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Thread: Found Part of the Problem

  1. #1
    AZKC
    Last trip was a downer, boat broke right away was just going to let it sit but got a little bored today and yanked the valve covers.
    Found the #3 intake pushrod tip had broken off and the #7 intake and exhaust pushrods bent happened at about 3-3500 rpm, I run flat top pistons, about a .570 lift Comp cam, roller tip steel rockers and Comp springs. I'm going to pull the rest and ck them but I'm stuck on what causes this :yuk:
    http://www.***boat.com/image_center/...shrods0002.jpg
    My Jetboat hates me:frown:

  2. #2
    Senior Member
    Join Date
    Jun 2009
    Posts
    10,871
    Usually push rods bend because they're the weakest link when you have a valve related problem. Check your valves, rockers and springs thoroughly. Chances are a valve(s) is not opening because it's bent or stuck in the guide and the pushrod bends when the lifter pushes it up, rather than opening the valve. You rarely see pushrods bend and be the "cause" of the problem, especially decent aftermarket chrome moly pushords which it appears you have. Usually something else has failed and pushrods being bent are the result. Keep diggin. Hopefully whatever you're dealing with will be limited to the top end. Also check the cam and lifters thoroughly. Lifters break too.
    Was it running fine prior to this incident? Or was is running somewhat down on power or poorly.

  3. #3
    AZKC
    It ran fine on the trailer but under a load it was running poorly not backfiring or anything, but I thought I was fighting bad gas that I didn't get completely drained. Was only on the water about ten minutes.
    I checked all the other pushrods and found another bent one on #5. Right bank 2,4,6. and 8 seem fine. But I did pull the plug on #7 and it's hammered Time to pull the head but not today it's gettin pretty dam hot out there and the beers gettin colder

  4. #4
    Cas
    how are the springs? did you check for bind?
    how about the cam? any flattened lobes?
    piston to valve clearance ok?
    pushrods the correct length?
    what do the lifters look like? they still in one piece?
    what kind of rockers and what's their ratio?
    all kinds of stuff that could of gone wrong but as Rex said, it's not often a problem with the push rod.

  5. #5
    AZKC
    how are the springs? Fine, Comp Cam Springs matched to cam
    did you check for bind? Yep
    how about the cam? Good shape
    any flattened lobes? Nope
    piston to valve clearance ok? That I'm going to re-ck
    pushrods the correct length? Stk length BBC Comp Cam 3/8"
    what do the lifters look like? Little round cylinders LOL
    they still in one piece? Yep
    what kind of rockers and what's their ratio? Comp Cam steel roller tip, Stk ratio 1.7 I believe
    I'm going to yank the head and ck the #7 hole out , I'm also a little concerned on what broke the tip on the #3 pushrod

  6. #6
    Floored
    please tell me you don't have a nylon cam sprocket. if hydraulic cam did you go 1/4 turn past zero or 1 full turn? with 1 turn and big oil pump, tight clearances and a little lifter pump up you could get this problem.

  7. #7
    AZKC
    Originally posted by Floored
    please tell me you don't have a nylon cam sprocket. if hydraulic cam did you go 1/4 turn past zero or 1 full turn? with 1 turn and big oil pump, tight clearances and a little lifter pump up you could get this problem.
    Nope the whole valve train is Comp Cam, timing chain stuff is also. Dual steel roller. I go about 1/4 to 1/2 turn past zero lash.
    I was kinda wondering about the valve adjustment myself actually. I do run a big oil pump and the clearances are pretty tight valve to piston.

  8. #8
    Floored
    well when you pull the head you will see if you tagged a piston with a valve. how about retainer to guide clearance? sometimes overlooked when new guides installed. just shootin ideas

  9. #9
    AZKC
    Retainer to guide clearance seems fine, I'm pretty sure the piston got dinged, just to lazy to go pull the head and see.

  10. #10
    Floored
    did you degre the cam? is yours the 305 mag? did you advance the cam?

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