hey guys,

my built b20v dropped a valve last night. 3 of the 4 pistons appear fine but one is just fucked completely.

when the piston exploded/valve broke the valve seat shattered as well and a fair amount of aluminum went up into the intake manifold and ended up in the other 3 cylinders where the pistons beat the shards into the head.

i know the head can most likely be fixed, although pricey, but im going to shelf it for a while and use a fresh head instead.

none of the cylinder walls are scared at all and the pistons appear to be fine. can i just replace the one piston and put it back together or should i replace all 4? should i get new bearings or just reuse the old ones? motor had 18500 when it dropped the valve.

i'd like to keep the bottom end in the car and just replace the one piston but im going to wait for ya'lls thoughts before i get started.

 

you'll at least want to replace the bearings. that rod saw an impact, which may have transferred heavily to the bearing, which probably damaged the bearing a little in a way you'll never see with the naked eye

 

You most likely have bits of metal debris throughout the engine since the piston came apart. The right way to do it is pull the engine and completely rebuild. The bearings are very likely scarred and damaged and the rings probably have metal embedded in the sealing face. The other pistons would need a professional to inspect them for cracks or other damage. Usually the metal bits will get pounded into the piston if they get trapped in between the piston and a quench pad, or any volume that is smaller than the piece of metal.

Of course, you could always half *** it, replace the one piston with the engine in the car, and see how long lasts.

 

when i dropped a valve, i bought new pistons, bearings, oil pump, had the block and rods checked out by my machine shop (vee village, downtown KC). then assembled it. unfortunately for me, i had to bore the cylinders to fix the dents in the walls.

 

thanks brian. i think thats what i've decided to do.