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Stewart Ballard

Crankshaft tolerance

Home away from home

My machine shop is asking me what the max tolerance is for both the main and connecting rod bores.

I gave him the pages form the manual for the engine spec but he didn't see it.

Keep in mind I may be asking this question completly wrong. If so feel free to educate me.

Also, I didn't see Jack Vines phone numbr or email listed in the services directory. I'll need to contact him soon for parts.

Posted on: 2014/4/8 9:59

Stewart Ballard

Owen_Dyneto

Re: Crankshaft tolerance

Forum Ambassador

Though specs don't vary too much, it would be helpful to know which engine you're inquiring about.

Posted on: 2014/4/8 10:03

Stewart Ballard

Re: Crankshaft tolerance

Home away from home

Duh! Its a 352 for the 55 400.

I am work and my boss keep distracting me.

Posted on: 2014/4/8 10:05

Stewart Ballard

Owen_Dyneto

Re: Crankshaft tolerance

Forum Ambassador

Engine specifications are in the Service Manual at the end of the Engine section. Clearances are in inches.

Rod bearing clearance 0.0005 to 0.0025. Rod end play (pair) 0.003 - 0.011.

Main bearing clearance 0.005 to 0.0025. Crankshaft end play 0.0035 - 0.0085.

Posted on: 2014/4/8 10:11

Stewart Ballard

Re: Crankshaft tolerance

Home away from home

I knew I would get something wrong.
Stopped by the machine shop on my way home.

They need the housing bore for the mains and the connecting rods or in layman terms, how big is the hole on the connecting rods and the main bearings.

He said they want to bring it back to standard (if needed).

Posted on: 2014/4/8 16:43

Stewart Ballard

Owen_Dyneto

Re: Crankshaft tolerance

Forum Ambassador

I know that resizing the rod big ends and the main bearing blocks (and align-honing them) is part of a good engine rebuild but I don't know where the actual measurements or specs come from, perhaps from the actual bearing shell manufacturer who would know how much "crush" was desired?

Sounds like a good question for Jack Vines.

Posted on: 2014/4/8 17:31

Jack Vines

Re: Crankshaft tolerance

Home away from home

Main bearing bore dia. 2.6875"
Con rod big end bore 2.390"

jack vines

Posted on: 2014/4/9 0:11

Owen_Dyneto

Re: Crankshaft tolerance

Forum Ambassador

Jack - I'm curious - where does one find those dimensions or how does one calculate them if the actual specs can't be found?

Posted on: 2014/4/9 10:22

Jack Vines

Re: Crankshaft tolerance

Home away from home

The American Engine Rebuilders Association (AERA)has an on-line data base for members called PROSIS. I always check there first.

After noting the PROSIS dimensions, I then measure and confirm with a Sunnen dial bore gauge.

jack vines

Posted on: 2014/4/9 10:57