What would cause this?

02 2500 Avalanche · February 1, 2003

Well I finaly got around to adjusting my lash on my 454 for my '61 apache. Every rocker arm set with no problems but the #2 piston's push rod on the intake valve acts like it is hitting the piston. I adjusted the rocker arm about 50 different times to see if I could get it right. The intake is not on the engine so Im sure that Im on the back side of the cam lobe. Can anyone help me fix this? Thanks

Alex

02 2500 Avalanche · February 4, 2003

Anyone have any theories as to what the #### is going on?

Alex

cyrylyn · February 4, 2003

can you swap out the pushrod?

02 2500 Avalanche · February 4, 2003

Yup I swaped that intake push rod for another intake push rod and it still acts like the valve is hitting the piston. Wish I had a bore scope

Alex

02 2500 Avalanche · February 8, 2003

"Calling CMTRX81, CM to the engine forum, we have a kid with an engine problem, need your help right away"

americanmuscleman · February 12, 2003

How are you tightening the rocker arms? Like whats your procedure?

You shouldn't be opening the valve at all while your setting your lash. As long as your lifter is riding on the base circle of the cam, it shouldn't matter what pushrod your using.

Also, if your using roller rockers and not stamped steel rocker arms... check to make sure your "trunion" (the middle of the rocker that rotates and slides over your rocker stud) is not flipped upside down. Its common for the trunion to be machined on one side, and not on the other. The machined side should be facing up.

Describe how your tightening your rockers and setting your lash.

02 2500 Avalanche · February 13, 2003

I make sure the lifter is on the base circle of the cam and not on the lobe. I get the push rod at zero lash and tighten down the rocker arm nut anothe 1/2 turn and then snug down the set screw on the nut. I have comp cam pro magnum roller rockers.

Alex

americanmuscleman · February 13, 2003

Sounds like your doing things right then. If the rocker arm looks like its too high on the rocker stud, double check to make sure the trunion isn't flipped the wrong way. Otherwise thats the right tightening procedure.

I don't understand whats seems wrong? Can you not make that 1/2 turn to tighten the rocker nut then? Like the valve is frozen and the valve won't go down just a little bit while your tightening the rocker nut? If so, its got to be one of a few things. Either the body of the rocker arm is touching the spring or retainer, or the body is touching the rocker stud. It isn't very likely that the valve would get "tighter" in the valve guide. It will get looser the more miles the motor has. It could also be your valvespring. If you hit the valve (not the spring) with a soft hammer, will the valve drop down a little bit, just to check that the spring or valve isn't the problem?

02 2500 Avalanche · February 14, 2003

Nope, I checked and none of those seem to be the culprits. Im begging to think I lined up the wrong timing marks on the cam gears, the cloyes timing chain gear has 3 different choices for timing.

Alex

americanmuscleman · February 14, 2003

Alex, even if your timing is off, that wouldn't effect how you set up your rocker arms. You can set the lash right even if the cam is degree'd wrong. You probably know this, but I'm just repeating it incase you don't.

02 2500 Avalanche · February 14, 2003

I know but the problem is not with the rockers. The valve seems to be hitting the piston when then valve is all the way open and is not letting the engine turn over.

Alex

americanmuscleman · February 16, 2003

Alex, has the engine ever run before? Was this engine just built?

If your having PTV (Piston To Valve) clearance now, and you didn't before, something has changed. Assuming the engine ran or turned over fine before, and doesn't now, you had to have either put a higher ratio rocker arm on (like go from a 1.7 to a 1.8) and you didn't have PTV clearance to do that, you milled the heads or changed heads, you put a higher lift cam in, your timing is off, or you have a bent valve.

If your suspect of valve hitting the piston... take the rocker arm off that one valve and try to turn the motor over. If the motor still won't turn over, you know its not just that valve or rocker arm.

Another huge possibility is if you have the timing marks off, the valves are opening at the wrong times, and that could easily be your problem. I'd double check the timing. The more I think about what you wrote above, this is what I think the problem is.

02 2500 Avalanche · February 18, 2003

Ya I am thinking the timing marks are off. The engine is brand new, it has never been run before. Iam just in the process of finishing it up. I will pull the timing chain cover off and see, just have to get a gear puller to take off the balancer.

Alex