Engine Machinist help, not boat related

OK, maybe I am confusing myself..........................maybe a engine machinist can advise?

I have a 1994 350 SBC, I am trying to determine if the crank shaft has been turned down. if so, how much?

Here's the numbers that I am dealing with:

Connecting rod;
from Haynes Manual:
Dia. 2.0988 to 2.0998 in.
Actual; 2.0940

Crank Shaft mains:
From Haynes: Dia. 2.4481 to 2.4490 in.
actual; 2.4320

Any help is appreciated.

Thanks,
NT

Couple things. Forgive me, are you using a mic? Have you checked the mic and know it is calibrated and good? Have you checked it with another tool to verify it?

Your crank apprears to be .005 under on the main and .0065 on the rod, which is damn near impossible to run correctly without being "noisy". It would be a HUUUUGE gap relatively considering.

How does the journal surface look? What did the bearing surface look like when you took the crank out?

Brian

nordictom said:

OK, maybe I am confusing myself..........................maybe a engine machinist can advise?

I have a 1994 350 SBC, I am trying to determine if the crank shaft has been turned down. if so, how much?

Here's the numbers that I am dealing with:

Connecting rod;
from Haynes Manual:
Dia. 2.0988 to 2.0998 in.
Actual; 2.0940

Crank Shaft mains:
From Haynes: Dia. 2.4481 to 2.4490 in.
actual; 2.4320

Any help is appreciated.

Thanks,
NT

Click to expand...

I assume HB is Huntington Beach?

I know it is a jaunt, but if you want, you are welcome to bring the crank by we can check it against my mics and check/calibrate yours with standards.

Brian

wsuwrhr said:

Couple things. Forgive me, are you using a mic? Have you checked the mic and know it is calibrated and good? Have you checked it with another tool to verify the numbers?

Your crank apprears to be .005 under on the main and .0065 on the rod, which is damn near impossible to run correctly without being "noisy". It would be a HUUUUGE gap relatively considering.

How does the journal surface look? What did the bearing surface look like when you took the crank out?

Brian

Click to expand...

Hi Brian,
yes, I am using a mic & calipers. I know both are good. The main journals looked ok, and the rod journals had scratches. The reason I am working on the engine is a loud knock when it gets to operating temp. The bearings for both looked worn.



Thanks,
Tom

Ill admit I am not the Chevy spec expert, I checked a couple sites

Rod journal should be 2.0990-2.1000

Mains should be 2.4484-2.4499

Rear main should be 2.4477-2.4488

nordictom said:

Hi Brian,
yes, I am using a mic & calipers. I know both are good. The main journals looked ok, and the rod journals had scratches. The reason I am working on the engine is a loud knock when it gets to operating temp. The bearings for both looked worn.



Thanks,
Tom

Click to expand...

Well that would be accurate with that much clearance. Oil pressure should have been shit as well.

Sounds like the crank is worn and needs to be ground.

Have you checked the journals and made sure they were round?

nordictom said:

The bearings for both looked worn.



Thanks,
Tom

Click to expand...

Which is why I asked about the how the bearings looked. I imagine the journals aren't very round and are just flat wore out and need to be ground.

wsuwrhr said:

I assume HB is Huntington Beach?

I know it is a jaunt, but if you want, you are welcome to bring the crank by we can check it against my mics and check/calibrate yours with standards.

Brian

Click to expand...

You are correct, Huntington.

I am checking it in the motor. Just loosened everything up & let it down enough to get the mic on it.

Thanks for the offer.

Tom

I checked the journals, they are within .0002 of round.

I have been looking for a 5.7, very few in salvage yards. kinda leaning towards a gm crate motor from Jegs, for $1500. I hate to do that since I just put a new set of heads on this motor. Engine machine shop prices really don't seem to make sense on a daily driver.


Thanks

nordictom said:

You are correct, Huntington.

I am checking it in the motor. Just loosened everything up & let it down enough to get the mic on it.

Thanks for the offer.

Tom

Click to expand...

Oh my. :yikes

Well at any rate, the measurements, bearing condition and the noise is suspect to you have a clearance problem.

nordictom said:

I checked the journals, they are within .0002 of round.

I have been looking for a 5.7, very few in salvage yards. kinda leaning towards a gm crate motor from Jegs, for $1500. I hate to do that since I just put a new set of heads on this motor. Engine machine shop prices really don't seem to make sense on a daily driver.


Thanks

Click to expand...

Buy a short block, use your heads on that.

Did you have the noise before you put heads on it?

Brian

wsuwrhr said:

Buy a short block, use your heads on that.

Did you have the noise before you put heads on it?

Brian

Click to expand...

looking at short blocks, the GM warranty is pretty good on the long block.

if it did, it wasn't noticeable.

nordictom said:

looking at short blocks, the GM warranty is pretty good on the long block.

if it did, it wasn't noticeable.

Click to expand...

well then.....are you sure the noise isn't valvetrain/lifter adjustment related?

I think main clearance is .0035-.005, so that deal isn't good but isn't too bad....

I think rod clearance is around .0025.

.0065 additional clearance is HHHUUUUGE on rods, shit would have sounded like a diesel first starting up and worse going on down the road.

Something tells me you have other issues, possibly ALONG with the bottom end clearance, and now you are pretty deep in it anyway. Hard to say what the correct course of action is at this point.

Brian

nordictom said:

looking at short blocks, the GM warranty is pretty good on the long block.

if it did, it wasn't noticeable.

Click to expand...

Sounds like you have a slightly used set of new heads, and a worn bottom end assembly, for sale.

wsuwrhr said:

Sounds like you have a slightly used set of new heads, and a worn bottom end assembly, for sale.

Click to expand...

pretty much.............:grumble:

What heads are they I might have somebody who could use them

mjc said:

What heads are they I might have somebody who could use them

Click to expand...

The heads are on a 1994 5.7 TBI motor. not for sale yet.