what could cause 16 bent pushrods on start up after cam swap
10-22-2003, 03:01 PM
#62
Re: what could cause 16 bent pushrods on start up after cam swap
the LT1 has 1.5 RR stock. I dunno the lift of the Comp 305 though...
10-22-2003, 04:07 PM
#63
Re: what could cause 16 bent pushrods on start up after cam swap The cam, springs, and lifters were all slightly used. I have seen tons of cam installs done with stock pushrods so I thought I would be alright but as I said before, I was wrong. I bought some new pushrods from CMotorsports and they should be here by Friday. After lots of questions and lots of answers by you guys I have seen where I went wrong and that was by lashing the valves while the engine was not running. Thanks for all the help and I will let you know how she pulls when I get her running this weekend!
10-23-2003, 03:00 AM
#67
Re: what could cause 16 bent pushrods on start up after cam swap you can set the valve lash with the motor off and there should still be no problems. You will receive a little tapping until the lifters pump up but thats it. Hardened or not, the pushrods shouldnt have bent. Stock pushrods can handle way more stress than the 305 cam can deliver. What procedure did you use to set the valve lash with the motor off(intake close set the exhaust and when the exhaust opens you set the intake)?
305 with 1.5 RR's: 220/230 .510/.510
305 with 1.6 RR's: 220/230 .544/.544(aprox.)
pushrods arent really affected by high milage. The tips may wear down very slightly with high pilage causeing a variance in valvetrain geometry but it would be miniscule and resetting valve lash would correct this. Stock pushrods, hardened or not, can easily handle that cam all day long. If the lifters didnt have oil and then pumped up after install, it wouldnt cause the pushrods to bend, it would just open the valve a tad more but no where near enough to cause PtoV clearance issue. My first thought would be that the valves hit the tops of the pistons and so the valvetrain found the weakest link, but he said that the tops of the pistons had no scratches. This is a very interesting problem...I for one am very interested to see what the issue is, and if its because all 16 pushrods couldnt handle that small cam, then I've learned something new.
305 with 1.5 RR's: 220/230 .510/.510
305 with 1.6 RR's: 220/230 .544/.544(aprox.)
pushrods arent really affected by high milage. The tips may wear down very slightly with high pilage causeing a variance in valvetrain geometry but it would be miniscule and resetting valve lash would correct this. Stock pushrods, hardened or not, can easily handle that cam all day long. If the lifters didnt have oil and then pumped up after install, it wouldnt cause the pushrods to bend, it would just open the valve a tad more but no where near enough to cause PtoV clearance issue. My first thought would be that the valves hit the tops of the pistons and so the valvetrain found the weakest link, but he said that the tops of the pistons had no scratches. This is a very interesting problem...I for one am very interested to see what the issue is, and if its because all 16 pushrods couldnt handle that small cam, then I've learned something new.
10-23-2003, 12:17 PM
#68
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Re: what could cause 16 bent pushrods on start up after cam swap I fully agree with what gangly said. I think alot of people are thinking the the lifter is going to grow in size or somthing when it is fully pumped uP. When in fact its just the internals of the lifter that will become more firm and have less give when they pump up . with very little change is size, This hole thing does not make sense. Some facts are missing here. I truely think that the valves must have hit the pistons. Is it possible that they hit just enough to bend the push rods but not make any marks. I doubt it. So I will have to go and say that it was somthing to do with the springs binding up. Now if they did do this , it would explain the no marks on the pistons and valves and the bent pushrods.Now if this holds true i would say that you may alos want to check your lifters. Becasue if this secnario is true then there is a good change that now you may have a few colapsed lifters.
My last theory is this and dont take it wrong cause i dont know you. But it is very possible that you are a jack *** and just messed up the backlash very badly and in fact the valves did hit the pistons, but you did not want to sound like an *** so you said that it did not happen.
well thats just my 2 cents..
My last theory is this and dont take it wrong cause i dont know you. But it is very possible that you are a jack *** and just messed up the backlash very badly and in fact the valves did hit the pistons, but you did not want to sound like an *** so you said that it did not happen.
well thats just my 2 cents..
10-23-2003, 03:43 PM
#69
Re: what could cause 16 bent pushrods on start up after cam swap Im not a jack *** and I did lash the valves corrctly. Im pretty sure that coil bind was the culprit so before I put anything back together, Im ordering springs good for a .600 lift just to be on the safe side.
10-24-2003, 12:15 PM
#70
Originally Posted by 96SCTA
I fully agree with what gangly said. I think alot of people are thinking the the lifter is going to grow in size or somthing when it is fully pumped uP. When in fact its just the internals of the lifter that will become more firm and have less give when they pump up . with very little change is size, This hole thing does not make sense. Some facts are missing here. I truely think that the valves must have hit the pistons. Is it possible that they hit just enough to bend the push rods but not make any marks. I doubt it. So I will have to go and say that it was somthing to do with the springs binding up. Now if they did do this , it would explain the no marks on the pistons and valves and the bent pushrods.Now if this holds true i would say that you may alos want to check your lifters. Becasue if this secnario is true then there is a good change that now you may have a few colapsed lifters.
My last theory is this and dont take it wrong cause i dont know you. But it is very possible that you are a jack *** and just messed up the backlash very badly and in fact the valves did hit the pistons, but you did not want to sound like an *** so you said that it did not happen.
well thats just my 2 cents..
My last theory is this and dont take it wrong cause i dont know you. But it is very possible that you are a jack *** and just messed up the backlash very badly and in fact the valves did hit the pistons, but you did not want to sound like an *** so you said that it did not happen.
well thats just my 2 cents..
10-24-2003, 04:13 PM
#71
i just did, i couldnt push it down but a fraction of a millimeter if even that, but regardless, even if the lifter pumped up some crazy amount, it wouldnt push the valve down that much farther to where it could make contact with the piston, and he said there was no contact with the piston anyways. sounds like a spring issue which still makes me wonder how the pushrod bent, but something just isnt right here, like something is being left out, but I dunno, I could be completely overlooking something.
10-24-2003, 07:17 PM
#72
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In spite of some of the overly caustic replies this is a pretty good thread.
I like point made about it being coil bind. If the rockers were too tight, which they weren't since he did not tighten them a lot before startup, the motor would run poorly and shake right, but not bend all that stuff up.
I like point made about it being coil bind. If the rockers were too tight, which they weren't since he did not tighten them a lot before startup, the motor would run poorly and shake right, but not bend all that stuff up.
10-25-2003, 12:10 AM
#73
Originally Posted by Pro Stock John
In spite of some of the overly caustic replies this is a pretty good thread.
I like point made about it being coil bind. If the rockers were too tight, which they weren't since he did not tighten them a lot before startup, the motor would run poorly and shake right, but not bend all that stuff up.
I like point made about it being coil bind. If the rockers were too tight, which they weren't since he did not tighten them a lot before startup, the motor would run poorly and shake right, but not bend all that stuff up.
10-25-2003, 01:20 AM
#74
if they were loose enough for the pushrod to come out of the small, depressed bowl it pushes against, then you would have heard some crazy clacking sounds coming from the motor right when it fired up. the trunion is the part of the rocker arm that the rocker arm studs come up through(the middle piece that actually "rocks" within the rockerarm).
Last edited by Gangly; 10-25-2003 at 01:23 AM.
10-31-2003, 08:47 PM
#75
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I'm betting on coil bind. The springs he used were good for .550 lift. The lift on his cam, a 305 with 1.6 RR's: 220/230 .544/.544(aprox.), so he is only .006 in from coil bind if everything is set up perfect. Combined with his setting up the valve lash on possibly collapsed lifters, and BAM, coil bind and bent pushrods. IMHO
