knocking, bent pushrod, now what?

[gimmieaclue]

Just put a new riser, a new to me exhaust manifold and all new gaskets (including head gasket) on my 470. She started right up so I retorqued the head bolts after it warmed up and let'er run in my driveway for another 20 min or so and all was well. All the work was done because of a corroded riser and exhaust manifold.

This morning I get the boat down to the dock and its acting hard to start and when it does there was a pretty good cloud of smoke and some serious knocking so I shut it down.:facepalm: Got it home and found a bent pushrod, not real bad but bent. Would a slight bend cause a lot of racket? What would be a likely cause? I've read a lot about stuck valves but it was running fine last night. Yes I had to pull the rockers last night to torque the head again but it ran fine afterwards. Maybe a lifter?

Any help would be appreciated,
thanks

I should add that the knocking went away with a little throttle and that it backfired a little when I turned it off also the plugs looked/smelled fouled.

 

[achris]

Re: knocking, bent pushrod, now what?

Did you check the valve clearance after you reassembled it? If you didn't you may have a push rod (or 3) that is too long.... You need to check the clearances as per the book, page 11, section 3A, service manual #8.... Also check that the head is positioned correctly, same book and section, page 9...

Which rod bent?

Chris........

 

[Bt Doctur]

Re: knocking, bent pushrod, now what?

#4 valve guide could have jammed the valve stem if there was a water issue from the riser, only other way is something hit the valve .

 

[gimmieaclue]

Re: knocking, bent pushrod, now what?

I didn't think it was necessary to check the valve clearance after reassembly because nothing had changed except the maybe the gasket thickness, but I'm not much of a mechanic so maybe I should have?

I did follow the manual when installing the head.

It was the #4 exhaust rod that bent.

There shouldn't be an issue from the riser as its new along with the gaskets and blocking plate. I do wonder about the used manifold though. Its doesn't show much wear but it might be cracked I guess. I've read that water in a cylinder could be the cause of a bent rod but I would think that the piston would stop also not allowing much of a problem (just a theory).

Would the slightly bent pushrod be the cause of all the knocking or should I be looking further?

 

[Silvertip]

Re: knocking, bent pushrod, now what?

The head gasket has a specific thickness and because it is a gasket, not exactly the same identical crush thickness when tightening the head bolts as the old one. Think about it -- the cam is below head. The push rod goes to the top of the head, moves the rocker arm which opens the valves. By changing the head gasket you altered the geometry -- slightly perhaps, but enough to warrant checking valve clearance. Is it also possible the new risers were not installed properly and that there was water in that cylinder. Removing the plug should verify that. Water doesn't compress.

 

[stonyloam]

Re: knocking, bent pushrod, now what?

The clearance is 100 thousandths (0.100 inch) It would seem unlikely that a couple of thousandths difference in head gasket thickness would be a problem. IMHO. If the pushrods were returned to their original position, it should have been OK.

 

[gimmieaclue]

Re: knocking, bent pushrod, now what?

The clearance is 100 thousandths (0.100 inch) It would seem unlikely that a couple of thousandths difference in head gasket thickness would be a problem. IMHO. If the pushrods were returned to their original position, it should have been OK.

kinda what I thought, especially since only one pushrod was bent. I bagged and labeled everything when I took it apart so I'm confident that everything was returned to its original position.

 

[gimmieaclue]

Re: knocking, bent pushrod, now what?

Just ran a coolant system pressure check and its not holding pressure, very slow leak, so I have a couple of silly questions cause I'm not a mechanic:

I already had the rockers off from yesterday so I figured both valves are closed and that I should be able to do a leak down test to check the head gasket, is this true? (cylinders aren't holding pressure if it is true, hopefully I'm doin something wrong)

If I did install the head gasket wrong :facepalm: wouldn't I have coolant in my oil? There's none.

A little confused because after I got'er back together she started right up, probably ran it a total of an hour in the driveway, everything sounded good. No problems till it in the water.

As for now I'm gonna try and track down the coolant leak, I can hear a faint drip when I have it pressurized (14lb)

Once again, thanks for any feedback in advance

 

[Silvertip]

Re: knocking, bent pushrod, now what?

Are you certain you had the push rod seated properly in the lifter body and the rocker arm. If it wasn't it is very possible the valve train was severely out of adjustment (way too tight) and immediately upon starting bent the push rod. And yes, it could have then snapped into proper position but since it is now bent it is causing the rattling. Something caused the rod to bend. That can only happen by interference from a piston striking a valve, a valve stuck open, a misadjusted lifter, or components that are not aligned/seated properly. Did you use sealant on the head bolt threads that go into the water jacket?

 

[gimmieaclue]

Re: knocking, bent pushrod, now what?

I'd like to think I had the push rod seated when I put the rocker back on but I'm not positive.

ah crap, I didn't use sealant on the head bolts :facepalm:....after reading your post and checking the manual I sure didn't. Imagine there's a good chance that's where my coolant leak is.......couldn't find it anywhere. I'll get those sealed tomorrow and pressure check again.

Thanks for the response

 

[stonyloam]

Re: knocking, bent pushrod, now what?

ah crap, I didn't use sealant on the head bolts :facepalm:....after reading your post and checking the manual I sure didn't. Imagine there's a good chance that's where my coolant leak is.......couldn't find it anywhere. I'll get those sealed tomorrow and pressure check again.

You may use Permatex (NAPA) Aviation Sealant as a substitute for the Perfect Seal.

 

[hobbystock98]

Re: knocking, bent pushrod, now what?

what color was the smoke? if the block and head were not cleaned really well of old gasket you will get a leak. compression and or water. as for the bent push rod id pull the head and check for piston damage. if there is not any piston damage or any evidence of something striking the pistons i would be leaning towards a seized valve i have not done a lot of boat work but been around race cars most my life. valve train failure can get ugly.

 

[Ryanlewis2010]

Re: knocking, bent pushrod, now what?

please advise as to how the pressure test went i think that maybe my problem cause i cant seem to find a leak in the riser manifold Thanks Ryan