Fletchmo72

So here's the thing, I'm planning on rebuilding my '72 350 to get more power. I know what I want the car to feel like, be able to do, but it's hard to know what HP I'm aiming for. It has a TH350, 3.23 rear end with posi. The carb has been rebuilt and is tuned as well as possible. Timing curve is correct. No other power-robbing issues that I know of, such as manifold or head leaks.

Here's an example: If I punch it from a dead stop it will not chirp the tires (they are 60's with good tread). I want to be able to burn those tires on occasion if I choose. Even from a 10 to 15 mph roll, I want enough power to spin those tires a bit if I stomp on it.

This is what I'm looking for. Any thoughts/opinions welcome.

redoldsman

Maybe you are asking the wrong question. Maybe you should be asking "how much torque is enough". You might want to start thinking 455.

Fletchmo72

Yes that too. I have thought about a 455, but I'd like to keep the original 350 if possible.

47 Convertible

[QUOTE=Fletchmo72;1043594]So here's the thing, I'm planning on rebuilding my '72 350 to get more power. I know what I want the car to feel like, be able to do, but it's hard to know what HP I'm aiming for....

Here's an example: If I punch it from a dead stop it will not chirp the tires (they are 60's with good tread). I want to be able to burn those tires on occasion if I choose. Even from a 10 to 15 mph roll, I want enough power to spin those tires a bit if I stomp on it.
__________________________________________________ ___

I'm not an expert by any stretch of the imagination but I do know you gotta build the whole package, not just the engine, to be able to get maximum performance out the HP and Torque.

One key is the torque converter which should have a "stall speed" of about the same rpm as the rpm at which the engine makes maximum torque. If you make max torque at 3,500 rpm then the stall speed of your torque converter should be there too. Having a stall speed like a stock torque converter, say 1500 rpm when your engine maxes torque of 3500 means you won't launch with spinning tires with your 350 or even with a 455 unless they are built to the far edge of what is streetable and enjoyable to drive.

Another key is the rear end ratio. 3.23 doesn't seem to me (again, not an expert here) to be tailored to getting the spinning tires at start or even rolling along. I'd think a ratio in the high 3s or even 4.10 would help a lot to take advantage of engine performance off the line.

While you're at it better think about beefing up the transmission that is going to have to absorb a sudden, higher torque load to get those good launches that spin tires and to do the tire spinning from low mph.

Double whatever you put into the engine in build cost to bring the rest of the drive train up to the same performance level. Otherwise I think you will be disappointed.

There are several engine and drive train experts on this forum who haven't chimed in. If and when they do please pay close attention.
Jerry

joe_padavano

Performance comes from the entire package, not just the engine. How much does the car weigh? What rear gears and tire diameter? What exhaust? What trans?

3.23 gears and the 2.52 first gear in a TH350 are limiting factors also.

Koda

Torque, not HP, like said above. A Cutlass was not a muscle car in normal, stock, form. Do you know how to power brake? That is how you spin out from a light, not just slamming the pedal down. You are going to be hard pressed to do anything within normal budget to a 350 to get wild ***, floor it and it breaks loose, performance. Plus, I'm not sure you want that as it's really not safe or usable without better tires and wheels.

Best thing for more power is bigger engine. There's a reason 442s have big blocks. If you want to keep the original 350, put it on an engine dolly in the corner of the garage, and, if you ever have to sell, put it back in and sell the car as stock, and the BBO torque monster by itself. This way, you can also build a mammoth beast while you are driving you car.

Something else you can consider is changing the rear end and the transmission. I LIKE highway gears. I find I am happy with 3.08s and I do not require rubber-raping madness from a stoplight. However, low gears, like 3.73s, are the key for takeoffs, and the best solution is an overdrive transmission with low geared rear end. This way, you have ballsy takeoff, but you are not turning 4000 rpm on the interstate.

Joe is a powertrain expert, and an expert in everything else Olds. I'm just a mechanical engineer, but maybe my stuff can help too.

budg

My 72 cutlass has a 350 with 3.42 gears and I can punch it at a dead stop and smoke the tires no problem . I am running 235 /60/15s all the way around. It should be possible with a 350 .

oldcutlass

What is your timing setup, I used to spin 225/70/14 tires without power braking on a tired old 330HP and a Jetaway with 3:08 gears.

Fletchmo72

Wow, that's interesting. You have a slightly lower gear, but still seems like my car should be doing better. Do you have posi in that?

Fletchmo72

Did you mean 330 CI? I don't know how to describe my timing set-up, exactly. Only that I tried to follow the the guidelines I've read on this forum. I can tell you I'm running full manifold adjustable vac advance.

budg

Yep , posi and a shift kit, other than that all I know is what I have been told. Apparently bored .030 over with a mild cam. Edelbrock intake and carb, HEI and headers with a nice exhaust system. The first thing is getting your fuel and ignition system dialed in to see where you are presently.

What carb and exhaust setup do you have? I formerly had a stock 72 with a 2bbl and stock exhaust , I couldnt squeal the tires on a wet fall day with stock 14 inch tires.

70cutty

Build a 455. Biggest mistake I made was dumping money into 350. Full rebuild no corners cut, bigger valves, ported heads, custom cam and bunch of other goodies and I was not satisfied with the outcome. May car has 3.42 gears and 295/50/15 tire, while I was able to break loose from dead stop, couldn't spin them when rolling.
Now with 350 on the stand and 463 under the hood, if I stomp on it at 35 it will easily break loose.
The cost is about the same whether you build 350 or 455, even a mild BBO will be much more fun than 350. JMO.

Fun71

Just for information, back in the early 80s my 1970 Cutlass Supreme in factory form (350-4bbl and 2.56 gears) would smoke both rear 225-70-15 tires across an intersection. Proper tuning helps a lot.

wr1970

Eh i don't agree with some of these opinions.I think a stroker crank, heads will need to reworked to match combo proper cam good pistons and rods gear change to 342 or 355 posi 2800 stall headers get rid of the point dist if you have one go hei. Make sure you have a perform or better intake. Then i think you can get what you want. What i do agree with is a 455 can get you there easy. Cost wise not cheap but Copper will tell you how to do a 350 on the cheap side. He has done it.JMO

Fletchmo72

I have almost the same setup as you describe. But a rebuilt Quadrajet carb, 1-5/8" tube headers into 2-1/2" dual exhaust.

Fletchmo72

I'm starting to think that's pretty good advice. I know a guy with a rebuilt 455, wants only $1400 for it, and he would probably take less.

Olds 455

Yeah...I kinda thought you'd get all sorts of replies to your post. You should be able to smoke the rear tires from a dead stop with your current setup. Maybe not 15 mph, though. Makes me think something is not exactly right about your current engine. You would need about 300hp/350lb-ft from a 350 to do what you want. A 455 is such an easy swap and a stock unit would light up the tires like you want with no problem.
I have an original 455 with a mild cam and 3.08 posi rear that lights up both tires at 30mph in first.

Fletchmo72

That's impressive. I know the compression ratio was higher on the 70, giving it more horsepower.

Fletchmo72

Thanks for that info and example. Yeah, your comment and others is making me think my rig is not running at optimum. Especially when its only got 12k miles on the rebuild by the P.O. Although I think stock pistons were used.

Fletchmo72

I appreciate all these responses. Any recommendations on what size jets to use in the quadrajet? I do have a book on the subject but I'm still not sure what to use or try.

Fletchmo72

I checked out your pics--that is a beautiful motor! What kind of $$ (ballpark) to build something like that?

floor_it

i take it you're not refering to this stuff?
an essential for a bacon sandwich.
the answer to your question would be: "lots"

Fletchmo72

Gotta get me some!!

VC455

Fletch...

Have you checked the torque converter? If it is not working correctly, you would have those same symptoms.

You should be able to build about 2000 to 2500 rpm with your foot on both the accelerator and brake. Don't do this for more than a second as it creates massive heat in the trans.

Gary

Fletchmo72

Fletchmo72

First, love that wagon! No I haven't checked the torque converter, but I will now. Appreciate the suggestion.

Zacc

I have a nummbers matching 72 Cutlass Supreme badged as a 442. It has a 455 bored 30 over , mild cam, headers and striped out with ss2 wheels. It is a real headturner. I am happy as a clam with this car.screw the chevelles and Goats that you always see. At show there arent many 72 Cutlasses. Put a 455 in it and have more fun . But BE HAPPY WITH WHAT YOU HAVE!

Fun71

Less than 2 points more compression and everything else essentially the same is not going to make a bunch more horsepower.

Another FYI, back in high school a friend had a 71 Supreme 350-4bbl with a 2.56 rear. Our cars ran dead even off the line and I started to pull him slightly at the top of first gear, so those "paper" horsepower numbers showing the '70 with 310 and the '71 with 260 were essentially BS.

Fletchmo72

But '72s were only 180 HP!

Fletchmo72

Thanks. I'm leaning that way

Fletchmo72

1500 on the stall speed, that's all. Elsewhere I've been reading how high stalls make the car feel sluggish around town with light acceleration, as opposed to flooring it. So I'm confused: with a low stall like I have, shouldn't I be getting all the torque right away?

Fletchmo72

Here's my timing set up: (HEI distributor with adjustable vac advance)
14 initial
24 mech adv. (soft springs on the weights, advance kicks in right away)
15 vac adv. off manifold vacuum
53 All in

Fun71

That was the rating for the single exhaust version. 1972 was the only year that Olds provided power ratings separated by exhaust configurations. Apparently, the 68-71 were all dual exhaust setups, and from my experience, had about the same power as the 71-72 350-4bbl engines. We know that the GROSS ratings were wildly inaccurate (as in over rated) and the NET ratings were more real-world numbers.

1970
350-4bbl = 310 hp (GROSS)

1971
350-4bbl = 260 hp (GROSS), 200 hp (NET)

1972
350-4bbl
single exhaust = 180 hp (NET)
dual exhaust = 200 hp (NET)

350-2bbl
single exhaust = 160 hp (NET)
dual exhaust = 175 hp (NET)

Note that the above engines used the same camshafts and the differences were a bit higher compression in 1970 and minor carb tuning differences for each year. That can't make 50 more horsepower in the 70 engine vs the 71 engine's GROSS ratings.