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1931 Rods

Guest 1956Packard

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Guest 1956Packard

I hate to ask this but I will anyway....

A couple of years or so ago, some kind sole passed me some information - specifically....


a re-print of an article on how to machine a set of Packard babitted rods to accept insert bearings. I think this was an older article??


a list of the years (and models) of rods that will exchange with '31 rods

Sorry to ask again. Blaim it on failed hard drives and poor house cleaning.

If anyone can pass this info along again, I promise to take better care of it.


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Guest Trunk Rack

I do not recall seeing such an article. But you have the right idea - going to modern "shell/precision" steel backed "insert" bearings for a "driver".

The problem that Packard had with its poured babbit rod bearings, was that long stroke slamming those heavy rods around. Combined with fearfully low final drive ratios the shock loads on those crank-pins was fierce.

I do recall seeing a General Motors tech. report bragging about how Buicks and Chevies with "poured babbit" rods would survive some high speed driving ( heck - on suburban residential streets today the road speeds are higher than cross country speeds were when your engine was designed...!) and the typical 5" stroke Packard would start losing its con. rod bearings at less than 2,000 mi. of high speed service.

Go look up a news article on opening day of the Penn Turnpike (late 30's) and what happened to poured-babbit bearing equipped cars who tried to keep up with the "insert" bearing cars when driven REALLY fast!

The reason Buick and Chevie got away with it clear into the early 1950's, was their babbit overlay was much THINNER than Packard's practice. The thinner the babbit over-lay, the less it is subject to fatigue fracture. But even they would "pound out" eventually if you drovve really fast for any length of time.

Elsewhere in this and other forums you can read all kinds of wise guys who "know" poured babbit will work. Ask them to show you the copies of the letters they wrote to the auto industry of today in which they tell today's engineers that they are wrong for using inserts!

Seriously, I am obviously VERY prejudiced against poured babbit as a bearing material in "high speed" motors (meaning most post 1920 "big" engines).

In my view, using poured babbit today, especially in fast, powerful cars like "big" Packards, should not be an acceptable shop practice unless the car 1) is going to be a "trailer queen" and 2) you engrave on the block in bold letters " THIS MOTOR HAS POURED BABBIT BEARINGS - DO NOT DRIVE OVER 35 mph !"

Not sure if "late production" (meaning 1935-1939) Packard "senior" rods will work in the '31's. Even if they do, you cant get those "flanged" inserts ( or can you-someone just e mailed me someone is thinking of going into production on them - hmmm....what "clearances", crank-pin size, etc. are they set up for ??).

Cant recall what the earlier rod big ends look like. Seems to me a smart machinist with a good Sun hone should be able to clean em out to use a modern off-the-shelf rod bearing.

About those flanges. I'd rather not discuss that; have some friends still in the business who feel very passionately about them. Suggest you go thru old SAE tech papers at a well-equipped library, and come to your own conclusion. Bottom line, brazing some "bumps" around the big end to take up the correct clearance-space where the flange used to be, works just fine, (so you can use a modern off-the-shelf "insert") works just fine. The "flange" was a left-over "overkill" concept from the old "T" head days of engineering.

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Guest 1956Packard

Thanks for the info Trunk Rack. I believe the article was in a magazine produced by one of the Packard clubs many years ago.

I can't say where the interchange info came from??

I am leafing through my manuals as I remember there was a change in the rods post 1931, but units up until 193? still interchanged.???

Any help is appreciated I don't wish to go from my memory as it obviously sucks 'cause I can't find the info.


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let me try to give you the right information on connecting rods. first the replacement bearing you are most likely looking for fits a standard eight/ super 8 from 1935-39. Packard itself in one of its parts books that you can retrofit insert bearings in an earlier engine specifically, The 1933-34 Packard Parts book says, the following:"We are shipping for connecting rod replacement a rod with a detachable type crank pin bearing. This bearing is not included in the rod assembly part number, but must be ordered separately.

the bearing insert that a lot of people used was from a chrysler slant 6. even if you used these bearings the first thing you need to do is to machine out not hone the id of the rod. also, when you do this you machine into the connecting bolt area. once that is done now you have to deal with the excess side clearance. remember that packard used flanges on poured babitt as well as inserted bearings. this was done for a reason. namely that the piston and piston pin are said to be full floating meaning that it is the flange on the rod that keeps the rod centered in the bore and centered on the shaft. so that now led to people welding up the side of the rod. this is a problem because the heat anneals the rod and now it is steel to steel contact on the crankpin cheeks. so this promotes wear to the crankshaft and develops heat. some people even left the side clearance alone meaning they didn't reduce it. this is a problem because now the rod has too much side clearance and they move forward and backward and it too damages the crankshaft. another problem that arises is it reduces oil pressure because now there is too much clearance and you lose pressure from the sides of the rods.

contending that poured babbit is bad is shear mechianical BS. the problem with poured babbit is when the shaft has to be resized namely to lets say .030 under now you are asking for problems because with that much babbit the bearing can not dissapate the heat. and it can lead to a failure. so this sounds like im making an arquement for inserts right. Wrong if you read the parts books for std and super 8 the insert bearings (from 1935 39) were only available to .015 oversize.

the answer is in the babbit material. insert bearing and poured bearings used what is called SB meaning high lead tin Babbit. it wasn't until 39 that CA babbitt was used in the inserted bearing that is Copper tin babbitt. now CA has an advantage over SB because it can dissapate heat easier. but it also is harder and not as complyant as SB material. another problem that needs to be stated is in those earlier days all car companies did not have the techincial knowledge to harden shafts to any great depth so the last thing you want to do is to regrind any crankshaft below .020 unless you reharden it. the engine oil that was used in those days was non detergent. that type of oil allows dirt to settle to the bottom of the crankcase. while detergent oil keeps the dirt in suspenesion.

when it comes to gearing remember THAT ALL ENGINES CAN BE OVERREVED just earlier cars have less tolarance for it than newer cars.

Bottom line is - putting insert bearings into a rod that was designed for a poured babitt creates a lot of problems. just don't regrind your shaft greater than .015 and you will be fine and the car will cruise all day at 65mph. if you need to go greater than .015 then you need to repair the shaft and reharden it.

By the Way we make the std and super 8 bearings - Standard and Super 8 bearings for Packard 1935 - 39

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If the article on rod conversion you're referring to is the one I have in front of me, it wasn't printed by one of the Packard clubs but in the CCCA Bulletin. Send me a PM with your email if you want a copy.

As to the Library Director's comment that you can cruise "all day at 65 mph", I rather doubt it, especially if you have a closed car, most of which had 4.69 rear axles. I've got a lot of miles of experience with my 34 Eight with babbitt and a 4.69 rear, and I'd suggest more like 50-55 for an all-day cruising speed, if you must.

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Guest Trunk Rack

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Library Director</div><div class="ubbcode-body">Owen,

I stand corrected on the cruising part - </div></div>

you should also 'stand corrected'( did I read you correctly?) on your belief that the sintered copper lead bearing only came out in '39. Not according to what I have seen over the years, and I have pulled one or two (possibly one or two more) Packards apart for engine work.

When I worked in Charlie's shop in the mid 1950's I dont recall EVER seeing ANY "insert" Packard V-12's we took apart, that did NOT have "copper-lead" inserts (again, we are talking about 1935-1939 production - most of you know the "smaller" displacement V-12 ('32 - '34) had poured babbit).

Well, with the exception of one that had been over-hauled at soem point, probably in a Packard shop, probably during WW-II (when for a short time Packard Stores was supplying some kind of silver/alum.-coated insert for the Twelves).

I DO agree with you that it would be a TERRIBLY bad practice to weld on a rod, and/or monkey around with the bolts (would set up potential 'stress focus' areas, just asking for rod bolt failure. Sad to say too many of the eights threw rods anyway - no need to provoke em.

Hopefully, would-be rod re-workers will see your post and LISTEN to you. You are sure right about that !

More about your being right about messing with Packard con rods by welding. Steel-to-steel contact. You are so right - VERY bad.

That is why Charlie brazed, rather than welded bronze "bumps" to get the right side clearance, and used bronze. That way, we had an oil cushioned "contact" area of dis-similar metals with different "co-efficients of friction". You KNOW YOUR STUFF ! Again, hope people LISTEN to you about that.

And yes, I couldnt agree more - keeping the engine speed DOWN is the only way to get a "poured babbit" engine to survive. However, I think even a steady 50 mph is asking for trouble, given the 4:41 and 4:69 rear axle ratios that came "stock'.

As many of you know, Packard put a lot of man-hours, engineer-research time, and time on its test track blowing up Packards trying to figure out a way to get the "poured babbit" system to work on the higher speed roads coming into service in the late 20's early 30's.

They failed. They tried all kinds of "gimmicks" from oil coolers (think that was '33; might have been '34) "finned" rod caps on the eight cylinder cars, etc. etc. Explains why Packard was so proud of finally getting the "precision/type" copper-lead inserts for '35 & later production.

Those of us who do NOT have engineering degrees with a "speciality" in mechanical engineering, would do well to see what is considered good practice in the reciprocating engine industry !

So glad to see guys like you in the business who actually KNOW what they are talking about & doing!

The kind of guys I hung around with, working on pre-war long-stroke Packards all agreed with me that "inserts" were the ONLY solution to getting any kind of service out of "big" Packards of ANY year.

Yup. if the driver of ANY of the big Packards we "did" in those days, had a sense of humor and a bad temper, suggest you dont try and catch em and pass em...!

(added later)

Do I understand correctly that YOU are the shop that is now making correct factory-type "inserts" for the "Standard Eight"?

If that is true, anyone who owns a "Standard Eight" who does NOT contact you with an order, "drop" their lower crank-case (yeah, I know, in modern terimonlogy they are stamped sheet metal and called oil pans, but we Packard guys know what the pre-war Packards were built like...!) get their crank-pin specs to you, and order a set, should have their cars confiscated, and be issued warm beer for the rest of their lives.....!

IF THAT'S YOU - CONGRADS - when can I send you a check for a set of V-12 rod bearings - true - my "factory originals" have only about 170,000. of extreme speed service on em, but who knows, could wear em out some day !

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