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I am currently polishing crank journals and fitting main bearings on my ’35 Pierce and some thoughts from research I did 30 years ago resurfaces. I had dug up 1930’s Society of Engineer’s reports on the engine design problems back then to try and do my best rebuilding my ’36 Packard to survive freeway driving. Now that I am doing my Pierce I just went back through them again, with the question of how to best keep the mains and con rod bearings alive. Unlike my Packard, I am not planning to install high speed gears or overdrive.
I have thought about trying to write a tome on the subject, there are lots of non-intuitive conclusions in the 1930’s papers, but will take some time to sort through the conflicting data and analysis.
However, one thing I think is pretty clear I thought I would pass on: Avoid a lot of throttle from a stop or at low speeds after driving at highway speeds on summer days. Also, multi-vis oil is a good thing. Pierce’s used babbitt bearings that are forgiving of dirt but can’t take high temperatures. I think a lot of bearing failures are blamed on high speed, but it is more than likely the damage leading to the failure was caused from hot bearings at low speed and high load, even though the final failure occurs during high speed driving. At high speed even a very hot oil film should be sufficient to prevent any surface contact between bearing and shaft, but at slow speed/high loads the film is more likely to break down and allow metal to metal contact. Babbitt is prone to rapid overheating and cracking under those conditions. Babbitt side flanges on the connecting rods as used by Pierce were noted as being prone to cracking and failure.
Bottom line, the thing to avoid is a lot of throttle in high gears after getting off the freeway on a hot day. Keep a light touch on the throttle and delay shifting until the engine has a chance to cool down. This type of failure is what led to adapting copper-lead inserts, and Pierce’s large main bearing surface area shouldn’t be expected to be complete insurance against this problem. Large surface area can react more load but in turn generates more heat, so it becomes a bit of the dog chasing its tail increasing bearing surface area.
I am also reconsidering not bypassing the oil temperature regulator after re-reading the paper on it.
Jim
Jim,
I’m not sure but oil has improved alot in the last 80 years when those papers were written. Jim
Jim, yes they have, with multi-viscosity being one of the best improvements. My doomsday bearing failure scenario should be less of a concern now than when these cars were new, however my concern is all the details that go into an engine rebuild that can overwhelm the advantages of things like better oils.
My point of departure on this is that if this was 1935 and my car was factory fresh except for 1000 break-in miles, it should have no problem running at 65 mph with original gearing and all.
Further on the plus side, these engine designs were tested at max throttle and probably ~4000+ RPM, so even running at ~3000 RPM on the highway is significantly below their capability.
However, my Pierce engine was rebuilt by somebody in the ’60’s and about 50 miles were put on it before it was parked again for the next 50 years. All in all the bearing re-babbitting looks good but I can only determine how good the bond is by destroying it, and then I get to go through a few thousand dollars having someone else re-babbitt and line bore it, with no assurance it will be any better than what I have. One thing that is a reasonable assumption is that either way it won’t be as good as the original factory build, so taking precautions to compensate for the likely deviations from the original is what I am about.
My Packard has early copper-lead inserts that were notorious for problems relining. Packard had demonstrated them by running on the test track wide open averaging 92 mph continuously for 7 days and nights. My original inserts were serviceable but had worn the crank, so I hard chromed the crank up to standard and used the original bearings. Hard-chroming the crank weakens it, and I had aftermarket pistons that obviously hadn’t been tested in multiple engines at 4200 RPM as the originals had. For that reason I put in a high speed gear set to slow the engine down.
My Pierce has serviceable original pistons, good crank, a 4:23 rear end but a non-factory re-babbitt job. RPM at speed shouldn’t be an issue if I keep bearing temperatures down and don’t tempt fate by lugging at high load at high temperatures.
With the 50 miles put on it in the 60’s and acceptable but tight clearance my crank had significant drag (>10 ft-lbs) when the main caps were installed and torqued. Babbitt is forgiving, and that level of drag would have probably worked itself out with a good break-in, but I just finished hand-fitting each bearing and reduced the drag to 3 ft-lbs.
Bearing failures on babbitt rebuilds seem to be reasonably common. One of the papers was a by a Studebaker engineer who noted that just the presence of a copper washer in a cleaning solution dipper had disastrous results on a batch of babbitt. Is the guy re-babbitting today as meticulous and knowledgeable as the guy who did it at the factory day in and day out with a process engineer over-seeing? Maybe, maybe not.
As an aside, it is maddening that spell check insists on capitalizing “Babbitt””!
Jim”
I know that I’m over simplifying, but I always wondered about multi viscosity oils in older engines.
A 10W/30, for example, is 10 weight oil at ambient temperature, and 30 weight oil at engine operating temperatures.
So, I start my antique engine, full of bunny rabbit bearings, with 10 weight oil the only thing between crank and journals. That doesn’t make sense to me. Yes, in a new, insert, thin bearing surface engine, fine, but will it make my rabbit more bunny, that’s the question.
My Pierce lives in a temperature controlled room, so the possibility of starting it at 20 degrees ambient is pretty small. I run straight 30 weight, in that and my Cord and Packard, and don’t have problems.
I’m sure the discussion will continue.
Just my 10 cents worth. I have a 1912 6 cylinder Napier which of course has babbitt bearings They are the ORIGINAL factory ones & so are now 103 years old! I cruise this car on the highway at around 50 to 55 mph for some hours at a time. The crankshaft is of the “bentwire” type with 4 mains & all the journals are only 1 3/4″ diameter. Over the last 55 years I have covered around 30,000 miles ( I know this sounds a bit like a fantasy, but it is true.)In the early years it was my everyday car. We have done trips of 4000 miles at a time. Australia like the US is a BIG country. Also the bearings have survived teenage enthusiasm!!! I have used multi grade oil ever since it has been available. Early on it was Shell X100. Since the engine has no filtration oil changes are at 1000 mile intervals. I have inspected the bearings over the years & in the last couple of years & taken them up via shim removal. I only had to remove a .002″ shim to get them to correct clearance. I agree that everything depends on the EXPERTISE of the guy doing the re babbetting & I have had a number of failures on my other vintage cars (Lancia Lambda) when done in modern times. Here in Australia it is a regular discussion point at Club meetings.So what is the difference between the 1912 guys at Napier & what we get now? I realize that it is a multi faceted issue.
Ps. The Napier has a 4.55 rear end & around 30 mph in top per 1000 rpm.
After two engine rebuilds, John Ciselak installed insert bearings in my ’36. From the condition of the babbit bearing replacements in the first two attempts, I really don’t think one can be sure that the babbit being sold is a reliable product. When rod caps are removed, and the babbit is all checked and messed up, what other conclusion can one come to?
I agree with inserts for rods, the only downside is that a failure of an insert will likely damage a crank much more than the failure of a babbit bearing.
There are different qualities of babbit, just as there are different grades and qualities of any metal. Also, there’s both science and art to pouring and finishing babbit correctly, and like a lot of trades, we’re losing people who know how to do it correctly.