How underpowered is the Olds 307?

[Joe V]

I have read much feedback from many for members regarding the 307's significant lack of power.  But underpowered can mean many things - off the line power, overtake power, maintaining speed in high gear, etc.   When comparing an 89 FWB 307 to 79 FWB 425, and looking at the online acceleration comparison specs below, I was surprised.  I know what a torque difference of the level shown really means, but I expected to see a much different picture on acceleration.  Especially in 0-100km/h.  Maybe the published acceleration numbers are wrong, but interesting cars like the following that are in great shape but with the 307 pop up regularly.  https://www.ebay.com/itm/1989-Cadillac-Fleetwood-Brougham/323452078655?hash=item4b4f3f0a3f:g:KUwAAOSw3KhbnsVX&vxp=mtr

Right now I'm working through the information regarding 75/76 and 77-79 CDVs that many have posted - thank you.    But to advance my understanding and answer the question of why you wouldn't just buy a $3-$4K Cadillac in great condition just to license, insure minimally, keep on the street, and enjoy, how really underpowered is a 307 powerplant and how does it show up in daily driving?

["Cadillac Kid" Greg Surfas 15364]

Joe,
Those acceleration numbers seem very slow. A 77 CDV with the 425 in good running condition should cover the quarter mile in something like 16 seconds at a trap speed of about 80 MPH.
Greg Surfas

[Joe V]

Here's the 1/4 mile data.  89 FWB on the left, 79 FWB on the right.

[Scot Minesinger]

I suspect that most Olds 307 engines are not running properly.  The diverter is often bad (which takes out the cat conv.), timing is not correct, numerous original vacuum hose leaks, and etc.  Accordingly you may read many disappointing reviews. 

I worked on an Olds 307 two years ago and the owner requested that the power be increased, he wanted to investigate adding dual exhausts and other owner changes.  I found that although the engine seemed to run smooth and apparently OK, it was way off.  The timing was 23 degrees off (setting timing is like an hour process!!!), diverter was bad and etc.  Once it was mechanically good, he abandoned his requests for modifications, which I agreed with.

I drove a 4.1 powered Cadillac in good mechanical repair and it is terrible.  Do not buy one.  Any comparison to the Olds 307 is not correct.  The 307  is not ideal, but it is better than the 4.1 by a long shot.  Buying a Cadillac between the years 1975 thru 1979 will be way better.

Plus, not sure that the Olds 307 was used in 1989 (1988 might have been last year, it was a carb.).  I think by 1989 it was a fuel injected Chevy engine in 5.0 and 5.7 versions - check it out.

[Scot Minesinger]

BTW agree with Greg.  The 425 powered Cadillacs enjoy strong acceleration even by today's standards, and the Olds 307 is adequate.

[Joe V]

Looks like both the 307 and the  Chevy 305 were options.  The comparison site shows the Chevy as the towing option.  My inclination is to doubt the data from what has been posted about the 307, but even the 1/4 mile data does not suggest its underpowered with the 79 425 beating it by 8 yds and a fraction of a second. 

[T J Lankes]

I have a '79 SDV and find that the low end torque and acceleration are relatively strong and the engine never strains to deliver the power.

The close acceleration times between the '89 307 car and the '79 425 car are in large part due to the different rear axle ratios.  The standard rear axle in the '79 is a very low 2.28 compared to the standard 2.93 ratio in the '89.  That's a BIG difference.

But drive both and see how they feel to you.   If you find a 307 car that you like for only 3-4K it might be just fine.

One other note, The 3 speed auto (TH-400) in the '79 is a more robust transmission than the 4 speed (THM-200-4R) in the '89.

[Jon S]

I had a 1984 Oldsmobile 98 Brougham with the 307. It was a absolute pig!

[bcroe]

I went through this decades ago.  How come my 80 sedan is so much slower
than my same engine 68 sedan?  My conclusion was that they went to a
2.41:1 axle to make the 3 speed more like an overdrive with only 2,3, and
4th gears.  Good economy but no launch.  My fix was to install a switch
pitch TH400 trans, giving back a lot of launch and taking a full second off
my 0-60 mph.  It did other things better too with electronic control.  How
many times have I said a big late 70s car, esp a Seville, could be much
faster with the same engine?

The 307 came with a 4 speed, pretty optimum for that engine, but the 425
struggles with its axle.  They are not far apart up to 90KM/hr, but the
425 really leaves the 307 in the dust above that. 

I went to the Olds 403, with switch pitch the sedan does 7.5 sec 0-60
and 91 mph quarter mile with the stock axle.  Bruce Roe

[V63]

The 5.0 was first offered in 1986...and a 5.7 ‘tow package’ was available in 1987?

I had a 1987 5.0 and they were pretty pathetic. I think if I still had it, I would convert it to the weekend EFI’s now available. I think that would perk it up just enough to be acceptable.

[bcroe]

The 5.0 was first offered in 1986...and a 5.7 ‘tow package’ was available in 1987?

I had a 1987 5.0 and they were pretty pathetic. I think if I still had it, I would convert it to the weekend EFI’s now available. I think that would perk it up just enough to be acceptable.

I think you would do a lot better to just put in an Olds 5.7L.   Those
quickie EFI conversions DO NOT have the electronic spark advance
the CCC 5.0L uses, in my experience more important than how the
fuel gets in.  A good (usually factory) EFI has it, not something that
can be optimized in a weekend.  Bruce Roe

[Dr. John T. Welch]

The GM 307 (VIN code “Y”) engine  was a remarkable and durable product.  Genetically it dates from 1959-1962 when it was designed (“clean sheeted”) as a modern derivative of and replacement for the original Oldsmobile 303 Rocket V-8 introduced in 1949. The engine existed in various displacements in Oldsmobile products from 1963 through 1986 and served other divisions of the old General Motors through 1990.  Structurally and in features that are most important to profitable mass manufacturing, the 307 was very similar to the original Rocket V-8. It was an improvement mainly in casting techniques to reduce weight. Overall architecture of the engine was  almost exactly that of its 1940s predecessor. Ironically, it did not benefit from  the concurrent and short lived engine programs within Oldsmobile (1958-1961) that produced the sophisticated aluminum 315s in naturally aspirated and turbocharged variants. Production of those engines was miniscule compared to the family of larger displacement engines of the 260, 330,400, 425,455 and ultimately the  307 variant for the years 1963-1990. The real dog of these engines was the 260.

The 307 Y engine was produced  in the original Lansing, MI  Oldsmobile Kettering Engine Plant - the same plant where all of its V-8 predecessors were made beginning in 1948!  It is a remarkable engineering achievement that a carburated  engine designed in the mid 50s was evolved to meet strict federal emission standards of 1990. That’s the kind of engineering and investment amortization that the old GM was famous for.

The 307 Y was the last GM carbureted  engine to be US EPA federal emission compliant to applicable standards for the model year in which it was used. It took redox catalytic downstream treatment, air injection, exhauast gas recirculation,  computerized electronic ignition (but still HEI distributor style) and  computerized electronically controlled Quadrajet carbs to do it. All made to last for the mandated 50,000 mile federal emissions performance warranty period. This was a very delicate high wire act and the 307Y had the highest non-compliance rate in EPA 227 conformity after 50,000+ miles for any domestically manufactured powertrain. People abandoned them in droves when confronted with compliance repair costs in mandatory test juristictions.

The repair costs centered mainly around poor knowledge and understanding of the E4MV electronic Quadrajet carburetor and the complicated electronic/vacuum controls for the upstream and downstream air injections systems. If these components were not adjusted exactly to the factory specifications, emissions failures and performance degradation occurred.  When properly serviced to factory specs, these engines performed very well and were very durable. This engine employed the final iteration of the original GM “Computer Command Control” system introduced in 1979 for CA carbureted engines.
It was a real engineering tour de force and the most sophisticated final act in the story of the carbureted automotive engine as it approached extinction with the arrival of fuel injection strategies to meet increasingly stringent emissions standards.

Proper maintenance, careful servicing of the electronic Quadrjet carburetor and replacement of all the underhood vacuum control hoses with silicone polymer  replacements will keep any 307 running very well with surprisingly pleasant performance. A fellow at the  2017 Olds National Meet in Albuquerque
showed up with his southside Chicago beater 307 Y ‘85 Custom Cruiser with 400K miles.  Engine never opened and only recommended factory periodic maintenance performed. Inspiring outlier. The only 307 to own today is the 1985 version and beyond: they have billet steel camshafts and hydraulic roller lifters.

Comparisions with the acceleration for a 425 Cadillac have to consider the different gearing for the transmissions and differentials.  The 2004R was used with the 307Y and had step ratios of 2.74,1.57,1:1 and 0.67 Overdrive. The THM 400 behind the 425 had step ratios of 2.42,1.42 and 1:1.
Low end torque of the big 425 made up for the difference.   
 
 

[bcroe]

My own experience is that any of the emissions Olds small blocks just
keep running, 300,000 miles is no problem if you change the oil, etc. 
I think that aluminum engine was a 215 though, I drove them a third
of a million miles including the turbo.  A cast iron version showed up
in Buicks, the aluminum version went overseas.  Bruce Roe

[Jon S]

My experience with the best of the Oldsmobile engines - the 371 and 394's was that they were oil burners. Pontiac, Buick and Cadillac engines were far superior.

[D.Smith]

The 5.0 engine is a rocket compared to the HT4100s.   Not to mention a million times more reliable.

I don't know why people bad mouth the 5.0 motors.   I've driven many of those cars when new.  Perfectly fine performance for everyday driving.   Just because it won't spin the rear wheels across an intersection doesn't mean it sucks.   We are buying luxury cars not muscle cars.    Sure its nice for bragging rights to say your car can blow the doors off other cars but for 99% of new Cadillac buyers they just want good take off from a red light and the ability to pass on the highway.   

Don't forget starting in 75 the rear axle gearing was aimed at maximum fuel economy.  That didn't help performance either.    The early seventies may have had monster engines but single digital fuel economy was normal if you didn't feather that gas pedal.   The Olds 455 Toronados were EPA rated at 6.8 mpg

[TJ Hopland]

I used to see a lot of the late 80's 307's with choke and cat issues.  A stuck closed choke or plugged cat will give you a very smooth running engine that just doesn't have any power.  At night in the dark you could see the manifolds and cat glowing orange from the extra heat.     That was the full size wagon engine so between the Brougham and the wagons there were a decent number of em around even in 89. 

Talking about axle ratios and terrible performance look at what you got in say a Chev in around 79.   They were doing the same thing as Cad trying to get the MPG up but their engines didn't have the torque the Cad did so they were even worse off the line. 

[Dr. John T. Welch]

If forum members will recall, 1977-1979 were the incestuous years for application of GM engines across divisional and automotive product lines.  The rapidly advancing fuel economy and emissions regulations coupled with consumer preferences and expectations led GM to cross pollinate engines among divisions .  Conceptually, this was nothing new to GM. They had done it before in the instance of the Pontiac V-8 used in light and medium duty GMC trucks, and elsewhere in Canadian and other international markets.    However, this time it didn’t work in the US as customers were outraged that their Oldsmobile 88 in many cases had Chevrolet engines of nominally the same displacement.  Still, “it wasn’t an Oldsmobile Rocket V-8 and that is what I thought I was getting when I paid for this car”!!”  That’s when GM began identifying the engines in their US cars as “Manufactured by General Motors in a plant owned by General Motors”.  This was the beginning of the end for divisional identity and powertrain autonomy within GM.  It was not rational to have four automotive divisions each producing their own 350 cubic inch displacement engines with no  major component  or manufacturing commonality as was the case in 1976-1979. And each divisional engine family required expensive development to  common EPA emissions standards.  Only the strongest  engines from a manufacturing cost and reliability standpoint survived: the Olds V-8s and the Chevrolet large and small blocks.  And that’s the way it was until the funerals of divisions and the LS era now upon us.

Earlier I mistyped the displacement value for the advanced aluminum Oldsmobile engines of the early 60s.  It was 215 cubic inches not 315. I also inadvertently left out BC Roe’s favorite Olds engine, the 403, when listing the displacements of the surviving Olds engines through the 70s. The 403 block casting was unique in that it had siamesed bores for 2-3 and 6-7 cylinders. This constrained service overboring and limited the safe reuse of these blocks.

The 307 Y was the happy warrior/survivor in all of this, being used in both FWD and RWD GM product. When well maintained and respected for what it is, it still gives remarkably good service. When neglected and abused it reacts like any wife. I would like to be around when the fellow at the Olds National Meet changes the timing chain and gears on his 400K mi engine. Where did all that nylon go??


A common occurence in the owning of a 307Y is misery and ungodly expense associated with the electronic Quadrajet E4MV carb to restore emissions compliance. Outwardly, the E4MV looks just like any Quadrajet that has been around since 1965.  The innards are ingeniously electronic and must be respected as such.  Service people in the field ignored this and in frustration would attempt service as for any non electronic unit...  big mistake and very expensive for the owner.  In frustration a “rebuilt” unit would be installed,  and they usually were way off spec as well as 3-4 times as expensive as the older non electronic units.  I’ve purchased cars where owners had paid in excess of $2000 for driveablilty issues and still had poor or non operating vehicles. Simple service per the factory manual always solved the problems.   

[D.Yaros]

A common occurence in the owning of a 307Y is misery and ungodly expense associated with the electronic Quadrajet E4MV carb to restore emissions compliance. Outwardly, the E4MV looks just like any Quadrajet that has been around since 1965.  The innards are ingeniously electronic and must be respected as such.  Service people in the field ignored this and in frustration would attempt service as for any non electronic unit...  big mistake and very expensive for the owner.  In frustration a “rebuilt” unit would be installed,  and they usually were way off spec as well as 3-4 times as expensive as the older non electronic units.  I’ve purchased cars where owners had paid in excess of $2000 for driveablilty issues and still had poor or non operating vehicles. Simple service per the factory manual always solved the problems.

Our '84 Rivi had the 307 engine.  It took 4 attempts and much time and dollars to get it to pass the WI mandated emissions test.  It terms of performance it was adequate, and nothing more.  The first clue to not expect much was that 85 MPH was the max speed on the speedometer!

[gkhashem]

My experience with the best of the Oldsmobile engines - the 371 and 394's was that they were oil burners. Pontiac, Buick and Cadillac engines were far superior.

I may not have as much experience as you but I have two 394s, each one when well maintained and tuned up START EASIER than my 390, 429 and 425 when sitting for more than a few days. Also they run so much smoother and quieter than the Cadillac engines especially the 425 which sometimes likes to quiver some. From what people have told me, including my 69 yo mechanic who has worked on cars for almost 50 years and went to GM Rochester carburetor school, it was not easy to get the 425 Cadillac to idle smoothly at times. Just a fact from my experience and his. Also he actually thinks the Rochester is a better carburetor than the Carter so he would not agree with most people here too. I bet the reason for that is the Rochester yes is more complex but that may be why people do not like them since maybe they do not understand them or know how to rebuild them properly. The only Carter I have is in my 1966 429, and that car hates to start after sitting more than a few days, even more so than my 1959 390.

Also the Oldsmobiles have from 45,000 miles to 50,000 miles and do not burn any noticeable amount of oil. But neither do my Cadillac engines.

I could put a cup of water on top of my Oldsmobile air cleaners and not see any vibration. Also while the are running they are so quiet you can hardly tell they are running.

Also do not tell me the Cadillacs are not well maintained, all of my cars are.

Now for the 307 Olds, I have one in a 1984 Olds Delta 88 and yes it is a challenge at times, but it usually only a problem when going up a long incline, yes it will struggle then but 95% of the time it seems fine but no speed demon. It may be the extra weight of the Cadillac is enough to expose the lack of power more than in an Olds 88.

[Scot Minesinger]

The 307 Olds engine I worked on was in a 1985 Buick Riviera.  Dr. Welch was kind enough to guide me thru how to make it run as it should.  I wrote about this on my first response to this thread.  After I had it running well as per factory specs following the shop manual it was a nice running engine with decent power.  The late 1970's/early 1980's was a terrible time for GM quality and it would not surprise me if some further attention was need to brand new Olds 307 engines at the time.  If the engine is within factory specs it should be fine. 

I owned a 1978 Olds Delta 88 w/350R engine and a 1985 Chevy Caprice w/305 V8, and the quality in every was was far superior on the Chevy which ran 300,000 miles all on the original drive train and the a/c still worked after dong nothing ever to it.  I sold the Chevy which ran well at 300k miles to a friend and they eventually traded it in and got $1,200 because even past 300k miles everything still worked and it ran good (speedo only went to 99,999 miles).

One of my friends locally just purchased a 1988 Cadillac RWD Brougham with the Olds 307 and he enjoys it (he also owns a 1954, 1959, 1964, and 1968 Cadillacs all in good running order).  He knows what power is.