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351C Engine knock :(
#1
Turned on my 72 this morning as I was going to take it for the monthly drive to make sure all was good. Turned it on and a knock was there. A tapping I guess. A revved it up a little bit to hear a 2 loud thuds. That that point I let off the gas and shut her down. I removed both valve covers to inspect and on one of the rods it looks as if it was hitting the edge at the opening where the rod is in. I am not entirely sure just yet.

It just came from no where. Oil level good along with all the other fluids.

Think its rod knock? Time for a rebuild?

Suggestions please. And if its rebuild time. Whats the difficult of a intermediate mechanic. I know how to do a bit but never really messed with engine internals.

Suggest a good kit or brand to get the parts. Also if it is rebuild time. .030 over a good choice? After the walls are inspect and checked for thickness
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#2
Gibson_Junk;102068 Wrote:Turned on my 72 this morning as I was going to take it for the monthly drive to make sure all was good. Turned it on and a knock was there. A tapping I guess. A revved it up a little bit to hear a 2 loud thuds. That that point I let off the gas and shut her down. I removed both valve covers to inspect and on one of the rods it looks as if it was hitting the edge at the opening where the rod is in. I am not entirely sure just yet.

It just came from no where. Oil level good along with all the other fluids.

Think its rod knock? Time for a rebuild?

Suggestions please. And if its rebuild time. Whats the difficult of a intermediate mechanic. I know how to do a bit but never really messed with engine internals.

Suggest a good kit or brand to get the parts. Also if it is rebuild time. .030 over a good choice? After the walls are inspect and checked for thickness

Push Rods can get bent and go bad......Does she got alot of miles on that motor?

I would recommend not buying anything for it till you get it apart...And have it checked over...Heads...Crank...Rods..Piston then block...you realy dont know what your in for till you get in the middle of it...Counts how many miles..Has she been rebuilt?..and if so did they do it right or wrong? Is it over bored all ready? Hard to know till she all tore apart...But i would take the push rods out..See if there bent..They can sound like a rod knocking sometimes....I had a freind with a ford 460...It started bending rods while we was going down the road...It sounded like the motor was toast!! It was making horrible knocking sounds...Come to find out..Soft valve seats in the head turned out being bad..and it started bending push rods left and right.
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#3
Sounds as though your lifter stuck/top broke and the rod popped out of the lifter. Shine a flashlight down a hole near it on either side and see if you can't see what happened. Or just pull the suspected rod out and look down that hole but I would do that second since strat down the hole lifter may look O.K..
Replacing lifters is actually quite easy and a good time to throw in a new cam/timing gear set. They sell them in a kit with everthing you need.

[Image: 2rr7aiv.png]

Just cruising along minding our own business when BAM!!! The LAWS show up.
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#4
Well I pulled off the side I thought it was coming from and yup. Pulled out a push rod. Bent and scared up. I shined a light down there and its looked fine. As I think I caught it time enough to prevent tons of damage. As I am sure there is still more then just push rod damage I will be inspecting more.

[Image: 2mwuov6.jpg]

[Image: 64ikc9.jpg]

hyena429;102072 Wrote:
Gibson_Junk;102068 Wrote:Turned on my 72 this morning as I was going to take it for the monthly drive to make sure all was good. Turned it on and a knock was there. A tapping I guess. A revved it up a little bit to hear a 2 loud thuds. That that point I let off the gas and shut her down. I removed both valve covers to inspect and on one of the rods it looks as if it was hitting the edge at the opening where the rod is in. I am not entirely sure just yet.

It just came from no where. Oil level good along with all the other fluids.

Think its rod knock? Time for a rebuild?

Suggestions please. And if its rebuild time. Whats the difficult of a intermediate mechanic. I know how to do a bit but never really messed with engine internals.

Suggest a good kit or brand to get the parts. Also if it is rebuild time. .030 over a good choice? After the walls are inspect and checked for thickness

Push Rods can get bent and go bad......Does she got alot of miles on that motor?

I would recommend not buying anything for it till you get it apart...And have it checked over...Heads...Crank...Rods..Piston then block...you realy dont know what your in for till you get in the middle of it...Counts how many miles..Has she been rebuilt?..and if so did they do it right or wrong? Is it over bored all ready? Hard to know till she all tore apart...But i would take the push rods out..See if there bent..They can sound like a rod knocking sometimes....I had a freind with a ford 460...It started bending rods while we was going down the road...It sounded like the motor was toast!! It was making horrible knocking sounds...Come to find out..Soft valve seats in the head turned out being bad..and it started bending push rods left and right.

As for miles it has 72xxx original miles on its. The previous owner said its was rebuilt 30xxx miles ago. I doubt it though since when I got it everything was covered in tons of grease. And if it was rebuilt they most likely were not professionals. Its not bored that I know if. But when I get it check all this will be questioned.
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#5
It's but a scratch.

[Image: 11jmcuc.png]
351C Bold Manners, Brash Attitude
Favorite Teams: Michigan Wolverines and Whoever Is Playing Ohio State.

When I drive past a herd of cows, the cows MOO at me
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#6
Pushrods only bend 1 of 2 ways. They hang on the edge of the lifter as they popped out. OR valve never opened.

[Image: 2rr7aiv.png]

Just cruising along minding our own business when BAM!!! The LAWS show up.
  Reply
#7
marks73;102079 Wrote:Pushrods only bend 1 of 2 ways. They hang on the edge of the lifter as they popped out. OR valve never opened.

You need to take a block of hardwood and place it over the affected valve and give it a few taps with a hammer to make sure it's not stuck in the guide...[should have a springy feel]
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#8
marks73;102079 Wrote:Pushrods only bend 1 of 2 ways. They hang on the edge of the lifter as they popped out. OR valve never opened.

I'm sure there are more ways than thatSmile

For example they definetly bend when the rocker stud/bolts break. Ask me how I knowSmile


Greg
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#9
As James says, it may not be bad at all. But I would question the 72,000 original miles statement based on the "everything covered with grease" and more importantly, the rebuild 30xxx miles ago. Why would someone need to "rebuild" an engine with only 42K miles?

Refresh my memory about the engine you have. If you need/want to go the rebuild route, I am living testament that it can be done by an inexperienced guy willing to take his time, buy, borrow or rent some specialized tools, and be anal about taking pictures and placing parts in labeled baggies and plastic containers. More to come about that if that's the direction you choose to take.

Keep us posted about what you find, and good luck! Smile

Doc

[Image: 6y14ea.jpg]

Project started 8-7-10
Completed: All new suspension, rebuilt 351C H Code bored .030 over with mild cam and intake, new 3.50 TracLok, custom exhaust system
Current "mini-project": interior upgrade Undecided
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#10
Gibson_Junk;102068 Wrote:Suggestions please. And if its rebuild time. Whats the difficult of a intermediate mechanic. I know how to do a bit but never really messed with engine internals.

Suggest a good kit or brand to get the parts. Also if it is rebuild time. .030 over a good choice? After the walls are inspect and checked for thickness

As an intermediate mechanic, it can be done. I have one under my belt. In the middle of number 2. But I do have friends with engine building expertise that come over and help with the hard stuff.

You do need a good machine shop. To save you time, the shop can do all the bottom end work(short block- Install crank/pistons/cam/timing chain)

You can do the top end- Add heads, intake/carb, water pump. But, you need to measure your pushrods, which is a bit of a pain.

Cost will depend on what needs to be done to your motor. Whether you need new pistons, crank needs to be reground, and a zillion other things. Guys here claim to rebuild motors for $800. On my 351C, I am at probably $2700(machine shop and parts).

To check on the current state of your motor, do a compression check of the cylinders. If you get like 120# in each cylinder +/- 10 pounds, that is probably a good sign. You can also degree your cam to measure your lift to give you an idea of what is under those lifters.

Not fun. Good Luck.

[Image: 11jmcuc.png]
351C Bold Manners, Brash Attitude
Favorite Teams: Michigan Wolverines and Whoever Is Playing Ohio State.

When I drive past a herd of cows, the cows MOO at me
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