Crankshaft Counterwieght Hitting Thrust Bearing

[Rich1972C20]

I'm rebuilding a 350 chevy and I put in new crankshaft bearings. When I put in the crankshaft the counter-wieght hits the thrust bearing t the point I would have to really force it to go in.

I bought another set of bearing just to see if they shipped the wrong ones and the same thing happened. I know you can sand down the bearing to get the proper clearance but this being basically the first rebuild I'm doing I'm concerned I'm overlooking something. It a stock crank and the bock has not been aligned honed.

Is this common that cranks may not go in without some sanding of the thrust bearing?

THanks guys

[Chaparralman1974]

Are you sure that it is a 350 crank and not a 400 crank? I would double check the casting, and since you mentioned you have not align honed it, I would recommend taking it back to the machine shop and getting that done. I ended up having to make a return trip the the shop to have mine align honed because the crank was a tad too tight for my liking.

Good Luck!
Clay

[Rich1972C20]

I checked the casting and its a 350 (3932442).

[RustyPile]

I have built hundreds of SBCs and, never once, have I seen counterweight interference with a bearing.. The crankshaft has a ring that runs against the thrust bearing. That's how crankshaft endplay is controlled. I've seen instances where this ring is missing or broken for whatever reason.. The counterweight cannot contact any of the bearings. Are you sure you have the thrust bearing in the correct location???

[54blackhornet]

Get some more experience eyes on this build l

[truckster]

A picture or two might help.

[Rich1972C20]

I went to take pictures and there was enough space that it went in after I shifted the crank with a little effort. Its real tight so I'll sure I'll need to sand the bearing to get the right clearance.

This'll sound terrible but from all the videos I've seen they just drop right in, so it got me concerned when mine didn't. Paranoid nicking the bearing surfaces.

Thanks for the help.

[Steeveedee]

Originally Posted by rustypile

i have built hundreds of sbcs and, never once, have i seen counterweight interference with a bearing.. The crankshaft has a ring that runs against the thrust bearing. That's how crankshaft endplay is controlled. I've seen instances where this ring is missing or broken for whatever reason.. The counterweight cannot contact any of the bearings. Are you sure you have the thrust bearing in the correct location???

+1

[Bob B.]

Could you have a bent crankshaft?

[truckster]

Originally Posted by Rich1972C20

I went to take pictures and there was enough space that it went in after I shifted the crank with a little effort. Its real tight so I'll sure I'll need to sand the bearing to get the right clearance.

This'll sound terrible but from all the videos I've seen they just drop right in, so it got me concerned when mine didn't. Paranoid nicking the bearing surfaces.

Thanks for the help.

If you're having to sand the bearing there's something that's not right. It might be worth the money to have a reputable machine shop check it out. There's nothing fun about starting up a newly-assemble engine and hearing a rod knock.

[HO455]

At no point should "Sanding" the bearing be an option.

Those parts either fit correctly
or they are the wrong part.
or they are installed incorrectly.

The bearings were manufactured to precisely fit a properly machined crankshaft down to .001 thousands. Sanding can only destroy those precise clearances.

All the bearing clearances in your engine are part of a balanced system. The oil pump supplies X amount of oil volume. Each bearing is engineered to bleed a certain amount of that total volume back to the oil pan. If one bearing bleeds too much oil it robs oil from other bearings in the engine. If the bearing clearance is too tight then the bearing overheats and fails.

For example if a high mileage engine is experiencing rocker arm failures it may be due to loose bearing clearances on the crankshaft bleeding off the oil that needs to be forced up to the rocker arms.

There is no way we can help without pictures but ideally you need some experienced eyes and hands on the engine to determine the problem and what the fix is.

I'm not trying to be an a$$ here but it is so easy to turn all those new parts and machine work into scrap iron within minutes of the initial fire up. Trust me when I say you don't want to know the feeling that comes from that.

[kwmech]

Pictures are going to be must have here. Something is jacked up

[1970 CST Short Wide]

Was the Crank turned ? Do you have the correct size Brg - Std .010 .020 etc.?
I was an automotive machinist for 16 years and Never sanded or even heard of sanding Crank Brg. Take it to a machine shop or find someone with engine building experience
Before you damage something

[1970 CST Short Wide]

Please let us know how this turns out

[Rich1972C20]

I want to clarify that I'm talking about crankshaft end play. I'm not sanding the bearing surfaces. BTW the bearing clearances were in spec.

The initial clearance with the new set was .001 so I got it into spec (.005). I polished the surface smooth with 2000 grit wet sand. The crank spun smoothly every step of the way during assembly (torquing caps, installation of pistons, setting in new pushrods, etc..)

The engine is assembled less the intake and exhaust manifolds, I set the lash on the rockers and the engine rotates manually with resistance that seems reasonable. If anyone has a range on what torgue values to expect on the newly refurbished engine that would be helpful. I understand this might be difficult due to many variables but I'm using a mild hydraulic roller camshaft.

I know nothing is guaranteed but should I still be worried?

[HO455]

I just read this thread on the Pontiac website. It may help you as there's not that much of a difference in the 2 V8's as far as rotational torque.

http://forums.maxperformanceinc.com/...Crank+rotation

[Rich1972C20]

Thanks. I'll measure mine.

BTW I have a totally stock 72 400 formula and 69 GTO. Didn't do much to each.

[Rich1972C20]

Thanks I'll measure mine.

[HO455]

Originally Posted by Rich1972C20

Thanks. I'll measure mine.

BTW I have a totally stock 72 400 formula and 69 GTO. Didn't do much to each.

To cool! Neither one of mine are very stock. Both have oddball stroker engines I built for them.