I just had to do this on one cylinder. My dump truck developed a hard miss on the way home from a job. Had no clue what could be wrong. Decided the easiest and fastest thing to do was just remove the valve cover and do a visual inspection. I immediately noticed the valve rocker arms on cylinder 2 looked different than the rest. Had a bent push rod which i suspect was caused by too much slack in the valve lash. Luckily both rods did not fall into the bottom area and cause damage. Even the valve adjustment nut was still sitting in the top on the head. Anyway we weren’t able to find the proper position by pinning the engine. So we manually rotated the crank until the rocker arms were at their highest position and then adjusted it. Kind of like an old Chevy 350 gasser and it worked fine. Wasn’t 100% sure it would but we started it afterwards and ran perfect no more miss. My opinion is that the reason to pin the engine is so you can adjust half of the system at once instead of manually spinning it for each adjustment position. Basically it makes it faster. I drove it 25 miles afterwards and no problems so i guess we did a decent job. I decided not to adjust any of the other ones because i didn’t want to make things any worse in case our method of adjusting the problem cylinder was wrong. Now i plan on getting them all properly adjusted by a professional.
You're correct - pinning the engine is only so that you only need to rotate it once. The standard method you use like on any other old pushrod style mechanical engine would work just as well, you just may have the rotate the engine more to get it all done. It's fortunate you caught it before more damage was done. While it's not a bad idea to get the adjustment checked if you aren't sure if you got it right, if you did the one cylinder, I see no reason why you couldn't do the full engine and save the money of paying a shop to look at it. Just follow what's in the video and it should go fine for you.
There wasn't necessarily any sort of running issue that prompted me, just that it was time to do it (at 100k) and I had no idea if the initial adjustment (due at 30k) was ever performed. Valve adjustments are generally to be done on schedule. If you're actually noticing a running issue that can be fixed by a valve adjustment, then things have gone too far. The engine was performing fine before I did the adjustment. I have a pretty keen ear for engines and it did feel/sound like it could be doing better, but there wasn't anything in the form of a miss or indication of problems. After the valve adjustment it did sound a little stronger but there was no noticeable difference in horsepower. It probably did have a minor improvement in fuel economy but nothing earth shattering. Basically if you've got around 100k miles on your 3126, especially if you don't know if it's been done before, it's a good idea to do.
Very informative. I am definitely going to check my valves now.
I just had to do this on one cylinder.
My dump truck developed a hard miss on the way home from a job.
Had no clue what could be wrong.
Decided the easiest and fastest thing to do was just remove the valve cover and do a visual inspection.
I immediately noticed the valve rocker arms on cylinder 2 looked different than the rest. Had a bent push rod which i suspect was caused by too much slack in the valve lash. Luckily both rods did not fall into the bottom area and cause damage. Even the valve adjustment nut was still sitting in the top on the head.
Anyway we weren’t able to find the proper position by pinning the engine. So we manually rotated the crank until the rocker arms were at their highest position and then adjusted it. Kind of like an old Chevy 350 gasser and it worked fine.
Wasn’t 100% sure it would but we started it afterwards and ran perfect no more miss.
My opinion is that the reason to pin the engine is so you can adjust half of the system at once instead of manually spinning it for each adjustment position.
Basically it makes it faster.
I drove it 25 miles afterwards and no problems so i guess we did a decent job.
I decided not to adjust any of the other ones because i didn’t want to make things any worse in case our method of adjusting the problem cylinder was wrong.
Now i plan on getting them all properly adjusted by a professional.
You're correct - pinning the engine is only so that you only need to rotate it once. The standard method you use like on any other old pushrod style mechanical engine would work just as well, you just may have the rotate the engine more to get it all done. It's fortunate you caught it before more damage was done.
While it's not a bad idea to get the adjustment checked if you aren't sure if you got it right, if you did the one cylinder, I see no reason why you couldn't do the full engine and save the money of paying a shop to look at it. Just follow what's in the video and it should go fine for you.
@@TedsGarage Good idea
thanks for the video! I have one of these engines!
👍
Thank you
are the cylinders numbered one through six from the harmonic balancer?
Do you remember how the engine was preforming before the valve adjustment? What prompted you to do a valve adjustment?
There wasn't necessarily any sort of running issue that prompted me, just that it was time to do it (at 100k) and I had no idea if the initial adjustment (due at 30k) was ever performed. Valve adjustments are generally to be done on schedule. If you're actually noticing a running issue that can be fixed by a valve adjustment, then things have gone too far.
The engine was performing fine before I did the adjustment. I have a pretty keen ear for engines and it did feel/sound like it could be doing better, but there wasn't anything in the form of a miss or indication of problems. After the valve adjustment it did sound a little stronger but there was no noticeable difference in horsepower. It probably did have a minor improvement in fuel economy but nothing earth shattering.
Basically if you've got around 100k miles on your 3126, especially if you don't know if it's been done before, it's a good idea to do.
are the cylinders numbered one through six from the harmonic balancer?
Yes. 1 is the "front" of the engine (which is the harmonic balancer).