push rod OMC 460

[nightowl]

Had water intrusion and bent exhaust valve pushrod, What what length do I buy?......in the parts manual online it says its a OMC p/n 0914123 .06 OS (oversize), would this be the correct one?.....I was told there is no adjustment but you can get undersized and oversized pushrods, would there be markings on the pushrod to indicate if over/under sized?.......also since I have never replaced a pushrod is it as simple as lossen rocker and insert pushrod then retighten?....not sure on torque value.

Thanks
Jim
89 OMC 460

 

[HT32BSX115]

Re: push rod OMC 460

Howdy,


I am pretty sure you can just buy a pushrod from Fomoco or any wrecking yard for a stock 460.


It is just simple replacement by the way.....A 460 has hydraulic lifters. There's no torque.The service manual will probably tell you to just crank it down until it touches and turn it a couple of turns more etc.... (@TDC compression, for that cyl)

Thanks Nutcase!I knew someone would jump right in with the RIGHT procedure!!!


What caused your water intrusion?



Regards,


Rick

 

[zbnutcase]

Re: push rod OMC 460

Yes there is a torque spec as the 460 uses bolt down fulcrums, and its 20 ft-lbs, and do it with the valve closed, and let it sit for 10-15 mins afterward to let lifter bleed down.

 

[nightowl]

Re: push rod OMC 460

Thanks for the reply, the marina thinks it was the exhaust manifold(not verified yet), that was the damage(bent rod) found so far when I tried starting it after stalling and engine hyrolocked. Could the valve be "tuliped"? or damaged connecting rod ?.....there is water in the oil also.

Jim

 

[coheej]

Re: push rod OMC 460

If it was hydrolocked, you could possible bend or even break a rod. The piston could also break. You also could have bent a valve. You need to do a leakdown test to look for damage. You don't need to replace the pushrod to do this. When you do get around to replacing the pushrod; since these are not adjustable you need to watch as you tighten the rocker nut. Tighten it until there is zero lash, then watch how much more the nut turns til you get to the correct torque. calculate how much the pushrod pushes the lifter down or measure it. The lifter should have about .060" preload. That's why they sell an oversize and undersize. The exhaust pushrod should be adjusted when the intake valve is approaching the closed position.

 

[nightowl]

Re: push rod OMC 460

so....adjust nut till zero lash then tighten till 20 ft-lbs, from what i have read should take 1/4-1/2 turn if correct push rod length..............sound right?

Jim

 

[coheej]

Re: push rod OMC 460

so....adjust nut till zero lash then tighten till 20 ft-lbs, from what i have read should take 1/4-1/2 turn if correct push rod length..............sound right?

Jim

1/4 to 1/2 would probably be in an acceptable range. You can estimate the preload by knowing the thread pitch of the rocker arm stud or bolt. If there were 20 threads per inch, then the rocker would move down .025" for 1/2 turn of the nut or bolt. This would be at the pivot point of the rocker. The pushrod end of the rocker would move down somewhat more than this depending on what the rocker ratio is. If the ratio is 1.7 (not positive that right for a 460) is would move down about .040". So your preload would be .040". That should run fine, wouldn't hurt if it were a little more.

 

[rodbolt]

Re: push rod OMC 460

only TWO things that will bend that pushrod.
1 is the valve was stuck and the lifter came up and something had to give.
2 is the valve was stuck open when the piston whacked it and something had to give.
its FUUUUKED.
ya got way more issues than a simple pushrod.
its a very substantial piece of tubing that WONT bend unless something bad went wrong in the head.
we have spun stock pushrods over 7500 RPM with NO issues.

 

[HT32BSX115]

Re: push rod OMC 460

If it was hydrolocked, you could possible bend or even break a rod. The piston could also break.

Not with the starter you wouldn't. It just doesn't have the power to bend a rod... If the engine was running and ingested water, well, that's a whole 'nuther situation......That will definitely bend or break a rod


My previous wonderful OMC 460 had riser gasket leaks on both sides.

It would allow a small amount of fresh (I didn't operate in salt!) water to leak into open exhaust valves after shutdown.


If I tried to start it, it would exhibit the evidence of hydro-lock. I.E. it would crank until the cyl with water in it came up on compression. Then it would stop. (VERY abruptly)

If I tried to keep starting it, it would eventually start and run fine.


If I let it sit for 45 min to an hour, (or over night) it would always crank right up.

It did that ALL summer!

I tore it down in the fall, and discovered that the riser gaskets had been leaking for quite some time. there was evidence of water sitting in more than 1 cyl for a long time. Had it been salt water, the engine would have frozen up long ago.


Also, Rodbolt is right. The only way you would bend a pushrod is if a valve was rusted/stuck shut and didn't move when the cam pushed on it.....I don't think the 460 is an interference engine so if the valve was stuck open, the piston wouldn't touch it.....

Something had to give though, and it was the pushrod.

If you have old manifolds, YOU NEED TO REPLACE THEM. If the risers are old you NEED to replace them too.


Good luck. Everyone I called when I tried to replace mine didn't have any and wasn't going to get any. (don't go looking for a coupler either)

(Hardin marine does have manifolds for around $1900)
I don't know what you would do about risers though..... I think you'd have to use theirs or somebody else's SS riser pipes etc..... I didn't look that far into it....

Risers, manifolds, and couplers are some of the most replaced wear items in a marine engine. But since there are not that many 460 King Cobras out there the after market has been slow to support them and probably will never fully support them because they are slowly dwindling away.


Your other option is to do what I did.


Remove the OMC junk and replace it with either a Volvo Penta 454/DPS or a Mercruiser 454/Bravo I/II/II

I opted for the Merc because I found one first!

Your mileage may vary....



Cheers,


Rick

 

[nightowl]

Re: push rod OMC 460

I removed the other rocker cover and saw another bent push rod, which i removed. I turned the engine over to watch the valvetrain (all spark plugs removed) and saw that another rocker wasnt moving and the pushrod was broken in half (other piece is inside). This has salt water in oil did the valves rust shut?......can I compress spring to test?......need to remove intake manifold to remove broken push rod?

Jim

 

[coheej]

Re: push rod OMC 460

Lay a straight edge across the valve stems. Are they all the same height? Are the ones with the bent pushrods different than the others. If there's no difference, you could compress the spring if you have a spring compresser that will work on an installed Ford head to see if it was stuck. Otherwise you could tap the top of the stem lightly with a mallet to see if it was solid or whether it moved slightly. Don't depress the valve too far if the piston is at the top of that bore.

 

[HT32BSX115]

Re: push rod OMC 460

the marina thinks it was the exhaust manifold

(or riser)

That is the most common reason valves are stuck. Water gets into the cyl VIA the open exhaust valve. If it's salt water, EVERYTHING it touches corrodes VERY QUICKLY.

This has salt water in oil did the valves rust shut?......can I compress spring to test?......need to remove intake manifold to remove broken push rod?

Salt water in the oil? How long has it been that way when you discovered it?



If you have pushrod remnants that have dropped down into the valley, you'll need to remove the intake manifold.

If the engine has sat for a while before you discovered the problem, you really should pull the heads and inspect them.

If salt water sat in any cyl for very long, you'll be removing the engine.

Sorry about that.




-----------------------------
Since my last post, it appears that you may be able to buy exhaust manifolds again for about $600-700 each.....(I couldn't find risers though)

If you're going to keep the 460, you should get them while you can. The 460 engines are dwindling in the sterndrive market and the aftermarket probably won't make them for long. (I don't know what you'll do for a coupler if you need one though)

If you're planning to rebuild the engine, you should probably consider adding full closed cooling.(if it's available....)



Regards,


Rick

 

[nightowl]

Re: push rod OMC 460

Thanks for the info Rick,

I now have 2 bent push rods and a boken one, all on exhaust valves. Not sure if thats a coincidence, I poured mystery oil down carb to oil cylinders, would this just oil the intake valves and not exhaust?....could i oil the exhaust valves?.......maybe pour down the exhaust part of exhaust?
I had the boat for sale but no interest. If I did free up valves (assuming there stuck) am I good to go?...or do I need to pull heads and bring to shop.

Jim

 

[Bluestream]

Re: push rod OMC 460

I would be taking the heads off and do a full inspection. I suspect there are other interbal issues with that motor. May need a full re-build?

 

[coheej]

Re: push rod OMC 460

Thanks for the info Rick,

I now have 2 bent push rods and a boken one, all on exhaust valves. Not sure if thats a coincidence, I poured mystery oil down carb to oil cylinders, would this just oil the intake valves and not exhaust?....could i oil the exhaust valves?.......maybe pour down the exhaust part of exhaust?
I had the boat for sale but no interest. If I did free up valves (assuming there stuck) am I good to go?...or do I need to pull heads and bring to shop.

Jim

Normally, if a valve sticks, it sticks where the stem goes through the guide, not on the seat. Your oil is not reaching that area.

If you do think you have freed up the valves (if they are stuck), how are you going to determine that? Put in more pushrods and hope for the best.

You need to find out if they are stuck with a spring compresser or tapping on them: or bite the bullet and take the head off as previously mentioned.

What happened to the broken pushrod?

 

[rodbolt]

Re: push rod OMC 460

your engine is simply fooked.
kinda like was mentioned before.
at a minimum the heads need to come off,sent to a machine shop for repair.
just how life is now.
then your manifolds need to be tested and the risers simply replaced.
adust the lash on a 460 may require various length puhrod lengths and care when grinding valves.
be aware, the amount of stupid information on the net is rampant.
it may look cheap for you but it also may be wrong and cost you more.

 

[HT32BSX115]

Re: push rod OMC 460

all on exhaust valves. Not sure if thats a coincidence,

It absolutely is NOT a coincidence!................

It IS due to the salt water that ran into those exhaust valves (open or not) from the leaking exhaust manifold/risers.(or riser gaskets)


I'm with Rodbolt........ the heads have to come off.

When they do come off, you'll see how much damage that may have been done to the cyls that HAD open exhaust valves (from salt water sitting in them) and you'll be able to determine if the engine is completely junk or if you can get away with cleaning out the cyls somehow......confused


Since you said you're going to sell it....I do hope you tell any prospective buyer what has happened to it....

I hate to say this but ANY boat with an OMC 460 King Cobra installed almost has negative value even with a well running engine.........

If you want to just get it running and sell it, your best bet might be to get a "wrecking-yard" 460 truck engine and new manifolds & risers, and sell it then.


I don't know what a wrecking yard engine would cost........maybe $600 or so......That with 2 new manifolds and risers would set you back a total of about $2000-2300 with all the incidentals.....

Is the boat worth that much?