1963 Buick Riviera engine rpm

[robcroft6363]

Hi - Looking for anyone who has a original tach, or aftermarket, in their '63 Riv. I feel it revs quite high, but its hard to determine especially when the car is only used in the summer. I have owned for 16 years but never noticed the "high" rpm/mph until this year. (Am I too used to my modern car?)  I temporarily hooked up a tach I purchased, switched it to 8 cyl, ran the wires from under hood through side vent window to the dash. I got the foll. numbers:

40 mph- 1500rpm

50-          2150

60-          2600

70-          3000 

With Dynaflow trans its is impossible to know what "gear" youre in as it correctly does not "shift".  Would be great to hear from other owners with their RPM/MPH, so I can relax and enjoy the car. 

[TerryB]

Did you change tires recently?

[rocketraider]

Those numbers are on par with my 1964 Oldsmobile Starfires with 3.42 gearing, so I'll venture you've just gotten used to modern cars that loaf along at 1500 rpm at 70mph. And that are constantly shifting their multiple speed automatics trying to keep the engine in the EPA-approved rpm band for emissions.

 

Granted the Oldsmobiles have HydraMatics but in 3rd gear they're operating in 1:1 direct drive. Daresay the Dynaflow is still experiencing some slippage at that point.

 

Scroll down thru the Forums until you find the Buick Forums and the Riviera subforum. People there will have insight.

 

Here you go:

 

https://forums.aaca.org/forum/73-buick-riviera/

[robcroft6363]

Thanks Terry, good point but no they are standard 710x 15 bias ply!!

 

Rocketraider nice to know numbers are on par with your 64. I think the Riv has same gearing. I must be getting too used to my 6 speed Audi!!  Thank you

[joe_padavano]

4 hours ago, robcroft6363 said:

40 mph- 1500rpm

50-          2150

60-          2600

70-          3000 

 

Well, those 7.10x15 tires are nominally 28.88" in diameter. Assuming a 3.42 rear axle ratio and trans in high gear (1:1), the theoretical RPMs without allowing for slippage in the trans come pretty close to your observed numbers.

 

40 - 1592 RPM

50 - 1990 RPM

60 - 2388 RPM

70 - 2786 RPM

 

I'd say you're right where you're supposed to be.

[Frank DuVal]

Yep, people forgot how fast the engines in non-overdrive cars operated. A Corvair with 3.55 gear ratio runs 3500 RPM to do 70 MPH.   It sounds so fast compared to anything with an overdrive transmission.

[robcroft6363]

Thanks Terry, good point but no they are standard 710x 15 bias ply!!

 

Rocketraider nice to know numbers are on par with your 64. I think the Riv has same gearing. I must be getting too used to my 6 speed Audi!!  Thank you

[robcroft6363]

Thanks Joe/Frank. Good to know my numbers are close. Dynaflow must be OK!!

[Pfeil]

On 5/16/2023 at 2:10 PM, robcroft6363 said:

Hi - Looking for anyone who has a original tach, or aftermarket, in their '63 Riv. I feel it revs quite high, but its hard to determine especially when the car is only used in the summer. I have owned for 16 years but never noticed the "high" rpm/mph until this year. (Am I too used to my modern car?)  I temporarily hooked up a tach I purchased, switched it to 8 cyl, ran the wires from under hood through side vent window to the dash. I got the foll. numbers:

40 mph- 1500rpm

50-          2150

60-          2600

70-          3000 

With Dynaflow trans its is impossible to know what "gear" youre in as it correctly does not "shift".  Would be great to hear from other owners with their RPM/MPH, so I can relax and enjoy the car. 

With Dynaflow you are (unless you are manually using LOW) you are only in one gear, high gear Just like the original Chevy Power Glide until 1952. The torque converter is doing all the multiplication or reductions instead of gear changes. As said earlier your rpms in high range seem as it should be. Buick designed the transmission to utilize the best engine rpm for the application of load, road speed and throttle opening. 

Even though Hydra-Matic transmissions are in direct drive in the mechanical section of the transmission the output to the tail shaft isn't really direct because of the connection between the engine and the transmission has slippage from the torque converter. The only automatics that were designed to somewhat remedy the situation was 315 Controlled Coupling Hydramatic, 375 HydraMatic (Roto) and 1961-63 Tempest Torque transaxles. All three of these automatics have a feature called "split torque" where in high gear power is divided mechanically and through either the fluid coupling (315 and Roto) or torque converter (TempestTorque) For example when Roto HydraMatic is in high gear only 40% of the engine torque goes through the coupling and 60% it is in mechanical connection. In high gear these transmissions were more efficient than any other automatics until automatics started coming with lock up converters.

CVT, Constant variable transmission with converter lock up are very efficient. They put the engine rpm exactly where it's supposed to be depending on load, speed and throttle position. For example if I'm driving at 70MPH on level surface, with cruise control on my rpm is 2,100 and approach a slight hill approaches rpm gradually climbs to 2500 to meet the condition of the load. Throttle and the variable transmission ratio work together seamlessly. At that same speed I decide to pass a car, I floor it The ECM and the TCM work together to put the engines maximum HP and Torque and apply it to the transmission ratio. That means the engine goes right to the sweet spot and stays there and as road speed increases the trans variable ratio is going higher to maintain the engine in that sweet spot. With one of my cars that amounts to 6,200 RPM, that's where the highest hp and torque intersect. This very same idea is what Charlie Chayne was trying to do in the mid 40's with Dynaflow. His problem solved the gear change problem through the torque converters multiplication, but could not control the RPM sweet spot perfectly, nor eliminate the amount of slippage wasted. Todays cars solve the problem by using CVT or by using multiple speed automatics 5,6,7,8,9,+ speeds-they come close, but they can never stay in the sweet spot like a CVT, plus they are very expensive.

Edited May 20, 2023 by Pfeil (see edit history)

[Rusty_OToole]

In the early to mid seventies car makers went to unusually high (low numerical) rear axle gears in an attempt to get better mileage out of existing V8 engines. Cars went from around 3.5:1 to 2.9:1. This gave them better hiway mileage at the cost of acceleration. The trend continues to this day, although newer models compensate with 4, 5 or 6 gears in the transmission.

The up shot is older cars seem to be screaming at hiway speeds compared to the late models. But no need to worry, normal hiway speeds will not hurt them.

[Pfeil]

29 minutes ago, Rusty_OToole said:

In the early to mid seventies car makers went to unusually high (low numerical) rear axle gears in an attempt to get better mileage out of existing V8 engines. Cars went from around 3.5:1 to 2.9:1. This gave them better hiway mileage at the cost of acceleration. The trend continues to this day, although newer models compensate with 4, 5 or 6 gears in the transmission.

The up shot is older cars seem to be screaming at hiway speeds compared to the late models. But no need to worry, normal hiway speeds will not hurt them.

My 1962 and 1963 Pontiac Catalinas came stock with 2.69 rear axle ratios. This was the standard axel ratio for the standard 389 V-8 (267hp) with an automatic. StarChief on the other hand (389 V-8 & 283hp) being 7"longer and heavier had a 3.08 and Bonneville (389 V-8 and 303hp) had a 3.23, still the 62 Grand Prix had (389 V-8 and 303hp) a 3.42. BTW those Pontiacs could be ordered with a 2.56 all the way to a 5.10 rear axle ratio. When my dad special ordered our 59 Catalina out of the zone office it came with a 3.08 safety track (to run on the street) and a 3.90 and 4.10 safety tracks in the trunk for drag racing.

In 1968 I ordered a 1969 Pontiac LeMans with a 330hp 354" engine, M40 (T400) and a 2.56 safety track. I also have a 3.08 and 3.23 safety tracks for it. I still have that car and right now it has the 3.23. That car ran high 14's with the 2.56 gears and went through the traps in 2nd gear.

My 76 Olds Omega with a 250" chevy six, T350 automatic came stock with a 3.08 posi. I wanted to order a 2.56 but they wouldn't let me. I felt fortunate though because the let me get the THM350 instead of the THM 200 it was supposed to get. -The advantage of ordering out of the zone office!

[Frank DuVal]

OK, Pfeil, what is a safety track? I did Google, and nothing except hood safety catches came up.

 

Out here we call them rear axles, and third members.  Nothing safe about them.😁

[rocketraider]

It's Pontiac-speak for limited-slip rear. The same thing Chevrolet calls "Positraction".

[Pfeil]

On 5/20/2023 at 8:33 PM, rocketraider said:

It's Pontiac-speak for limited-slip rear. The same thing Chevrolet calls "Positraction".

Sorry Frank and Glenn, my fault I misspelled the name. Safe-T-Track. If Frank looked it up the way I just spelled it, he would have found it.