Bent push rods

FullCircle said:
YOU CANT HAVE PUSHRODS

AND

A

TIMING CHAIN

OR

A

CAMBELT.


MUTUALLY EXCLUSIVE FEATURES.
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Simply not correct!

The small block chevy engine which is used by mercruiser and volvo and in the past by omc has a a crankshaft driven timing chain turning the camshaft and haydraulic roller followers / push rods which actuate the rockers / valves.
 
I quoted your message. What you said was (in capitals) "YOU CAN'T HAVE PUSHRODS AND A TIMING CHAIN ...........MUTUALLY EXCLUSIVE FEATURES".

Sorry, but you were wrong - not much to misunderstand there - and I'm sure neither of us would want AJ 305 to be confused when he's in trouble over his engine.
 
andrewbarker said:
I quoted your message. What you said was (in capitals) "YOU CAN'T HAVE PUSHRODS AND A TIMING CHAIN ...........MUTUALLY EXCLUSIVE FEATURES".

Sorry, but you were wrong - not much to misunderstand there - and I'm sure neither of us would want AJ 305 to be confused when he's in trouble over his engine.
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The timing chain obviously refers (as does a timing belt) to an OHC engine...
 
FullCircle said:
The timing chain obviously refers (as does a timing belt) to an OHC engine...
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Correct re belts but not chain. I could quote you about 12 OHV pushrod actuated engines, both diesel and petrol that drive the camshaft by chain and there are indeed many more I am sure. You are correct however that it is more common to see gear drive, but it ain't necessarily so!
 
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VicS said:
Maybe that does not read as you intend it to.
You have a camshaft, be it an overhead one or not and something must drive it. An overhead one can be chain driven or belt driven.
An OHV camshaft is frequently chain driven but can be gear driven. Cannot think of a belt driven one but there is no reason technically why it should not be.

Push rods mean it's OHV not an OHC.

I think as suggested you have to check the camshaft timing but I doubt if you'll find it wrong.
Pretty certain that the problem will have been caused by sticking valves.
Whether or not they have been struck by a piston is another matter. It may or may not be possible. Always is possible with a diesel engine but not necessarily so in a gasoline engine. Depends on engine design.

Also perhaps be checking for broken valve springs.

A Boatmike says its a strip down job until the likely cause is found.
.
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Vic
read what you have just written:

"An OHV camshaft is frequently chain driven but can be gear driven. Cannot think of a belt driven one but there is no reason technically why it should not be"

An OHV engine can have the camshaft halfway up the engine and it will push pushrods to operate the overhead valves. These are traditionally driven by chain or gear inside a timing chest.
An OHV engine can have the camshaft on top of the engine as well, driving the valves directly, in which case it is known as an OHC engine, these do not have pushrods in the accepted sense and can be driven by a cambelt or a chain.

So you see if you describe an engine as OHV it can be a pushrod engine OR an OHC engine!

I mean I could go on to talk about side valve engines OR inlet over exhaust engines but dont want to bore peeps do we?

Stu
Mwah!
 
Morgana said:
Another option is that one of the cam lobes, or followers has failed.....

But I stick by my early suspicions.... I'd start with the timing belt....
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Ill agree with what Vic MEANT to say, normal pushrod engines dont use cambelts. Our MD22s dont have pushrods. I suspect what he said originally, seized valves OR rockers. Ive straightened pushrods out in an emergency before now. I would take the rockers off, check they are free and if so get a hammer and use the stale to push each of the valves to see if they moved, bearing in mind that some of the cylinders could be on top dead centre stopping the valves moving, in which case turn the engine over a touch to check. If he can get them moving, maybe lube them as well, then straighten the pushrods and assemble temp to run it to check all is working before lashing out on new bits
Stu
 
VicS said:
Not sure I see how a locked piston can lead to bent push rods !

I am tempted to suggest engine running cold or only run for short periods causes condensation under the rocker cover. That leads to rust on the valve stems, they fail to open freely and the consequence is bent push rods.
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The piston on the up stroke with a bore full of water could force the valves shut and bend the pushrods in the process.

It is unlikely though and probably wouldn't bend both inlet and exhuast at the same time.
And at this point it would be locked solid so you would be unlikely to get it to turn over again without draining the water off.

Cant see it being the cam chain either as they dont really jump a tooth which is what it must of done to put the timing out. But then it would bend all the others when you finally got it started if it had?

Rob
 
Stu.

Hurriedly written perhaps but what is normally understood is that OHV engines have push rods and rockers operating the valves from a camshaft lower down the engine. OHC engines on the other hand although, I agree, having overhead valves have, as the description implies, an overhead camshaft as well. You'd describe car engines after the disappearance of side valve engines (reckon the last in popular cars must have been the Ford 100E) as OHV and modern ones with overhead camshaft as OHC

The point is that the engine in question is an OHV design, (with pushrods and rockers) and that the camshaft is chain driven, making refereneces to cam drive belts irrelevant.
 
The timing chain obviously refers (as does a timing belt) to an OHC engine...
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The "timing chain" can refer to a chain driving an overhead cam shaft (often these days done with a belt rather than a chain) It can equally refer to the chain driving the camshaft on a push-rod operated overhead valve engine or even on a side valve engine.
 
Hi guys thanks for all the responses v helpful.

Removed exhaust manifold and riser today appears to be the original and has signs of water leakage. Removed plugs and turned engine over just to remove any water that may of been sitting in cylinders, gave a good dose of WD as well. So am thinking leaking exhaust manifold maybe corroded exhaust valve and seized it solid, but how would this explain the bent intake push rods. Appears to be no water in cylinders so can rule out hydralic lock, also engine was still running ok, so am thinking timing is still ok.
 
Perkins 4107 and 4108 do the same from time to time, that is bending pushrods. Usually the cause is one of two reasons.
Firstly a broken camshaft follower, which is unlikely to be broken x 3 times at the same instant so to speak. So it may be a camshaft timing problem.
The second cause on the Perkins is corrosion and seizing of the rocker assembly. This usually occurs if the engine is left for a long period, lacks lubrication to the rockers or there is water in the engine oil.
If I were you I would check the free movement of all the rockers, and then if they are OK, look at the bottom half of the engine
 
FullCircle said:
I will believe just this once that you misunderstood me. Suggest reading a little more closely.

Thats why I called it an overhead valve engine. The camshafts on those are *usually* driven by gear off the crankshaft.

Happily we haven't introduced Desmodromic valve gear intot his conversation, nor yet hydraulic tappets.
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Well all misread you as an overhead valve engine can have push rods and a chain or gear driven camshaft...

Ok clever clogs lets talk sleeve valves:) We ll stay off opposed piston!
 
aj305 said:
Hi guys thanks for all the responses v helpful.

Removed exhaust manifold and riser today appears to be the original and has signs of water leakage. Removed plugs and turned engine over just to remove any water that may of been sitting in cylinders, gave a good dose of WD as well. So am thinking leaking exhaust manifold maybe corroded exhaust valve and seized it solid, but how would this explain the bent intake push rods. Appears to be no water in cylinders so can rule out hydralic lock, also engine was still running ok, so am thinking timing is still ok.
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OK lets get away from the piss ing contests, the only way that the rods can bend is if the camshaft is pushing the rod and there is something stopping the rod moving at the other end! Either the rocker is not moving or or the valve is not moving, thats it! Your mission is to find out which, then to find out why. Forget the bollox of water in the cylinders, if there was water in there the piston would stop moving, the crank would be stopped and consequently the camshaft would be stopped and no movement of the pushrod would occur, therefore no bend ( I dont know why I am explaining this, the most elementary description of how an internal combustion engine works!) Thats it seemples!!
Stu
 
skipper_stu said:
OK lets get away from the piss ing contests, the only way that the rods can bend is if the camshaft is pushing the rod and there is something stopping the rod moving at the other end! Either the rocker is not moving or or the valve is not moving, thats it! Your mission is to find out which, then to find out why. Forget the bollox of water in the cylinders, if there was water in there the piston would stop moving, the crank would be stopped and consequently the camshaft would be stopped and no movement of the pushrod would occur, therefore no bend ( I dont know why I am explaining this, the most elementary description of how an internal combustion engine works!) Thats it seemples!!
Stu
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Calm down Stu, we're all just trying to help and eliminate problems.

OP- Examining the valves / rockers on that engine are pretty simple so i'd strip that area back and check all is free-moving
 
pappaecho said:
Perkins 4107 and 4108 do the same from time to time, that is bending pushrods. Usually the cause is one of two reasons.
Firstly a broken camshaft follower, which is unlikely to be broken x 3 times at the same instant so to speak. So it may be a camshaft timing problem.
The second cause on the Perkins is corrosion and seizing of the rocker assembly. This usually occurs if the engine is left for a long period, lacks lubrication to the rockers or there is water in the engine oil.
If I were you I would check the free movement of all the rockers, and then if they are OK, look at the bottom half of the engine
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Its a V8 petrol engine. Whats the perkins got to do with it?
Stu
 
Fire99 said:
Calm down Stu, we're all just trying to help and eliminate problems.

OP- Examining the valves / rockers on that engine are pretty simple so i'd strip that area back and check all is free-moving
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Id already said that while everybody else was going on about how clever they are!
I despair sometimes, grump grump!!
Stu
 
aj305 said:
Hi guys thanks for all the responses v helpful.

Removed exhaust manifold and riser today appears to be the original and has signs of water leakage. Removed plugs and turned engine over just to remove any water that may of been sitting in cylinders, gave a good dose of WD as well. So am thinking leaking exhaust manifold maybe corroded exhaust valve and seized it solid, but how would this explain the bent intake push rods. Appears to be no water in cylinders so can rule out hydralic lock, also engine was still running ok, so am thinking timing is still ok.
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Jeez! I just despair at the so called "experts" on here pissing one another off with terminology. It's all totally bloody irrelevant chaps! Get a life!
To AJ.... As I thought it's wet in there and has PROBABLY corroded the stems of both the inlet and exhaust valves. It gets to the chamber of the exhaust valves first but just think what happens if you turn the engine over with water in there.... It does not need to fill the cylinders and develop a hydraulic lock. It just needs to be wet. Inlet valves can suffer too but not quite so commonly as exhausts, but I have never found a "wet" engine top that was confined to the exhaust entirely. Don't forget that a little water in a petrol engine cylinder will stop it firing....Then it's just a pump... I guess what MIGHT have happened is your anti-syphon valve blocked and water got back up to the exhaust port of the offending cylinders. Thence through to the cylinder of one of them and knackered the inlet too. On the other hand I have seen engines progressively distruct due to the exhaust not opening, or sticking open, or.....who cares!!! It's happened! Just make sure when you restore the status quo that you ensure that anti-syphon valve is clear... Or it will happen again!
 
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