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  #1  
Old 01-01-2015, 03:51 PM
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Default Replacing bent pushrods in a 390

When I first fired up my 390 a couple of months ago, it ran smoothly. But recently it started running rough. There was a load tapping noise under the left valve cover. When I removed the cover I discovered that there were bent push rods in the 3rd, 4th, 5th, and 6th positions. Likewise the right side had bent rods in the 3rd and 4th positions (see photo).

How was this engine even running?

Can anyone offer advice as to what caused this and how to remedy?

Thanks very much.
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  #2  
Old 01-01-2015, 04:52 PM
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The same thing happened to me. I had five year old gas in the tank, and it had turned to varnish, and that got on the valve stems and froze them up.

Use this as an excuse to have the heads rebuilt, and install hardened valve seats so you can safely use unleaded fuel.

And get rid of every bit of that old fuel and the deposits that are now in your fuel system:

Drain your tank and have it professionally cleaned. Use a full can of carburetor cleaner to flush out your fuel line. Buy a new fuel pump, and rebuild your carburetor.
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  #3  
Old 01-01-2015, 04:54 PM
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That's usually caused by sticking valves. Tap on the valve with a rubber mallet. If it feels solid then the valve is probably stuck. If all the valves are free then it could be the lifters.

John
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  #4  
Old 01-01-2015, 08:25 PM
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This is serious. First, make sure you have oil flow to the rocker shafts. If valves are run dry, rocker arms can score and seize, then they can stick down, then the pistons will bend them back up. I cannot emphasize the importance of oil flow. You don't need a lot but you should see it coming out of all the rocker arms.

For any engine that sat for a long time or a newly built "dry" engine, I pull the distributor, put a 1/4" drive over the oil pump intermediate shaft and run it counter clockwise. I pull the rocker covers off and watch. A newly built engine will take a while to fill the rocker shafts with oil, then you can see it coming out each arm.

An old engine may have the rocker shafts plugged up with sludge. Take the rocker arms off each shaft, look for scoring and clean all the parts. CLICK HERE

Check for broken valve springs and keepers that might be missing. If everything looks ok, smack each valve with a rubber mallet. You should see them return immediately and hear a hollow sound as the valve seats. If you don't, pull the head and look for a good engine machine shop.

You didn't give much background about this engine, so troubleshooting cannot be specific. I assume you are describing valves from #2 & #3 cylinders.

It's a good idea to blow air down your spark plug holes to detect valve leaks. - Dave
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Old 01-13-2015, 01:08 AM
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Quote:
Originally Posted by HighwayThunder View Post
...Can anyone offer advice as to what caused this and how to remedy?..
Well?
What did you find?
I understand this was a new rebuild with new heads. Did you prime the system? Did you watch oil lube each rocker arm? What oil pressure are you getting? - Dave
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  #6  
Old 01-16-2015, 10:29 AM
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Default Bent pushrods follow-up

Apologies for the delayed response.

There was some leaded gas that I had drained and filtered from the old tank. I didn't know how to dispose of it, so I mixed some with an equal amount of unleaded and used it in the engine. I thought it would do no harm. How wrong I was. From the responses to my post and from other references on the web, I'm convinced that has been what led to the bent pushrods. Luckily, the one silver lining is that the engine was being fueled via a gas can attached to the fuel pump – my new gas tank is uncontaminated.

In deciding how to proceed, I'm taking into consideration previous problems. Before the initial start-up water had gotten into the engine via open spark plug ports. (There’s no garage, although I've since installed a car port.) The water sludged up the oil, which took several oil changes to correct. Nonetheless, the oil still turns a tad milky-looking.

The other problem is cause for further embarrassment. There's an oil leak coming from the rear of the engine when it's running (i.e., with oil pressure). Worst case, that's a faulty rear crank seal; if lucky, it's a loose oil plug.

I think the best route is
  • · remove the engine;
  • · run the oil pump to determine the source of the rear leak;
  • · drain the oil and clean out all oil passages;
  • · clean any bad oil from the inside of each hydraulic lifter;
  • · remove the heads and clean any sticky fuel deposits from the valves; check valves for smooth operation;
  • · modify the head oil passage for better lubrication of the rocker shaft;
  • · clean the carburetor;
  • · repair the cause of the rear engine leak;
  • · reassemble the engine with new pushrods;
  • · reinstall the engine.
Thanks to everyone who weighed in. Your comments and advice are invaluable.

Cheers,
Richard
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  #7  
Old 01-16-2015, 11:55 AM
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Quote:
Originally Posted by simplyconnected View Post
...Did you prime the system? Did you watch oil lube each rocker arm? What oil pressure are you getting?..
I wrote a rather lengthy response to you and asked a few questions, none of which were answered.

Something else is going on in your engine. A little bit of water will evaporate and go away. It doesn't take several oil changes to clear it up.

You are still getting water in your oil, and now your pushrods are bending. (DING DING DING) Big red flags. I have never heard of gasoline bending pushrods. Old gas smells like varnish and it usually gums up your carburetor. If mixed with new gas it will burn but it won't develop the right HP.

You have new Edelbrock heads. Remove them and carefully inspect your head gaskets. Also, inspect your intake manifold gaskets around the water holes. You probably have a rear main oil seal leak BUT the leak could come from a rear plug (there are four oil and one cam). This cam plug is inserted the correct way:


Let's see pictures of your build. As you pull the engine and take it down to the block, take 100 pictures. This isn't about personal feelings (embarrassment) or finger pointing. This lesson has been played out many times. FE engines are NOT like Chevy engines, they are a lot harder. Most Chevy builders run into the same issues you just ran into. If we had good clear pictures to look back on, we can usually identify your problem. Every angle needs to be covered. We want your build to be better than 'factory' and we don't want any failures to repeat.

If you need to see how any part of this is done, refer to my link and follow my 390 build. - Dave
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  #8  
Old 01-17-2015, 05:15 PM
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There are two clarifications that need to be made to understand the history of the engine. The first is the “water via the spark plug ports” issue. That occurred prior to initial engine start, August 2014. The water actually flooded the cylinders – when I removed the heads there was standing water on top of the pistons. I dried, vacuumed, cleaned with compressed air, and then sprayed the cylinder walls with WD-40; reinstalled the heads and intake using new gaskets. The water had also infiltrated the crankcase turning the oil to a thick sludge. I changed the oil and filter 4 times, and removed the oil pan the first few times to get out any remaining sludge. Also disassembled the rockers and cleaned out the rocker shafts.

The second clarification is that the rebuilt engine had been stored “dry” for about a year before it was installed in the car. The oil leak coming from the rear of the engine originated with the initial start-up in August 2014. I understand that it’s possible that the crank rear seal dried out during storage and for that reason may be the source of the leak.

Following are responses to your other questions.
  • The oiling system was primed and there was oil flow to the rockers prior to initial start-up.
  • Actual oil pressure is indeterminate because the dash panel instrumentation is not installed. But now that I mention it, I can (and will) hook up the instrumentation without the dash. (I’m working outside and the weather has been uncooperative. The dash panel has to be painted before install but I can’t paint outside or inside, the latter because my wife forbids it due to the odor.)
As always, your advice is appreciated.

Cheers,
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  #9  
Old 01-17-2015, 05:26 PM
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When you removed the heads did you inspect the valves, guides and seats. Standing water in the cylinders will certainly cause the valves to rust to the seats and guides. This would be the reason for the bent push rods. As for the oil leak it's possible the seal dried up but it's also possible it was installed incorrectly.

John
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Old 01-17-2015, 09:00 PM
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People put their cars 'to bed' all the time. An engine may be safely stored indefinitely if you fog the combustion chambers and replace the spark plugs. That keeps the water out and the cylinders from rusting. Of course, the carb needs to be covered as well.

Never depend on your dash gauges for initial oil pressure readings. Use a cheap mechanical oil pressure gauge, screwed into any one of the oil gallery plugs. It may be removed later or not. I remove mine so I can use it on the next engine.

Seals are always greased when installed. Later on, oil will displace the grease but they are always kept oiled. Dry rubber against rotating steel will heat up and destroy itself in no time.

Oil floats on water. Draining it would remove the water first then the oil, unless you ran engine with water in it.

It makes sense that the engine ran ok for a bit, then it didn't. Water makes a terrible lubricant after it washes the oil away. Rusty valve stems would have bent the pushrods immediately but that's not what happened. Your Edelbrock heads have stainless valves and manganese bronze guides that do not rust.

Pay close attention to your bearings. The last thing we want is a freshly balanced crankshaft that's galled-up with bearing tin.

Once you clean the pan of water, the only reason to do it again is if water is re-introduced. Where is it coming from? Are you using antifreeze on startup?

When you pull a head, naturally water will pool in the piston tops because it leaks out of the coolant ports. That's no big deal. I've used a garden hose to wash my short blocks, just to get the antifreeze out. Then, simply drain the pan but don't start the engine until it's dry. Sometimes I use gasohol to suck up water and wash contaminated oil out of the pan. Fill with fresh oil.
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