Brad Chapin

As a new guy on the block I’ll apologize now for asking questions that I’m sure have been discussed a thousand times already- I just haven’t had a chance to sift through hundreds of older posts! Ha

So as a new guy with a new project- any recommendations for cost effective ways to get a little more pep out of the 350 in my 72 cutlass supreme convertible?

It runs smooth and cruises well- the big boat just doesn’t have much get up n go!

Any recommendations of where to start, what to do, what NOT to waste money on, etc. would be greatly appreciated! I’m an open book with blank pages. Just learning about the car and what it has to offer!
Thank you in advance for your time!

boese1978

First couple things you will be asked is :
A- Budget?
B- How much more "pop" do you want?
C- Post pictures

You could go from a stock rebuild to a SB stroker with an Aluminum top end if you wanted.

Welcome!!

Brad Chapin

I guess whatever the best bang for the buck would be!
Not really looking to throw a huge amount at the engine right now- more or less just getting a game plan together for things to budget for and do over time!
Pocketbook requires planning and saving 😜

I’d like enough “pop” to have a little bit of the American muscle feel... certainly not looking to take the front wheels off the pavement or burn the rear wheels up in an evening.... unless I really wanted to 😉

Brad Chapin

boese1978

Swapping rear gears and headers is not too much $$$$$, big change right off the bat.

Fun71

First of all, what do you currently have? From the pics in your other thread I saw single exhaust. According to the factory specs, dual exhaust is good for 15-20 HP. Then if it's a 2bbl carb, swapping to 4bbl is good for more power.

1972 350 factory specs:

Carb..........Exhaust..........HP @ RPM..........FT-LBS @ RPM
2-bbl..........single.............160 @ 4000..........275 @ 2400
4-bbl..........single.............180 @ 4000...... ...275 @ 2800

2-bbl.........dual................175 @ 4000...........295 @ 2600
4-bbl.........dual................200 @ 4400...........300 @ 3200


Keep in mind that the 71-72 engines had pathetically low compression ratio so if you want to do a cam swap you have to remain fairly conservative to prevent overcamming the engine and killing low RPM power.
As said above, one of the best bang-for-the-buck upgrades is swapping the rear gears. Most of these cars came with 2.56 rear gears so swapping to something in the 3.xx range is like installing an engine with a LOT more power.

Brad Chapin

Thank you!! That’s all great information!
You're correct- stock everything currently- so stock exhaust manifolds, single exhaust and a stock quadrajet (not sure if that’s how it’s spelt) carb.

If i was to switch out the gears for a 3.xx rear end would it also be recommended to convert to a limited slip diff at the same time? I was just flipping through my OPGI catalog and saw the limited slip/posi rear ends- not sure how significant the cost difference is.

Brad Chapin

As I’m looking..... does anyone know what the stock “spline” rear axel is for a 72 cutlass supreme? Looks like there are a lot of different options out there! 😬

70cutty

My advice is, switch the gears to something little more aggressive like 3.42. Don’t waste a penny on a 350, save it and put a 455 in it.
OPGI is probably the most expensive vendor out there. MOs t of the parts can be found cheaper at Summit, Jegs or rock auto. I would definitely do a posi at the same time when you replace the gears. Your 71 is a corporate rear end, just look up parts for 8.5” ten bolt rear.

Fun71

OK, so simply installing dual exhaust should give you some power gains. You can retain the factory exhaust manifolds and simply cap off the crossover port on the drivers side manifold - that is how the factory dual exhaust cars were set up.

The factory rear is an 8.5 inch 10 bolt with 28 spline axle shafts that are the bolt-in style (as opposed to the c-clip style).

I would swap to a limited slip diff along with the new gears, or if you can locate one, swap the entire rearend for one that has better gears. That is an easy job for the casual gearhead, but installing and properly setting up ring and pinion gears is quite a bit more challenging.

OLDSter Ralph

Please keep in mind your car was originally built/equipped as a nice cruising car, not a "performance" version. Do the dual exhaust, rear end gears and "anti Spin" (posi), if it doesn't have "Anti Spin" already.
If you want to go fast, start with another car. A convertible is the heaviest body style, except for the station wagon.
.......Just my two cents worth.

72442conv

Agree, gears first (remeber that your speedo will be way off if you go from 2.56 to 3.23/3.42 so you will need correct speedo driven gear), then a dual exhaust. See if you can have someone recurve the distributor, a performer type intake may make a little more power too. With the low compression a cam change would have to be very mild...

olds 307 and 403

Disagree. The 350 is a better platform to build more reliably. Especially with the lighter stronger stroker crank levels the field a lot. I suggest the headers, dual exhaust and 3.08 gears if you plan a lot of high speed driving.

70cutty

Headers, dual exhaust and 3.08 gears and it will still be a turd.
IMO for anybody that's looking for more power, cheapest way to get there is 455. I wish somebody told me that 15 years ago.
Been there done that. My 350 had 38k miles on it. Performer intake, 4 barrel carb, hooker headers, ignition, dual exhaust were the first things I've wasted money on. Sounded better but still no major difference in power. Then I decided to rebuild it with better parts, had bigger valves installed, wasted all kinds of money on porting, got a custom grind from Mark, no corners cut, and it was still a turd. My friends 5.0 was running circles around my car.

After dumping all that money into building my 350 and still getting smoked by Hondas and Mustangs (I'm sure bunch of you can relate whether you wanna admit it or not), putting a 455 was the single best thing I have done to my Cutlass. It's so much fun to drive, it's addicting. More power than tires can handle.

cutlassefi

That’s why I pushed to get the Stroker crank done for the Small Block Olds.
Granted not everyone can afford them but after dumping a bunch of money into a small block like you did originally Edin, wouldn’t it have been nice to just transfer everything to something that’ll make big block type power AND torque? I would hope it would.
Op- you’ll really need to raise the compression somehow first, that’ll open up a lot more options for you.

coppertopgmc

He did say he didn’t want to put a lot of money into it , I would change the rear end gear ratio/ convert to posi while your at it, I went to 3.73 in my 71, that might be a little steep so maybe 3.42 or mid 3.50’s and dual exhaust as for headers personally I don’t care for them, I’m going with Thornton 350jr manifolds, won’t make as much power as headers but not as big of a pain as headers in my opinion. As for going to a 455 over 350 is another matter of opinion, what’s it going to cost to buy one, I have three or four laying around but it’s taken me years to come up with them and if he does find one what’s it going to cost and will it need rebuilt, I would change the intake and maybe a mild cam and new timing set then save up for a complete rebuild later when you have the money to do so.
.

Brad Chapin

Thanks everyone!
Obviously like anything in life there’s a lot of personal preference involved! But having multiple opinions to research is great for me since I didn’t even know where to begin!
It is indeed correct that I cannot currently sink a ton of money into the car- otherwise I’d skip right to purchasing a kick *** rebuilt or new crate engine and away i’d go! For the foreseeable future it’ll be- listen, learn, research and save.
I hope to continue getting great all around answer to my future inquiries- hopefully y’all don’t get too annoyed with my endless novice questions 😜

coppercutlass

1 :Build a differential that will work now and down the road. a 3.42 as mentioned before will be a huge improvement but invest in its future. (make upgrades that make it live )

1.5: exhaust, a good tune like curving the distributor and re jetting the carb if you added headers with your exhaust work.

2 : build a trans that will work now and again down the road. Those 2 things well done wont cost more than 2 grand depending on who you use and power levels that you forsee in the future.

3 : rebuild the suspension to suit your needs.

4 : build a kick @$$ engine that will work well with all the updates that where done prior.

Everyone wants to build a fast engine but fails to realize everything around it has to work well to be at its best. You see many people boast horsepower numbers but unless you can truly make those Dyno HP numbers reflect something on the time slip on the 1/4 mile they are just a salesman's pitch . It does not take much to have a fun car that can light the tires up and put a smile on your face. Paying for an engine to make X amount of horsepower when you don't intend to use an engine to its full potential is a big waste so keep that in mind. Just my 2 cents.

droldsmorland

I don't see any mention of tuning and verifying the health of what's already there?
Verify engine health with a wet n dry compression check. Check for timing chain slack. Then optimize what's there with a good supper tuning. Install a High-quality Corvette point set, new Spiral core wires, Autolite plugs etc... then optimize the timing curve.
Clean and lube the centrifugal advance, verify the vacuum advance is ok. Give it as much timing it will handle without spark knocking. Make sure the other two timing events are dialed in. (details of this everywhere here, search me).
K&N air filter. Definitely, have the carb rebuilt (this alone will be a noticeable improvement if done properly to include AVS door tuning).

You might be surprised at what the results are with simple accurate fine tuning & attention to details.

Then yes next step is a dual mandrel bent free flowing exhaust. IMO, Don't go with headers...yet. Headers best complement a cammed up, higher compression, larger CFM carbed engine. With a stock engine your doing it more for looks. Then you gotta deal with the leaks, burnt plug wires and brake distribution block relocation etc...The Factory exhaust manifolds will be fine and leak free for a stock engine.

Then start playing around with hard parts such as converter and gearing. If you need more torque then dive off the deep end with engine upgrade machine work, trans rebuild with shift kit, bigger carb/intake, headers etc.
If you do it in logical steps you will be much happier(and richer) versus tossing money at parts that don't match the application EX: Installing a large cam & carb before exhaust and gear improvements...which I call the horse pushing the carriage approach. It will lead to frustration and baldness and an empty wallet.

cutlassefi

Sorry but I have to disagree on some of this.

Sorry to disagree but some of this is unfounded, plain and simple.