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Buick 1940 cruise speed high rpm


Robby120113

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Hi all. 
 

since im quite new to these car and always have driven army truck and jeep i was doing research about the buick before buying it. I have read here somewhere on the forum and interweb that cruising at 50mph should be easy. Yesterday i did a longer distance same as today but if i do 50mph i feel the engine still has alot of over power when i push the pedal but at 50mph it sounds the engine is overrevving, temp stays ar 180 and oild pres at 30. Is there something to be done to lower the rpm or was the info i have read wrong?

 

thanks

car is a buick 1940 model 41 with original engine

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33 minutes ago, Robby120113 said:

if i do 50mph i feel the engine still has alot of over power when i push the pedal

Not sure what you mean by this, "has a lot of over power" I have never heard that description before, not familiar with it.. Do you mean you think that it feels like it still has more power to go faster?

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50 MPH was fast in 1940 and many old cars were still equiped with lower differntial gearing.  I think you should be happy at 50 MPH with enough

power to pass slower cars when needed.  I once rode in a 40 Buick at 70 MPH with 5 other guys in the 405 Freeway in LA, no problem, but I have no

idea what the rearend gearing was.  The owner was from LA had just completed a 4000 mile Great American Race, Boston to LA in a 35 Buick and

I'm sure the 40 Buick was geared for LA Freeway driving.

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It is likely that your car has the 4.44 rear gear ratio. It's going to sound pretty busy at highway speeds, but 50-55 MPH should not hurt it. We have grown accustomed to overdrives and low gear ratios and lots of sound insulation in our modern cars. As a result, your 1940 Buick sounds like it is working very hard, but you are not hurting it. 60 MPH or more for extended periods of time will probably result in some wear eventually, but these are durable engines that people used as regular cars for decades. It sounds much worse than it is and it is unlikely that you are hurting any of the parts if everything is healthy and working within spec.

 

It's hard to re-train our ears to ignore what sounds like an engine in distress, but it probably is fine. It will tell you when it's working too hard, either with higher than normal temperatures or valve float. 50-55 MPH is well within the margin of safety and you are not hurting the engine. 

 

If you search this forum, you will find dozens of discussions from people who own small-series late-30s and '40s Buicks who want to change the gear ratio. It's possible and there are ways to do it, but it's a little complicated and involved due to the torque tube. Some gear sets are a direct swap and some need a lot of labor. There's no easy solution, unfortunately. And remember that installing a more highway-friendly gear ratio will make the car a little tougher to drive around town and it will be slower to accelerate. There's a balance somewhere, but sadly there's no easy solution for these cars beyond simply driving them within their limits and enjoying them for what they are and how they were when they were new. It was a different world then.

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Book says it should have 650-15 tires, so the cheapest/easiest way to make a RPM drop, is to use the tallest size that will fit, 

 

your speedometer will then be wrong, but there are small ratio changing units to install on the speedo cable to fix that.  They are called speedometer adapters, made by Dana or Spicer/etc.

 

If the tire diameter is a lot bigger, it will slow down that motor enough to notice a good difference.  I'm totally against running these prewars screaming,  and I don't believe for a moment that it won't hurt them.  It will wear the engine out much sooner for sure, and listening to that screaming really spoils the moment. Many first time owners sell the car for that reason. It sucks!

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@matt. Thank you for the reassuring words

@F&J i dont want to sell the car yet. Just love the look of it and how it brings me to the 1940 in my still original interior. But since i live in the Netherlands i dont have many parts available here and since shipping a whole axle will be out of thexquestion is there something available that will fit in a box to lower my gear ratio? Or is the only way to change the whole axle? I drive quite a bit so it would help to lower the rpm

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7 hours ago, F&J said:

Book says it should have 650-15 tires, so the cheapest/easiest way to make a RPM drop, is to use the tallest size that will fit, 

 

your speedometer will then be wrong, but there are small ratio changing units to install on the speedo cable to fix that.  They are called speedometer adapters, made by Dana or Spicer/etc.

 

If the tire diameter is a lot bigger, it will slow down that motor enough to notice a good difference.  I'm totally against running these prewars screaming,  and I don't believe for a moment that it won't hurt them.  It will wear the engine out much sooner for sure, and listening to that screaming really spoils the moment. Many first time owners sell the car for that reason. It sucks!

1939 series 40 have 16 inch wheels and series 60 have 15inch. Am sure 1940 is the same

 

11 hours ago, Robby120113 said:

Hi all. 
 

since im quite new to these car and always have driven army truck and jeep i was doing research about the buick before buying it. I have read here somewhere on the forum and interweb that cruising at 50mph should be easy. Yesterday i did a longer distance same as today but if i do 50mph i feel the engine still has alot of over power when i push the pedal but at 50mph it sounds the engine is overrevving, temp stays ar 180 and oild pres at 30. Is there something to be done to lower the rpm or was the info i have read wrong?

 

thanks

car is a buick 1940 model 41 with original engine

From 1940 to 1955 the diff centre/crown wheel & pinion will swap over. A 3.6 ratio compared to the standard 4.44 is popular, but hard to buy.  In 1939 & 1940 3.9 was an option, but hard to find. Disassembling the torque tube/drive shaft takes some work.  Most people prefer to swap the complete diff centre housing c/w gears (!pumpkin to some)and not just the gears into the original main housing/axles/brakes

 

https://forums.aaca.org/topic/257235-wtb-pinion-and-ring-gear-for-my-1940-56s/

https://forums.aaca.org/topic/113863-rear-axle-ratios-1948-1955/

 

 

Photo is a 1940

 

40buickaxle002s.jpg

 

 

Edit

People buy the centre housing assembled

https://forums.aaca.org/topic/220550-49-buick-super-4101-diff-and-axle-shafts/

 

Edited by 1939_Buick (see edit history)
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Cars were geared lower in those days and sound busy at hiway speeds compared to today. 50 MPH is well within the car's capabilities and will not hurt anything if the car is in good condition. Easiest and cheapest way to change the gearing is to install oversize or larger diameter tires. If you do this you can check your speedometer against the GPS in your phone  or by timing mile posts. Any inaccuracy can be corrected by changing the speedometer gear in the transmission, this can be done in a few minutes if you can get the appropriate gear.

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  • 1 month later...

3.90s! Great! It'll go 60 MPH without any harm. Ignore the sound, it's OK. I drive my Limited at 60-65 MPH for hours on end and it has 4.20s, although the larger tires put it at about a 3.8. You aren't hurting it. It may sound a little busier than a modern car, but that's OK. How are your valve adjustments? That can make a car sound louder than it is.

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Robby, 

It sounds to me that what you need is a little friendly mentoring from someone who is more familiar than you with these old cars. Find a local club chapter, and/or go to some local old car events. Soon you will find someone who is very familiar with driving cars like your 40 Buick, from a long history of doing so. Then ask them to ride with you or drive your car, and give you a frank opinion on whether your engine is straining, or whether you are simply not used to driving old iron at highway speeds. In no time at all you'll have your answer, and some peace of mind. Good luck! 

Edited by lump (see edit history)
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3;90 should be perfect. Let's say that if you swapped to a much lower number like 3;00, then the first and reverse gear will seem to be "geared up" way too much, meaning you'd have to ride the clutch to get it to move.   Any of these prewar cars had higher ratios on first and reverse to make the car feel normal when using a rear axle ratio in the mid to high 4;00s. 

 

  I agree that if your valve setting are too loose, it will sound like it's revving more than it really is.

 

The other thing is that many people that get their first car of that age, might be used to how quiet and also how overdriven the modern cars are.

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Buy some ear plugs. Your car will sound busier at hiway speeds than a new car but not much you can do about it. If engine is in top shape, your oil pressure is good, and you use good oil you won't have to worry. Keep in mind, the life of any 1940 engine is around 100,000 miles or less, with a couple of overhauls. If you drive the car every day, you will wear it out faster than a modern car. But, the engine can be rebuilt easier than a modern car.

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Hey guys. Thanks all for the nice words. I drove a 1942 willys jeep and a 1943 dodge weapon carrier before this. Also both can reach uo to 45 mph. So i thought this will be a bit more smooth. Its nice that i already have that rare rear diff. Car keeps suprising me. As for the noise from the engine. After the replacement of the valve pushrods (that i had to make shorter to fit) i set all the valves to 017 play. With a cold engine that is. I think i will redo it since i now drove a bit and will set them to 016. 
when done i will make a small video and place it here. You can also see a bit of the dutch country side. 

Edited by Robby120113 (see edit history)
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3 hours ago, Robby120113 said:

After the replacement of the valve pushrods (that i had to make shorter to fit) i set all the valves to 017 play. With a cold engine that is. I think i will redo it since i now drove a bit and will set them to 016. 

That could be part of your problem. They are supposed to be set .015 inches hot. That is, .381 MM. If the valve adjustment has been neglected the ends of the rocker arms and valves could be peened over and no longer capable of proper adjustment. Even so, proper adjustment will make them as quiet as they can be under the circumstances. If everything is in good shape you should not be able to hear the engine running with the hood closed. Other than a low hum.

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It is best to adjust them with the engine running. You need to get it up to full operating temperature (driving, not just running at idle) and then at a really low idle speed, you can pull the valve cover and adjust them with the engine running. It can be done with a screwdriver and a wrench but a dedicated valve adjusting tool is a bit easier. 

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So that should be 13x.9+15= 26.5" tire diameter/13.25 radius

 

Using rpm: 168 * gear ratio (3.9) * mph / tire radius this give 3 grand at 60 mph. Particularly since the stroke is over 4" that is A Lot.

 

Personally prefer 2k rpm @ 70 mph and have  for long interstate travel since the first fuel crisis. Though in the 70's with a 3.08 (economy) gear we ran 3k on the highway all of the time. I really like OD transmissions.

 

ps '41 Buick straigt 8 has 275 Ft-Lbs (373 NM) @ 2200 RPM (old style) which should be plenty for a 2k 70 mph cruise. All you need is the right gearset.

Edited by padgett (see edit history)
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4 hours ago, padgett said:

So that should be 13x.9+15= 26.5" tire diameter/13.25 radius

 

Using rpm: 168 * gear ratio (3.9) * mph / tire radius this give 3 grand at 60 mph. Particularly since the stroke is over 4" that is A Lot.

 

Personally prefer 2k rpm @ 70 mph and have  for long interstate travel since the first fuel crisis. Though in the 70's with a 3.08 (economy) gear we ran 3k on the highway all of the time. I really like OD transmissions.

 

ps '41 Buick straigt 8 has 275 Ft-Lbs (373 NM) @ 2200 RPM (old style) which should be plenty for a 2k 70 mph cruise. All you need is the right gearset.

 

A 1940 Buick Model 41 should have 650-16 inch tires. 650-16 tires typically would have a diameter of approximately 29.1 inches. I have no idea where you got 26.5 inches as the tire diameter. 

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" I have no idea where you got 26.5 inches as the tire diameter. " - 8th posting

Learned to use .90 profile for bias ply tires (Dunlop RS5) back in the '60s

Also the real value to use is the loaded wheel radius, not the unloaded.

 

For a 6.50x15 I get 26.7" less 1/4" for the load. Make more sense now. For a 6.50x16 I'd get 27.5" Now would someone with a tape measure please teach us all what the real diameter is please ? I don't have a tire that size so had to make a SWAG.

 

I stand by the 2k rpm at 70 mph as optimal for a gasabuggy on pump gas and with 275 lb-ft at 2200 rpm a '41 Buick should have no problem with that. 3.7 axle and a period correct B-W R-10 would do nicely.

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I never have been able to understand how the world's leader in automobile manufacturer took so long to discover overdrive. By 1940 virtually all American manufacturers had began using od, except GM. To my knowledge it would be 1955 before it was offered by Chevrolet.

 

There are people out there that have engineered and regularly repurpose od's from other manufacturers. The units are plentiful and rather inexpensive.

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1 hour ago, Buffalowed Bill said:

I never have been able to understand how the world's leader in automobile manufacturer took so long to discover overdrive. By 1940 virtually all American manufacturers had began using od, except GM. To my knowledge it would be 1955 before it was offered by Chevrolet.

 

There are people out there that have engineered and regularly repurpose od's from other manufacturers. The units are plentiful and rather inexpensive.

It is interesting to see what is available for my car. But i live in the netherlands and the parts and knowledge is different than in the states. Is there a overdrive option for my car?

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1 hour ago, Robby120113 said:

It is interesting to see what is available for my car. But i live in the netherlands and the parts and knowledge is different than in the states. Is there a overdrive option for my car?

 

The simple answer to your last question is  - no.

 

Perhaps you should invest in an electric tachometer to prove just what revs the engine is running at. A tachometer should not be too expensive - under $100 I think - and is easy to set up.

 

As others have noted all of these old cars sound like they are working hard compared with newer stuff with taller gearing, and more importantly, better sound insulation.

 

My 1929 Studebaker has 4.66:1 gears, although it is on 20" tyres. At 50 mph it is doing about 2,500 rpm but it does sound very busy, due to the lack of sound insulation. A future project is an overdrive transmission. Simple enough to do with an open drive shaft but, again, as others have noted, the Buick's torque tube makes it difficult.

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See here

Was an R-10 for sale here for a grand about a year ago..

"Manufactured by Borg-Warner Corporation, the overdrive option was offered on 22 different car models. Over two million overdrive options were sold by 1950 "

"Studebaker sold the most overdrive options by far, though a variety of other companies including Chevrolet, Ford, Frazier, Hudson, Kaiser, Lincoln, Mercury, Nash, Packard, and Willys-Overland also offered the overdrive as an option"

 

Suspect it would not be hard to adapt one to a Buick 3-speed, during the gas crisis there was a way to drill one hole and mount to a Saginaw four speed.

 

I thought about adding one to my Sunbird but the SCCA said it would put me in Modified. Would the AACA change your class if period-correct ? YWTK

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It is VERY hard to add an overdrive to a Buick with a torque tube. I installed one on my 1929 Cadillac with a torque tube and it was a pretty substantial undertaking. Another member added a Gear Vendors overdrive to his '41 Century, so it can certainly be done, but it isn't an easy installation by any means, and requires advanced machining, welding, and fabrication. I have a Gear Vendors unit on the shelf but I'm hesitant to install it in either of my remaining cars because of the magnitude of the job involving a torque tube, and I've already done it once.

 

Again, your car already has appropriate 3.90 gears in it. It may sound busy, but it is not hurting it to drive at reasonable speeds. Do the math as others have suggested to see actual RPM. Just punching it into a generic calculator with stock sized 650-16 tires that are roughly 29 inches tall, you will be at about 2500 RPM at 55 MPH and about 2700 at 60. That is not going to hurt the engine at all. You're safe, everything is OK, rely on the numbers not your gut or your ears.

 

https://www.crawlpedia.com/rpm_gear_calculator.htm

 

Drive it!

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Agree 6.50x16s are larger than 6.50x15 which I what I thought was specified in the 8th post. I bow to you Matt since have them on hand and can measure and agree shortening and fabbing a torque tube mount and shortening the driveshaft is not trivial. My Sunbird also had a bar from the back of the trans to the real axle.

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Thanks all. First i just did the valve adjustment with running easier. My first time and how cool was that. I dont have the tool so get the screwdriver on the jumping rocker is a fun challenge but the result is instant. I did it after driving from work to home. Engine sounds much better at idle. This weekend i will go for a drive again to see how much difference there is. I have the stock tyres indeed. Just curious, since i still have pretty much original car as for interior etc. All my windows are dated 40-1 so i would say January 1940 and two or so are 39-12. Is this rare that i still have all original glass or are replacements also dated?

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2 hours ago, Robby120113 said:

Thanks all. First i just did the valve adjustment with running easier. My first time and how cool was that. I dont have the tool so get the screwdriver on the jumping rocker is a fun challenge but the result is instant. I did it after driving from work to home. Engine sounds much better at idle. This weekend i will go for a drive again to see how much difference there is. I have the stock tyres indeed. Just curious, since i still have pretty much original car as for interior etc. All my windows are dated 40-1 so i would say January 1940 and two or so are 39-12. Is this rare that i still have all original glass or are replacements also dated?

 

While it is possible to get replacement glass with the date codes reproduced, it is much more likely that the glass is original, especially since they are not all exactly the same on your car. Most of the glass in my 1937 Model 61 has the original glass with the original date codes.  

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  • 3 months later...

Well,  I have to disagree.   Installing over drive is fairly easy.  I installed my first back in 2015.    It is in my 1938 coupe.   With the standard 4.44 rear,  I cruise 2350 at 65 mph.    My longest trip was a 1800+ round trip and it was an easy ride.   The fellow in Circleville Ohio did the mod's for Lloyd Young for many years.   Lloyd passed but the machinist still does the mod's.    I'm putting one in my 35-58 now and expect to have it on the road by Mar.  or Apr.   He is 'Glen'  at 1-614-571-4908.     Details,  I'm in Florida at   Oldbuickjim@gmail.com    .

050C7D58-3C77-4264-BE59-FDE4AA8CAA84.jpeg

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  • 1 year later...

For those who in Europe  who want to go a bit faster to keep from becoming a speed bump,  here is a option.   Buy a rear end from a car,  here in the states with the same year.   Remove only the torque tube from the transmission flange all the way back including the third member.    Then send it to Glen and have him modify the rear to insert  the Over Drive in the torque tube.   Now you have a over drive in three pieces.   Front torque tube,  then the drive shaft , and finally,  the over drive with attached third member.    The modified  front torque tube and drive shaft will be no longer than 3'.   The O.D. assembly with the modified third member  would be about the same.   So the shipping  box would be around the size of a normal skid.     This way you have a one way  shipping trip to get an over drive in your car..    If that sounds OK,   I  would highly recommend   rebuild the ring and pinion area with new bearings.   The rear pinion bearing is a 'roller' style bearing and the front bearing is a "double row ball bearing".       Then at a minimum,  on your original rear end,   after you are ready to assemble it,  REPLACE  the outboard roller bearings that are located just before the brake backing plates.   I can just about guarantee that those bearings have not been greased since it was new.   That bearing has two seals that create a cavity thar you put new grease in (about half full) and you will never, in your life time , need to re-grease the roller bearings.  I have found some that were OK   but several that were about trash.    Please read your service manual on setting the two semi-roller bearings that support the axels into the ring gear .   A rear end guy will adjust them. You will already have the 'lash' set when Glen replaces the new  pinion gears.    Remember,  you are ending up with a rebuilt rear that will be quiet  and last for another 75 + years.   I'm prejudice,  the over drive gives me the great highway speeds and regular gearing like it was designed for in slower modes for city driving.    

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