Oldsmobile 307 Engines

[S2500Dog]

Hey everyone,

I would like your personal experiences and thoughts concerning the 5.0 Oldsmobile V8 built as the very last Carburetor Engine capable of passing emission tests. I heard that this motor was better quality than the Chevy 305 and Oldsmobile 307 High-Output being produced at the same time during the years.

 

[gmchevroletruck]

I would be curious to hear about this as well...the 307 was, and still is, not an engine you heard much about. I've had a 305, it lasted a very long time, if you ask me, too long, as I wanted it to die so I could swap it out with a 350 (cliche, I know, but hey...they're great).

I used to have a curiosity years ago, about the 307, and never got around to learning much about them. Forgot for many years...

This should be an interesting thread, I'm putting it on my watched topics too.

+1

 

[genynnc]

Funny both engines are considered 'hi po' for the 80's when we have 4 cylinders Civics & Corolla's with more ponies today. Anyway, I don't think one or the other has any advantages as far as quality goes.

I do like the bore/stroke combo of the 307 better than the 305 but I'll probably take the 305 over the Olds engine because the [censored] Chevy heads still flow better than the 307's.

 

[Fazzone]

Our family has had 3 vehicles with them. They are very lacking in power from my experience, but VERY fuel effiecient(this may be due to the gearing though in these cars-I swapped out the 307 in my olds for a 455 and still averaged 15+ mpg)! My grandfather has a 83 Park Ave that if treated nicely would get around 30 mpg on the hwy. Not bad for a old carburated car that weighs around 5,000 lbs. Also, like most Olds engines, they last FOREVER, dads is nearing 300,000 and the only major repair was a timing chain. He averages around 20 mpg commuting to work. The only problem with the engine is it is a major PITA to work on. Everything is bolted on top of everything else. When I put a water pump in one of the cars, I had to remove the a/c, air pump, and ps pump. That and the thing is held on with like 8 bolts which some are small and easy to break or strip the threads on.

 

[ToyotaNSaturn]

Completely agree w/Fazzone.
--Underpowered? Yes
--20-21MPG on a carbureted V8 back in '84. Who knew?
-- in -15F weather, it started right up on the 1st crank, with a carb!
--the car around it rusted away, but the engine was humming a long...84 Olds Cutlass 2-door rear-drive

 

[duaneb9729]

my dads '77 olds delta 88 would get 21 to 22 mpg, and that had a 350 in it.

my dad still misses that car.

i had a 91 chevy pick up that would get 20 to 21 on the highway,
a tb 305.

 

[Zaedock]

Olds 307's were nice engines. My brother is a big Olds guy.
He has a '74 Omega with a 350 Rocket. The engine is very far from stock now, with adjustable roller valvetrain and other go-fast goodies. Inside the glose box, the sticker specifically states to use high octane fuel. That's cool for 1974.

 

[eljefino]

What I find funny is the caprice wagon (and the olds version... delta 88 maybe?) had the 307 (what they had at that factory?) but the sedans had the chevy 305.

Brother in law had a chevy 307 in his 68 nova.

I believe there were some hondas, toyota corollas, and subaru justys that used feedback carbs until 1990/91 while the 307 was phased out by then. Its last appearance IIRC was the cadillac fleetwood.

 

[Jason2007]

In one of the recent mags, either Hot Rod or Popular Hot Rodding one of the engine builders made over 430 HP from a 307 Olds.

 

[andyd]

My Dads old 68 Chevy C20 had a 307 mated to a 3 speed going to a 4.88 diff. Even with 17 " tires it was pretty quick

 

[Kestas]

My 71 Cutlass with the 350 engine gets 16 mpg.

 

[Oldswagon]

I've owned several 305 Chev's and 307 Oldsmobiles (I still have one vehicle with 307 right now). Hands down, the 305 is a far superior engine. The 307 Olds is VERY underpowered. Yes, most 80's V8's put out little power, but the 307 was at the bottom of the list. Most 307's were rated at 140 hp. Compared to the typical LG4 305 (4bbl, rated at about 150hp), or the 302 MPFI (150hp with single exhaust in Crown Vics), the 307 feels like isn't even in the same league. I've owned both the 305 and 302 in fullsize cars from this era while I had a 307 car, so I could do a back to back comprision.

Like someone else mentioned, they are generally a pain to work on, especially in a AIR and A/C car. Fuel economy is okay, but no better than a 305 Chev or a 302 Ford. Durability is poor compared to other Olds engines (at least in my experience). My 307's all showed blow-by problems at a young age. I never had that with a 305 or 302 (although a 302 I had started to have a rod bearing noice around 200K), and the Olds 350's we've had were virually indestructable.

In my opinion, the 307 Olds is the worst Olds V8 ever made, next to the 260. The only good thing about a 307 is that it makes an easy swap for a 350 Olds.

 

[Oldswagon]

Originally Posted By: eljefino
What I find funny is the caprice wagon (and the olds version... delta 88 maybe?) had the 307 (what they had at that factory?) but the sedans had the chevy 305.

Brother in law had a chevy 307 in his 68 nova.

I believe there were some hondas, toyota corollas, and subaru justys that used feedback carbs until 1990/91 while the 307 was phased out by then. Its last appearance IIRC was the cadillac fleetwood.


This was Roger Moore's GM cost cutting at its finest. To simplify production, during the 1986 model year Chev and Pontiac wagons switched to 307 Olds from the 305 Chev's. This was done so that all wagons used the same engine. Wagon bodies were identical from the firewall back, so it just simplified production lines. It's too bad GM didn't use the 305's in the wagons, because these cars were a lot heavier than the sedans and needed the extra power (The 305 was rated at 165-170 hp between 1986-90, vs 140hp for the 307). Part of the reason may have also been to try and use up all the 307 engines GM had produced, and to prevent a Chevrolet engine from being used in a Buick and Olds line so that they didn't have a replay of the 350 Olds incident in 1977.

I don't know if it's a sign of how good the 307 was that it remained carbed until 1990. If anything, it was GM's lack of investment in this old dinosaur. Today, 307's have a reputation as being a tough engine to get past emissions testing. Carbed 305 Chev engines don't share this same reputation.

 

[gmchevroletruck]

Originally Posted By: genynnc
Funny both engines are considered 'hi po' for the 80's when we have 4 cylinders Civics & Corolla's with more ponies today. Anyway, I don't think one or the other has any advantages as far as quality goes.

I do like the bore/stroke combo of the 307 better than the 305 but I'll probably take the 305 over the Olds engine because the [censored] Chevy heads still flow better than the 307's.


Wow that was way off base. Neither of those engines were considered "high performance", not in the 80s, not ever. And by "ponies", I'm sure you meant "horsepower", saying that Civics and Corollas have more power today than these engines did then. Crazy comparison for many reasons, but I'll touch on a few: for one, high-revving "horsepower", as it appears in a Civic or Corolla, is not going to move a heavy car or truck very well in normal driving conditions, which is what these powered. Both of those engines had much more torque, which will do that, and had it at much lower rpms than a Civic or Corolla of today. Furthermore, comparing an 80s economy engine for large cars and full-sized trucks, to a modern, higher-technology engine of today, of any size, is pretty pointless. Sorry if this comes off as rude, but I can't let that one slide. Nobody said either of these were performance motors. They never were.

Also keep in mind that these engines were made during the no-power-available-anywhere-era, due to extensive emissions control requirements, courtesy of our ever-auto-friendly government, and courtesy of a "fuel crisis" in the early 80's.

If you really want to do a comparison, look up the torque and horsepower curve / numbers for a 1980 Civic / Corolla, and a 1980 model 305 / 307. Or better yet, put the motor from that era Civic / Corolla in a full sized Oldsmobile, or a full sized truck, and see how it performs.

 

[gmchevroletruck]

Had a 90 Chevy pickup with the 305 as well, and it got great mileage with the 3.42 rear gears, even with only a 3spd tranny. Had "decent" low end torque, towed a trailer with it occasionally, hauled heavy loads. It was no powerhouse, always made me wish for a 350, but it did all I asked of it, ran smoothly, and got decent mileage. Never totally loved the motor, but couldn't hate it either.

 

[OVERKILL]

We had a 307 in an Olds wagon. 1986 Custom Cruiser. It, like mentioned in this thread, started with pretty substantial blow-by at a young age.

Always started, tranny died before the engine did. The 302 in my dad's Lincoln felt like it had TWICE the power of this thing though.

I have never been impressed with it or the 305. Both engines were underpowered, given that the 302 was making 225HP with some neutered truck heads and an intake that resembled a straw..... In Mustang duty of course. And even those parts were an upgrade for the version fitted in the Panther cars.

The 305's miniature bore size also made genuine performance upgrades a fantasy. Since all the good heads have larger valves that won't clear.

There were a lot of very bizarre things going on during the 80's though.

Also, I think that the 307 was the first GM V8 to receive roller lifters if I remember correctly.

I also echo the sentiment of the Honda/Toyota "power" argument being ridiculous. I raced (and slaughtered) a Maxima with my '87 GT. His buddies were all going on about how the car must be well over 300HP and I looked at them all, with a straight face and told them it was 225. The guy looked like he was going to throw up. Area under the curve is highly underrated........

 

[BuickGN]

Originally Posted By: gmchevroletruck
Originally Posted By: genynnc
Funny both engines are considered 'hi po' for the 80's when we have 4 cylinders Civics & Corolla's with more ponies today. Anyway, I don't think one or the other has any advantages as far as quality goes.

I do like the bore/stroke combo of the 307 better than the 305 but I'll probably take the 305 over the Olds engine because the [censored] Chevy heads still flow better than the 307's.


Wow that was way off base. Neither of those engines were considered "high performance", not in the 80s, not ever. And by "ponies", I'm sure you meant "horsepower", saying that Civics and Corollas have more power today than these engines did then. Crazy comparison for many reasons, but I'll touch on a few: for one, high-revving "horsepower", as it appears in a Civic or Corolla, is not going to move a heavy car or truck very well in normal driving conditions, which is what these powered. Both of those engines had much more torque, which will do that, and had it at much lower rpms than a Civic or Corolla of today. Furthermore, comparing an 80s economy engine for large cars and full-sized trucks, to a modern, higher-technology engine of today, of any size, is pretty pointless. Sorry if this comes off as rude, but I can't let that one slide. Nobody said either of these were performance motors. They never were.

Also keep in mind that these engines were made during the no-power-available-anywhere-era, due to extensive emissions control requirements, courtesy of our ever-auto-friendly government, and courtesy of a "fuel crisis" in the early 80's.

If you really want to do a comparison, look up the torque and horsepower curve / numbers for a 1980 Civic / Corolla, and a 1980 model 305 / 307. Or better yet, put the motor from that era Civic / Corolla in a full sized Oldsmobile, or a full sized truck, and see how it performs.


I completely agree.

Comparing it to the same era Civic would be more realistic. But I would still like to see a modern Civic 4 banger try and move one of those 4,000lb cars. You could just cut off the bottom half of the tach because it wouldn't move out of it's own way below 6,000rpm.

 

[BuickGN]

Originally Posted By: OVERK1LL
We had a 307 in an Olds wagon. 1986 Custom Cruiser. It, like mentioned in this thread, started with pretty substantial blow-by at a young age.

Always started, tranny died before the engine did. The 302 in my dad's Lincoln felt like it had TWICE the power of this thing though.

I have never been impressed with it or the 305. Both engines were underpowered, given that the 302 was making 225HP with some neutered truck heads and an intake that resembled a straw..... In Mustang duty of course. And even those parts were an upgrade for the version fitted in the Panther cars.

The 305's miniature bore size also made genuine performance upgrades a fantasy. Since all the good heads have larger valves that won't clear.

There were a lot of very bizarre things going on during the 80's though.

Also, I think that the 307 was the first GM V8 to receive roller lifters if I remember correctly.

I also echo the sentiment of the Honda/Toyota "power" argument being ridiculous. I raced (and slaughtered) a Maxima with my '87 GT. His buddies were all going on about how the car must be well over 300HP and I looked at them all, with a straight face and told them it was 225. The guy looked like he was going to throw up. Area under the curve is highly underrated........


LOL. That's funny, the typical import argument.

Ford's 302 always outperformed GM's small V8s with the rare exception of the high revving 5.0 in the 60s. Even then, I'm not quite sure of the specs. But I guess you could compare the Boss 302 to it and GM loses again.

To the rest of this thread, many weird things went on in the 80s. I have an unbelievable stock of turbo 3.8L cranks. Got them for $20 back in the junkyard and they go for $500 now. In '86 and '87 GM had an overstock of the turbo parts and everything went FWD with a smaller flywheel bolt pattern in '88 so if you found an '86-'87 3.8L in any RWD car there was a 33% chance that you were getting a turbo crank and all had the good "109" block. Made for a little extra money on the side since most people didn't know this.

 

[Oldswagon]

Originally Posted By: OVERK1LL
I have never been impressed with it or the 305. Both engines were underpowered, given that the 302 was making 225HP with some neutered truck heads and an intake that resembled a straw..... In Mustang duty of course. And even those parts were an upgrade for the version fitted in the Panther cars.

The 305's miniature bore size also made genuine performance upgrades a fantasy. Since all the good heads have larger valves that won't clear.

There were a lot of very bizarre things going on during the 80's though.

Also, I think that the 307 was the first GM V8 to receive roller lifters if I remember correctly.



Yes, the high-output 305's were never really on par with the 302 HO, but they were able to squeeze 230 HP out of the last TPI 305's. The difference was that the 302 HO's could easily make way more power with aftermarket mods, compared to the 305 which was much closer to its limitations.

However, comparing the lo-po engines in the fullsize cars, the 302 wasn't really a better performer than the 305 in my opinion. When I had my '88 Grand Marquis it was definitely quicker and more powerful than the '85 Olds Delta 88 I had at the time, but it was still pretty underpowered and slow. It wasn't any faster than my old 305 powered Parisienne by an stretch; I thought they were both pretty on par performance wise. However, both my 305 and 302 cars were reliable, fuel efficient, and ran 200K with virtually no problems. Acutally, if I remember correctly, on old MSP tests, the late 80's 302 Crown Vics and 305 powered Caprices ran pretty neck and neck performance wise. However, the late 80's 350 powered Caprices (especially the TBI units) were significantly faster than the VV 351 powered Vics.

The 307 got roller lifters in 1985 which was before the small block Chevy. The 307 was last used in 1990, in GM b-body wagons and Cadillac Borughams. 1991's all used Chev engines.

 

[OVERKILL]

The 351 they fitted to the Vic was an embarrassment. It was simply and utterly a turd in every sense of the word. The worst part is, that engine has some fantastic performance potential

Swapping some (junk) Mustang E7's onto my Townie's engine with an Explorer intake and FMS Alphabet cam dropped the car's ET two entire seconds. It is still breathing through 2 1/4 exhaust and iron manifolds. Still has the stock 3.27 T-Lok and the stock converter. Never got around to putting the 3.73's or 2,500RPM stall I have here in it.

That was a real eye-opener as to how much they left on the table with that engine, and those were parts that were readily available when that engine was produced.....