Burtz Block

[Hipopinto]

Hey all

As you well know I’m new to this group

I have been researching options for engine rebuilding and stumbled across Burtz Blocks

This seems like a FANTASTIC solution to a dwindling supply of rebuildable cores.

Finding a machine shop that can actually pour Babbitt is few and far between

With a counterbalanced crankshaft 5 main bearings and strong rods this should be a bullet proof combination.

I have always read that compression ratios above 5.5 tend to “flatten” bearings with a “modern” crank and bearings could the compression be bumped up? Maybe to 8.5?

The end result would be much cooler running engines and more usable power

My car as it is runs very well but I’m thinking about my cousins car. He has a 31 roadster that my late uncle was dissembling but he passed suddenly leaving an unfinished project.

His core is in need of a full rebuild and I’m only thinking

Thank you all for listening and I look forward to your replies

Dave

[shew01]

My (rebuilt) engine runs fine, but when it comes time to rebuild it, I plan to consider a Burtz block. It’s not that much more expensive than a quality rebuild, and you get a new engine out of the mix.

Search for Burtz block on this forum. You’ll find a treasure trove of facts and opinion.


Sent from my iPhone using Tapatalk

[jack backer]

Compression has no effect on babbit. Babbit was used effectively on diesel engines at 19 to 1 compression ratio. Improperly maintained/adjusted rod and main bearings cause babbit failure.

[BRENT in 10-uh-C]

Originally Posted by Hipopinto

Hey all

As you well know I’m new to this group

I have been researching options for engine rebuilding and stumbled across Burtz Blocks

This seems like a FANTASTIC solution to a dwindling supply of rebuildable cores.

Finding a machine shop that can actually pour Babbitt is few and far between

With a counterbalanced crankshaft 5 main bearings and strong rods this should be a bullet proof combination.

I have always read that compression ratios above 5.5 tend to “flatten” bearings with a “modern” crank and bearings could the compression be bumped up? Maybe to 8.5?

The end result would be much cooler running engines and more usable power

My car as it is runs very well but I’m thinking about my cousins car. He has a 31 roadster that my late uncle was dissembling but he passed suddenly leaving an unfinished project.

His core is in need of a full rebuild and I’m only thinking

Thank you all for listening and I look forward to your replies

Dave

Dave, I have been around this hobby for over 60 years, ...and professionally since 1997. A couple of things I have noticed during the last decade or so, is the amount of false, -or misleading information that today's hobbyists tend to pass around about Model-As. (Likely happens in other hobbies too with more prevalence since social media has become popular but I see it very prevalent in this hobby.)

I will address two of your opinions stated above. First, while I do not know yours or your cousin's age, I can say with certainty that there are more qualified craftsmen casting good quality bearings in Model-A engines than what was available to the hobbyist some 30 years ago. The quality (-and availability) of good materials used to cast bearings has never been better now than what we had available in the past 50 years. The quality of tooling necessary to do this craft that is found in these shops today is also better overall than it has been in decades. I don't know your cousin's location, but I feel comfortable that he likely has a shop nearby that can more than capably rebuild his engine.

Your second comment about cast (-babbitt) bearings being flattened in engines using over 5½:1 compression falls into the category of 'People will only believe what seems believable to them!' and I am unsure where your myth came from. For many years prior to insert bearing shell conversions being done on Model-A engine blocks, Larry Brumfield manufactured a cylinder head that had a 5.9 compression ratio factored at standard bore. He also manufactured a Super Brumfield with ratios exceeding 7:1. Many other head manufacturers during the 1940s - 1970s manufactured heads for bangers that often exceeded 8:1 that made great power and the cast bearings lived with those ratios. Heck, many early trucks and marine diesel engines used babbitt bearings and had compression ratios well past 15:1 compression (-nearly 3X your 5.5 number) and these engines provided many, many hours of reliable service. Therefore, it is my opinion that your myth has no merit and was likely started by someone who was stretching the truth to promote insert bearing conversions.


Now with this said, Terry Burtz's engine is a nice piece that does have a place in today's market. I would agree that his combination should be very bulletproof with the internal components that he offers in his package, however with that said, the same can likely be said with using an original engine block as the foundation and choosing a counterweighted (i.e.: SCAT) crankshaft and a few other aftermarket components too. My point is since you are 'new', please keep an open mind as you do your research to understand we live in a society today where people often place inaccurate or misleading information onto the web for unknowing people to read and thus assume it must be accurate simply because they read it on their computer.

[Hipopinto]

Got it!

How do I find a machine shop in the Cleveland Ohio area that can handle this?

I have built several performance engines and the shops I use for that work really don’t know where to send me?

I never considered “other” engines and Babbitt bearings as a comparison! That makes perfect sense!

I do realize what you are saying with the internet as well. So many are naysayers and regurgitate disinformation that people like myself start to “believe” it!

Thank you for everything!

Dave

[MrBruce]

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Dave, Brent is correct there are a lot of opinions even on the FB. You have a rebuilder that's been around for many years in Shandon, OH about three hours from you? Ron's and their number is 513-738-7353. Babbitt has been around for many years and my Model A engine was built over 40 years ago (it is tired and ready for a rebuild) but it has been driven hard and never had any issues with it. The Burtz engine is a nice unit (I had one but just didn't have the shop to do what was needed) There are plenty of blocks and parts out there and still many who will still babbitt although my 26 years with Clevite I tend to push inserts and was selling bearings to people for inserting Model A blocks for years.

[Terry Burtz, Calif]

Originally Posted by Hipopinto

Got it!

How do I find a machine shop in the Cleveland Ohio area that can handle this?

I have built several performance engines and the shops I use for that work really don’t know where to send me?

I never considered “other” engines and Babbitt bearings as a comparison! That makes perfect sense!

I do realize what you are saying with the internet as well. So many are naysayers and regurgitate disinformation that people like myself start to “believe” it!

Thank you for everything!

Dave

Dave,

The weak link in a Model A engine is not the Babbitt. In-line diesel engines using Babbitt have very stiff crankshafts and main bearings between every cylinder.

The weak link in a Model A engine is the flexible crankshaft with 3, 1.625-inch diameter main bearings and 4, 1.500-inch diameter connecting rod bearings.

Crankshaft flexing wallows out the soft Babbitt and the flexing becomes more severe with higher compression and RPM. Inserts help to limit the amount of wallowing because the soft Babbitt layer is much thinner than a poured bearing.

A SCAT crankshaft with the same number of small journals is just as flexible as a stock Model A crankshaft and will not fix the inherent design problems.

Ford recognized the inherent design problems in the Model A engine and the Model B engine had larger crankshaft bearing journals.

There is a builder in CA that is hoping to get 400 HP out of the new engine with a turbocharger, electronic fuel injection, and electronic ignition.

[Terry Burtz, Calif]

Originally Posted by MrBruce

Dave, Brent is correct there are a lot of opinions even on the FB. You have a rebuilder that's been around for many years in Shandon, OH about three hours from you? Ron's and their number is 513-738-7353. Babbitt has been around for many years and my Model A engine was built over 40 years ago (it is tired and ready for a rebuild) but it has been driven hard and never had any issues with it. The Burtz engine is a nice unit (I had one but just didn't have the shop to do what was needed) There are plenty of blocks and parts out there and still many who will still babbitt although my 26 years with Clevite I tend to push inserts and was selling bearings to people for inserting Model A blocks for years.

MrBruce,

"(I had one but just didn't have the shop to do what was needed)".

Please tell us more about "what was needed".

The "new engine" parts are ready to assemble after deburring and cleaning and no machine work is needed.

[Synchro909]

Before the Burtz engine was available, I used a rebuilt engine to tow a heavy camper many tens of thousands of miles but after the most recent trip, it was showing "tired" signs. To me, one of the new engines was a no brainer with its stiffer crank shaft, more main bearings, full pressure lubrication and new metal - just as I would have written on my wish list.
The rebuilt engine has a Burlington crank shaft and new rods. All run on inserts. The middle main bearing is pressure fed at 25psi. It has a modified cam - no more lift than the original but more duration and began life with a 5.5:1 head and downdraught carburettor. The compression now is 105-110 psi which is near enough, 7:1 after the head has been "flattened" a few times. As good as that engine has been, I'm expecting the new one to be a lot better.
I realise probably none of you guys will put your engine through such torture but IMO, the way mine has preformed, an engine rebuilt like it would last a long time in a solo car.
BTW, we cruise at 50 mph for many hours at a time day in, day out for weeks with the camper behind. It weighs about 900 kg (2,000 lb) An average trip is about 8,000 miles.
I wouldn't hesitate (subject to the approval of the banker) to buy another Burtz unit. Mine was one of the first and no "extras" other than a flywheel were available with it then. (Engine number 15)

[Hipopinto]

Synchro

What kind of “power” do you anticipate?

I’m curious more than anything

The more I look at this the more I like it!

Thank you for sharing

Dave

[BRENT in 10-uh-C]

Originally Posted by Synchro909

Before the Burtz engine was available, I used a rebuilt engine to tow a heavy camper many tens of thousands of miles but after the most recent trip, it was showing "tired" signs. To me, one of the new engines was a no brainer with its stiffer crank shaft, more main bearings, full pressure lubrication and new metal - just as I would have written on my wish list.
The rebuilt engine has a Burlington crank shaft and new rods. All run on inserts. The middle main bearing is pressure fed at 25psi. It has a modified cam - no more lift than the original but more duration and began life with a 5.5:1 head and downdraught carburettor. The compression now is 105-110 psi which is near enough, 7:1 after the head has been "flattened" a few times. As good as that engine has been, I'm expecting the new one to be a lot better.
I realise probably none of you guys will put your engine through such torture but IMO, the way mine has preformed, an engine rebuilt like it would last a long time in a solo car.
BTW, we cruise at 50 mph for many hours at a time day in, day out for weeks with the camper behind. It weighs about 900 kg (2,000 lb) An average trip is about 8,000 miles.
I wouldn't hesitate (subject to the approval of the banker) to buy another Burtz unit. Mine was one of the first and no "extras" other than a flywheel were available with it then. (Engine number 15)

Wow, how did you determine you had removed enough volume from the chamber to increase the compression ratio all the way to 7:1??

[nkaminar]

The Burtz engine is basally and assembly project. You have to clean up the engine and do some deburring, but the rest is just assembling the parts. If you have any experience in engine rebuilding it is actually easy. You have to keep your shop and the parts clean, like any engine rebuilding. It can actually save you tons of money and the engine will perform well for many miles, well beyond your lifetime. Plus you can hop it up as needed for your driving requirements. Terry posts very good assembly instructions on his site.

[Synchro909]

Originally Posted by BRENT in 10-uh-C

Wow, how did you determine you had removed enough volume from the chamber to increase the compression ratio all the way to 7:1??

7:1 was a guess. It was a gradual increase. A little was gained each time I had the head off. A compression of 110psi divided by one atmosphere (14.5) is 7.6. It sounds a lot and it is - quite fussy about ignition timing.
I estimate I'm getting about 70 hp out of that 3 main bearing engine and considering what I have done with it, I can't complain.

[Synchro909]

Originally Posted by Hipopinto

Synchro

What kind of “power” do you anticipate?

I’m curious more than anything

The more I look at this the more I like it!

Thank you for sharing

Dave

The Burtz engine has a 6:1 head on it, Webber carburettor and a "modified B cam. (.308 lift but more duration than the original - not wild but I don't want wild. I want drivable) Timing with an unmodified A distributor limited to 22°. Oil supply is by a modified V8 pump with a relief valve set at 32 psi. At 10psi per 1,000 revs, that is plenty for what I do. Best guess on power is about 70-75 ish and it is a pleasure to drive.
Once I reach about 55 mph, things are coming together pretty well. Economy is excellent and still plenty of "let's get going" from the engine.

[BRENT in 10-uh-C]

Originally Posted by Synchro909

7:1 was a guess. It was a gradual increase. A little was gained each time I had the head off. A compression of 110psi divided by one atmosphere (14.5) is 7.6. It sounds a lot and it is - quite fussy about ignition timing.
I estimate I'm getting about 70 hp out of that 3 main bearing engine and considering what I have done with it, I can't complain.

Ok. Maybe others will chime in, but all of the 7:1 heads I have messed with have a lowered roof in the combustion chamber simply because you cannot take enough off of a 5.5 head without getting piston interference. If the 'squish' area over the piston is minimal, it is my experience this will cause detonation issues where setting for optimum timing is a struggle as you have suggested.

As I'm sure you, and most others will agree, using a compression gauge to determine the ratio is rarely accurate. To confirm this, think about when you are taking the reading. Most will crank the engine over a minimum of 4-5 times while obtaining the reading, and each time the piston makes a cycle, the gauge reading gets higher and higher. The first time the piston comes up is more likely the closest correct reading on the gauge. The only accurate way for most people to determine a C/R is to CC the chamber and calculate gasket areas, etc.

[nkaminar]

I want to make one comment about Babbett bearings. The insert bearings consist of a steel shell with some copper and then Babbett metal added. The Babbett metal is what is actually against the journal (the oil film is actually between the Babbett and the journal).

[BRENT in 10-uh-C]

Originally Posted by nkaminar

I want to make one comment about Babbett bearings. The insert bearings consist of a steel shell with some copper and then Babbett metal added. The Babbett metal is what is actually against the journal (the oil film is actually between the Babbett and the journal).

So allow me ask a question regarding thicknesses, ....would you rather buy a new set of tires that has 10/32" of tread depth, -or tires with 3/32" of tread depth?? It seems like someone would get 3X more mileage when they start with the 10/32" depth tires.

So if the same thought was applied to Model-A engine bearings, wouldn't someone get 3X more longevity out of a babbitted engine over a inserted engine if the same quality of bearing materials was used, and all mechanical parts were of equal specification and condition??

[hazelhoff]

Why would you own an A, drive it, fake the engine ?

[jack backer]

Provided the babbit bearing is properly maintained the extra thickness is beneficial

Another observation about babbit vs insert bearings..

When a babbit bearing fails it rarely destroys the crankshaft journal it bore.

When an insert bearing fails it invariably destroys the borne journal.

[bbrocksr]

Originally Posted by BRENT in 10-uh-C

So allow me ask a question regarding thicknesses, ....would you rather buy a new set of tires that has 10/32" of tread depth, -or tires with 3/32" of tread depth?? It seems like someone would get 3X more mileage when they start with the 10/32" depth tires.

So if the same thought was applied to Model-A engine bearings, wouldn't someone get 3X more longevity out of a babbitted engine over a inserted engine if the same quality of bearing materials was used, and all mechanical parts were of equal specification and condition??

No. The thicker the Babbitt the more compressable it is, the more it compresses the more it fatigues and starts cracking and falling out.
That is why High performance and race engines use Tri-metal bearings.
Tri-metal bearings have a steel back , copper underlay to support the thin layer of Tin/Babbitt. The copper underlay is not nearly as compressable as Babbitt and as a result less fatigue and longer bearing life.
Bill

PS Read up on Clevite 77 bearings.

[Terry Burtz, Calif]

Quote:
Originally Posted by BRENT in 10-uh-C View Post
So allow me ask a question regarding thicknesses, ....would you rather buy a new set of tires that has 10/32" of tread depth, -or tires with 3/32" of tread depth?? It seems like someone would get 3X more mileage when they start with the 10/32" depth tires.

So if the same thought was applied to Model-A engine bearings, wouldn't someone get 3X more longevity out of a babbitted engine over a inserted engine if the same quality of bearing materials was used, and all mechanical parts were of equal specification and condition??




No. The thicker the Babbitt the more compressable it is, the more it compresses the more it fatigues and starts cracking and falling out.
That is why High performance and race engines use Tri-metal bearings.
Tri-metal bearings have a steel back , copper underlay to support the thin layer of Tin/Babbitt. The copper underlay is not nearly as compressable as Babbitt and as a result less fatigue and longer bearing life.
Bill

PS Read up on Clevite 77 bearings.




Bill,

Your answer to Brent's question is correct. Thank you.

The new engine uses 12 pairs of Clevite CB-745P standard size tri-metal bearings.

For those that want to learn about modern bearings, please see: Clevite “Light Vehicle Engine Bearings” catalog EB-20-18 (https://www.mahle-aftermarket.com/me...s/eb-20-18.pdf)

[BRENT in 10-uh-C]

Originally Posted by Terry Burtz, Calif

No. The thicker the Babbitt the more compressable it is, the more it compresses the more it fatigues and starts cracking and falling out.
That is why High performance and race engines use Tri-metal bearings.
Tri-metal bearings have a steel back , copper underlay to support the thin layer of Tin/Babbitt. The copper underlay is not nearly as compressable as Babbitt and as a result less fatigue and longer bearing life.

Terry, to an extent what you are saying is correct, ...and generally this issue as you are describing is found when improper methods are performed in the casting & machining process by rebuilders.

Most rebuilders today use WAY more shims (-i.e.: thickness) than what Ford used originally, and many rebuilders fail to peen the freshly cast metal for the purpose of compacting it simply because they don't know to do that, -or it is an effort to save time. Burnishing also falls into this category. As you correctly stated, this often causes fatigue & cracks in the bearing. When the proper composition of babbitt is used, and when process is done correctly, the additional compaction, fatigue, and cracking is not seen. As we have discussed above, engines with nearly triple the compression ratios have utilized poured and cast bearings with many years of great service to their credit. In the scenario of using an insert bearing that has the same compaction as the cast bearing, the wear should be the same with little to no difference between the two types of bearings, HOWEVER when the babbitt on the insert shell has worn 0.002", that bearing is reached the end of its' life cycle whereas the cast bearing has the ability to remove one or both shims and continue many more miles.

[bbrocksr]

Originally Posted by BRENT in 10-uh-C

Terry, to an extent what you are saying is correct, ...and generally this issue as you are describing is found when improper methods are performed in the casting & machining process by rebuilders.

Most rebuilders today use WAY more shims (-i.e.: thickness) than what Ford used originally, and many rebuilders fail to peen the freshly cast metal for the purpose of compacting it simply because they don't know to do that, -or it is an effort to save time. Burnishing also falls into this category. As you correctly stated, this often causes fatigue & cracks in the bearing. When the proper composition of babbitt is used, and when process is done correctly, the additional compaction, fatigue, and cracking is not seen. As we have discussed above, engines with nearly triple the compression ratios have utilized poured and cast bearings with many years of great service to their credit. In the scenario of using an insert bearing that has the same compaction as the cast bearing, the wear should be the same with little to no difference between the two types of bearings, HOWEVER when the babbitt on the insert shell has worn 0.002", that bearing is reached the end of its' life cycle whereas the cast bearing has the ability to remove one or both shims and continue many more miles.

Hey Brent, Terry didn't say that , I did and Terry agreed.
Bill

[nkaminar]

From the reference listed by Terry above, Bearing life versus Babbett thickness. Even though the bearing life is maximum at minimum thickness, some thickness is needed for various reasons.

What the graph shows is that an insert bearing will last 10 times as long as poured bearings (250 vs. 25). (Depending on how you read the graph it could be 8 times as long, but still longer.) Also, based on my experience on various engines, when the insert bearings need replacing, the journal is normally still good and new insert bearings can just be installed.

What the reference also says, in so many words, is that an oil filter is important to have. And that proper assembly is very important.

[Terry Burtz, Calif]

Originally Posted by BRENT in 10-uh-C

Terry, to an extent what you are saying is correct, ...and generally this issue as you are describing is found when improper methods are performed in the casting & machining process by rebuilders.

Most rebuilders today use WAY more shims (-i.e.: thickness) than what Ford used originally, and many rebuilders fail to peen the freshly cast metal for the purpose of compacting it simply because they don't know to do that, -or it is an effort to save time. Burnishing also falls into this category. As you correctly stated, this often causes fatigue & cracks in the bearing. When the proper composition of babbitt is used, and when process is done correctly, the additional compaction, fatigue, and cracking is not seen. As we have discussed above, engines with nearly triple the compression ratios have utilized poured and cast bearings with many years of great service to their credit. In the scenario of using an insert bearing that has the same compaction as the cast bearing, the wear should be the same with little to no difference between the two types of bearings, HOWEVER when the babbitt on the insert shell has worn 0.002", that bearing is reached the end of its' life cycle whereas the cast bearing has the ability to remove one or both shims and continue many more miles.

Brent,

I agree with some of what you say, but believe that your reply is directed to the comments made by Bill, not me.

Please keep in mind that the inherent design problem in a Model A engine is the flexible and under-supported crankshaft.

Insert bearings are not new. The Dodge "Fast 4" engine built in 1927 and 1928 was a 4 cylinder, 5 main bearing design that used Federal-Mogul insert 6345B for the connecting rods and Federal-Mogul main bearing set 277M.

Terry Burtz

[Terry Burtz, Calif]

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Originally Posted by nkaminar

From the reference listed by Terry above, Bearing life versus Babbett thickness. Even though the bearing life is maximum at minimum thickness, some thickness is needed for various reasons.

What the graph shows is that an insert bearing will last 10 times as long as poured bearings (250 vs. 25). (Depending on how you read the graph it could be 8 times as long, but still longer.) Also, based on my experience on various engines, when the insert bearings need replacing, the journal is normally still good and new insert bearings can just be installed.

What the reference also says, in so many words, is that an oil filter is important to have. And that proper assembly is very important.

Neil,

Thanks for looking at the Clevite catalog and displaying the graph.

Sometimes thicker is not better and results in a shorter life.

[Synchro909]

Originally Posted by BRENT in 10-uh-C

Ok. Maybe others will chime in, but all of the 7:1 heads I have messed with have a lowered roof in the combustion chamber simply because you cannot take enough off of a 5.5 head without getting piston interference. If the 'squish' area over the piston is minimal, it is my experience this will cause detonation issues where setting for optimum timing is a struggle as you have suggested.

As I'm sure you, and most others will agree, using a compression gauge to determine the ratio is rarely accurate. To confirm this, think about when you are taking the reading. Most will crank the engine over a minimum of 4-5 times while obtaining the reading, and each time the piston makes a cycle, the gauge reading gets higher and higher. The first time the piston comes up is more likely the closest correct reading on the gauge. The only accurate way for most people to determine a C/R is to CC the chamber and calculate gasket areas, etc.

I get no piston interference - yet but I don't know how many times I can flatten the head. I'm sure a lot of the increased CR is due to the over sized bores. (0.060" over)
Agreed on your comments re compression readings. The figure I quoted was after your 4 or so cycles so maybe the true number is not so high.

On another matter, have you had experience with the rear (inserted) main bearing starving for oil? I have seen a couple of examples of the insert being pretty chewed up. Fortunately, the journal was OK and a new insert was all it took. Before fitting them, I cut a spiral groove in he top insert to get oil towards the back of the bearing. I stopped the groove about 10mm (3/8") from the edge of it. I run 20w50 grade oil and I'm thinking that something like 15w40 might be better. Watchya reckon?

[Hipopinto]

Guys this is giving me tons of info I really appreciate all of this

Thanks again
Dave

[jack backer]

Terry is your engine fully pressurized?

[Terry Burtz, Calif]

Originally Posted by jack backer

Terry is your engine fully pressurized?

Jack,

Yes, the "New Engine" has 17 pressure-fed bearings and all oil passages are drilled in cast iron bosses. There are no fittings or loose oil tubes.

The 17 pressurized bearings include 5 main bearings, 5 camshaft bearings, the rear main thrust bearing, 4 connecting rod bearings, the camshaft thrust bearing at the front of the cylinder block, and the camshaft plunger thrust surface.

More details can be found at www.modelaengine.com, www.burtzblock.com, and https://www.facebook.com/groups/1123377268114692

This thread has opened a can of worms with those that believe in the original thick-poured Babbitt bearing design with a flexible crankshaft and those that understand modern engine design.

[HotRodHell]

Originally Posted by Terry Burtz, Calif

Jack,

Yes, the "New Engine" has 17 pressure-fed bearings and all oil passages are drilled in cast iron bosses. There are no fittings or loose oil tubes.

The 17 pressurized bearings include 5 main bearings, 5 camshaft bearings, the rear main thrust bearing, 4 connecting rod bearings, the camshaft thrust bearing at the front of the cylinder block, and the camshaft plunger thrust surface.

More details can be found at www.modelaengine.com, www.burtzblock.com, and https://www.facebook.com/groups/1123377268114692

This thread has opened a can of worms with those that believe in the original thick-poured Babbitt bearing design with a flexible crankshaft and those that understand modern engine design.

I sold my last model A about 8 years ago and recently became interested in having a Model A again. Doing a little research i came across your improved engine. I then became real serious about an A or B car. I even put a 600hp car on the market.
I believe in the superiority of your block and internal improvements.

[4bangerbob]

Originally Posted by Synchro909

I get no piston interference - yet but I don't know how many times I can flatten the head. I'm sure a lot of the increased CR is due to the over sized bores. (0.060" over)
Agreed on your comments re compression readings. The figure I quoted was after your 4 or so cycles so maybe the true number is not so high.

On another matter, have you had experience with the rear (inserted) main bearing starving for oil? I have seen a couple of examples of the insert being pretty chewed up. Fortunately, the journal was OK and a new insert was all it took. Before fitting them, I cut a spiral groove in he top insert to get oil towards the back of the bearing. I stopped the groove about 10mm (3/8") from the edge of it. I run 20w50 grade oil and I'm thinking that something like 15w40 might be better. Watchya reckon?

Increasing the Bore size increases the compression ratio, A standard bore engine verses a bored cylinder bore has a smaller volume then oversized bores and will result in a lower compression ratio. A standard bore model A engine with a 6 to 1 cylinder head will produce a compression ration of approximately 6.38 on an engine bore .125" oversize.

[Dodge]

I don't know how many babbitt motors have gone 400,000 miles but I know of several
insert bearing motors that have....

[Synchro909]

Originally Posted by Dodge

I don't know how many babbitt motors have gone 400,000 miles but I know of several
insert bearing motors that have....

400,000 miles would be a modern motor with hardened bores, thin rings and al the other things engineers have done to extend their life. I bet NO model A engines, inserts or no will have gone close.
That said, 400,000 miles is chicken feed for a decent truck engine many of which have (as has been said) Babbit bearings.

[jack backer]

Full pressurization is the key for insert bearings, it keeps them clean and cool.My observations about insert and babbit bearings was predicated on the stock A splash and gravity method of lubricating rod and main bearings.

[nkaminar]

Synchro, Just curious. What modern truck engines have poured bearings? I assume you meant poured bearings. Or do you mean antique truck engines? I know modern Diesel engines can go a million miles or more and I assume they are all insert bearings. Please contribute to my education.

By the way, there were some photos of cars in the 60's in Australia Surfer's Paradise recently in The Old Motor. https://theoldmotor.com/?p=191760