Quit your complaining, where do you think all these threads come from on 60 year old cars?
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| what causes bent pushrods? https://www.slantsix.org/forum/viewtopic.php?t=65055 |
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| Author: | relic-lover [ Mon Jun 29, 2020 7:45 am ] |
| Post subject: | what causes bent pushrods? |
My project is to get a 61 valiant which has been parked 10 yrs running again. I got it to turn over and idle but did not like the amount of blue smoke from the exhaust. This car has only 28k original miles so I thought it should not smoke. I guessed the rings have collapsed or the valve seals may have crumbled away. So my plan was to do a inexpensive ring job and put new gaskets in the motor. I pulled the motor using the Dutra slant 6 book as a guide and have begun to inspect. I got a couple of surprises... The motor is very original. It had a steel manifold to block gasket and also a steel head gasket. The manifold bolts had no triangle washers only conical ones (on every bolt). I also found you should not order std size rod bearings based on the assumption the engine is original. After cleaning off the block stamping I found "R170 830 +X" (the plus being a malteze cross). Referred to the shop manual and more marks on the crank counter weights to find this motor came new with .010 under size rod journals and also .010 under size main journals. Now to the issue... The pushrods for the intake valves on the number 1 and 6 cylinders were bent pretty badly. What am I looking for in the valve train, guides, and valves to determine the cause of the bent pushrods? |
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| Author: | hyper_pak [ Mon Jun 29, 2020 7:53 am ] |
| Post subject: | Re: what causes bent pushrods? |
Sure the mileage is not 128000? If the valve adjustments get loose you can have a pushrod move over and bend when it gets out of the cup. On those cylinders, do you see small valve contact points on the tops of the pistons? Also, check the chain for teeth missing or it's jumped time. Washers could have been changed years ago, 61 was a long time ago! Good luck with the project! |
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| Author: | Dart270 [ Mon Jun 29, 2020 8:51 am ] |
| Post subject: | Re: what causes bent pushrods? |
If the valves become stuck closed (or partially), then you can bend pushrods too. Sounds like a fun historical and rebuilding expedition... Lou |
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| Author: | ProCycle [ Mon Jun 29, 2020 9:14 am ] |
| Post subject: | Re: what causes bent pushrods? |
Or if they stick open. The pushrod can come off the rocker and bend when the cam pushes it up and it binds between the side of the rocker and the opening in the head. |
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| Author: | nitro_rat [ Mon Jun 29, 2020 10:33 am ] |
| Post subject: | Re: what causes bent pushrods? |
Back in the day, steel shim head and intake/exhaust gaskets were over-the-counter parts. Your engine was probably overhauled back in the late 60's/early 70's. Check the pistons and measure the bore, may find oversizes there as well... |
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| Author: | Joshie225 [ Mon Jun 29, 2020 12:02 pm ] |
| Post subject: | Re: what causes bent pushrods? |
If you run the engine on old gas or didn't clean the tank well enough the varnish will travel through the fuel system and stick to the valves and stick them in the guides bending the pushrods. This happened to my '64 Valiant. The previous owner thought he was doing something good by running the car monthly, but he did so on old gas. Car barely ran until I replaced 3 intake pushrods. |
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| Author: | relic-lover [ Mon Jun 29, 2020 9:18 pm ] |
| Post subject: | Re: what causes bent pushrods? |
Thanks all for the replies. I reinspected the piston tops, the rocker arms,and the area in the block near the lifters. I did not see any evidence of contact. piston tops just had a light carbon coat and the other surfaces were dark with old oil. I have not removed the timing cover yet to look at the timing set. I removed the pistons tonight, the ridge at the top of the bore looked to be about .010 inch. Enough to make your finger nail click but not enough to make a ridge reamer mandatory. Also still need to disassemble the #1 and #6 cyl valve and springs to see if there is sticking there or a weak spring. In regard to stale gas, old gas may have been in the system prior to it being parked. But I modified the trunk floor and fit a new 1963 dart gas tank, sending unit, fuel line and fuel pump into it when preparing it to run again back in February this year. If the valves are sticky in the guides, does one just use carb cleaner and brushes to wash the guides out? Or does it take machining to get the guides cleaned up? |
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| Author: | Joshie225 [ Mon Jun 29, 2020 9:51 pm ] |
| Post subject: | Re: what causes bent pushrods? |
Carb or brake cleaner on a round wire brush will clean up the guides. But if the valves have metal smeared on the stems then you're looking at replacing the valves and guides. |
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| Author: | relic-lover [ Fri Jul 17, 2020 7:49 am ] |
| Post subject: | Re: what causes bent pushrods? |
Starting to get the motor back together. The issue was some sort of sticky varnish like deposit. The #1 and #6 intake valves were immovable in the guides, until penetrating oil and carb cleaner was used to dissolve the gunk. The piston pins and the lifters had similar issues although not as dramatic. Used a lot of cans of carb cleaner to clean the surfaces up. Now fighting "feature creep" ... The new paint on the engine block makes me want to paint the air cleaner housing and the starter and the engine bay. Next it will be the entire car. |
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| Author: | jcc [ Sat Jul 18, 2020 8:17 pm ] |
| Post subject: | Re: what causes bent pushrods? |
Quit your complaining, where do you think all these threads come from on 60 year old cars?
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