I just rebuild my engine (pistons/rings/all bearings), and now my oil pressure is extremely low when engine is hot (5-10 psi at idle, and 25 when accelerating). I rebuild engine because 2 of the connecting rods were bent (due to hydro-lock). I replaced main and rod bearings and put new oil pump. I know that there is something wrong with the rebuild. On the beginning I thought that there is something wrong with oil pump, but now I think that maybe main bearings are bad. When I was rebuilding the engine I just replaced bearings, and now somebody told me that I should check clearance on crankshaft. What should I do next? Is there any way to chceck clearance on main bearings when the engine is in the car? If the clerqnce will be to big, how to change it? (buy difrent bearings?)
Thanks

 

well the only way to do it incar is with plastigauge. Then get some bearings .001 under to make up the difference. If that doesn't solve the problem then things need to be ground under and you have to go to a .020-.030 bearing, which means a whole tear down.

Bret

 

So I can buy a .001 bearings and just replace the old ones? And if that won’t help I will have to get the engine machined? Is that right?

 

was your crank turned?

 

What do you mean bu that?

 

did the machine shop fiddle with your crank?

is it a new crank?

new rods?


spin a bearing?

turning is like boring, but for the mains on the crank. you typicaly take .010 off to smoothen it up

 

The crank is old and the rods were used before (but in another engine). There was nothing wrong with main bearings before rebuild. I did that during connecting rods replacement (two of them were bent). What is your advice for me?

 

Ohh man, just take everything back out, you need to get the crank turned, then get it balanced to your flywheel aswell, get it balanced to your flywheel or neutrally balance the flywheel & the crank, you can get little I tihnk called plastiguages they are a piece of paper, you put it inbetween the plain bearing(main) & torque down the main caps to specified torque, take the caps back off & measure the line of the little guage with a ruler/vernier/feeler gauge, that will tell you what the clearance is, you will know then how much thicker/thinner the bearing should be, if the difference is .005, just add/remove another 1lb of torque to compensate & measure again. make sure you do all that, also you might wanna check the condition of the bearing races (where bearing sits), use moly lube on all the bearings, not too much but enough to cover everything. Enjoy.

 

Why shuld I turn the crank or balance anything if everything worked before? The only thing that forced me to do the rebuild were two bent connecting rods, that I replaced.
Thanks

 

When you bend a rod, or seize a bearing it's going to destroy the crank journal and at least destroy the surface finish so the engine just eats up bearings. All of these little things are extremely important if you want it to run forever.

Bret