To make a long story short I had dropped one of the nuts that hold the fuel lines in the spyder down the intake (didn't see it go in) and the result is now a tapping sound which never stops. I pulled the engine and here is the resulting damage to the piston. There is no damage on the heads or valves or anywhere else in the motor. The lifters, pushrods, bearing and everything else I have looked at are fine. There was a compression ring on the piston that was seized to the piston (resulting in low compression). Due to being screwed over on craiglist on a engine I don't have the money to overhaul the engine and am now in repair mode. I am going to replace the piston,rings and bearings on the cylinder but and unsure what caused the tapping and don't want to put it all back together and the noise still be there. Any ideas what else it could be. The compression on all the other cylinders is fine. Thanks

Since I thought the engine was bad when it happened I did drive it for months with the tapping. The oil pressure is fine and the idle is steady. I had no issues at all how it was running, just the annoying tap. Could the seized compression ring have caused the piston to rattle in the cylinder?

 

Have you pulled the head?

Could be the piston but also something else damaged when the nut passed the engine.
As a minimum I would at least on the damaged side:

- check the affected rod for straightness and bearing damage
- check the affected piston for damage and check the ring grooves (better replace it)
- check all pushrods for being straight and not out of round
- check all pushrods ends for gauging or other damage
- check all rockers for abnormal wear
- check all rocker studs for wear (use all new locking nuts when putting it together)
- check all valve stems (caps) for wear
- check at least the valves of the affected cylinder but better of this head for wear and out of round (straightness)
- check at least the valves seating faces and valve seats of the affected cylinder

A tapping or knocking sound similar to a leaking exhaust manifold gasket can also be a damaged valve seat.
With debris passing through the engine I would suspect such damage at least in that cylinder.
Debris may be blown into another cylinder on that bank through the exhaust manifold or the EGR passage, this being the reason why I would suggest checking the whole bank and pulling that head.

These engines being so low on hp are incredibly strong and can take a lot of punishement.

Good luck

 

Man sorry to hear this..You have to pay attention when ever your around an opening of any kind.Next time if you have any openings stick a rag I it,that way you know nothing will drop in it..

 

I will never make this make again, first and last time this will ever happen. The only cylinder that is damaged is #1. I cant believe there is no damage on the cylinder wall or even marks on the head. When the engine was running I could take the plug wire off and the tapping went away. The compression was good on all other cylinders and this one was at 80 and hope it was just the seized compression ring. Well I guess I will see, at least this gave me an excuse to change all the control arms lol.

 

Sorry to hear of your problems.

Have machine shop check for bent rod if you ran a nut through the cylinder. They will probably want to resize it in any case and you will need the new piston pressed onto the rod anyway. You can check the valve sealing with machinist's blueing, but you will probably want to replace the valve stem seals on any cylinder you take a valve out of (keeper slot on valve cuts them when valve comes out - use protector when installing).

Replacement piston/pin or any replacement rod should weigh the same as the old one within a few grams, or you will have a balance problem. There are light and heavy versions of the cranks, pistons, and rods - as well as two manufacturing locations. Don't mix them up. Here's an article that everyone should read before replacing deep parts in a 4.3 V6.

http://www.crankshaftcoalition.com/w...degree_engines

Try to clean the honing grit up well after using a diddly-ball glazebraker (rings will never seat without breaking the glaze on the cylinder). Any left-over grit in the engine will end up in the bearings. Problem is that glaze breakers sling grit everywhere. I'm assuming you have the engine out and that the ridge in the cylinder has been reamed so the new top ring doesn't break when it hits the ridge worn in the cylinder.

Good luck! Many people try this type of bare-bones repair to try same some money but few succeed. I really wouldn't recommend it but it's your vehicle and your time/money. Main issue is getting junk/grit from the repair job/honing in the bearings, as it is usually impossible to clean things out properly without complete disassembly.

 

Lesmyer is absolutely correct.

two weeks ago took apart a big block chevy at my friendly machine shop which used up more than a quart of oil over 200 miles.
Found it full of glass debris and corundum from sand blasting most probably the spider or heads but could also have been the exhaust manifolds.
All to be redone including bearings as it is from a vintage 70's Corvette.

Turned out to be the intake manifold which had been sand blasted for re-painting.

Sand and abrasives = no good in an engine. Most probably ends in complete disassembly if properly done.

 

All of this was checked and when we started the engine up last night for the first time the tap is back and even sounds worse now. The piston, rings and bearings were replaced and the head was checked at the machine shop. Time to start from square 1 again. Anyone else have any ideas?

 

So all is done now. I replaced the bad lifter (new lifter I just put in) and now she runs like a bat out of hell. Thanks for all the help