blueovalz Posted July 2, 2005 Share Posted July 2, 2005 I bent two pushrods (same cylinder) two weeks ago on the highway at normal speed. I heard an irregular ticking noise develop (with ear plugs in as I couldn't hear it without the earplugs) for about 15 minutes prior to them really letting go. All parts looked good, and there did not appear to be any backed off parts (polylocks, etc). By the time I pulled over and pulled the covers, I had one broken and one bent pushrod. Two rockers damaged, and 2 valve tips wiped out. I put clay in the piston valve reliefs today, and the results of turning the motor over with the starter at speced lash, and a compressed gasket, was a measured .140" Piston-to-valve clearance (and about .090" on the sides of the valves). No carbon was knocked off the valves or the pistons upon initial inspection. I've not actually tested them, but the springs are supposed to have a 500# open pressure. The cam is a solid roller of relatively mild specs. Anybody have any ideas on what caused this. I've decided to have the springs checked out anyway prior to buttoning this thing back up and getting it on the road. I'd sure like to figure out what caused this and any ideas would be appreciated. Quote Link to comment Share on other sites More sharing options...
zgeezer Posted July 2, 2005 Share Posted July 2, 2005 We had similar problem with early 302W running mild hydraulic lifter cam. We broke cast rocker arms, springs, and bent pushrods. All at cruising speed, 2800 rpm or so. We replaced springs and spring retainers. The problem was solved. The spring retainers, purchased at close out prices, turned out to be a GM product. If your pistons are not chewed up, I would look very closely at the entire spring & retainer assembly. g Quote Link to comment Share on other sites More sharing options...
jap tin Posted July 2, 2005 Share Posted July 2, 2005 Check for tight valve guides, they can stick a valve open . Quote Link to comment Share on other sites More sharing options...
grumpyvette Posted July 3, 2005 Share Posted July 3, 2005 What causes bent pushrods? 99% of the time its CLEARANCE ISSUES,spring bind, rocker to rocker stud, retainer to valve guide, piston to valve,retainer to rocker arm,pushrod to guide slot, ETC. or a cam thats been indexed to the rotation of the cam vs piston badly,or non correct valve train geometry Quote Link to comment Share on other sites More sharing options...
blueovalz Posted July 3, 2005 Author Share Posted July 3, 2005 Well, this was what I always thought as well, but with all that clearance between the piston and valve (it was actually a lot more than I thought), I am beginning to wonder if the springs have softened up some and perhaps some clearance problems are existing at red line (7500). Anyway, thanks all for taking a look at the post and the responding. Quote Link to comment Share on other sites More sharing options...
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