HELP! Loud tapping!

[Moody Blu']

We were out in the 22 classic, boat has a 383 stroker, lunati pro mod kit for a bottom end. We were in LBI, it ran great all day, went out in the ocean and it was rough, I never once winged the enigne. We came back in and were running around 5,000 rpm from the bayside back to the ketch in lbi all bay.. when the no wake buoy came up I slowed down and all of a sudden BANG BANG BANG. I lifted the hatch and heard it really loud. I took out my phone and recorded it in case the boat all of a sudden died. I havent taken the valve covers off yet and im hoping its a bent push rod or something int he top end so i can fix it fairly fast. It sounds really loud though. I dont understand how it could ever bend a rod oil pressure was good the whole day and its fresh oil. this was the second weekend out in it. Im hoiping to get it running fast. Im posting a video perhaps the motor heads here will be able to know just by the sound. It does sound like its coming from the starboard side. the phone I recorded it with has 4 microphoens on it and makes for a directional stereo hi def recording and after playing the vid it seems like its more fromt he starboard side. but when we were there in person it was so loud it was hard to differentiate where it was coming from.

Hopefully you all can shed some light on to what you think it may be.

[problemchild]

Have you done a compression check? I suspect your going to see a lot of bent part parts in and under the head. You can use a screw driver as a stethoscope. Might help you verify which side to start on.

[duckhunter]

I replied on TOS as well. I wouldn't crank anything before you determine what happened. Sounds like a dropped valve, but who knows. Whatever it is definitely isn't good, and you don't want to make it worse with parts slinging around inside your motor.

I'd start with pulling both heads and go from there. Good luck!

[Conquistador_del_mar]

I replied on TOS as well. I wouldn't crank anything before you determine what happened. Sounds like a dropped valve, but who knows. Whatever it is definitely isn't good, and you don't want to make it worse with parts slinging around inside your motor.

I'd start with pulling both heads and go from there. Good luck!

I agree about tearing it down before running again. My money would be on a spun connecting rod bearing on the crank since it sounds like my Warlock 548 engine did when it spun a bearing. Good luck with the results.

[mario]

pull the valve covers

[Moody Blu']

whats a vale cover never heard of that before?

I'm definately not starting it again. I sure do wish they made valves different so they could not drop into the cylinder. Like a thread on top of the valve i mean how many people have dropped valves because of a broken spring and the retainers fell off. it boggles me that there are not aftermarket valves with a lock nut on top to save the valve from dropping..

Yes im gonna pull the valve covers and go from there. Hopefully I will see the problem and know my course of action. I hope its just a push rod but that sound is loud.

this motor has dart 200cc heads with 72cc chambers and the bottom end is a lunati pro mod stroker kit capable of 800hp and its making half that 400hp so I do not think it spun a con rod bearing, anything is possible though.

I will find out next weekend.

please if anyone has any other ideas let me know, I know its all shot in the dark. just trying to figure out what possibilities i need to look for.

[Capevettes]

You might get lucky and find a rocker backed off the stud a bit. I heard a very similar noise in one of my old Corvettes and the rocker arm nut had backed off. Bent push rod is another suspect. Good luck.

[maddad]

Sounds like a cylinder is not firing because an intake valve is hung open or broken and cylinder's pressure is going into the intake manifold. Maybe even just a loose spark plug?

[Bobby D]

1970 Ski Sporter
Back in October 2010 during my last run for the season my motor (HM 351 Ford W) backfired, started to quit, backfired again and shutdown. It happened at the marina and I was able to throw a rope to the tractor guy and he pulled me over and on to my trailer and pulled me out of the water. All summer long the Donzi ran like a top and this was first time I had any indication that something was wrong. when it happened I noticed my vacuum gauge begin to bounce around and than the motor quit. All the gauges read normal during all this, including oil pressure and water temp, which always reads cool, the motor sounded like it was only running on about 5 or 6 cylinders? Figured the fluctuating vacuum reading was telling me I had an imbalance in the cylinders and that it could be a valve problem. What I did was pulled the valve covers and checked the to see if the camshaft was lifting open the valves and closing them by turning the engine over with the key (pulled the coil wire) didn’t want to fire the engine up. Figured it's possible a rocker got loose or a pushrod may have bent? Everything looked good so the next thing to do was a compression test to see what’s going on inside.
Here is what I found:
No compression in the #6 cylinder. Performed an internal inspection with a bore scope (see snake) and was surprised I was able to get a decent look at what was going on. Cranked the engine over and could see that the intake valve was not closing fully, although it did move up but still remained open. Also could see the piston and it looked OK, bottom line had to pull that head for repairs.
Pulled the head and found the exhaust valve seat came out of the head and jammed the valve in the open position so that’s why I had no compression in that cylinder. Next I got the bad news from the machine shop that the head could not be repaired so found a good head (the pervious owner had a set in his shop) with matching numbers. Had to replace one exhaust and one intake valve and then rebuild it.
Put it back together installed the rebuilt head and autolite plugs per HM specs and everything ran fine.
Good Luck moving forward.
Bob

[MOP]

My old motor sounds like valve train, pull the covers maybe a rocker/push rod let go.

[Moody Blu']

My old motor sounds like valve train, pull the covers maybe a rocker/push rod let go.

youve heard rockers and push rods that get that loud? im hoping thats what it is

[problemchild]

I like the bad intake valve theory. Rod or crank bearings would've lost serious oil pressure

[Conquistador_del_mar]

I like the bad intake valve theory. Rod or crank bearings would've lost serious oil pressure

Nope. My 548 still had excellent oil pressure even with the spun connecting rod bearing on the crank that stacked the rod end outwards to make contact with the windage tray and block (my memory is that it also touched on the block). I thought the same thing until it happened to my engine.
I should add that I am only guessing about the noise in this thread.

[Pismo]

Any news on this?

[MOP]

He got it apart it was a rocker like I said, the sound was a dead give away. The double click clack is always valves a bearing is a consistent one knock each revolution not a double hit, I am pretty sure judging how it was banging back in the second movie it went lean. As the RPM's dropped when he backed off it went bang and broke the rocker.