So, I'm in the process of finishing up this 390 rebuild. Right now I'm putting the rocker shafts on and ran into an issue. From the instructions I could gather I loosen the rocker shafts in sequence with the crank turned past TDC on 1 to the XX mark, or 45 deg past. Then it says to rotate back to TDC on 1 to tighten them back up in sequence. So, I tightened them down as such at 1/2 turn at a time. Right at the last half turn at the back,no. 3 exhaust pushrod bent up like a bow all of a sudden. After thinking about it and rechecking the length of a couple pushrods I realized that lifter and a couple others did not bleed out at all while tightening them down. I bled all the air out of the lifters with break in oil and a hand pump before installing them and they were mostly all the way pumped up but now this happened. So, the question is what do I do now? I don;t want to bend a bunch of push rods on start up but now I got the intake on it and can't really get the lifters out. Also at this point I'm afraid of damaging the lifters or something. Thanks

 

Not a lot of feedback here so I'll throw this out there...Probably shouldn't have primed the lifters,let the oil pump do it.That ship has sailed so you might try this...Tighten the shafts evenly till the offending pushrod(s) are just tight and let it sit.Check it a while later to see if they are freed up a little,if so,tighten a little more.Should eventually force the oil out of the lifters.

 

Well, I appreciate the response. I wondered if I should have primed them before or not and decided to. Oh well, fair winds and following seas. Now I have a different issue. I was able to get the lifters to bleed out eventually but when I tightened all the rocker shaft bolts down it seems as though I have some serious rocker geometry issues going on. I think this problem was here all along. The engine was "rebuilt when I got the truck but always had valve train noise and bent pushrods. Yada yada I'm rebuilding it. Anyway when I tightened them down it bent a pushrod on an exhaust valve. the spring was all the way to coil bind and the engine would not even rotate. I loosened the rocker shaft stand bolts about 2 turns and the turned the engine over and it still bent more pushrods even then.. The springs were recommended by the cam manufacturer and installed to the specified height. I measured every single pushrod at 0 lash on the base circle of the cam lobes and added .050" for preload. Custom length (now effing bent) pushrods. I don't understand this much variation other than the heads must have been milled or something and now the rocker ratio and geometry is all messed up and I don't know how to compensate for it at this point. WTH is going on and where do I go from here? Hopefully I didn't damage the lifters...UGH!

 

Did you check retainer to guide clearance ?

 

No I did not. They are Comp cam retainers with much more clearance than stock. I did not think to do that. IDK maybe a thing. I'll check. Thanks

 

I guess the only thing that I can see that would correct this issue would be to shim the rocker shaft stand up or use adjustable rockers. Or both. Any thoughts?

 

Just a wild guess but did they build it with a really high lift cam?

 

So yeah we can go ahead just scratch this thread. Come to find out after I went out and started checking and measuring that the POFS calipers that I got from harbor freight were jacked up and were adding .200" to my measurements and so I order pushrods that are all .200" too long. Whatever, guess I'll start over measuring for pushrods.

 

The first thing I would do is make sure all the valve tip heights are the same. If they are all over the place you can end up with a lifter preload problem.