13th Dec 2010, 11:10

I couldn't agree more. People don't seem to understand these car were designed with materials set up to be run with the emissions and computer systems. Most people who try it may initially gain a measly amount of horsepower. Eventually after not having enough back-pressure from a catalytic converter, and the other systems the engine was built to run on, the valves will overheat and warp, and the engine will start misfiring, dieseling and overheating, turning the car into an even more gutless pig.

Leave the factory engine alone. If you want power, rip out the whole works and get a big block from the late 1960's to early 1970's, and do it right.

On the other hand, I actually installed the complete Computer Command Control (CCC) System from a 1982 Buick Electra 307 V8 onto a 1978 Oldsmobile 98 Regency with the factory Oldsmobile 350 V8. I have messed with the timing, spark and compression just a fraction to get a little more HP, but not enough make the computer panic. Everything was installed, even all the vacuum lines and A.I.R tubes. With 2.56 gears in the rear and a rebuilt, beefed up 4-speed automatic TH200-R4, I am averaging close to 24.5 MPG on long highway trips. I installed a tach and my car is barely turning 1900 RPM's at 75 MPH. No toggle switches or cheater switches. It was pretty time-consuming and tedious to do, but well worth it.

14th Dec 2010, 03:51

For those having difficulties with the late 80s 307, particularly if you have one in a Cadillac Brougham (which is becoming somewhat collectible), or of course a Cutlass, which is already collectible, I think it would be well worth just getting a rebuilt 307 from the 1981-1984 series and installing it. Anyone have any idea how much that would cost? I seem to remember having Chevy small blocks rebuilt and installed in Caprices years ago, for maybe $700-800 or so.

16th Dec 2010, 19:12

I would say forget the 5.0 Liter V8's of this era altogether. The Chevy 305 and Oldsmobile 307 are reliable and indestructible, but you will never get decent performance out of them. The 1980-1984 307 is really not much of an improvement over the 1985-1990. The fuel injected 305 Chevy V8 from I believe 1986 on up is probably the best of the bunch. But even so, you're still not matching the standard power of GM's old titanic 350 motors.

If you go through the trouble of ripping out the motor, you are better off just going with a good strong Chevy or Oldsmobile 350 V8. The old Cadillac 425, 472 and 500 are nice, but parts are very hard to come by. I also prefer to get more than 10 MPG City and 18 MPG on the highway. No way you're going to do that with a Cadillac Big Block. With a car this big, there truly is "No Re-placement for Dis-placement."

9th Jan 2013, 16:11

Can you give a step by step of how you installed a tachomter? I would like one in my 87 Cadillac.

28th Feb 2013, 13:53

You know what, I may sound like I'm on something for saying this, but I actually like the Chevy 305 and the Olds 307 V8 engines. Yes, they're not that fast, but they are sturdy and reliable, and they deliver decent fuel economy in the larger cars. I'll give some performance up for sheer reliability. And I don't know why, but these engines have a sort of charm about them for me.

14th Jun 2013, 15:17

I agree. I'm quite fond of the 307, as it was extremely reliable and durable in all three early 80s Delta 88s I had through the years. I've had many 305s in Chevy Caprices as well, and they were fine, but for some reason - I think torquey-ness and smoothness - I prefer the Oldsmobile 307.

16th Aug 2014, 11:22

I have a 472 Cad engine. Since the Brougham was basically the same car from 77-87, wouldn't the mounting holes for these engines (the 472 and 500) be there in the frame?

19th Aug 2014, 21:55

The 472 and 500 c.i.d. engines were used in the full-size 71-76 models. The largest engine offered in the 77-92 version I believe was a 425.

12th Oct 2020, 21:54

I had several Olds 307 V-8s in large RWD 1980s Buick wagons. My experiences with them ranged from disappointing to disgusting: half of them self-destructed from trying to pull too much weight.

What I would suggest for those with Olds 307 V-8s... is to swap in an Olds 403 V-8 from the late 1970s: same block, just 94 more cubic inches.

I have a Chevy 305 V-8 in my '89 Caprice. It's far more responsive... but even these are lacking a bit in displacement... for the freeway. It needs a Chevy 350.

12th Oct 2020, 21:56

An Olds 403 CID V-8 would be a far better choice than another 307: same block but 94 more cubic inches!

12th Oct 2020, 21:57

The Cad 425 is a great engine... but only used from '77 through '79.

13th Oct 2020, 21:19

Or consider an Olds 350. The 403 is also a good idea and engine, but was only made for 3 years. May not be easy to find one.

Sorry to hear of your bad luck with the 307. We had an Electra and a LeSabre with that V8; both were strong reliable runners even though you won't win races with them. I've seen a few top out at 300k miles.

14th Oct 2020, 04:27

What would you consider “too much weight”? I used to haul a small boat in high school with one of these Buick wagons and never had any issues.

15th Oct 2020, 16:07

Of course it's more responsive; in 1989 the 305 used fuel injection, giving the engine more HP.

Why this was never done to the 307 remains a mystery. On the other hand, when the 305 was carburated, the HP ratings were maybe 10-15 higher than the 307. Not much to brag about there. If you ask me, both engines were were good applications for the time. I like the 307 better as far as smoothness and durability.