305-Any easy mods?

[01ps]

I just picked up an 85 Olds Cutlass Supreme. Pretty good shape, runs well, but seeing the 140hp power rating in the manual makes me laugh. My other car, a Volvo 240 with a 2.3 makes about 130 using half the cylinders!

Anyway, I figure there must be some power hidden in there that could be gotten fairly easily (and cheaply)? Mine is a factory 305, not the usual 307, becuase it is Canadian. This is acutally the first domestic I have ever owned, so I am kind of stumped about where to start. The only thing I have done so far is change to plugs and remove the cat and muffler and replace it with a glasspack. I am going to replace the wires and cap soon.

Any suggestions? Pollution crap that can be removed? Any small block forums that may be able to help?

[djmoore85]

Originally Posted by 01ps

I just picked up an 85 Olds Cutlass Supreme. Pretty good shape, runs well, but seeing the 140hp power rating in the manual makes me laugh. My other car, a Volvo 240 with a 2.3 makes about 130 using half the cylinders!

Anyway, I figure there must be some power hidden in there that could be gotten fairly easily (and cheaply)? Mine is a factory 305, not the usual 307, becuase it is Canadian. This is acutally the first domestic I have ever owned, so I am kind of stumped about where to start. The only thing I have done so far is change to plugs and remove the cat and muffler and replace it with a glasspack. I am going to replace the wires and cap soon.

Any suggestions? Pollution crap that can be removed? Any small block forums that may be able to help?

If you want to take the time, it's not an easy mod, but remove engine, rebuild it/bore it out, or just change the cam profile. Also, I had a truck with the 305, and replaced the 2bbl with a 4bbl, put splitfire plugs, and opened the exhaust. Not a whole lot I ran into that that truck wouldn't pull or do. If you ever want to bolt a supercharger on top, you'll have to rebuild for a blower anyhow, so on those oldies anything you want to do worthwhile, strip the engine and build from scratch. Headers and full exhaust job would do some help too.

[curtis73]

There are things that can be done, but unfortunately the three main things holding you back are all internal. The cam, head flow, and compression are all pathetic. The 305's main design restriction is its tiny bore which limits valve size and therefore breathing. Don't ever expect to make lots of hp, but building a nice street torque engine should be easy.

I might suggest finding some factory 305 heads, mill them for more compression, do a 3-angle valve job, and do some mild porting at home and then slap them on. That should get you up near 175 hp. A cam change will put you over 200 easily.

But here's the rub, and this is why you ALWAYS get the 350 suggestion... in the end, you'll have a 250-hp 305 that costs waaay more than a 300-hp 350 in its place. You'll be purchasing heads, cam, lifters, valve springs, plus all the labor involved with valve jobs and porting, plus gaskets, carb tuning... whew. Or for $800 you can get a 275-hp 350 long block and take an afternoon putting it in.

The 305 is 87% the displacement of a 350, but it doesn't have 87% as much power potential due to those small bores and lack of any really good heads. There is plenty of potential in them, but you'll always be $$ ahead to swap in a 350. And, since they are 100% externally identical, its a bolt in that can't fail. Intakes, carbs, emissions equipment, trannys, motor mounts, everything.

Oh, and by the way, about your smog question...

You can remove the air injection pump. That will get rid of about 7 lbs of junk but won't affect power (other than the .5 hp it took to run the pump) You should however keep the charcoal canister and EGR. Neither one are affecting power on that engine, and they do wonders for the environment... really. If you took the EGR off, you'd end up using more fuel, having to recurve the ignition and fuel, and you wouldn't make any more power. Honest. The tests have been done. If I were rebuilding the whole thing with an Edelbrock intake, I might delete it since I would be doing a custom ignition and fuel curve anyway

[MagicRat]

Originally Posted by curtis73

You can remove the air injection pump. That will get rid of about 7 lbs of junk but won't affect power (other than the .5 hp it took to run the pump) You should however keep the charcoal canister and EGR. Neither one are affecting power on that engine, and they do wonders for the environment... really. If you took the EGR off, you'd end up using more fuel, having to recurve the ignition and fuel, and you wouldn't make any more power.

I may as well weigh in here.

Canadian-spec cars of this vintage almost always came with either an air injection pump OR a catalytic converter, but never both.
Sometimes, American spec cars (with both systems) were imported, depending the the Cutlass demand and supply back in '85.

Take a look for the air pump, but do not be surprised if its not there.

As stated above, the 305 is not worth rebuilding, when a 350 will fit.

However, you can perk things up a lot with some bolt-on mods. It will not produce miracle power, but will improve the power enough that the expense of a new 350 may not be worthwhile.

Best of all, bolt-on mods, such as headers, intake manifolds, carbs and decent ignition systems can be used on almost any pre-1988 350 engine. So if you do decide to upgrade to a 350 in the future, you can transfer these parts to the new engine.

Go for headers (they are available for a small block Chevy 305 in that chassis). Use header tubes that are a bit on the small side, for diameter, if possible. They will work slightly better for a mild engine.

Get a custom made exhaust for it. True dual exhausts would be nice, but not necessary and may be a bit difficult because of the single-hump transmission crossmember. The factory Cutlass 442 set up was a fat single pipe to a transverse muffler located behind the rear axle with dual outlets. Such a set up will be fine for a 305 or mild 350.

BTW keep the muffler reasonably quiet. In some parts of Canada, nothing tells the cops that you cut the catalytic converter off faster than a noisy glass pack muffler. (Tickets for tampering with the emissions controls to follow)

You should have the stock 4 barrel Quadra-jet carb already. If not, get a 4 barrel intake and carb for this, . The cast iron factory one is okay, and really cheap, used, but an aftermarket Edelbrock or Holley is better. Go for a dual-plane design.
There are lots of used ones around, cheap, but just be careful about their condition.

You will find extensive debates about carbs, too.
Look here for some pros and cons on various designs, including some stunningly insightful comments by me:
http://www.automotiveforums.com/vbul...d.php?t=331440

There are lots of other fine tuning things you can do. You can find lots of power in the details. BTW unlike American spec cars, there is no computer carb or distributor controls, so correct tuning is critical.

Given this is a Canadian car, our winters and rust will play havoc with certain systems. Locating and correcting such problems will help power output.

1. Locate a tuning book on whichever carb design you want to use. (Even the stock Quadra-Jet carb, if applicable) HP Books has some excellent, informative guides to tuning carbs. Depending on where you live, some of the local performance parts shops or Canadian Tire may carry them.

2. If you have the stock 4bbl carb, and you plan to keep it, check the secondary valves' operation. There is a little linkage that prevents the secondaries from opening until the choke is fully open. These linkages often get sticky and prevent the secondaries from opening at all, which redues power. This linkage is easy to free-up or bypass.

3. Make sure the distributor works properly, including the advance mechanism. A worn mechanical advance mechanism (spring-loaded weights) and a seized vacuum advance system will kill power.

4. Use a timing light, make sure the advance system works properly, Try advancing the initial ignition timing at idle approx 2 degrees more than stock and see if that helps power. If the engine pings or is difficult to start, back it off a degree or so.

5. Speaking of vacuum advance, this car will have a thermal vacuum switch on the intake manifold. It allows the distributor advance to use manifold vacuum advance when the coolant is below approx 120 deg. F and ported vacuum when above.
I can almost guarentee you that it is seized and giving you manifold vacuum advance all the time, which reduces power. You can bypass the switch in about 2 minutes and run ported vacuum all the time.

6. If you do keep the stock exhaust manifolds, you will find a thermal-operated heat riser valve on the passenger-side. This valve will close when the engine is cold to force more exhaust through the intake manifold exhaust-heat passage. These little darlings love to get rusted shut (in Canada!) and kill power. Either wire yours open or remove it from the manifold

7. Replace the stock air cleaner. It's restrictive, with a small snorkel. Often, the vacuum operated warm air diverter valve is stuck/rusted on, forcing the engine to use warm air off the exhaust manifold ducting all the time, which reduces power.

[mazdatech177]

oh god dont do it man... its just not worth it

[01ps]

Thanks all for the info, especially Magicrat. Very detailed, and exactly what I was looking for. I was not planning on racing the thing, but with 305 inches of displacement, I figure there must be some wasted power there somewhere. I disabled the warm air divertor already, and I am sure I see some improvement, since it was still closed after 15 minutes of driving. The heatriser was next on the list. I will play arounds with the timing a bit too, and check the thremal avance switch too.

I got a Haynes manual for it today and have been reading up a bit. The manual only shows the US 307, but I am sure many of the basics are similar. Like I say, I have never owned an american car, let alone an old one, so this is kinda new to me.

[MagicRat]

Virtually all of the suggestions I made have been used on my full size GMC van with a 305, same vintage as yours, with considerable success.

If you come across a Chevrolet Haynes manual that covers rear wheel drive sedans, especially the Monte Carlo, try that for engine info on the 305 .

The Oldsmobile 307 differs in tuning specs and details. Although the 307 and 305 are very similar in basic design, virtually no parts interchange except the carburetor.

Fortunately these cars are very straightforward, and relatively simple to understand and repair.

Good luck!

[01ps]

Originally Posted by MagicRat

Virtually all of the suggestions I made have been used on my full size GMC van with a 305, same vintage as yours, with considerable success.

If you come across a Chevrolet Haynes manual that covers rear wheel drive sedans, especially the Monte Carlo, try that for engine info on the 305 .

The Oldsmobile 307 differs in tuning specs and details. Although the 307 and 305 are very similar in basic design, virtually no parts interchange except the carburetor.

Fortunately these cars are very straightforward, and relatively simple to understand and repair.

Good luck!

Thanks again. I thought about getting a Monte manual for that reason.

[jveik]

lol if the cars any good, just build a streetable 350 up to about 400 horses lol, if its a rust bucket, dont do anything at all its not worth it lol