Hey all, I was out running my baja today and the motor started making a loud tapping noise, I was running at 28 to 3k rpm.

Previously it over heated to 200 degree max. I flushed the hose feeding the water pump and found shells blocking it. all ok.

It was running normal temp today when this happened. I was thinking that i might have blown a head gasket by running it hot previously. Could this be the case? Thanks

1999 Baja Boss 509 Pro charged. with less than 100 hours on it.

Head gasket from overheating it previously-maybe
Valve train problem-possibly
Rod knocking-hope not!
I have a o2 bung in my exhaust manifold on bottom side- the plug has fell out before-makes terrible racket but I doubt thats your case!

Check you exhaust manifold gasket, make sure you "tap" is not an exhaust leak they sound the same sometimes.

+1

also that engine wont blow the head gasket @ 200 deg..your averige 454 vortec BB in subs and trucks run at 210deg,,my BB in my sub will go to 220 geg sometimes with the ac on and theirs over 400 k on it and never been apart..

if the manifold gaskets are good and you being from florids i guess you run in salt i would also make sure the risers are not leaking water into the cylinders.

The risers and manifolds are newer with only 100 hours on them. And i fresh water flush religiously ...

Try a few things....

Is there a high amount of oil usage? Yes, prolly blow-by and can be dbl sure if there is oil smoke coming out of the dipstick tube of oil fill.

Do you use full synthetic and an aftermarket cam? If yes, you might have lost a lobe....

Hyd. or solid lift? If hyd., could have collapsed one.

It there a miss when this noise happens? If yes, again....could be a hung valve....or broken/weak spring.

Or...maybe a bent pushrod....or loose rocker arm

Compression testers are cheap. I recommend doing your own test....determine off the bat if there is a low cylinder....and if there is....then hope it is pushrod or lifter...

After comp. test, repost or shoot me a pm and I'll advise your next step....

Schumaker Performance built this motor. Block GM 4.50 bore 509 ci

Crank chevy forged 4in stroke, Heads Edelbrock alum marine ret port

Valves Fer s.s intake fer Inconell exhaust, Springs 8005 plus insky 155lb at 1.900''

100 Insky Locks and Chromoly Retainers, Custom Length Comp pushrods, Crane gold 1.7 roller rockers

Came Crane hyd roller 139671-610'' .632'' lift, Pistons Mahle forged flat top, Rods GM HP 7/16 bolt hp 4340 steel.

Bearings CL 77h series STD rods STD mains, Fel pro mls Head Gasket.

Do you have flappers in the exhaust tips?? If so, overheating it could have burned up the rubbers, I have heard these sound pretty bad before when they go.

call Mike Flanigan at ProMarine/Statement (Pinellas Park) - thye recently serviced my boat and did a great job.

Thanks for the in-put. It sounds worse than a "tap"