Bent pushrods
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Logistics Pro
Joined: Jun 2004
Posts: 4,840
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From: South Central Utah
Thanks for all the replys. The tough part is after I do a repair, is to go and try it and find out it didn't fix it. LOL
Maybe a dumb question, but what makes #3 different? I asked a friend about the pushrods once and he said "#3"?. TMI mentioned the EGR. When I installed this engine I blocked off the thremac and heat-riser passages through the intake manifold to block heat. It runs mostly on propane and a cold manifold is prefered. Propane performs better if the vapor temperature is around 65 degrees F. There is no EGR valve an the engine either.
Just curious.
Thanks
Maybe a dumb question, but what makes #3 different? I asked a friend about the pushrods once and he said "#3"?. TMI mentioned the EGR. When I installed this engine I blocked off the thremac and heat-riser passages through the intake manifold to block heat. It runs mostly on propane and a cold manifold is prefered. Propane performs better if the vapor temperature is around 65 degrees F. There is no EGR valve an the engine either.
Just curious.
Thanks
Junior User
Joined: May 2003
Posts: 91
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You should check the valve train for the correct pre-load.
Anytime a head is rebuilt ( Especially when an NFL game is on ) these clearances will change at random. You can have to much ( Seat ground to far ) or not enough ( Stem ground to far ) per-load on the lifter.
Anytime a head is rebuilt ( Especially when an NFL game is on ) these clearances will change at random. You can have to much ( Seat ground to far ) or not enough ( Stem ground to far ) per-load on the lifter.
Senior User
Joined: Feb 2003
Posts: 149
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From: Houghton, MI
not to bring up an old thread, but...
I have the same problem in a 400 that has about 6k on it. Bent both pushrods in one cylinder. I am thinking posibly the cam lift is too much for the springs. Thing is it is a slightly built engine, and I didn't build it.
I think possibly the cam lift is too much for the springs.
Is it possible to use a magnetic base dial indicator to try to get a measure of cam lift? I would really like to not pull the head off.
thanks,
Dan
I think possibly the cam lift is too much for the springs.
Is it possible to use a magnetic base dial indicator to try to get a measure of cam lift? I would really like to not pull the head off.
thanks,
Dan
Senior User
Joined: Feb 2003
Posts: 149
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From: Houghton, MI
So I would use the dial indicator to measure how much the valve stem moves up and down, correct?
They are single springs, I don't know if they are stock or not. The rockers are stock, I am pulling a couple springs to bring to the machine shop to check the height/rate.
DanO
They are single springs, I don't know if they are stock or not. The rockers are stock, I am pulling a couple springs to bring to the machine shop to check the height/rate.
DanO
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Logistics Pro
Joined: Jun 2004
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From: South Central Utah
My 400 had over 50k miles on it before it ever bent a push rod. I had been up the same road with the same load, same speed, same everything probably 25 times with no problems, then it decided to start bending push rods.
To fix the problem, I just don't push the truck as hard any more. I pushed the original engine a lot harder for over 180,000 miles and never worried for a second. The crank broke at 184,000 miles under no load and a very low rpm, 45 mph in 4th gear. The new motor runs great except when I push it in third geat WOT for a long period of time, then, there goes the pushrods in #3. Oh well, dam re-man engine.
Good luck.
To fix the problem, I just don't push the truck as hard any more. I pushed the original engine a lot harder for over 180,000 miles and never worried for a second. The crank broke at 184,000 miles under no load and a very low rpm, 45 mph in 4th gear. The new motor runs great except when I push it in third geat WOT for a long period of time, then, there goes the pushrods in #3. Oh well, dam re-man engine.
Good luck.
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Joined: Jun 2004
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Best wishes
My challenge with bent push rods.
The heads on my 351m received a 3 angle valve job and knerled guides.
My brother did this for one of his Vo-tech projects.
After the rebuild on the block and reinstall of the heads,
the motor developed the bent push rod syndrome.
After new stock rockers. Another bent push rod. Shims under the rockers
made for me by my machnist father inlaw. About 3000 more miles and bent
push rod. Order from Napa shorter pushrods. More Valve cover Gaskets.
About 5000 miles another bent push rod. Installed another shorter pushrod
Same postion. Ran for awhile till it bent the valve and broke.
Removed Head brought to Redroster pro valve job dude.
He listened to my story and I'm sticken to it. He took the exhaust and intake springs and keepers
off the offending cylinder stacked them up next to each other and showed methat they were mixed up and different.
The valve seat was not ruined he replaced the valve and spring set up!
I reinstalled the head and another set of vavle cover gaskets.
THe truck has run Happily ever after 30000 more miles towing and plowing.
The heads on my 351m received a 3 angle valve job and knerled guides.
My brother did this for one of his Vo-tech projects.
After the rebuild on the block and reinstall of the heads,
the motor developed the bent push rod syndrome.
After new stock rockers. Another bent push rod. Shims under the rockers
made for me by my machnist father inlaw. About 3000 more miles and bent
push rod. Order from Napa shorter pushrods. More Valve cover Gaskets.
About 5000 miles another bent push rod. Installed another shorter pushrod
Same postion. Ran for awhile till it bent the valve and broke.
Removed Head brought to Redroster pro valve job dude.
He listened to my story and I'm sticken to it. He took the exhaust and intake springs and keepers
off the offending cylinder stacked them up next to each other and showed methat they were mixed up and different.
The valve seat was not ruined he replaced the valve and spring set up!
I reinstalled the head and another set of vavle cover gaskets.
THe truck has run Happily ever after 30000 more miles towing and plowing.
Senior User
Joined: Oct 2003
Posts: 347
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From: in a house
motorhead, you would have to over come the bleading down of the lifter to get a good measurement. also the movement of the valve stem is affected by the rocker arm ratio.
what you would have to do is remove the rocker arm. clamp down a chisel holder over the push rod opening in the head using the rocker bolt and a big washer. position a straight push rod in the chisel holder about where it would normanly sit. tighten the thumb screw in the holder just enough to support the push rod. rest the indicator tip in the oil hole of the push rod and turn the engine till your on the base of the cam and zero the indicator. thats about it.
what you would have to do is remove the rocker arm. clamp down a chisel holder over the push rod opening in the head using the rocker bolt and a big washer. position a straight push rod in the chisel holder about where it would normanly sit. tighten the thumb screw in the holder just enough to support the push rod. rest the indicator tip in the oil hole of the push rod and turn the engine till your on the base of the cam and zero the indicator. thats about it.
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Thread Starter
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Logistics Pro
Joined: Jun 2004
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From: South Central Utah
Couldn't say about the retainers. Won't have the covers off for some time. I just bought one intake and one exhaust valve spring for a 1979 400. One spring is roughly 1/4 inch shorter than the other.
I too thought the "smaller" spring would be for the exhaust.
I too thought the "smaller" spring would be for the exhaust.
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