Rod bearing clearance
Thread Starter
Racer
Joined: Nov 2001
Posts: 478
Likes: 3
From: Huntsville AL
Rod bearing clearance
Calling all experts, I'm trying to determine if I need to pull my block for rework. Can anyone tell me what clearance is too much on the rod and crank bearings??? Thanks for the help guys, you are great.
YBnormal drive a vette
YBnormal drive a vette
Safety Car
Joined: Oct 1999
Posts: 4,101
Likes: 10
From: NorCal
Re: Rod bearing clearance (Ybnormal)
It might be helpful if you gave a little more info. How do the bearings look? Were there problem leading up to this point? As a generic rule of thumb in new engines, I like around .0025 for a street engine, and maybe a little more in race engines. Used, it's a bit more involved, depending on crank condition, type of service, bearing condition, etc...
Hans
Hans
Thread Starter
Racer
Joined: Nov 2001
Posts: 478
Likes: 3
From: Huntsville AL
Re: Rod bearing clearance (Ybnormal)
Thanks for the response guys, sorry should have given a little more info. 81 350 not sure how long since last rebuild. I have had the car 7 years as only a weekend cruiser. Bearing only show normal wear, don't appear to be out of round, cylinders show no lip at the top of the bore. Is the .0020 to .0025 sound about right for a stock 350 for rod and crank bearings clearance? How much is to much? Thanks in advance guys.
YBnormal
[Modified by Ybnormal, 12:10 PM 4/25/2002]
YBnormal
[Modified by Ybnormal, 12:10 PM 4/25/2002]
Le Mans Master
Joined: Apr 1999
Posts: 6,134
Likes: 46
From: Raleigh North Carolina
Re: Rod bearing clearance (Ybnormal)
Here are some typical specs... right from factory GM service manuals... that doesn't necessarily make them desirable though.
283: .0007 - .0027
307: .0007 - .0028
327: .0007 - .0028
350: .0007 - .0028
400: .0009 - .0030
400: .0009 - .0025
366: .0014 - .0030
396: .0007 - .0028
396: .0009 - .0025
396: .0014 - .0030
427: .0007 - .0028
427: .0014 - .0030
427: .0009 - .0025
427: .0018 - .0034
454: .0009 - .0025
454: .0014 - .0030
Service limit is .0035... meaning at .0035 it's time to install new bearings.
As you can see, the specs vary, even for the same displacement engine.
I only looked at 2 different GM year manuals.
My personal preference is to run them at .001 - .002, in favor of longevity.
That's where I have had the most reliability.
283: .0007 - .0027
307: .0007 - .0028
327: .0007 - .0028
350: .0007 - .0028
400: .0009 - .0030
400: .0009 - .0025
366: .0014 - .0030
396: .0007 - .0028
396: .0009 - .0025
396: .0014 - .0030
427: .0007 - .0028
427: .0014 - .0030
427: .0009 - .0025
427: .0018 - .0034
454: .0009 - .0025
454: .0014 - .0030
Service limit is .0035... meaning at .0035 it's time to install new bearings.
As you can see, the specs vary, even for the same displacement engine.
I only looked at 2 different GM year manuals.
My personal preference is to run them at .001 - .002, in favor of longevity.
That's where I have had the most reliability.
