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By crab - 16 Years Ago
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Got the bird back running and when I started it up cold this evening I heard it pop and bend number 4 intake. Got new valve job, set all the valves to 18 thou. cold with slight resistance on the feeler, did each cylinder in firing order at respecive TDC when setting the valves. Did notice however some seemed looser at a different spot on the cam for some reason, wondering if they expand when hot or tighten up.
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By crenwelge - 16 Years Ago
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Valves clearances do get closer as the engine reaches operating temperature. Lots of things can cause a push rod to bend. The simplest being it was bent a little bit in the first place. I would look at the lifter with a light and see if it is ok and then check the valve to make sure the keepers are still in place and see that it is closed. If everything looks ok, I would put in a straight push rod, pull the coil wire out so it won't start, and crank her over a few times and see that everything functions properly.
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By crab - 16 Years Ago
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Going to have to let Mctim64 reply on that one, he did the head but I'm certain thats not the problem. New spiral groove guides installed.
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By crab - 16 Years Ago
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dinosaur (4/29/2009)
I still after all these years of working on cars as a hobby and a profession (50) haven't learned the importance of checking and rechecking EVERYTHING, or else. Never take anything for granted, or at face value.I agree completely, however when dealing with a master machinest I bow to their expertise and knowledge, it may have been a fault in my adjusting.....
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By charliemccraney - 16 Years Ago
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dinosaur (4/29/2009)
I still after all these years of working on cars as a hobby and a profession (50) haven't learned the importance of checking and rechecking EVERYTHING, or else. Never take anything for granted, or at face value.
I have to agree to some degree. I've had a rebuilt head from a master machinist and one of the keepers was not fully seated. Had I not looked things over, who knows what damage would have resulted. The point is, even the best in the business make mistakes.
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By simplyconnected - 16 Years Ago
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Charlie, whenever I do a head, I use a rubber mallot on each valve spring assembly. You can do this when the head is in or out. It's important to use your senses. Smack each valve hard enough so the valve opens a good amount. It will immediately return and make a hollow noise. All the intake valves should sound the same. All the exhaust valves should sound the same. If any one sounds different, or if one sticks, NOW is the time to fix it. If a keeper is very weak (highly unusual), it will break now. Keepers seat themselves during this "test." Certainly, a bent pushrod can be caused by adjusting the rocker arms too tight. Too much rocker arm ratio with too many spring shims will do it, too. The rocker arm will continue to travel as the spring is totally collapsed. Either the pushrod bends or a rocker arm breaks, whichever one is weaker. Properly installed valve train components usually outlast piston ring life by a few times. I usually adjust them "sloppy" (.025"-.030") cold, and run the engine without spark plugs while I look. It's called, COLD TEST. If all's ok including oil pressure, I run it again with plugs (HOT TEST). The lifters might sound loud but the engine still runs smoothly. After all the parts are happilly warmed and seated, I fine-tune my lash adjustments for .019"-warm. I never bent a pushrod yet (TG).
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By mctim64 - 16 Years Ago
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If it stuck a valve in the guide you would see the spring is a little lower than the rest. You did get new guides and I hone and brush each one to make sure no debree is left behind. And I do hit each valve to make sure the locks are seated. Put another pushrod in, adjust the valves and do a quick compression check to see if the valve stuck the piston.
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By Doug T - 16 Years Ago
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crab (4/29/2009)
Got the bird back running and when I started it up cold this evening I heard it pop and bend number 4 intake. Got new valve job, set all the valves to 18 thou. cold with slight resistance on the feeler, did each cylinder in firing order at respecive TDC when setting the valves. Did notice however some seemed looser at a different spot on the cam for some reason, wondering if they expand when hot or tighten up.It sounds like you have a cam timing error, based on the statement "some seemed looser at a different spot on the cam" There are two classic Y block timing errors: following Eichman's Ford Y Block book instructions or doing it like a Chev ie putting the marks on the timing gears together instead of 12 pins apart. I doubt the a the engine would run with either of these errors but it would bend pushrods because the valves will hit the pistons.
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By crab - 16 Years Ago
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To add, I put another pushrod in right away, started it up and everything sounds normal. Think I will go thru and check all of them one more time just to be on the safe side.
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By crab - 16 Years Ago
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Same shafts, I did clean and inspect them however and they looked good. This is a new top end on an engine with 81K miles, it may have just been a bad pushrod or something but we drove the car the day before and it ran great.
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By mctim64 - 16 Years Ago
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Just for the record, the head I sent crab was a rebuilt 113 with new cast guides, hard steel ex seats and good used (refaced, so they were checked for run-out) intake valves. The exhaust valves were left out so crab could install new ones of his own.
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By Ted - 16 Years Ago
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You didn’t mention how long your car was down for repairs so I’ll touch on fuel age as being a possible culprit. Old fuel can allow the vehicle to crank up okay but a varnish build up occurs in the intake guides on that first intial drive. As long as the engine is heated, a problem usually doesn't surface. Once the engine cools, this buildup will allow the valve to drag extremely hard in its guide and bent pushrods are the first indication of something going on. This is something that will be seen on the intake valves and not the exhausts and it’s only when the engine has cooled and is restarted cold that this particular problem comes to the forefront. But from experience, the fuel typically smells old (turpintiney) at the exhaust when it's old enough to do this.
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By crab - 16 Years Ago
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Thanks Ted, I had previously drained all the old fuel from the tank, about 10 gallons sat in there for 15 years. We have been adding a bit here and there to get it running, so I suppose its possible that could be partly the cause. I did put 4 gallons in yesterday before starting it, and we plan to fill it when we get near a station.
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By crenwelge - 16 Years Ago
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I would get rid of every drop of the old gas. In fact I buy repop gas tanks for all my old jalopies. It doesn't take much stale gas to cause an intake valve to hang open. You can add a stabilizer to gas when it is fresh and prolong the life of the gas, but once it is stale, it is nothing but trouble.
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By crab - 16 Years Ago
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Same thing happened again tonight, same valve and I saw it stuck down. When I came back from the phone it was up, so I replaced the pushrod and it started normal. Took the car out and drove to the gas station for a fillup, and ran it hard on the freeway for about 6 miles. Car sounds and runs great, hoping the fresh 15 gallons of fuel will clear things up. Either way, we need to just run this thing a while I think and hopefully things will settle down. I got to admit, that little 312 with 3.56 gears gets up and goes real good, 60-80 don't take long at all.
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By Unibodyguy - 16 Years Ago
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I just experianced the same thing as Crab with my truck, and for what reason I don't know why. Rebuilt rocker shafts, all new NAPA pushrods, and been driving the truck about 2-3 days a week with a lot of new fuel going trough it. I go and recheck all the valves for adjustment and their all where I set them when I did them last. There is no fuel problem since I fill it about every other week. The last time this happened I was driving back from our new house we bought, ( about a 90 miles round trip) backed off on it coming up to a stop sign, and when I took off it started missing a little, but was better at speed. I took the valve cover off and two pushrods were not under the rocker, one exhaust and one intake on different cylinders, just doesn't make any sense to me. I've probably got 1200 miles on a new motor now. Michael
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By mctim64 - 16 Years Ago
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Some what related, I have a customer with a 460 in his service truck and he would bend a pushrod about once or twice a year till he got about 25000 on the truck. He just kept putting new pushrods in, never bent a valve and the thing runs great otherwise. Go figure.
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By GREENBIRD56 - 16 Years Ago
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Sometimes this pushrod issue has to do with certain intake bolts, that if replaced with the wrong length - stick down into the pushrod passage. Its worth looking down the holes with an inspection light - or looking for signs of contact on a bent part if you fish it out without losing it into the valley.
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By Duck - 16 Years Ago
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Back in 1976, my grandfather gave me a '63 F-100 w/ a 292 to drive back and forth to H.S. When he gave it to me he told me to always add some MMO to each tank of gas, & some at oil changes, to keep the valves from sticking & pushrods from bending/ falling out. I did so religiously the 5 yrs or so I had it, and he was right - worked like a charm... /Duck
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By crab - 16 Years Ago
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/Duck (5/2/2009)
Back in 1976, my grandfather gave me a '63 F-100 w/ a 292 to drive back and forth to H.S. When he gave it to me he told me to always add some MMO to each tank of gas, & some at oil changes, to keep the valves from sticking & pushrods from bending/ falling out. I did so religiously the 5 yrs or so I had it, and he was right - worked like a charm... /DuckI use it.
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By pcmenten - 16 Years Ago
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I think there used to be a product that was a top-end lubricant. MMO might fall into that category, but the one I'm thinking of came in a 4 ounce container. I think it could go in either the crankcase or the fuel tank.
Anybody remember something like this?
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By 2DRHRDTP57 - 16 Years Ago
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AZ28 (5/2/2009)
Sometimes this pushrod issue has to do with certain intake bolts, that if replaced with the wrong length - stick down into the pushrod passage. Its worth looking down the holes with an inspection light - or looking for signs of contact on a bent partif you fish it out without losing it into the valley.
Ditto Steves comment, I have done this my self and had the exact thing happen, with the valve covers off you can see if this is the problem. 
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By Ted - 16 Years Ago
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For those of you running bronze guides, these do prefer additional clearance at the valve stems or sticking valves come to the forefront thus causing pushrod retention to be a problem. Doing a search on this site will bring up old posts regarding bronze guides.
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By GREENBIRD56 - 16 Years Ago
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Ted - Have you machined your own guide inserts or purchased them? If you are able to make your own this might be a useful product. My outfit has been using a "new" sort of high strength bronze for extreme service requirements. It is made by BRUSH WELLMAN and goes by the trade name "ToughMet". Our mining crawler parts have traditionally used manganese bronze for severe duty applications - it has 105/110K tensile strength and 60/65K yield strength. But if it runs dry - and the mining lube application systems are sometimes less than reliable - the manganese bronze has a pretty high coeficient friction that builds heat and causes collateral damage (spun bushings are typical because they swell and the steel bores do not swell at the same rate - which eventually makes them grab the shaft). The ToughMet has the same tensile strength and a very high yield strength - like 90/95K. But....it has a much lower "dry" coeficient of friction - which cuts way down on the collateral damage situation. Mining systems that have high "survivability" - or will run "wounded" are very popular, so some of our customers are big believers in this product. We've built several sets of these bushings and our customers have helped test them by beating the daylights out of the parts and running machines as much as a week with the grease lines broken. So far - very good results.
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By Ted - 16 Years Ago
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AZ28 (5/4/2009)
Ted - Have you machined your own guide inserts or purchased them? My own preference are the screw in bronze guides (Atlas brand on the package but Winona sourced) which does not require a complete removal of the old guide. The old guide is simply threaded internally and the new bronze is spiral fluted into the threads and honed to size. More on these at the following link. http://www.y-blocksforever.com/forums/Topic7050-3-2.aspx
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By Unibodyguy - 16 Years Ago
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Well, I for one on my truck did the intake bolt "test" that Steve mentioned. I could find or see any problem there. I'm going to take a bunch of pushrods with me when I go on shorts trips just in case. As much fuel as I ran though my truck I can't see how that would be the problem. I used all new NAPA push rods the last time I did this. ( replacing them all 16) After that I probably put 800-900 miles on the truck. When I bought the truck now that I think about it, it had 2 bent pushrods when I got it? I just keep trying. Michael
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