bad main bearing
 

I m no machinst...took my block to machine shop, they state main bearing went along with piston, 22 degree clearance on main. My mechinic states its impossible looking at picture that it went, and clearence should be diagnosed with main caps on and torqued - which machine shop measured with cap and bearing off...who to believe. Engine had 10min run time...detonation due to leaking intake...This bearing look bad is what im asking. Thanks for the input, pardon the english.

Re: bad main bearing
 

Is this english or spanish? Not sure what you are asking here dude?

Re: bad main bearing
 

That bearing definitely doesn't appear to be wiped out. It didn't spin either. It doesn't look great but it's not toasted.
Bearing clearance is measured with the bearing installed and the cap bolts torqued.

Re: bad main bearing
 

Thanks Crazy...I think Jasper is killing these local shops and they want to add work to jobs that really dont need it. Thanks for the confirmation.

Re: bad main bearing
 

Doesent look that bad ,not brased out, alittle trash in the babbit.Did its job asorbed it.

You # on clearence ?? is it .022 or .22 if its.022 that is a little tight. I bet money its not .22. if its .022 its the engine builders fault!!!! Oil presure?

What does the pistion look like?

Re: bad main bearing
 

I agree also clearance is checked with a dial bore gage and reads in thousands of an inch. :D

Re: bad main bearing
 

Re: bad main bearing
 

here picks

http://www.engineparts.com/Motorhead...gfailures.htm#

Re: bad main bearing
 

Also if it leaned out/detinated it would beat out [wear]the top of the rod bearing. look at the upperbearing that the pistion is hurt.

heres a thread with some bearing picks ,last ones have 118 hours with .0027 to .0034 mains,Just took them out last week and was showing some wear :drink:

http://www.offshoreonly.com/forums/s...t=500efi+build

Re: bad main bearing
 

Although he wants to replace all pistons, im just going to do the one that is bad. He was able to hone the wall ok...I think ill replace all rod bearings though. And reading Raylor's post about the new main bearings they are making with a special coating might not be a bad investment.

Re: bad main bearing
 

Damm thats nasty.What did the rod bearing on that piston look like?

The exhaust valve looks sunk into the seat to me .Need to ck valve job on that hole, all that alumiun went thru the seat

Re: bad main bearing
 

There is absolutely no reason to change the other pistons unless there is something wrong with them. If all 8 are going to be removed it would be wise to measure them as well as the cylinders to verify the piston-to-wall clearance but you can get a pretty good idea of their condition by closely inspecting the cylinder walls for scuffing, scratching, things of that nature.
While you have the heads off you might want to verify the valve spring installed height. You might find out that, as Strip Poker noticed, the seats are quite low resulting in low spring pressure or needing too many shims to get the pressure up to specs.

Re: bad main bearing
 

They are going to replace 1 piston, rings, all rod bearings and mains, shave head, hand hone 1 clyinder, checked for cracks on heads, clean up valves - claims its ok...for 1200.00
I gave them the block and heads seperate, they will return same way....strippoker, the rod bearing was toast.

Re: bad main bearing
 

Dtile: Who is doing the machine work?

Re: bad main bearing
 

Brocks in tarpons springs,fl Im new to the area.