I can usually figure out just what the hell is wrong with my cars, but this one... This one is pretty unique. I've got a 1968 ford galaxie. I thought I'd be cute and build a smog motor 400M for it and plop it into the car to replace the clapped the hell out 390 and c6. Well the build went alright(though behind schedule by a LONG shot), cam break in went good. Now around 20 miles in the rear intake manifold gasket started leaking. I figured I'd kill two birds with one stone and fix that oil leak while I had the heads off to put the new inner valve springs in as well. But what's this? A BENT PUSH ROD?! What the!(Yeah, see picture below) According to comp cams this particular cam grind(265DEH) should play nice with my motor. and while I had the heads off I made sure there was no kissing of the valve and pistons. all was good, at least on the bottom end. I suspected a stuck lifter. I took the lifter out, examined the bottom of it with a straight edge, and then plunged it down a bit with a small bolt and a vise to ensure it wasn't stuck. Again, all was good. What the hell is going on here? and why was it only cylinder 2? does a stuck lifter only "stick" when under pressure? am I just being retarded? I also noticed a high cold start oil pressure(70 PSI). But once it warmed up it dropped to 40PSI. Could this have caused the bent pushrod, maybe? Should I use a thinner oil? Engine stuff: 400M(4" bore, 4" stroke) Stock Heads(polished and ported) Pistons- 9.5:1 CR (with my stock heads) part number KB2347 COMP CAMS 265DEH grind cam kit(cam, lifters, springs, seals, retainers) Some 400 crank kit from ebay.(originally 351m block, heh.) Edelbrock 1405 600CFM carb Edelbrock performer 400 intake manifold This engine was wicked right after break in. Anything beyond 1/2 throttle from a dead stop would be enough to break the tires free. I want my performance back! Anyone have any ideas? I've eliminated all I could think of. I bought spare pushrods for experiments. Thankfully they're only $1.99 each. I have 4 total pushrods to spare. That means 3 attempts to remedy this situation before I have to buy more. Oh yeah, and thanks in advance.
Pull that rocker arm off and turn it over. Look at the square shaft under the fulcrum and see if there is any evidence of it hitting the rocker arm body: If that appears to be the case, bust out a file and make the rectangular slot in the rocker body longer.
I had a similar problem a few years ago on a '77 400 I rebuilt. I found out the shop that did the heads got a couple of valve guides ever so slightly too tight. When the engine got warm and at higher speeds, the tight guides would swell and grab the push rod just enough for it to bind and bend. Never did it at idle or slow speed. Pulled the heads and sent them back to the shop. Found 2 guides just under minimum clearance. Touched them up with a fresh hone to mid spec numbers and ran the engine over another 100,000 without any more valve problems. Good thing too, because each time a push rod bent, my wife was driving! It is wonderful to restore domestic tranquility!
-gimpyshotrods I'll pull the rocker arm and see tomorrow. Guess I'll be giving these 60 year old machine files a workout. -duecemac I spared no expense with this rebuild. That includes not bothering with any machine work on this block or heads. But I think your wife might just be a little throttle happy.
When this happened to my old, worn 400M It was both the pushrod and lifter, so the oil system went from pressurized to splash. My assumption was an overrev. Bought a new pushrod and lifter for a few bucks, glued the manifold back on and was back on the road the next day.
We just had an AMC 360 that was bending push rods due to a stuck intake valve. Ours was caused by varnish but a tight guide or binding rocker could do it too.
Something has to prevent the rocker arm from moving far enough so too much pressure is put on the push rod. Usually it's the valve hitting the piston but you say there is no sign of that. A tight valve guide would make it harder to push and cause it. The rocker arm hitting the fulcrum is another. The last is coil binding of the valve springs. When a machine shop rebuilds heads, they check valve spring tension and if it's low, they might add a shim under the spring. If new springs are installed, it is sometimes necessary to mill the spring seats for more spring clearance. When the valves and seats are ground, the valve sits deeper in the seat and the stem is higher on the upper side of the head. The assembled height is checked and the end of the valve stem is ground to get the proper height. The spring retainer groove is higher giving the spring more room but lowering it's tension. If a new valve is used, it will sit higher in the seat so the spring retainer will be closer to the head leaving less room for the spring so the tension will be higher. The average machine shop only checks for the minimum tension not the maximum and they will be checking for stock lift unless they are told otherwise. The push rod that's bending might be in a position where a new valve was installed or a spring was shimmed so the spring bottoms out. With non adjustable rocker arms, if you mill the head or the block or both, it changes the distance from the lifter to the rocker arm. Usually the hydraulic lifter will have enough range to cover that. With a solid lifter camshaft, either the proper length push rod has to be selected, adjustable push rods used or a shim put under the fulcrums. Thicker head gaskets can also be used to make up for the material milled off. If a heavier set of springs were installed, you might need stronger push rods. If you installed new push rods, that one might have been defective. It could have had a slight bend or the material wasn't as stiff.
Well I double checked the lifter today, plunging it slightly further down than last time. Still not stuck. I examined the rocker arm as well and couldn't find any evidence if it bottoming out and binding. Perhaps it was just a defective pushrod coupled with the high cold start oil pressure? I buttoned up the motor again today so I'll see if it bends again after I run it.
If you have access to a granite block (or counter top), or a piece of plate glass, roll the replacement pushrod on it. You should be able detect any bend in it that way. As soon as there is a little bend, the structural integrity under load is compromised.
Look very closely at valve guide . No clearance when hot , I've had a few Fords suffer from this issue after rebuild . It will loosen up with slow running , but best to ream the guide a few thousands larger and drive it like u stole something in it !
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