Crankshaft play

[Purplestaff]

I am rebuilding a 350 for my truck, it's out of a 1991 Chevy half ton. I got all the new bearings in, I polished up the crank and there's quite a bit of vertical play in the crankshaft, you can even see a gap. is a little bit normal? what does this mean? is the bearing cap/block more oval from getting hot or something?

 

[stutaeng]

You should check the clearances with plastiguage. I don't know if the local parts stores has that stuff.

Did you get standard bearings? They sell different sizes depending on wear and machining.

 

[Purplestaff]

You should check the clearances with plastiguage. I don't know if the local parts stores has that stuff.

Did you get standard bearings? They sell different sizes depending on wear and machining.

yeah I got standard, Ill see on Tuesday if the parts store has that stuff.

 

[stutaeng]

yeah I got standard, Ill see on Tuesday if the parts store has that stuff.

I "think" the bearing clearances should be 2 to 2.5 thousands, or so....

Probably worth finding a specific service manual to see what it recommends. The rod clearances are different.

 

[Hipster]

If you can feel veritical play it's way too much clearance. What were the bearings stamped that came out of that engine? Sure they weren't for an .010 or .020 under crank?

I typically see .0015 on the mains and .0018 on the rods with a fresh reground crank. You can't hardly feel that hence having to have measuring tools or plastigage. There are service limits in a manual but I don't like to build a street engine I'm looking for longevity out of too loose to begin with.

Don't forget the procedures for correctly setting the thrust bearing and checking endplay.

 

[Erik the Awful]

Yup, something's wrong. That's a solid no-go until you get it sorted. How did you polish the crank? Has the engine been apart before? Are you sure the crank hasn't been turned?