Do I need a Stall converter?

-
C2ndLTpigeon

C2ndLTpigeon

Mopar or no Car!
Joined
May 18, 2019
Messages
1,140
Reaction score
895
Location
Indio California
Hello,

I wanted to see if its worth it to spend the money on a stall converter. Right now my 73 Valiant has a 318, with huges whiplash cam and 3.55 rear gears the transmission has a B&M shift kit that I added when I did the rebuild otherwise it is stock with the stock converter.

It will soon be swapping out the 318 for a 340 I am building. Compression is about 9.1:1 and the cam is a Comp solid 270/270 with .468/.468 PN CL20-246-4

The car is just going to be a Street car with some more HP then my 318. About (340-360 HP)
My machinist recommends a 2500 Stall, but after seeing some older posts on here about the stock stall speed on stock converters leads me to ask is it worth it to spend that kind of cash.

Here is a pic I found showing the factory stall range, its for 72 but surely it cant be to far off for the following year.

stall.png
 
Last edited:
I stopped reading at "Whiplash cam". Yes, IMO you will benefit greatly from a good matched converter. ......not a 2500.
 
I don't think that 270* cam can make 350hp with stock factory heads, @ 9.1 Scr. But say it it's what you have and want.
By the time the lash gets taken up, that solid cam will measure less than 270*, how much, I cannot say, but rule of thumb is that when comparing a solid to a Hydro , the solid will be about one advertised size smaller.
Let's say that works out correctly, then your 270 compares to, a 262 hydro at advertised .008 tappet rise.
And let's assume your single-pattern 270 is on a 110 LSA. Let's install it 2* advanced, and we get an Ica of 59*. And I assume Indio is at sealevel.
Ok then, the Wallace Calculator says you combo should make around 153 psi CCP, which is Cranking Cylinder Pressure, which is pretty good. The V/P is predicted to be 125, which is about the same as a stock 9.2Scr318 or 9.2Magnum., which is non too peppy but not lazy. This would be a good number for your application.
But it won't be anywhere near 350 hp.
But that is not necessarily a bad thing.
Because you have that higher pressure, the TC will act like it should, stalling near it's rated stall. My guess is that you'll get near 2200 out of it.
With that and the 3.55s, it should be just fine for your application. I certainly would not spring for something just 300 rpm higher.
Now, having said that
Your power-peak with that cam should be near 4800 rpm, which with 3.55s and 27" tires is about 40 mph, in first gear. The guessed-at 110LSA, will NOT carry that power out too far, but for your application will certainly be fun. I'll guess at a shift rpm of 5300 to 5500.

And finally;
That cam has the potential to make great fuel-economy, probably better than any smog-era 318, but not with the 3.55s lol.

Read about V/P here

Cam Timing vs. Compression Analysis

Cam Timing vs. Compression Analysis
victorylibrary.com

Happy HotRodding
 
So you're going FROM the Hughes cam to the Comp? Why the downgrade?
 
AJ/FormS said:
I don't think that 270* cam can make 350hp with stock factory heads, @ 9.1 Scr. But say it it's what you have and want.
By the time the lash gets taken up, that solid cam will measure less than 270*, how much, I cannot say, but rule of thumb is that when comparing a solid to a Hydro , the solid will be about one advertised size smaller.
Let's say that works out correctly, then your 270 compares to, a 262 hydro at advertised .008 tappet rise.
And let's assume your single-pattern 270 is on a 110 LSA. Let's install it 2* advanced, and we get an Ica of 59*. And I assume Indio is at sealevel.
Ok then, the Wallace Calculator says you combo should make around 153 psi CCP, which is Cranking Cylinder Pressure, which is pretty good. The V/P is predicted to be 125, which is about the same as a stock 9.2Scr318 or 9.2Magnum., which is non too peppy but not lazy. This would be a good number for your application.
But it won't be anywhere near 350 hp.
But that is not necessarily a bad thing.
Because you have that higher pressure, the TC will act like it should, stalling near it's rated stall. My guess is that you'll get near 2200 out of it.
With that and the 3.55s, it should be just fine for your application. I certainly would not spring for something just 300 rpm higher.
Now, having said that
Your power-peak with that cam should be near 4800 rpm, which with 3.55s and 27" tires is about 40 mph, in first gear. The guessed-at 110LSA, will NOT carry that power out too far, but for your application will certainly be fun. I'll guess at a shift rpm of 5300 to 5500.

And finally;
That cam has the potential to make great fuel-economy, probably better than any smog-era 318, but not with the 3.55s lol.

Read about V/P here
[/URL]

Happy HotRodding
Click to expand...
Brian at IMM is doing some port work on the the stock X heads.
The 270 is 110 separation.
This is why I thought I would ask as I thought it may be a waste to spend that money on something only 300 RPM higher.
 
C2ndLTpigeon said:
Brian at IMM is doing some port work on the the stock X heads.
The 270 is 110 separation.
This is why I thought I would ask as I thought it may be a waste to spend that money on something only 300 RPM higher.
Click to expand...
Try it and if not happy swap down the road.
 
I always thought the lash zeroed up when the engine warmed up so if you lashed it to factory specs you would end up with zero lash.
 
Can you get a better et ( if it hooks ) ? Yes. Will it do a bigger burnout ? Yes.
Is it necessary for your combo ? I don't think so.
Will it be more fun to drive with a 2800 converter ? Absolutely.
 
If you get the 10 3/4" 2500 stall up it should be OK but it would be a whole lot more fun with a 3500 and you should be able to shift about 6500. Had almost the same set up and tried both ways, trust me.
 
C2ndLTpigeon said:
The engine that is in the car is a low compression 318 with a hughes whiplash, I am replacing it with a completely built 340. I am not changing the cam in the 318.
Click to expand...
I should have read more closely. My apologies. Although a stock 340 converter may be "enough", IMO, there are way better choices than 50 plus year old technology, especially where converters are concerned. Keep in mind a camshaft's lift has very little to do with converter choice. The duration and LSA however is what should be considered.
 
A 3500 stall in a low comp. with that cam small block will brake stall around 3000 I would never go lower then a 3000. If you use a 2500 you car will be a pig from a stop. Brake stall is not where the cars transmission grabs and pulls out. I use a 5500 on the street it idled somewhat free and pulled out as soon as I touched the throttle. Stomp the throttle down and its explosive. Converter is the most important choice for a good running performance automatic car. I never used anything lower then a 3500. All my original 340 cars in the past brake stalled at 2800 from the factory unless the trans was replaced

I bought a 70 340 swinger in 1971. Auto on column flashed stalled and left at 2800 shifted a 6000 when left in drive. Due to a light weight governor they had same as Hemi or max wedge that is what they came with. Also add a part throttle kickdown if you leave it full automatic. Three things that make them fun when left in drive

1. Proper converter
2. Light weight governor
3, Part throttle kick down

If you shift a auto trans not turned into reverse manual. Never take off in low take off in drive and pull it to low after the car is moving. Big difference you'll even feel it on the shift.
 
Last edited:
Did you ask Brian about a cam? Since he's doing the heads he'll know what size cam will best take advantage of his port work.
 
Oldmanmopar said:
A 3500 stall in a low comp. with that cam small block will brake stall around 3000 I would never go lower then a 3000. If you use a 2500 you car will be a pig from a stop. Brake stall is not where the cars transmission grabs and pulls out. I use a 5500 on the street it idled somewhat free and pulled out as soon as I touched the throttle. Stomp the throttle down and its explosive. Converter is the most important choice for a good running performance automatic car. I never used anything lower then a 3500. All my original 340 cars in the past brake stalled at 2800 from the factory unless the trans was replaced

I bought a 70 340 swinger in 1971. Auto on column flashed stalled and left at 2800 shifted a 6000 when left in drive. Due to a light weight governor they had same as Hemi or max wedge that is what they came with. Also add a part throttle kickdown servo if you leave it full automatic. Three things that make them fun when left in drive

1. Proper converter
2. Light weight governor
3, Part throttle kick down servo

If you shift a auto trans not turned into reverse manual. Never take off in low take off in drive and pull it to low after the car is moving. Big difference you'll even feel it on the shift.
Click to expand...
I agree completely with having a better TC. I have a 9" from PTC and love it. I thought the part throttle kickdown was a function of special valving in the valve body, not a servo.
 
dartindanno said:
Did you ask Brian about a cam? Since he's doing the heads he'll know what size cam will best take advantage of his port work.
Click to expand...
He was the one that recommended the cam, the pistons even though the compression is lower then the stock 10.5:1 I wanted something that will be good still on pump gas, he has used this setup before. Main reason I went with it is his experience with it. He also recommended the 2500 stall. but just weighing my options on to spend the money on one that is not much more then stock.
 
Oldmanmopar said:
A 3500 stall in a low comp. with that cam small block will brake stall around 3000 I would never go lower then a 3000. If you use a 2500 you car will be a pig from a stop. Brake stall is not where the cars transmission grabs and pulls out. I use a 5500 on the street it idled somewhat free and pulled out as soon as I touched the throttle. Stomp the throttle down and its explosive. Converter is the most important choice for a good running performance automatic car. I never used anything lower then a 3500. All my original 340 cars in the past brake stalled at 2800 from the factory unless the trans was replaced

I bought a 70 340 swinger in 1971. Auto on column flashed stalled and left at 2800 shifted a 6000 when left in drive. Due to a light weight governor they had same as Hemi or max wedge that is what they came with. Also add a part throttle kickdown if you leave it full automatic. Three things that make them fun when left in drive

1. Proper converter
2. Light weight governor
3, Part throttle kick down

If you shift a auto trans not turned into reverse manual. Never take off in low take off in drive and pull it to low after the car is moving. Big difference you'll even feel it on the shift.
Click to expand...
I agree with every letter of every word! 100%!
 
150 shot of spray will raise your stall and add 135 hp@5000
 
You must log in or register to reply here.
-

Back
Top