Hagerty Review

[NTX5467]

I never did see any specs on stall speeds from GM, back then.  I do know that the 1977+ Z/28s would all spin their rear wheels against the foot brake at 1800rpm when new.  They came with a V-6 torque converter from the factory.  On my then-new '77 LT 305 2bbl, it would go to about 1600rpm with no wheel spin against the brake.  The V-6 converter was also used behind the L82 Corvettes, which had THM350s behind them.

 

Only things I did see had to do with using 4cyl, 9" or 10" converters for V-8 drag cars, with the highest stall being the 8" Opel torque converter.

 

NTX5467

[RivNut]

Using the variable pitch converter from an ST300 in aST400 will give you the same effect.  It’s a bolt in. Same splines and the flex plates are drilled for both converters.  

[Frank DuVal]

On 10/16/2023 at 12:43 AM, RivNut said:

I experienced the woefully underpowered 307 in my 85 coupe on the way back home from the ROA meet in Harrisburg (Hershey) in 2010. Rather than return via Indianapolis and the route we took to Harrisburg, we opted to go to Gettysburg then take the scenic Blue Ridge Parkway home through West Virginia.  I was slowing 18 wheelers down when they got behind me when going uphill.  

Um, You mean the Blue Ridge Parkway run by the National Park Service?❓

1. The Blue Ridge Parkway does not go into West Virginia

2. Tractor Trailers are prohibited on the Blue Ridge Parkway.

 

But, maybe you came down to Front Royal Virginia on US15 then US 340, past White Post Restorations, then US 522, slowing those tractor trailers while going uphill,  and got on the Skyline Drive and continued to Afton, VA where the Blue Ridge Parkway starts (northern end) and continued down to where I-64 takes off west to West Virginia, I-77, etc. to go further west. Or  continue even further south and take I-77 west. That's a long drive at 35 MPH! ❗

 

Yes, I'm being picky, but I live near there now and used to travel the Blue Ridge Parkway in the winter in my worn out '50 Studebaker Champion when I was in college in Charlottesville. That was an experience, when I could figure how to get on the closed Parkway (due to weather) and motor on white knuckle..... 😱  Ahh, youth and college days! ❗

 

😃😃😅😅😄😄

Edited October 19, 2023 by Frank DuVal (see edit history)

[RivNut]

We did not drive the length of the Parkway. I don’t know where we left it but I do know we got onto some mountainous 

roads somewhere on our way home. That is a trip I’d just as soon forget.

[XframeFX]

12 hours ago, RivNut said:

Using the variable pitch converter from an ST300 in aST400 will give you the same effect.

Interesting to hear from those that did swap from the 13" variable Pitch to the smaller A-Body 12"variable pitch torque converter.

One member on this forum did PM myself saying he found the torque converter from a ST300 too loose in his G1 Riviera. I would've thought this Unit would be a better match since the Riviera is 400 lbs lighter than a full size Buick.

 

[Seafoam65]

The Olds 403 is a great engine........My bone stock 403 powered 79 Trans Am runs the quarter mile

in 15.4 with a 2:73 rear axle ratio. These engines have tremendous torque and are way underated by GM at 180 horsepower.

[NTX5467]

Not having researched things, BUT were all ST300s ONLY behind 2bbl V-8s with the 4bbl V-8s needing something a bit looser?

 

Key point would be to determine why that ST300 converter was "too loose" behind the bigger engine.  Did fuel economy go down?  Did the driver always change throttle positions as he drove down the road?  Several factors involved.

 

As to the Firebird w/Olds 403 . . . I owned one of those cars for approximately 24 hours, once.  I was getting a bit unpleased with some things on repair on my '77 Camaro Type LT 305, so I noticed a '79 TA, Red with t-tops, on our used car lot.  I went up to investigate it, with the intent of trading my Camaro for it.  The speedo and tach being swapped in location from the Camaro's locations could take some getting used to, but otherwise the car was pretty much what I would have ordered back then (other than the color).  I did notice that the factory Goodyear radials would soon need replacement, all around.  I also noticed one of the Prestone "flush adapters" already in the heater hose, too.  With the 403, it would lay two stipes of rubber, as PTrac was standard on TAs back then.  So I signed the papers and arranged to do the trade the next day.  Then, when I was getting the Camaro cleaned out that night, I got a bit sentimental and looked at what I had and decided I would only be getting more car payments.  Plus the unanswered question about the flush adapter being in the mix so soon.  NOT to forget how much trouble it would be to just check the air filter!  So, I backed-out of that deal.  My mother later discovered that her student (the prior owner) liked to "lay rubber" with the car, which explained why all four tires needed to be replaced at 20K miles from new.  I think I was better off, personally, for my situation.  I always liked those Firebirds, for many reasons, and still do.  But my desire to own one has passed, as I still have my trusty Camaro (with some upgrades and enhancements along the way).

 

I always liked Oldsmobile V-8s and respected their engineering as being some of GM's best, with their hierarchy in the GM lineup being near the top, they could do "more expensive" things that Chevrolet or Pontiac (due to cost considerations) generally could not, back then.  Obviously, emissions tuning hurt them more than some other similar motors, but the basic design always seemed to be good and durable.

 

As to the Olds 307 and 260, both "good" engine sizes, just that by that time, too much car weight with not enough gear in them to work as they could.  With some modern upgrades (including self-learning EFI also controlling the ignition) and an 8-speed automatic behind them, with 3-series gears, I suspect they would perform much better than they did in the "need to get fuel economy days" of the 1980s.  OR . . . better optimize the fuel/air mix with an annular discharge venturi carburetor, a true-dual exhaust, dual converter exhaust system (but quiet), with more optimized ignition timing and such, backed by an OD automatic with a bit looser lock-up torque converter.  I suspect that might help things all the way around AND be incognito.

 

Enjoy!

NTX5467

[EmTee]

My son had a '67 Cutlass convertible with the ST300 behind a 330 4BBL.  That car had good power and the switch-pitch worked well.  It performed much like a later TH350.

[XframeFX]

On 10/20/2023 at 8:38 AM, NTX5467 said:

Not having researched things, BUT were all ST300s ONLY behind 2bbl V-8s with the 4bbl V-8s needing something a bit looser?

My early years, thought it was an aluminum version of the Powerglide. GM had so much resources in those days, production transmissions galore. Increased sharing between divisions came later.

ST300s were fitted w/o the 12" variable pitch torque converter on Buick V6s all the way up to the Nailhead 401 on 1965/66 Skylark GSs with variable pitch. Images in my 1964 Shop Manual seems to indicate the same front pump as the variable pitch ST400. As for "Loose", 12" is still a large torque converter. Curious why it's a whopping 25 lbs lighter than the 13" Unit. The ST300 unit might be Loose in a heavy car but, the G1 Riviera's are 400 lbs lighter. "Loose" was an observation from one swap. Would like to hear from other outcomes with the switch.

 

3 hours ago, EmTee said:

My son had a '67 Cutlass convertible with the ST300 behind a 330 4BBL.  That car had good power and the switch-pitch worked well.

I too had a 1967 Cutlass Convertible with the same engine/trans back in the 70s. Was unaware of variable pitch and both, engine/trans were tired. It started with a puff and drove. So long ago, can't remember why I don't have it or where it went.

 

On 10/20/2023 at 8:38 AM, NTX5467 said:

As to the Olds 307 and 260, both "good" engine sizes, just that by that time, too much car weight with not enough gear in them to work as they could.  With some modern upgrades (including self-learning EFI also controlling the ignition) and an 8-speed automatic behind them, with 3-series gears, I suspect they would perform much better than they did in the "need to get fuel economy days" of the 1980s.  OR . . . better optimize the fuel/air mix with an annular discharge venturi carburetor, a true-dual exhaust, dual converter exhaust system (but quiet), with more optimized ignition timing and such, backed by an OD automatic with a bit looser lock-up torque converter.  I suspect that might help things all the way around AND be incognito.

The moniker: "THERE'S NO REPLACEMENT FOR DISPLACEMENT" is no longer true today. Before retiring, my last pick-up was an F150 w/3.5L V6 Ecoboost. It had torque right up there with the Ford 6.2L V8!

Yes, those small V8s from the 80s would indeed do better with modern induction/ignition/transmission control.

[RivNut]

My 2030 Encore GX has a 1.3 liter I3 ( 79 cubic inch) turbo charged engine that puts out 155 horse power. Remember when Chevy was so proud of their 283 cubic in V8 that developed “one horse power per cubic inch.   

 

The Encore GX can hold its own in stop and go traffic or on the highway.  Without the cruise control on, I often find the car in its sweet zone which is when I find myself in trouble around 83 mph.  I contribute a lot of that to the CVT transmission, it must have some really steep o/d ratios.  Passing trucks on old US 50 on the way to my sister’s is easy to hit 90 mph without breathing hard.  The redline on that engine is 6200 RPMs. And I get 36-38 mpg average.

[XframeFX]

1 hour ago, RivNut said:

Encore GX can hold its own in stop and go traffic or on the highway.

I sprung for a Wrangler 4XE when ordering opened up. After 30 months, still a mystery regarding the innards of its ZF 8HP75 PHEV Transmission. Ya but, how does . . . . . work? Torque converter creep in conventional auto transmissions is obvious but my PHEV trans, my wife's CVT trans? Many more observations and questions. Again, 30 months, no news.

Gotten quite familiar navigating/selecting the LCD GUI and settings to my liking.

What's really nice is staying in "Electric Mode" while in Stop & Go traffic. Engine off, no idling!

 

1 hour ago, RivNut said:

I contribute a lot of that to the CVT transmission, it must have some really steep o/d ratios

Depending what type of CVT it has.

The Dutch DAF Car intro'd around 1960 had a pulley CVT called the "Variomatic" and that was the only transmission offered. Typically it didn't offer much under-drive but it offered the same amount of over-drive. Solution? a steep axle ratio, something like 5.13:1. Curious to know if the DAF had transmission creep which I think is engineered into modern CVTs because consumers are used to it. The DAF car could go as fast in reverse as forward if you care to dare!

If a CVT has equal over/under drive, I've foundthe engine most responsive at approx 80 KM/hour (50 MPH) because it is direct 1:1 at that point. Cruising above that speed, overdrive is in-place and no more response without kicking it down a notch or two.

The Buick Encore GX might have a steep 5.XX:1 axle ratio to work with whatever CVT transmission it has.

 

 

 

Edited October 21, 2023 by XframeFX (see edit history)

[RivNut]

TRANSMISSION & AXLE

Type:	Continuously Variable Transmission
Application:	1.2L Turbo and 1.3L Turbo FWD
Variator ratio spread	7.0
Underdrive	2.621
Overdrive	0.374
Overall ratio spread	7.0
Reverse	0.67:1
Final Drive Ratio:	5.44

 

[telriv]

So Ed are you doing some prototype work for GM with that 2030 Encore???

 

Tom T.

 

 

[RivNut]

3 hours ago, telriv said:

So Ed are you doing some prototype work for GM with that 2030 Encore???

 

Tom T.

 

 

Nope. Leased it in April of 2020 and bought out the lease this past June because the residual value was established before Covid.  Figure we made about $4K between the residual value written into the lease and the price of comparable cars when the lease was up.

Edited October 22, 2023 by RivNut (see edit history)

[NTX5467]

The last company truck I had was a '23 Silverado Custom, with the standard 2.7L High-Output Turbo 4cyl.  310 horsepower and 430 torque, with the 8-speed GM automatic.  When I first heard they put a turbo 4cyl in a 1/2-ton pickup truck, I laughed, back then.

 

After I got that pickup, which had previiously been in our load car fleet for about 4K miles, I looked at the power figures and thought . . . not unlike the base 4bbl 396/325, 383/325, and 390/300 motors of the middle 1960s.  Add in the 8-speed lower gear ratios for good measure.  Power with much improved fuel economy, was the result.  I never did "see what it would do", but in normal driving it certainly ran better than prior 4.3L V-6s and not that much different than 5.3L V-8s in 1/2-ton pickups.

 

THEN I started researching the engine and discovered that it probably has more power left in it, IF anyone might desire it.  With a 4-cyl, the twin-volute turbo can work well, with a more uniform flow from the exhaust manifold.  In some cases, I could still feel a tinge of turbo lag, but by the time it was starting to be noticed, the trans had downshifted, the "calvary" arrived, and the right rear tire was starting to make noise.  Which, not wanting to look like an over-aged hot rodder, I backed off the throttle a little bit to keep the rear tire quiet.  That truck, to me, needed a PTrac!  THAT would be fun!   AND . . . all of this in a 5Klb 4-dr short bed pickup truck!  

 

I was more interested in what MPG it would produce, as I had already determined what the prior 5.3Ls could do in my freeway drives with cyl deactivation and such.  It was close enough to 25mpg that it would be tolerable for an every-day commute as an only vehicle, too.

 

Several YouTube videos from GM on the engine and others from actual owners proved that GM Powertrain did a great job with that engine.  I would not be afraid to own one, either.  Which makes the smaller Colorado (with the same engine) in the same power output a more appealing vehicle, too!  Forget the off-road versions, think "Sports Truck" that is more comfortable on a road course than on a rocky trail!  Not unlike the prior Dakota 5.9L R/T pickups!

 

THEN I discovered that little 2.7L Turbo motor can produce 27psi of boost!  YIKES!  Other than the twin-volute turbo, obviously, computer modulation of the waste gate/boost curve is a key factor in the production of 400 lbs/ft of torque from about 1500rpm upward.  Which can also mean "not a lot of throttle input" for "interesting" acceleration and greater ultimate fuel economy.  Great job, GM Powertrain!!!

 

NTX5467

Edited October 22, 2023 by NTX5467 (see edit history)

[XframeFX]

8 hours ago, RivNut said:

Variator ratio spread

7.0

     Underdrive

2.621

     Overdrive

0.374

     Overall ratio spread

7.0

     Reverse

0.67:1

Final Drive Ratio:

5.44

Ah ha, this CVT has equal overdrive/underdrive:

Underdrive is: 2.621:1

Overdrive is:   1/0.374 > > 1:2.67

So the axle has to be steep and is so at 5.44. A lot of friction for a hypoid but, this is FWD with parallel shafts.

Driving a CVT rental, I try to determine at what speed is 1:1 direct by feel. On my Wife's CVT, I use tire calculators and known gear mesh ratios from specs. About 80 KM/hour.

[XframeFX]

7 hours ago, telriv said:

So Ed are you doing some prototype work for GM with that 2030 Encore???

I don't think Tom T. Type-O'd 2030 Encore by accident, LOL

I think GM is designing the 2030 as we speak and possibly renaming the model a baby Riviera😝!

[RivNut]

10 hours ago, XframeFX said:

I don't think Tom T. Type-O'd 2030 Encore by accident, LOL

I think GM is designing the 2030 as we speak and possibly renaming the model a baby Riviera😝!

As you can tell by my response, I didn't catch that. If Buick/ GM ever brought back the Riviera name, I would hope it would be a two door sport luxury model.

[MikeJS]

12 minutes ago, RivNut said:

If Buick/ GM ever brought back the Riviera name, I would hope it would be a two door sport luxury model.

Good day.

 

Not sure whatever happened to this 2013 concept, wonder if it had anything to do with an American classic being designed by the Chinese...

 

https://www.caranddriver.com/news/a15115847/buick-riviera-concept-photos-and-info-news/

 

Woulda been kinda cool if it ever came to fruition...

 

Later.

Edited October 22, 2023 by MikeJS (see edit history)