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I have a 1972 Cutlass convertible. 350 bored 30 over. Comp cams 260h cam. 9.5-1 compression. Stock 2.73 gears. Th350 with Transgo shift kit. I was looking at the TCI Street Rodder as recommended on the Jeggs chart. I called TCI and they recommended the TCI Breakaway at 2000-2400 stall. I am now confused. Any other recommendations. Not a race car, just cruiser.
A good converter won’t feel mushy under normal driving. Just because it’s advertised as 2500, doesn’t mean the engine needs to rev to 2500 before the car moves.
I doubt you will notice much difference in the way the car drives just cruising. Stand on the throttle, the engine will rev up to its stall speed, then you will notice the converter.
I have a 10 Coan converter, it flashes to 4200, you wouldn’t notice it 95% of the time.
Let the cam and final gear dictate stall.
260* cam with a 273 Id go 1800 max.
You won't see a ton if any difference between the Rodder and Saturday Night. Only 100 RPM between them. Might as well go w/Saturday Night.
A tighter converter will give you a little better mileage, (1700 vs 2700 stall), less slip = better MPG. Not much but it will add up on a daily driver...if you care.
The stall needs to take advantage of the cam, induction, trans, and final gear.
It's common to over cam over carb and over stall due to testosterone(no offense Matt. 4200 is bigly kool! Must be fun especially trackside or to smoke the annoying Mustang at the stoplights).
Be sure to dial-in your ignition & Air Fuel curves.
Let the cam and final gear dictate stall.
260* cam with a 273 Id go 1800 max.
You won't see a ton if any difference between the Rodder and Saturday Night. Only 100 RPM between them. Might as well go w/Saturday Night.
A tighter converter will give you a little better mileage, (1700 vs 2700 stall), less slip = better MPG. Not much but it will add up on a daily driver...if you care.
The stall needs to take advantage of the cam, induction, trans, and final gear.
It's common to over cam over carb and over stall due to testosterone(no offense Matt. 4200 is bigly kool! Must be fun especially trackside or to smoke the annoying Mustang at the stoplights).
Be sure to dial-in your ignition & Air Fuel curves.
The 1.52 60ft times are definitely fun! 😁
You can see it in a data log at launch it flashes to 4200, as the car starts to move it drops to around 3700. Flash stall speed is always highest just as the input shaft of the trans begins to move. There is a bunch of science in converter design, that’s why I always suggest a custom converter if you looking for the best performance. There are thousands of different pump, stator and turbine combinations, in different diameters. The chances of a off the shelf converter being ideal for your particular build is slim. The off the shelf converters are a compromise for desired stall speed, drivability, and price.
Last edited by matt69olds; January 8th, 2021 at 06:16 AM.
A tighter converter will give you a little better mileage, (1700 vs 2700 stall), less slip = better MPG. Not much but it will add up on a daily driver...if you care.
I noted the slippage on my car with the Hughes 2500 RPM converter was around 250-300 RPM, which from what I read is the same as the factory converter. So as Matt said, a good quality higher stall converter will feel just like a factory converter during light throttle operation.
I agree, the 2000 to 2400 should be perfect. I went back to the stock 1600 stall TH350 from 2200 to 2500 stall that flashes at 2350 rpm when the 2004R was ran low on fluid. This was a 9 to 1 350 with a similar duration 214/214 cam and 2.78 gears. It went from 1/4 block burnouts to barely being able to spin the tires. The fun factor was gone.
Last edited by olds 307 and 403; January 9th, 2021 at 05:16 PM.
I have the same question for my 1972 Cutlass with a 350 and th350. When I purchased the car in 97 the owner told me that the cam was replaced but, I never got the details. To young and stupid at the time i guess. Everything else appears to be stock. There is nothing known to be wrong with my current converter but, now that I have the trans out for rebuild, it would be the perfect time to upgrade. Do I need to confirm the cam specs before I make a decision? Any other factors I should consider?
~David
Last edited by awidod; January 27th, 2021 at 08:57 AM.
How choppy is the idle? If it’s a smooth idle, something like the Hughes converter mentioned would work great. If it’s a rough idle, then a little more stall speed would be better.
Is the existing converter a stock 12 inch unit? If so, and it idled ok, then something stock or just a little looser will be good.
The idle is on the choppy side, struggles to run without stalling. Not sure if that is related to other issues though. I have not really been able to run it for any length of time. To the best of my knowledge it has the stock 12 inch converter.
It probably is stock and therefore stalls around 1600 rpm. Do you know any motor specs? What rear gears are in the car? Knowing your cam specs definitely helps a bunch. Unless you have vacuum leak or carb issues, both very possible, it sounds like a fairly aggressive cam. I say more than 2500 rpm stall, unless you have compression, cam and gearing is overkill. Plus a lower quality unit will slip at low speeds and may have slippage at highway speeds as well.
It probably is stock and therefore stalls around 1600 rpm. Do you know any motor specs? What rear gears are in the car? Knowing your cam specs definitely helps a bunch. Unless you have vacuum leak or carb issues, both very possible, it sounds like a fairly aggressive cam. I say more than 2500 rpm stall, unless you have compression, cam and gearing is overkill. Plus a lower quality unit will slip at low speeds and may have slippage at highway speeds as well.
Right now I don't know enough....lol. Other than the cam that the previous owner said was changed. It has the 350 with the th350 trans. I was working on identifying the rear end but, I cannot find anything stamped in the housing. As for the vacuum leaks and carb issues, I probably have both. I did the tire 1 rotation trick and it rotated 2 3/4 so, if that actually work then it would be 2.73. I will change the rear end fluid and count the teeth to confirm, just not there yet.
What is your idle set at? Yeah, a 2.73 sounds about right.
I believe I am about 900 RPM. Here is another question since I don't know what cam is currently installed. If I assume that everything is stock, including the cam, would a 2000-2400 be to much for a stock 350? I am thinking that with 900 RPM +1000 would put me in the low range of a 2000-2400 converter. I just don't want to go in the wrong direction but, If I can get a little more knowing that the cam has been replaced. Is that a valid way to look at it?
A good quality torque converter should work fine in that range. Basically it should act stock at part throttle around town and have similar slippage to stock at highway speeds. The difference is when you floor it, it should flash to 2000 rpm plus and launch the car. It may have been a stock replacement cam or possibly the generic 204/214 cam. I know talking to Hughes, their stall rating is rated at 500 hp. So on a mild engine, their 2500 converter will stall less. Guys on here have had good luck with their converters. Also make sure you buy a converter with lugs vs bolt and nuts. Jegs brand is a B+M converter rated at 2300 stall with lugs for just over $100.
A good quality torque converter should work fine in that range. Basically it should act stock at part throttle around town and have similar slippage to stock at highway speeds. The difference is when you floor it, it should flash to 2000 rpm plus and launch the car. It may have been a stock replacement cam or possibly the generic 204/214 cam. I know talking to Hughes, their stall rating is rated at 500 hp. So on a mild engine, their 2500 converter will stall less. Guys on here have had good luck with their converters. Also make sure you buy a converter with lugs vs bolt and nuts. Jegs brand is a B+M converter rated at 2300 stall with lugs for just over $100.
Thanks for the feedback....
I went with Part Number: 555-60402
GM TH350/TH400
10.75" Bolt Circle
Stall Speed: 2000-2300 RPM
There was a 2300-2600 but, as you mentioned it was a nut and bolt set up. I didn't feel that there was a need for that headache. Getting ready to send the transmission of for rebuild. Should have that back in less than a week and then the reassembly will begin (after replacing the brake system)
January 7th, 2021, 01:31 PM
