Packard Forum Index » Pre-War (1899-1942)

Dear All,

It has been a long time since I have posted. I have been lurking periodically, but not really enough to satisfy my Packard cravings. Unfortunately, work has required far to much attention over the past year.

I hope everyone has been having more fun with their cars than me!

Anyway, I am on vacation! So it is time to work on the 1930. I have a guy at Colvin Automotive helping me reassemble my 7th series eight (320). He would like to know what the housing bore for the main bearings is. I cannot find this information in the service book (Sizes and Measurements appendix), nor anywhere else.

He would like this information to be sure the bearing crush will be appropriate once the crank is in place and the caps tightened down. The bearings were re-babitted about 2 years ago.

Any help would be much appreciated.

Thanks,

Tom

Tom, I'm not 100% sure about this, but I think that bearing shell "crush" only applies to the modern type thin steel-backed shells and not to those very thick babbitted sections. Typically those heavy (1/4" or so?) halves are babbitted without final finishing, installed (they're located by pins, are they not?), caps tightened, and then the babbitt is line-bored to finished dimension. They should not be cut to finished dimensions other than in the installed position with a line-boring jig. Perhaps I'm wrong on this but that's the way several of the major engine shops do that specialize in the early classic-era engines.

Tom, sounds like the mechanic at Colvin's has no experience with poured babbitt bearings. Welcome back!

(o{I}o)

Welcome back Tom - glad to hear you are still motoring or at least trying to!

"He would like this information to be sure the bearing crush will be appropriate once the crank is in place and the caps tightened down. The bearings were re-babitted about 2 years ago"

The crush factor is a moot point at this point. If REusing the bearings regardless of babbit or inserts is the case then the only thing that needs to be done is to plasti gauge the bearings and then shim/file accordingly to achieve the spec clearence IF NEEDED.

Tom, it's not clear to me if you are "reusing" previously rebabbitted and sized (line-bored) shells that were removed from service 2 years ago, or speaking of shells which were rebabbitted 2 years ago, but not resized yet.

EDIT - your shells are bronze? And retained by dowel pins?

Thanks all for the responses. I kind of figured that the crush only applied to a modern bearing, but I wanted to make sure.

Dave,

The bearings were re-babbitted and line-honed 2 years ago. The crankcase has been sitting in my garage (in a crate, wrapped in plastic) since.

Cheers,

Tom

What about the crank???? Was the crank fitted to the bearings when they were line bored????
BOTTOM LINE: the crank must fit the bearings within service manual/service specifications.

Whats not clear to me here is that the bearings were finished some 2wo years ago and now someone is needing to know info about crush factors. The crank and the bearings ARE FITTED TOGETHER AS "MATCHED" parts AT THE TIME OF LINE BORING.

So if someother crank (not used 2 years ago) is now used then it needs to be plasti-gauged to the bearings to see if it is spec. IF NO crank was matched to line bored bearings 2 years ago then how did the shop at that time determine what spec to line bore the bearings to???? Most likely in that case they would have used the smallest UNDERsize spec. (more secularly as well as erroneously refered to as "OVERsized").

The crank, rods and crankcase were sent to a machine shop for rebabbitting and line boring/honing approximately two years ago. Presumably, they would have sized the bearings to the crank, given that they had it. The work was completed, and everything was shipped back to me, and has been sitting in it's shipping crate ever since.

The 'crush' problem was simply a mis-understanding. The guy helping me has not worked on engines like this one.

The current problem is that with the bearing caps only partially tightened down the crank will not spin. We have not tightened them all the way, but that will presumably make matters no better. So, it would appear that the final honing may not have been done by the shop I sent everything to.

Tom

Sorry to hear of the problems, sounds like time to get out the micrometers. Better that the bearings are undersize and probably just require another correct line-boring, than already too large. I really don't recommend the "scrape to fit" method, though some old-timers were apparently pretty good at it. Still done on ship shafts today.