Bent push rods????
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Junior User
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From: oregon
Bent push rods????
I am putting a 460 into my 75 250 which i am restoring. So i got everything together this weekend and tried to fire the motor for the first time. I turned the key and it turned over and didnt start. So i realized that i was 180 off with the distributed. So we fixed that. Then i got it started and it shook really bad and ran like crap. I shut it off and pulled the valve covers and discovered that i had 2 bent pushrods, on the number one and number six cylinders i think. Does anyone know what caused this, was it having it 180 out the cause. Any ideas would be greatly appreciated. Thanks Matt
Postmaster
Joined: Jul 2003
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From: okc
its a definite possibility, it would put undo pressure on valves and could easily bend something, you can try to put new pushrods in and see if it works, but you might be looking at getting the heads redone, hopefully a piston didnt get up close and personal with a valve and cause major damage....
FTE *******
Joined: Jan 2004
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From: Pittsburgh, PA
To have the dizzy in 180 out would not bend pushrods, the timing spark would not effect the mechanical parts. I have a question, did you just assemble this engine? If the engine is not stock, was it together and running before that you witnessed? I am asking because if it was just assembled and is stock, you could have made an assembly error. If its fresh together and is not stock, did you check for spring bind and piston to valve clearance? Did you look at the retainer to rocker arm clearance? Give us an idea as to what the history of the mystery is, and we can try to trouble shoot it from a common sense point of view with you.
FTE *******
Joined: Jan 2004
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From: Pittsburgh, PA
Piston to valve interferance is uneffected by putting the dizzy in wronge. All you did was spark at the wrong time, and while yes...this can put un needed forces on parts as ignition is going on at wrong times if at all...it will not, or never as far as I have seen or heard.....bent any parts. I think its a stretch to think timing the spark wrong can bend steel. Conversely... if the cam timing were not correct (ie. put the timing set in wrong...) this would dramaticly effect the valve timing in relation to the pistons location in the bore. This would in fact bend pushrods and valves.
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Junior User
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From: oregon
ya i just put this motor together. Everything is new and it is preety stock. Its 30 over with a mild cam. I had the machine shop just make a short block and i assembeled the rest of it myself. I have no idea what could have caused this, i hope it was just the timimg being so far off that did it and it didnt cause piston damage.
FTE *******
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From: Pittsburgh, PA
OK, I assume you assembled this engine and then put a big bar on a ratchet and turned the engine over at least 2 full turns? This will cycle each valve. If you forgot to do this, do me a favor and take all the pushrods out that were not damaged and put 4 good pushrods in the 2 cylinders that showed up damaged. Now get your bar and turn this thing by hand at least 2 full turns, heck, go 4. Now do it backwards 4 full turns. Did you make it or did something stop you? If you pull the plugs it will be way easier to turn over by hand. If this test is good, then we need to think a bit more, how where the rockers adjusted if they are adjustable...or do you have the stock non adjustable?
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Elder User
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My first guess would be that the rockers were too tight and the pistons and valves were having "intimate relations".
Brad
Brad
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Junior User
Joined: Aug 2004
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From: oregon
The rockers are the none adjustable ones though so i dont see how they could be out of adjustment. I am just thinking of putting two new pushrods in and firin it up to see what happens, but what do you guys think???
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Junior User
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From: oregon
I am just confused about this because the machine shop assembled this motor, i mean im sure the timing gears were put on rite and the cam was degreed correctly. I just dont understand what could have caused this besides the timing being 180 off.
Elder User
Joined: Jan 2004
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Run a compression test first to make sure you don't have a bent valve. If things hit hard enough to bend the rods, well...
The parts monkey at the store could have given you pushrods for the wrong motor, or someone may have accidently misboxed a set. Always measure your pushrods to be sure - especially with non-adjustable rockers.
Brad
The parts monkey at the store could have given you pushrods for the wrong motor, or someone may have accidently misboxed a set. Always measure your pushrods to be sure - especially with non-adjustable rockers.
Brad
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Joined: Jun 1999
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From: Everett, Wa
You didn't say whether it was an exhaust or intake pushrod. On my 429, within 3000 miles I bent, more like broke my number one exhust pushrod because the valve seized in the guide. No warning on this, I was on the freeway when it happend.
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Junior User
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From: oregon
i put two new pushrods in tonite got all of the rockers bolted down turned the motor over to get it on the compression stroke so i could set the timing, and the same damn two pushrods bent again. Its the number 1 and 5 exhaust that keep bending, so does that tell anyone anything. THIS IS SO FRUSTRATING!!!! Thanks Guys