ChvyCruzen

I have a theory about my problem, which is that I keep bending pushrods. I will explain each of my problems as brief as possible to tell you how I got my theory. I put in a CC305 cam with Crane hyd roller lifters and stock pushrods and rockers, 200 miles later, pushed the pushrod through the rocker. Bought hardened pushrods, and magnum rockers, 15 miles later, bent the pushrod (rocker was fine) on the same cylinder as before. Got a replacement lifter from Summit, as well as pushrod. As for tightening the rockers, I went to zero lash, then 3/4. I drove 1,000 miles then I bent another one, not the same cylinder as before. I called someone for advice, guy who machined my block, told me I was pre-loading the lifter too hard, I should only do 1/4 of a turn. So I decided to check other cylinders for bent pushrods, all but 3 pushrods were bent! I ordered a repacement, did 1/4 turn pre-load. 15 miles later... I am here again with a bent pushrod.

My theory is that the lifter is pumping out and cannot bleed itself out of the oil pressure and is generating more lift, more lift than the spring can handle, so I have a coil bind. Obviously, the pushrod is the weakest link, so that gives out.

I am curious, are the Crane hydraulic roller lifters bad? I am considering switching to Comp Cams and getting springs that can hold much more lift. My springs now can handle .550 lift. If I ever start pumping up, I should not get into a coil bind and wont bend anymore pushrods.

Anybody have any suggestions please?

Mikey97Z

I doubt it's the lifters causing your bent pushrods. Have you checked for coil bind on the spring at full lift? That would be my guess.

Shankels94TA

Hey, a customer's car had the same problem and we switched to Roller Rockers because you are not really supposed to use stock rockers on a higher cam lift motor. That is a reason the hotcam kit comes with Roller Rockers. If you can picture this, the stock rockers can only go so much each way once torqued down. So they are probably reaching max "rock" and since they are stronger than the pushrods guess which one gives? It could be other things but RR's fixed a hotcam car with stock rockers that bent pushrods and broke rocker studs Ok I see that you purchased the magnum's. If its still doing the same problem after the rockers then I would recommend guideplates especially with hardened pushrods(which i think is mandatory?) . Hope this helps you!! Later, Adam

FireAm94

I think hardened pushrods are mandatory IF you use guideplates...not the other way around.

Joe

ChvyCruzen

Well, I thought I was somewhere close to coil bind, like Mikey stated. My machine shop ordered the springs for me, and put them on for me, assuming it would hold my lift and they told me it should handle .550 lift. I felt tempted to check my springs. Installed height, closed - it sits 1.750 and then I removed it and checked the bind length, which was 1.235, and my calculations show .525 lift is when it binds. My lift with a 1.52 rocker on the 305 cam (.510 lift) is .517, a lifter only has to pump up .008 to get into a bind. I must have recieved a bad batch of lifters, since it is pumping up (this is second one that has failed). I now ordered Comp hyd roller lifters and K-Motion springs, installed height - 1.700 and bind is 1.050... which can hold up to a .650 lift. This here is going to help me prevent coil bind. I was getting into a coil bind, but at the same time, I had a bad lifter. My shop did not allow much room for error on this one, my spring should now have plenty of room in case something happens.

Luckily for me, I got $20 off and full refund on Crane hydraulic roller lifters.

MentalCaseOne

Dang!! I do not know much about valve train but I can see where things can go very wrong.... My thoughts are that your shop never took into consideration heat expansion either.

I wanna do valve train sum day but it hear so many horror stories...


Marvin