlane514]

How did you adjust your rockers?  What was your procedure?   You may have the valves too tight.

[Sartobuilt]

I had this problem once while replacing some head gaskets. The lifters were pumped up and not releasing. I ended up having to adjust them while running. What is happening is when you adjust to zero lash and then you add a quarter to a full turn of preload you are opening the valve instead of pushing down the plunger in the lifter. I tried to let it idle for a hoping they would bleed down, a couple did but not all. I then adjusted them while running you will notice while doing this that after zero lash and then adding your preload you will have your miss on that cylinder. You need to add your preload slowly 1/8 at a time.

[myersdp85]

How did you adjust your rockers?  What was your procedure?   You may have the valves too tight.

I adjusted them according to a chevy truck manual i have for this era of truck. I turned the engine over till i was a tdc on piston 1 and adjusted the valves to the order the book told me by doing Exuast 1 3 4 8 and Intake 1 2 5 7. According to the book i have it tells me to loosen the nut till slack is felt by rotating the rod then tighten the nut till there is no slack. Once that has or occured it tells me to turn the nut one full rotation in to finish the adjust ment. Once all those valves are done turn the engine one full rotation 360 deg and do the same for the remaining valves.

Im fairly sure it was push rods and not the cam. The engine was rebuilt at about 80k miles but they reused the original pushrods so they were wearing out and failing.

[Fairlane514]

Pushrods should not wear and fail unless something is wrong. They can bend and break, but wearing is not normal unless there is oiling issues. This is a hydraulic lifter camshaft right?

I assume you have standard stamped rockers or roller rockers with polylocks?

The  adjustment procedure you used should work on a stock cam, but with something a little more radical I would adjust one cylinder at a time. Turn the motor over until the exhaust valve begins to open and adjust the intake rocker on that cylinder. Then when the intake valve begins to close adjust the exhaust rocker. Then move on to the next cylinder.

The book is telling you to get zero lash and then one full turn.  Zero lash is done by feel and some people are past zero lash and then give it another full turn and you then have tight valves. After you loosen the rocker, use your thumb and fore finger to twist the push rod while slowly tightening the locking nut. As soon as you are unable to twist the pushrod with little effort STOP. This should have you at zero lash. Then tun 1/2 to one full turn and lock it down.  Again zero lash is some resistance to your twisting motion while just using your finger tips.

I think your valves are too tight.  If it appears you are pushing the valve open while tightening the rocker its too much.

[Sartobuilt]

Did you check to see if the pushrod was plugged? Try adjusting them all to zero lash, it will be a little noisy but it will confirm what I suggested in the post above.

Please don't refuse my advice. I have done allot of valve seals and head gaskets. Never had a problem with the Chilton adjustment procedure. But I had the same problem your describing, once out of a hundred. Check your compression that will also confirm that a valve is open.

[myersdp85]

How did you adjust your rockers?  What was your procedure?   You may have the valves too tight.

I adjusted them according to a chevy truck manual i have for this era of truck. I turned the engine over till i was a tdc on piston 1 and adjusted the valves to the order the book told me by doing Exuast 1 3 4 8 and Intake 1 2 5 7. According to the book i have it tells me to loosen the nut till slack is felt by rotating the rod then tighten the nut till there is no slack. Once that has or occured it tells me to turn the nut one full rotation in to finish the adjust ment. Once all those valves are done turn the engine one full rotation 360 deg and do the same for the remaining valves.

Im fairly sure it was push rods and not the cam. The engine was rebuilt at about 80k miles but they reused the original pushrods so they were wearing out and failing.

Ding ding ding you sir had the right answer. I worked on it this afternoon and the valve adjustment i used just made the valves too tight. I have a higher performance cam in it though i do not know what it is. The motor was rebuilt before i bought the truck but it does have roller rockers in the valve train and hydraulic lifters. I have had two push rods fail within the last year and a half or so and i believe both were subject to a lack of oil to a small extent. Im working on figuring out why my oil pressure gauge is maxed out whether its the sending unit or the gauge is bad i dont know yet.

Thanks for all the advice guys a half turn after the slack was adjusted properly helped out alot. It runs better quieter and smoother now. Much appreciated.

[Fairlane514]

Great news. On a roller rocker max would be 1/2 turn, I usually go 1/4, but you should be fine. Also after you tighten the set screw, bump the 5/8 wrench a little to really lock everything down. When you bump the wrench you might get about a 1/16 turn.

[thefarmboy21]

I ha this same problem today adjusting some roller rockers for my buddy. He read a full turn...I usually go zero lash period, so we settled on 1/2 turn. Way too tight. Made all kinds of noise and wouldn't run right. Backed them off 1/4-1/3 turn each, nice and string now.