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Replacing bent pushrods in a 390

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  • HighwayThunder
    Experienced
    • Nov 19 2013
    • 139

    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.
    Attached Files
    Richard, '66 Thunderbird Hardtop, 390FE, Edelbrock Al heads, Comp cam, Street Demon 650 carb. Visit my restoration blog at hwythunder.com.
  • Yadkin
    Banned
    • Aug 11 2012
    • 1905

    #2
    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.

    Comment

    • jopizz
      Super-Experienced


      • Nov 23 2009
      • 8460

      #3
      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
      John Pizzi - Squarebirds Administrator

      Thunderbird Registry #36223
      jopizz@squarebirds.org 856-779-9695

      https://www.squarebirds.org/picture_gallery/TechnicalResourceLibrary/trl.htm

      Comment

      • simplyconnected
        Administrator
        • May 26 2009
        • 8829

        #4
        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
        Member, Sons of the American Revolution

        CLICK HERE to see my custom hydraulic roller 390 FE build.

        "We've got to pause and ask ourselves: How much clean air do we need?"
        --Lee Iacocca

        From: Royal Oak, Michigan

        Comment

        • simplyconnected
          Administrator
          • May 26 2009
          • 8829

          #5
          Originally posted by HighwayThunder
          ...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
          Member, Sons of the American Revolution

          CLICK HERE to see my custom hydraulic roller 390 FE build.

          "We've got to pause and ask ourselves: How much clean air do we need?"
          --Lee Iacocca

          From: Royal Oak, Michigan

          Comment

          • HighwayThunder
            Experienced
            • Nov 19 2013
            • 139

            #6
            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
            Richard, '66 Thunderbird Hardtop, 390FE, Edelbrock Al heads, Comp cam, Street Demon 650 carb. Visit my restoration blog at hwythunder.com.

            Comment

            • simplyconnected
              Administrator
              • May 26 2009
              • 8829

              #7
              Originally posted by simplyconnected
              ...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
              Member, Sons of the American Revolution

              CLICK HERE to see my custom hydraulic roller 390 FE build.

              "We've got to pause and ask ourselves: How much clean air do we need?"
              --Lee Iacocca

              From: Royal Oak, Michigan

              Comment

              • HighwayThunder
                Experienced
                • Nov 19 2013
                • 139

                #8
                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,
                Richard, '66 Thunderbird Hardtop, 390FE, Edelbrock Al heads, Comp cam, Street Demon 650 carb. Visit my restoration blog at hwythunder.com.

                Comment

                • jopizz
                  Super-Experienced


                  • Nov 23 2009
                  • 8460

                  #9
                  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
                  John Pizzi - Squarebirds Administrator

                  Thunderbird Registry #36223
                  jopizz@squarebirds.org 856-779-9695

                  https://www.squarebirds.org/picture_gallery/TechnicalResourceLibrary/trl.htm

                  Comment

                  • simplyconnected
                    Administrator
                    • May 26 2009
                    • 8829

                    #10
                    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.
                    Member, Sons of the American Revolution

                    CLICK HERE to see my custom hydraulic roller 390 FE build.

                    "We've got to pause and ask ourselves: How much clean air do we need?"
                    --Lee Iacocca

                    From: Royal Oak, Michigan

                    Comment

                    • HighwayThunder
                      Experienced
                      • Nov 19 2013
                      • 139

                      #11
                      More information

                      In response to a request for more detail, I've uploaded photos of the bent pushrod aftermath. The heads have been removed and I've begun to clean the varnish-like residue that is coating the valves and pistons. Presumably, this was caused by the old leaded gas that was mixed into the fuel.

                      Is it OK to use lacquer thinner as a solvent, or is something else recommended?

                      Also, while I've got everything apart, I'm considering installing a roller cam system. I could use advice on part numbers, sources, and any other recommendations.

                      As always, thank you.

                      Cheers,
                      Richard
                      Attached Files
                      Richard, '66 Thunderbird Hardtop, 390FE, Edelbrock Al heads, Comp cam, Street Demon 650 carb. Visit my restoration blog at hwythunder.com.

                      Comment

                      • simplyconnected
                        Administrator
                        • May 26 2009
                        • 8829

                        #12
                        Upon seeing your pictures, I have more questions:
                        1. Did you use sealant on the bolts that go through water jackets?
                        2. Why are all your cylinders smooth and shiny?
                        3. Where is the crosshatch?
                        4. What alloy pistons did you use and what did you set your end gaps to?
                        5. What does your piston-to-cylinder clearance measure out to be?
                        6. Did you test your valves for any leaks? Are any bent?
                        7. What is the condition of your rocker arms and rocker shafts?
                        8. Do you have adjustable rocker arms.
                        9. Are you using the oil shields under the rocker shaft stands?

                        I see black oil coming from the water holes. You need something that dissolves water and oil. I would try gasohol since it is a mixture of both alcohol and petroleum. Denatured alcohol might work too. It is safe to use lacquer thinner or acetone, if you have lots of ventilation. Stay away from any substance that melts aluminum or iron like muriatic (hydrochloric) and sulfuric acids.

                        Summit and Jegs have roller cams. You will need different pushrods that can only be measured after you get your heads and rocker arms installed with the new roller followers because you need to establish the preload on your lifters.
                        There are lots of questions here. I'm asking because the only thing I know is what you told (or showed) us. Each engine build is very precision and must be double-checked before firing it up. The cost for materials is the same whether it is assembled correctly or not. The difference is, if anything is wrong it must be redone, which always costs more money.
                        You are in the deep south, far from Detroit. From here, I can only ask questions and suggest solutions. If I were closer I would come down there. - Dave
                        Member, Sons of the American Revolution

                        CLICK HERE to see my custom hydraulic roller 390 FE build.

                        "We've got to pause and ask ourselves: How much clean air do we need?"
                        --Lee Iacocca

                        From: Royal Oak, Michigan

                        Comment

                        • HighwayThunder
                          Experienced
                          • Nov 19 2013
                          • 139

                          #13
                          Upon seeing your pictures...

                          1. Did you use sealant on the bolts that go through water jackets? Yes
                          2. Why are all your cylinders smooth and shiny? Where is the crosshatch? I didn’t know to do that. Since I’m having the engine out, I’ll hone the cylinders. Do you think I need to replace the rings? The engine hadn’t been run much, probably under two hours total.
                          4. What alloy pistons did you use and what did you set your end gaps to? Pistons are hypereutectic aluminum
                          5. What does your piston-to-cylinder clearance measure out to be? Don’t know what that means in this context. The cylinders were bored .030 over and the pistons are sized to match .030 bore.
                          6. Did you test your valves for any leaks? Are any bent? None of the valves are bent. Aside from the bad fuel contamination the heads did not sustain any damage.
                          7. What is the condition of your rocker arms and rocker shafts? Those are in serviceable condition, as well as the lifters.
                          8. Do you have adjustable rocker arms. I WISH!! Adjusting valve lash by custom-fitting pushrods seems a bit primitive.
                          9. Are you using the oil shields under the rocker shaft stands? No. The stock shields don’t fit the Edelbrock heads. Edelbrock tech support told me I didn’t need them. However, it occurs to me that that would lower the rocker assembly by the thickness of the shield. Should shims be installed under the rocker stands to compensate for the missing shield?

                          I see black oil coming from the water holes. What you are seeing is not black oil; it’s the remnants of the “Right Stuff” sealant applied to the gasket around the water holes (per the Edelbrock installation procedure). In fact when I drained the ethylene glycol coolant from the engine it was as clean as when it went in, no contaminants whatsoever. I saved it and can reuse it.
                          Richard, '66 Thunderbird Hardtop, 390FE, Edelbrock Al heads, Comp cam, Street Demon 650 carb. Visit my restoration blog at hwythunder.com.

                          Comment

                          • Dan Leavens
                            Moderator / Administrator


                            • Oct 4 2006
                            • 6420

                            #14
                            What other TBird site would have this much technical data being exchanged between members? Good Stuff
                            Dano Calgary,Alberta Canada
                            Thunderbird Registry
                            58HT #33317
                            60 HT (Sold )

                            Comment

                            • simplyconnected
                              Administrator
                              • May 26 2009
                              • 8829

                              #15
                              Where do I start? Some engine builders will not be bothered with the precision a short block requires so they buy 'crate' engines. This is one area that separates the men from the boys.

                              **PISTON RINGS**
                              When fuel explodes it slams the top ring down and pressure behind the top ring pushes it out, hard against the cylinder walls. This cylinder area will show the most wear because as the piston moves down the bore, compression gets lighter until finally, the exhaust valve opens. Over time, the cylinder becomes 'bell-shaped'. As the cylinder wears away so does the outer circumference of the ring, and the 'spring' goes away so it doesn't push out as hard (or seal as well). Ring wear translates into a wider end gap that can be measured with feeler gauges. Cylinder wear can be measured directly.

                              Cylinder bores need to be straight, from top to bottom. That's why we bore them, so the rings don't flex in and out. If you put new rings on a worn cylinder, the rings will soon break from rapid flexing.

                              How far down the cylinder did you measure the rings' end gaps, and what measurement did you set them to?

                              Smooth cylinder walls cause your engine to burn oil. Think of the grooves cut into the interstate. Rain has somewhere to go and your tires do not hydroplane. That is how crosshatch works in a cylinder bore. Rings 'skate' over oil on the way down the 'intake stroke' then they carry the oil up to be burned off.

                              That tool with stones that you put into your drill motor is not a hone. It is a 'glaze breaker'. A real hone has stones that do not move (until they are mechanically re-adjusted) and the machine it is attached to has an amp-meter (ammeter) to show the motor load as the stones cut from top to bottom in the bore.

                              So here's how it should go...
                              Your engine machine shop determines how far to bore the cylinders, then the pistons are ordered. Each piston is measured and the bore is set to that size after honing and brushing.
                              The piston alloy you buy determines how 'tight' the piston sits in the bore. It's called, Piston-to-Cylinder Clearance, and this measurement is critical. Why? Because different alloys transfer heat at different rates. That also affects the end gap on your rings. The more heat transferred to the ring, the wider the gap must be because heat closes the gap to the point where your ring will bind and break.

                              I don't know how you stuffed new +.030" pistons into bores that were not bored or honed. Apparently your block was bored before you started. Otherwise the pistons would be extremely tight at the bottom and sloppy at the top of each bore.

                              Pistons come in sizes up to +.060".

                              I suggest you take the block down to 'bare' and bring it to a GOOD engine machine shop. The South is full of them. If you don't know who is good ask a dealership mechanic who they use because their business reputation depends on quality work.

                              You can assemble the engine but let them do all the machining. They will probably need new pistons to bore the cylinders. It's your job to measure, gap, and install the rings.

                              I use hypereutectic or forged pistons. They both use different ring end gaps. This is where you need to keep your head screwed on straight and perform proper ring end gaps, depending on the size of the bore and piston alloy.

                              When Ford built your engine, they did 1,000 per day, all the same. Because they are all identical, engineers easily determined what pushrod length to use with hydraulic lifters. Preload is up to .040", which is a lot.

                              Here we are, fifty years later with shaved blocks, aftermarket heads, no oil splash guards under the lifter shaft stands, etc. Mechanical lifters use adjustable rocker arms (like 427). If you reuse your hydraulic lifters and rocker arm assemblies, you MUST determine a new pushrod length using the same .040" preload.

                              It's no wonder your pushrods bent. Your block deck was probably shaved (making it lower) and you removed at least .035" of steel from under your shaft stands. Because the valves don't move, that drove your pushrods down at least .070" (twice the thickness of the shields). You also have different head gasket thickness.

                              After your heads are assembled and mounted and your timing chain is correctly installed, determine two critical measurements: Piston to Valve Clearance and Pushrod Length. You need tools. You can buy or make a pushrod with an adjustment jack screw.
                              I charge my #1 cylinder with compressed air and remove the valve springs. Then I wire the valves so they can't drop. I mount the rocker shaft with no pushrods, then I use the 'test' pushrod to determine .035" lifter preload on each base circle of #1 valves.
                              Install the test pushrod, set to length, in the exhaust lifter and under the rocker arm with the rocker shaft tightened down. Now, carefully rotate the engine by hand. As the lifter pushes the rocker arm, keep lifting the valve up and down. You should feel the piston on the down side and the rocker arm on the up side. At their closest point, use your feeler gauge to measure between the valve and rocker arm. If the valve ever touches the piston with zero gap, that's a big problem. At this point I will ask, 'what measurement do you get?' - Dave
                              Member, Sons of the American Revolution

                              CLICK HERE to see my custom hydraulic roller 390 FE build.

                              "We've got to pause and ask ourselves: How much clean air do we need?"
                              --Lee Iacocca

                              From: Royal Oak, Michigan

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