Ok so this may be a bit of a dumb question, but when measuring clearances on a crank, is it done with bearings in place? Or without? Or both?

 

measured with bearings in place and don't rotate the crank

 

http://www.c-speedracing.com/h...s.php

 

Ok so this is done with the NEW bearings correct? So I have to order bearings based on the letters/numbers on the crank/rods and then if the gap is too big I have to order a larger size?

Is this the idea?

 

What exactly are you trying to do?

If you spun a rod bearing, you have to have the rod checked and more than likely re-sized. It is also important to have the crank checked to make sure it is still round and within spec. IF the crank needs to be turned, the machine shop will let you know how far they have to cut it. Once that is done, you will know what oversized bearings you will need.

If you are merely checking the see which bearing you spun, wipe the bearing clean of any oil, place the plastiguage in the center of the bearing and torque the cap back on. Then loosen and read the spot against the chart on the package. This will tell you your clearance.

If you are working with main bearings, remember to never check mains with plastiguage while the engine in in the car (From underneath) The weight of the crank on the main caps will give you false readings on the plastiguage.

My suggestion is to ALWAYS have the crank checked if you spun a bearing. And you must have the rod checked and resized if necessary. If you spun a main bearing, you should have the block checked and line honed if it is out of spec as well.

As a special note: Take care to make sure your crank is not turned when removing the cap to read the plastiguage. Any rotational movement will give a false reading.

Now, if you are merely rebuilding an engine and have had all your machine work done, the shop should have told you if the crank was turned. They should have stamped the journal cut on the crank as well, usually on the #1 counter weight. Then you simply order the proper size beaings and use them to check all your clearances with the plastiguage.

I hope this helps.

BTW: If you can find a friend with a good set of micrometers, they are much more accurate than plastiguage. As a matter of fact, I particularly HATE plastiguage, a lot of people swear by it.

 

Oh, and the only dumb question is the one you dont ask!

Building an engine is a straight forward process. It's not that difficult, but there are little tricks here and there to make sure things are accurate. That said, you will get more and more confident the more you do it.

There is nothing more enjoyable than putting everythign together and firing that bad boy up for the first time... Well, maybe there are other things as enjoyable, but we cant discuss them on this forum.. LOL