Just got my fresh 390 back and into my truck last weekend. It developed a tap-tap-tap that would come and go at lower RPM's yesterday on the way to work, so at the advice of my engine guy I adjusted the valves last night. I started at TDC #1 and went through the firing order turning the crank 90 deg. and found #4 cyl exhaust (rear most valve on the RH side) valve to be loose. I adjusted it up to where I thought it should be. (snug to where you can't turn pushrod and add a 1/4 turn) My tapping went away last night and this morning, but on my way home tonight I was cruising through a 30 mph zone in 3rd turning about 3k rpm and all of a sudden clack-clack-clack-clack and the motor runs like crap. Obviously dropped a hole so i limped home about a mile and pulled the valve cover for a look. I went right to #4 tdc after not seeing an obviously bent or broken rocker arm and #4 intake pushrod (2nd one forward from the firewall) was bent and #4 exh. valve was loose again. I'm pretty sure the adjusters didn't back off so I'm not sure what to think. I don't just want to replace the bent rod if something else is wrong. I'll talk to my engine guy tomorrow and see what he thinks, but any help or ideas would be great.

details on engine build: 390 .030 over, 9.5:1 pistons, stock heads, crane 941 cam & lifters & springs, factory style adjustable rockers w/solid spacers and chromoly pushrods from DSC and stock bottom end.

 

You never tighten the rocker down snug and add a quarter turn on adjustable rockers. That is exactly why you have a bent push rod and maybe some others. Most adjustable rockers should have about .022" clearance between the valve tip and the rocker tip. I actually run mine at .018" but that is acceptable. Since you have no gap and they are tightened a quarter turn each there is no gap for heat expansion. Check your push rods for straightness, all of them and check your cam card and see the recommended lash (gap) and reset everything.

 

The Crane 343941 is a Hydraulic Cam..therefore it needs a lift preload..

I cant reseach in my head right now what might have gone arye?

I just dropped in real quik, but either the push rods were a tad to long..or you used to much preload, ??

Russ

 

Didn't realize it was a hydraulic cam. Carry on.

 

Aww know problem Doug...I have looked at so many Cams and Cam #s over the years I cant keep track either so dont feal bad....If it wasnt that 99% of the guys in this forum didnt run Crane Cams I wouldnt have known it was a Hydraulic either! LOL

Have a good day!

Russ

 

I think I see the problem.

"...until I couldn't turn the pushrod any more..."

You probably put waaaaay too much preload on it. The way to do it, is to turn it until you feel a slight resistance when turning the pushrod. This way you'll know that all the lash has been taken up. You still will be able to turn it! Even after you go 1/4 turn (I go 1/2 turn), you should still be able to turn it if you used assembly lube on everything.

 

Hed this happen in in my 428 that is in my 64 Galaxie, bent 2 pushrods on it's first trip after rebuild. I replaced the 2 along side to road and when I got home 7 more were bent. The lifters were stuck at the top of their bores and would not pump down, the rockers are nonajustable. Pull the lifters out and replaced with new and no more problem. Three 428s that wre built at the same time, using parts from the same place had the same problems.

 

Yes Kurt...I believe he read one of my notes wher I said to spin the pushrod in your fingers until your feal a drag on it...and then take it a 1/4turn down.. "not tell you couldnt turn it"...Oh well live and learn...

Russ

 

I'd venture that the 'coming and going tap tap tap' was the sign of a lifter that was collapsing intermittently. If it was #4, then when you adjusted the valve, the lifter could have already been collapsed or you felt no resistance because the lifter is leaky. That would let you turn the hydraulic into a solid lifter... sort of. And would cause the lifter to want to keep the valve open when it pumped up.
tom

 

I had a lifter when new clack every morning for 8 to 10 times, more when the lifter was on the cam nose. This was Crane's anti-pump up lifters, removed all, cleaned and replaced back in their original locations. From Crane and new I found a few metal splinters which prevented check valve function. I reinstalled them dry to make adjusting preload easy and accurate then pre-oiled motor again, no noise going on 249K miles.
.....=o&o>.....

 

Well now I'm really confused but thats ok this is what I did and thought I was supposed to do but I havnt got the tranny in yet so no harm done yet. When I installed the crane lifters I pumped them up in a half quart of the oil I am going to use. It took about 10 pumps each. I lubed the end and sides and dropped them in. I installed my rockers and got each cylinder at TDC and adjusted them to tight and then a quarter turn. From a post above I see that is to tight and I will adjust them to just feeling them touch and then a quarter so they should still have movement in them after adjustment. My question is do I need to bleed them down now? And then reset my rockers. Or did I do the the preload when I pumped them up on installation?

 

Per Crane's preload they want .020" to .060" on their lifters. To run at the minimum preload (.020") use a .035" feeler gauge at the valve stem, (.020" X 1.76 rocker ratio) = .0352". Take up clearance until the pushrod begins to get drag when turning, remove the feeler gauge and make a note of how much you turn the adjuster to repeat the last step "begins to drag" then without the feller gauge, turn down the adjuster that same amount as the step before. This will get you .020" preload. For .060" preload you would need .1056" at the valve stem.
.....=o&o>.....

 

Thank you Beamer, I think my problem is understanding the definition of PRELOAD. This is the distance of compression on the hydralic lifter from the top down at the proper height when set. Is this correct?

 

That's correct, depressing the pushrod cup into the lifter bore from its static or resting position against the wire retainer clip. Should you over rev or pump up the lifter it will stop against the wire retainer clip (.020" lifter or .035 valve stem) and give the valve .035" extra lift at full lift or .035" when the valve should be closed. This will prevent piston to valve damage as "normal clearances" are alot more than .035" Now should you of adjusted lifters so they are extended .020" from a fully collapsed position if they pumped up app .400" or .692" at the valve you'd have piston to valve damage. If you don't have enough feeler gauge use sheet metal or a drill shank (number or letter drills).
.....=o&o>.....

 

Thanks again Beemer, I'll reset them correctly