Push rods keep bending
04-07-2004, 12:50 AM
#11
3rd Gear Member
Join Date: Mar 2004
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Posts: 607
RE: Push rods keep bending
Perhaps I should clarify what I meant when I asked if you checked for piston to valve clearance, or if you checked the valve timing.
When you put an engine together, you should check (and recheck) that you get the timing marks right on the timing gears (or chain), especially if you added a new cam with higher lift. AND you should always check to be sure that there is clearance between the valve and the piston. You do this by placing clay on top of the piston in the general area where the valve is above it. Doesn't have to be very much. Then you place the head(s) on (with gaskets) and assemble the entire valve train assembly. Once assembled, rotate the motor by hand (rachet and socket) a few rotations to get all the valves to move a couple of times. Once this is done, remove the heads and see how much the valves have flatten the clay, and measure the thickness where it did flatten it. This will be your piston to valve clearance. There should a spec that you need to follow for your particular motor, which should be provided by the cam manufacturer.
Even if you reused the same cam, if you get the the cam to crank timing off by any chance when you reassembled it, it may allow the valves to open too early, and meet the piston at the end of it's exhaust stroke. This will definately make a rattling noise, and bend your rods.
At this point, to me, it sounds like you better repull that motor and check your pistons and valves as well. If you've got bent pushrods, more than likely you've got bent valves as well. Just hope you didn't crack a piston or 2 in the process.
I know it's probably not what you want to hear, but you've got to get to the root of the problem before you do anymore damage here.
When you put an engine together, you should check (and recheck) that you get the timing marks right on the timing gears (or chain), especially if you added a new cam with higher lift. AND you should always check to be sure that there is clearance between the valve and the piston. You do this by placing clay on top of the piston in the general area where the valve is above it. Doesn't have to be very much. Then you place the head(s) on (with gaskets) and assemble the entire valve train assembly. Once assembled, rotate the motor by hand (rachet and socket) a few rotations to get all the valves to move a couple of times. Once this is done, remove the heads and see how much the valves have flatten the clay, and measure the thickness where it did flatten it. This will be your piston to valve clearance. There should a spec that you need to follow for your particular motor, which should be provided by the cam manufacturer.
Even if you reused the same cam, if you get the the cam to crank timing off by any chance when you reassembled it, it may allow the valves to open too early, and meet the piston at the end of it's exhaust stroke. This will definately make a rattling noise, and bend your rods.
At this point, to me, it sounds like you better repull that motor and check your pistons and valves as well. If you've got bent pushrods, more than likely you've got bent valves as well. Just hope you didn't crack a piston or 2 in the process.
I know it's probably not what you want to hear, but you've got to get to the root of the problem before you do anymore damage here.
04-07-2004, 10:21 PM
#13
3rd Gear Member
Join Date: Mar 2004
Location:
Posts: 607
RE: Push rods keep bending
Yup, pretty much. I just elaborated on it more 
Remember, I'm a newbie here, so I can get away with it (or at least I hope I can 
)
Hmmm, you're a newbie as well. So maybe we can both get away with it [&:]
Remember, I'm a newbie here, so I can get away with it (or at least I hope I can )Hmmm, you're a newbie as well. So maybe we can both get away with it [&:]
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