400 bent pushrods
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3rd Gear
Joined: Nov 2022
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400 bent pushrods
New member, so go easy on me! I just purchased a 77 F250, 400, 4speed as a project. Overall pretty straight with a lot of potential (I hope!). Engine was dead on #7 when I bought it and the seller had only had it for a couple years with no history. I pulled the valve cover and found a bent (no longer in place) pushrod on the intake. I straightened it (yes, I know that's not advisable, just trying to see if it will run) and it fired right up and was no longer missing on that cylinder. Had a fairly loud tick on the passenger side and found #3 also had a bent pushrod. Straightened it also and seems to run fairly smooth. I am planning on replacing all of the pushrods, but should I check something else before I do? #7 valve moved easily, so i don't think it was a stick valve that caused this. No history, so could be over-revving, or??? Also, it has had an Eddlebrock intake and carb put on it at some time, not sure if they might have done a cam also. Is there an easy way to check if it has an aftermarket cam without disassembly?
Lead Driver
Joined: Nov 2006
Posts: 5,217
Likes: 506
From: Pa.
New member, so go easy on me! I just purchased a 77 F250, 400, 4speed as a project. Overall pretty straight with a lot of potential (I hope!). Engine was dead on #7 when I bought it and the seller had only had it for a couple years with no history. I pulled the valve cover and found a bent (no longer in place) pushrod on the intake. I straightened it (yes, I know that's not advisable, just trying to see if it will run) and it fired right up and was no longer missing on that cylinder. Had a fairly loud tick on the passenger side and found #3 also had a bent pushrod. Straightened it also and seems to run fairly smooth. I am planning on replacing all of the pushrods, but should I check something else before I do? #7 valve moved easily, so i don't think it was a stick valve that caused this. No history, so could be over-revving, or??? Also, it has had an Eddlebrock intake and carb put on it at some time, not sure if they might have done a cam also. Is there an easy way to check if it has an aftermarket cam without disassembly?
Hotshot
Joined: Feb 2004
Posts: 10,842
Likes: 2,612
From: The Shenandoah Valley
Could have been laying on a fender in 1988 and got knocked to the ground and stepped on by a 3 year old and daddy just never took notice nor rolled it, then put it all together and tried starting it and the slightly bent push rods bent more and daddy threw in the towel when his wife blew up over the whole deal.
I'd at least measure lift from base to open on good cylinders and compare to stock specs.
I'd at least measure lift from base to open on good cylinders and compare to stock specs.
Logistics Pro
Joined: Mar 2002
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From: Wake Forest, NC
I would suspect overrev with weak springs, especially if everything looks original.
You can also try pulling the timing gear and seeing I'd there are any numbers on the end of the cam but as mentioned degreeing the cam is best.
You can also try pulling the timing gear and seeing I'd there are any numbers on the end of the cam but as mentioned degreeing the cam is best.
Hotshot
Joined: Feb 2004
Posts: 10,842
Likes: 2,612
From: The Shenandoah Valley
I would expect some bent valves if over reved with weak springs, but OP said ran fairly smooth after straightening the bent pushrods.
If the heads were ever re-done and extra shims added under the springs .... that would have them stacking up maybe, depending on cam in place.
I'd add a vacuum gauge in addition to new pushrods. I use one and it will show every time at idle. How Im knew I burnt a valve years ago. If a valve is bent, it'll show but just won't show which cylinder is affected ... a ompression test would though.
If the heads were ever re-done and extra shims added under the springs .... that would have them stacking up maybe, depending on cam in place.
I'd add a vacuum gauge in addition to new pushrods. I use one and it will show every time at idle. How Im knew I burnt a valve years ago. If a valve is bent, it'll show but just won't show which cylinder is affected ... a ompression test would though.
Logistics Pro
Joined: Jun 2004
Posts: 4,805
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From: South Central Utah
I had a 1979 F-250 4wd with a reman 400 in it.
Every time I was pulling a good grade with a big load in 3rd gest it bent the push rod in #3.
I hated that reman engine.
Every time I was pulling a good grade with a big load in 3rd gest it bent the push rod in #3.
I hated that reman engine.
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Lead Driver
Joined: Nov 2000
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From: Albuquerque
You don't have to take the timing cover off to check cam timing. these engines have tons of valve clearance, a stock one probably wont hit the valve even it you hold it open and turn the engine over. Preload on the lifters is important. After engine machining it can change. If the lifter bottoms out it can bend a push rod.
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Lead Driver
Joined: Nov 2006
Posts: 5,217
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From: Pa.
You don't have to take the timing cover off to check cam timing. these engines have tons of valve clearance, a stock one probably wont hit the valve even it you hold it open and turn the engine over. Preload on the lifters is important. After engine machining it can change. If the lifter bottoms out it can bend a push rod.
How are you going to answer the OP's question without taking the timing cover off ? Explain please, I'm seriously interested to know? It sure would've saved me a lot of time recently.
Lead Driver
Joined: Nov 2000
Posts: 6,637
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From: Albuquerque
To check valve timing you find top dead center on cyl no. 1.Make sure it agrees with the balancer marks. You can use a timing tape that goes all the way around the balancer (make sure it fits the diameter. The you would use a dial indicater on cyl no. 1 int. valve to read the lift at .050. That will tell you if the cam is installed straight up. You could also check total lift and duration this way. If you don't know the specs on the cam it would be hard to tell if it's installed straight up (correctly). If you can define int/exh duration you can find overlap (seperation angle) and use that to find the zero install point It's easier for me to do than to explain it well. Comp cams etc should have how to's on it.
I once used a ruler to make a 360 scale and the enlarger on a copy machine to make a 360 degree tape of the right length. Tape it on temporatily.
I once used a ruler to make a 360 scale and the enlarger on a copy machine to make a 360 degree tape of the right length. Tape it on temporatily.
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3rd Gear
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*update* bought a new set of stock pushrods and finally installed them yesterday. Ended up finding 4 bent intake pushrods. Replaced all 16. All rockers look good and all valves seem to be working without sticking. Wasn't able to get an accurate reading on cam lift. Checked compression when done- engine was about 55*, all plugs removed, carb wide open. Lowest hole was between 125-130, highest was just under 150. Oil pressure sender was faulty so I put a 60#gauge in place of the and it pegged the needle: 70psi+ cold. Replaced the sender and when warm, low idle it is still almost halfway up on dash gauge. Took it for about a 15 minute low speed test drive. Seems to run very smooth until about 1500 rpm (not exactly sure, the tach that is on it isn't close to accurate) and then starts missing. Ran out of time to trouble shoot, but the miss isn't there at idle or just above. Not sure what's next, but just wanted to post an update. Strange that 4 of the intake pushrods were bent. Some have mentioned bad gas- how does this caues bent pushrods?
Thanks for the responses so far!
Thanks for the responses so far!
Lead Driver
Joined: Nov 2006
Posts: 5,217
Likes: 506
From: Pa.
*update* bought a new set of stock pushrods and finally installed them yesterday. Ended up finding 4 bent intake pushrods. Replaced all 16. All rockers look good and all valves seem to be working without sticking. Wasn't able to get an accurate reading on cam lift. Checked compression when done- engine was about 55*, all plugs removed, carb wide open. Lowest hole was between 125-130, highest was just under 150. Oil pressure sender was faulty so I put a 60#gauge in place of the and it pegged the needle: 70psi+ cold. Replaced the sender and when warm, low idle it is still almost halfway up on dash gauge. Took it for about a 15 minute low speed test drive. Seems to run very smooth until about 1500 rpm (not exactly sure, the tach that is on it isn't close to accurate) and then starts missing. Ran out of time to trouble shoot, but the miss isn't there at idle or just above. Not sure what's next, but just wanted to post an update. Strange that 4 of the intake pushrods were bent. Some have mentioned bad gas- how does this caues bent pushrods?
Thanks for the responses so far!
Thanks for the responses so far!
What is Detonation?
Detonation is the abrupt combustion or explosion of the fuel charge inside the cylinder. During normal combustion, the spark plugs ignite the fuel charge and the fuel has a consistent and even burn as the piston moves through the power stroke and chemical energy is efficiently converted to mechanical. In simplified terms, when detonation occurs, the fuel charge ignites quickly in an uncontrolled explosion, causing a pounding or hammering force on the piston rather than a steady push. Light detonation may not show any indication in the cab. Moderate to severe detonation could be noticed as engine roughness, vibration or loss of power and eventually engine damage.
Detonation is the abrupt combustion or explosion of the fuel charge inside the cylinder. During normal combustion, the spark plugs ignite the fuel charge and the fuel has a consistent and even burn as the piston moves through the power stroke and chemical energy is efficiently converted to mechanical. In simplified terms, when detonation occurs, the fuel charge ignites quickly in an uncontrolled explosion, causing a pounding or hammering force on the piston rather than a steady push. Light detonation may not show any indication in the cab. Moderate to severe detonation could be noticed as engine roughness, vibration or loss of power and eventually engine damage.
Lead Driver
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Don't worry about what cam is in it uf you are just trying to get it running.
Make sure each valve moves and put good push rods in it. do a compression test and if it's decent start it up and see what you have. if the compression test sucks pull the engine and rebuild it.
Make sure each valve moves and put good push rods in it. do a compression test and if it's decent start it up and see what you have. if the compression test sucks pull the engine and rebuild it.
Logistics Pro
Joined: Oct 2006
Posts: 4,031
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From: East Central Ia
I assembled a 390 for a guy, he was happy and went on vacation. Came back with a handful of bent pushrods, every time he put a load on it bent one. Machine shop had installed new guides in heads and set clearance on the tight side. Told me they didn't know it was a truck engine and they had more clearance. Problem solved and owner drove for years after.
Fleet Mechanic
Joined: Jun 2009
Posts: 1,312
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From: San Antonio, TX
I assembled a 390 for a guy, he was happy and went on vacation. Came back with a handful of bent pushrods, every time he put a load on it bent one. Machine shop had installed new guides in heads and set clearance on the tight side. Told me they didn't know it was a truck engine and they had more clearance. Problem solved and owner drove for years after.
If it was my engine, I'd probably just yank it and check it out top to bottom, inside and out. Not sure if you have the time/tools/know-how to do that, but something ain't right internally if you have multiple bent pushrods.
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