pushrod knock

[71chally416]

A bad valve job can make a tapping noise. It's the valves getting wedged on on the seats because of excessive seat runout. It's easy to tell if you just pull each valve onto it's seat without the spring and see it it easily opens right back up or gets stuck. The snapping noise you hear when you disloge it from the seat sounds like a tap when the motor is running. Don't mean to be Debbie Downer but I've seen that many times on customers heads.

[71chmark]

I would consider the valves but when I first setup the valve train I mistakenly set a lash on the valves and there was no knocking.  Just the rattling of the valve train.  It was only after I set about 1/2 turn preload that the knocking started.

[71chally416]

I usually use 1/8 turn. Just enough to stop the clicking. What cam are you using?

[71chmark]

When I bought the motor from a friend in 1994 he said he put the purple cam in it.  The research I did at the time pointed to .284/.484.  I think that's what's in there.

[71chally416]

So you have .548" lift with 1.7 rockers. Are you sure you have enough piston to valve clearance?

[nivvy]

So you have .548" lift with 1.7 rockers. Are you sure you have enough piston to valve clearance?

.548 minus .028 valve lash...... .520 he sould be fine....... 

[71chally416]

I would consider the valves but when I first setup the valve train I mistakenly set a lash on the valves and there was no knocking.  Just the rattling of the valve train.  It was only after I set about 1/2 turn preload that the knocking started.

I think it's a hydraulic cam ??

[71chmark]

I did the clay check with no lash and they didn't hit.  I also was able to turn it over by hand without any extreme resistance.  Then there is the stopping of the knock when the motor gets up to temperature.  Guess I'll take the heads off and have a look.  What a pain.  Have to drop the headers which means removing the clutch "Z bar" and the dipstick tube.  Not to mention jacking the engine over to get the torque wrench on.  Next the remaining water in the head runs over everywhere including into the cyclinders and that's just to mention a few which I am sure you are all aware.  Can you tell what a baby I am?

[nivvy]

pull the pushrods and enlarge the holes first.... if not then pull the heads and check the valves.....   

[71chally416]

Checking clearance with clay is fine if you use solid lifters. If they are bled-down hydraulics it's worthless. I pull the top of a couple hyd lifters and put a pc of rubber vacume tubing inside to hold the plunger all the way up when I check clearance with a hyd stick.

[71chmark]

I replaced the lifters when I replaced the heads and funny thing is I couldn't even depress any of the old lifters.  It's like they were frozen.  Thay had sat for over 12 years.  These were the ones installed when I tested the clearance so I think I got a good test.  You could push down really hard on the rocker while the motor was running and reduce the noise.  We cranked down on those and thought we had it but it was just that the engine had warmed up.  I don't think warm up would reduce the piston/valve hit but I can't explain why it effects the pushrods either.