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#1
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Help!! bent push rods
Well I did it put the new resto mp cam in today. tried to start the car and it turned over then wouldnt turn no more. so I took it apart again... and found 6 bent push rods? what gives . the cam is from MP the resto cam for a 383. any ideas suggestions. about what I did wrong!! ideas????
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#2
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Have your heads been milled? Did you use the right push rods?
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#3
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I did nothing to the heads..put the push rods back in original positions...
found more bad news...broken valves also...damaged pistons to.... |
#4
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Did you put the lifters in oil and pump them up?? IF so, that's why you have bent valves,push rods, and such.
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#5
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Are it's pistons compatible with that cam?
torch |
#6
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No I didn`t pump the lifters up...i`m dazed and confused... I did compare the old lifters to the new ones and the new ones are a hair taller....for what its worth. anybody know of a good machineshop in eastern iowa..
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#7
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Don`t know about the pistons I bought this car couple years ago off ebay. there flat top pistons...or they use to be.. I guess now I`ll know whats in there after I get it rebuilt.
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#8
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HOw much taller are the new lifters ?? I think you found your problem. IF so, I'd go back against who ever you bought them from and get them to pay for your new engine if they sent you the wrong ones.
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#9
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I got them from mancini racing. me and the guy discussed what I wanted the car to do i told him stock.. so we went with the 383 resto cam and lifters.
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#10
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sounds like you have the cam "timed" wrong, way off.
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#11
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don`t know...I did what the manual said....crank dot up cam dot down...mike
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#12
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check your dots again
this happened to me, except i bent eight of them. there was another "dot" on the cam gear that mistook for the right one. i got lucky though, it never started so all i had to replace were the pushrods.
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#13
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torch |
#14
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HE said he ligned it up dot for dot on the cam gears. I'd say it's because the lifters are too tall as he described earlier. Got the wrong part. It happens.
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#15
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From what he said, it appears that the outside of the new lifter is a hair (barely noticable) taller than the outside of the old lifters. As long as the seat is at the same height, the outside being 'a hair' taller won't make a difference.
He didn't specify if he reused the old pushrods or if those are new as well. I would pull off the timing cover and confirm that the cam is actually straight up. Then I would pull out the new lifters and confirm that the seat height is correct and also confirm that the seats will compress. If you have the right push rods, the lifter seats are correct, the seats compress, and the cam is still properly aligned, then it would point at an incorrect timing gear or the alignment pin on the cam is not correct. |
#16
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bent
maybe i misread what he said didnt he say cam dot up and crank dot up ? thought cam dot was down and crank dot was up but it is a big block so i'm not sure lol
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#17
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Roadrrr did you put in a new timing set? If so it's always possible it was incorrectly stamped. If your dots prove lined up check into the timing set. I've only seen it happen once. But you never know. |
#18
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i saw it was the wrong dot. or it has aftermarket domed pistons but he didn't say that, plus its a stock cam not a huge .600 lift cam. steve |
#19
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It sounds like the cam timing was off to me as well...I doubt a "hair" of difference between the old lifters and the new lifters would cause this kind of problem on a cam with .450/.458 lift, assuming it's the proper cam. |
#20
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help bent pushrods
I have a 496 stroker motor.I had a pushrod bend on me because my engine builder forgot to install a cam button,and the cam took a walk.therefore I ended up with a bent pushrod.
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#21
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It does matter because if the cam is 180° off the pistons will be at TDC while the valves ore open for the intake. When you line up the dots, You have to make sure #1 piston is at TDC and the valves are closed, otherwise the cam will think that Number 6 is at TDC based on the firing order (1-8-4-3-6-5-7-2 |
#22
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um, no. line up the dots. #1 is on the exaust stroke (tdc)
turn the crank 1 turn (cam turns 1/2, dots are now top to top, crank is in the same spot), #1 is on the compression stroke (tdc) you can line up the dots top to top, install your dist drive the same, put the rotor facing the front instead of the back, and wallah! for future reference (i have seen off timing chains before) either degree the cam in (i always do), or, what i did before i had a degree wheel, or if i am away and aint got it, take your old chain and gears, line them up, then, install the new set. if you have to move it much, something is wrong. |
#23
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#24
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The camshaft turns at exactly half the speed of the crankshaft. With the timing set on the engine, turning the crankshaft 360 degrees will result in the camshaft turning 180, so the dot at the bottom of the cam sprocket will wind up at the top of sprocket. Turn the crank another 360 and the dot will be at the bottom again. Am I missing something here? |
#25
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I am kind of confused here. TDC is TDC whether the cylinder is on the compression stroke or the exhaust stroke. What determines which cycle the cylinder is on is the position of the cam.
I can't understand why there would be a collision between pistons and valves if the cam was 180 degrees off, although the ignition would be off by that much. I think I understand what tk is saying. |
#26
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#27
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#28
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I don't see the difference. The only way that there could be pistons and valves trying to occupy the same space is if the cam was out of position by closer to 90 degrees, or 1/4 of a turn. Maybe more, maybe less, but 180* out will never cause a mechanical whoops. At least, that is how I imagine it. Help me out, guys. What do you think? |
#29
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DICK, you are correct. The cam can't be 180* out, it's simply positioning the cam as if it's on a different stroke. Now if it was 40* out then it might be a problem.
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#30
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Ok. Think of this. #1 is at top dead center. both valves are closed. now if you leave the crank alone and just turn the cam, the valves will open. but because the cam will turn 2 times to the cranks one, you can still line the dots up, but they will be in the wrong spot (180° off
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