: Bulking up your 307?



cmgrafmc
04-23-05, 10:22 PM
If they can get 300+ HP out of a 305, why can't someone do that with a 307? I'm not mechanically inclined and I've read through the suggestions people have given about boosting our 307's, but they all seem like band-aid solutions, no offense. We're talking a few horses here and there, it seems. Stock, the 307 might crank out 140 HP. It's not severely underpowered by any means, and yet we all probably feel a little hesitant about passing anyone on a two lane road.

So is it theoretically possible to gain another 100 HP or more from these things? If so, is it cost-prohibitive for someone disinclined to work on it him or herself? Is it really easier and cheaper to put in, say, a 405 or 455?

I talked to my mechanic about that, very briefly, and he said, "Just shut up and drive it." LOL At least he wasn't trying to get into my wallet.

Thanks


*EDIT* I was able to find some more info about this topic so a mod may delete this unless anyone finds it useful. Thanks*

Destroyer
04-24-05, 01:25 AM
The 307 is a good solid but underwhelming motor. Great for reliability but not much else. Can it crank out another 100hp? Yes I've seen it done. It would require modified earlier 350 Olds heads, more cam, compression, headers, intake, carb, ignition, etc.. not worth it when you can drop a stock small block Chevy in it or a big block B.O.P. or Caddy motor in it and get more power. Before I had my 91 Fleetwood which I put in an 87 Iroc 350, I had an 87 Brougham w/307. My biggest complaint with that car was its lack of performance. On the highway it wasn't too bad but off the line acceleration and passing performance (where I needed the power most), was lacking big time. Cadillac for some reason put crappy powertrains in their flagship cars and I just dont understand why. When I bought my 91 it had a 305, even so it was just a night and day difference performance-wise from my 87 307. With the stock 350 Iroc motor the car really woke up. Its no drag car but it really moves good for its weight, changed the whole personality of the car. Cadillac should have put Corvette motors in the Fleetwoods in the 80's with the tuned port injection and all.

Seriously, trying to mod the 307 is a waste of time. There are a variety of GM engines you can put in the Fleetwood and if you want to go faster and not spend an arm and a leg to do it, thats the way to go.

N0DIH
04-24-05, 02:18 AM
5.0L is really pretty small for such a large beast. But if you are determined....

Remember, the goal is torque, not HP. Build for a ton of torque and HP will follow.

For me, I would be scouring the boneyards for a 403 Olds and drop it in with the 307 parts. No one has to know. And it is only 185 hp, it has great torque and a large very efficient chamber with its 4.351 bore. Take advantage of it. Remember, you can't safely spin a 403 to over 5500 due to its hollow main webs in the block, which all 307's have too.

Any mod that works on a 307 works on a 330, 350 or 403 Olds also.

Name of the game is airflow, the more air and fuel you get into the engine per revolution will always gain you more power.

Cam is pathetic on the 307. It is made for emissions. Shoot for around .450 lift and 194/204 duration max. 204/214 I have done in a 350, the bottom end is much soggier than the factory cam. Larger engines can tolerate more duration than sammer engines. Moneydello has a lot of cams for Olds. Prices are just a bit steep.

Get some 1981-84 5A heads and intake (aluminum). They flow much better than the 85-up 7A heads, and 7A head intakes don't match antything ver a 283 Chevy. Fill in the center exhaust port divider to fully isolate the two center cyls. Headers are helpful, but not mandatory. Custom dual exhaust is well worth it. You can make the 2 pipes run down one side of the car without the cat converter.

Tweak Q-Jet.

cmgrafmc
04-24-05, 03:37 AM
Hm. Food for thought. I'd toyed with the idea of a 403 or 455 BOP since it'd mate up with my tranny and save me some money, at least until the tranny gives out. I'm still a ways away from doing anything, though. I'm a little disappointed with it right now: I just got back from picking up some family from the airport and BOY did it suck at times. I mean, I could do 65 when I was alone, but adding 4 other people and luggage...I had to floor it to stay at 60. And I'm STILL only getting 9 MPG (See thread regarding "Car Toys" and "ECM" if you need back story). I'd rather have the extra power even if I only get 17 on the highway...better than what I've got now!

Thanks for all the info, I'll mull it over.

N0DIH
04-24-05, 10:41 AM
455 is more fun, but heavier and you will need to upgrade front springs too. The 403 is nice because it will look 100% stock to 99% of the people you find. Only the few who know Olds engines will be the wiser, and even those will have to be looking HARD to find it. I did my 350 in my Cutlass that way. It was as stock looking as a 307 Olds ever was.

9 mpg with luggage? Seems like something else may be up. My 307 wasn't a slouch, but it was in a 3200-3300 lb Cutlass too. My first swap on your car would be rear axle. Get some gears first. A dirt cheap swap is snag a rear end from a HT4100 powered D body, those are 3.42's on a 7.5" ring gear. Do not buy into what everyone preaches that they are weak and won't survive. They have not driven one, not abused one. I have, and I have seen my friend running a built up 400 Pontiac to over 170 mph many times with one (2.29 gears!) and numerous 1/4 mile passes.

As long as you aren't putting slicks on it and driving HARD with a 7000# trailer on you are fine for daily driving. All HT4100's RWD cars came with 3.42's and the high altitude cars came with 3.73's.

Once you have that in place, go for a 350 or 403 Olds build up. The 350 will virtually do nothing for fuel economy, the 403 will hurt it some. The 455 definately will. A 1976 Olds 98 Regency with a 455 and 2.41 gears was EPA rated at 12 city and 18 highway. So with a 455, THM200 4R and 3.42 gears you can expect better than that if built reasonably. No big cams, build it for torque, plan on rpm to stay below 5500, and look for torque peak to center around 2500. This will get you low 20's on the highway with the above gears. Keep the computer, it will be fine with it.

ferrisworld
04-24-05, 03:28 PM
This is slightly off topic, but like, I always think about it like this. The almost top of the line Mercedes S class is the 500, which means that it has the 5 liter V8. The S class if I'm not mistaking actually has an almost identical wheel base to the D bodies, and weighs the same if not more, so if 5 liters can move it along just fine, they should be plenty for the brougham, even if you have to build it up some to make it fine. Then again you can get an S600 or even an S65 with V12s.

90Brougham350
04-24-05, 03:44 PM
How many miles do you have? Your cat might be coming plugged up, decreasing your performance. My opinion, save a couple hundred bucks, and grab the drivetrain and computer from a 90-92 Brougham at a local yard. The TBI 350 is a bit of a torque monster, it peaks at just below 2000 rpm at over 300 ft. lbs, it's mated to the stronger 700-R4, and BIG PLUS, has the 8.5 inch 10 bolt rear end.

Brian

pimpin88
04-24-05, 03:46 PM
9mpg on the highway!! i get 11mpg in the city and that is bad. but my highway is an acceptable 22mpg and i still have some tuning to do

N0DIH
04-25-05, 12:17 AM
This is slightly off topic, but like, I always think about it like this. The almost top of the line Mercedes S class is the 500, which means that it has the 5 liter V8. The S class if I'm not mistaking actually has an almost identical wheel base to the D bodies, and weighs the same if not more, so if 5 liters can move it along just fine, they should be plenty for the brougham, even if you have to build it up some to make it fine. Then again you can get an S600 or even an S65 with V12s.

I have personally driven 2000 S500 s/n around 328. It was a prototype made in Oct 1998. It did 60 to 125 in 14 seconds flat. It has a 5 speed automatic. It starts in second gear in "normal" driving. It was a whole lotta fun to drive!

HP is a function of airflow and velocity. Basically the combination of those that is volumetric efficiency. If our 307's or LT1's are only making 80% VE, and the S500 is making 95% VE. the 5L S500 is making a ton more hp per CID than a 5L Olds.

So if we can figure out how to get more air and fuel inside the engine revolution, the more HP we can put to the ground.

and with GM putting lethargic gearing in the cars like 2.56 or worse, it is no wonder our cars are dogs in comparisson. Those S500's have 3.73 or higher rear end ratio, with killer transmission ratios. Basically MB put huge $$ into the design, GM put virtually nothing into it.

cmgrafmc
04-25-05, 04:10 AM
I'm getting 9 MPG because it's operating at full rich. It was running that while the CE light was on but even now that the ECM was connected (remember, it seems to have disconnected completely) it's still getting 9 MPG, so I assume it's still at full rich. I'm calling my mechanic tomorrow to let him know; I'm sure he'll look at it for free. I mean, I didn't pay him a couple hundred bucks just to turn off the CE light! =P As for an engine swap, well, the 403 sounds appealing. I'll just have to wait a while untile I can afford both it AND a transmission. =( A few years away, I bet. Heck, I might not still have the car by then. Heh. OH, and to answer the question, I have about 74,000 miles on it.

90Brougham350
04-25-05, 08:24 AM
I have personally driven 2000 S500 s/n around 328. It was a prototype made in Oct 1998. It did 60 to 125 in 14 seconds flat. It has a 5 speed automatic. It starts in second gear in "normal" driving. It was a whole lotta fun to drive!

HP is a function of airflow and velocity. Basically the combination of those that is volumetric efficiency. If our 307's or LT1's are only making 80% VE, and the S500 is making 95% VE. the 5L S500 is making a ton more hp per CID than a 5L Olds.

So if we can figure out how to get more air and fuel inside the engine revolution, the more HP we can put to the ground.

and with GM putting lethargic gearing in the cars like 2.56 or worse, it is no wonder our cars are dogs in comparisson. Those S500's have 3.73 or higher rear end ratio, with killer transmission ratios. Basically MB put huge $$ into the design, GM put virtually nothing into it.


Engines don't make horsepower. They make torque by converting fuel into usuable torque. Power is torque multiplied by engine speed to produce a measurement of the engine's ability to do work over a given period of time. To get more inside the combustion chamber of a 307, however, would also begin to sacrafice the fuel efficiency that small V8s have. The best thing to do with a 305 or 307 or 283 is to keep them running well, and enjoy the great gas mileage. No matter what you do to the engine, unless you change the bore and the stroke, you're still only at 307 cubic inches, and the easiest and most effective way to achieve torque is through displacement. This means either chaning the crank or boring the cylinder walls, and by this point, simply swapping engines becomes about as much trouble. Tune your 307 well, and enjoy good gas mileage.

Brian

N0DIH
04-25-05, 12:43 PM
I have been wanting to have enough $$ to do some serious fuel economy experiments. But that is tough.

I understand that HP is a function of torque over time, I just wasn't trying to get too deep. I leave that to my friend with the phyics background. :)

Maybe time to start a fuel economy theory thread.....