Stall converter

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Jayro

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Hey guys,

Bit the bullet and got a fresh built engine. So it’s considerably my hp and more cam that my previous. I’m told I’ll now need a stall converter upgrade. How do you know what size to get?

Engine is a 351C with 4V heads and 380ish hp.

Also, removed the old engine today. How do you know what rpm the current one is rated at as there does seem to be markings on it?

Cheers
Jase
 

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Hemikiller

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I would gather the specs on your engine and talk to a torque converter company. They'll be best equipped to give you an accurate recommendation.

Factory converters will have a stamped two digit code on them. C6 trans of this era had one of two converters, the 1800 stall standard passenger car part, or the smaller diameter 2800 stall 351CJ unit.
 
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Hey guys,

Bit the bullet and got a fresh built engine. So it’s considerably my hp and more cam that my previous. I’m told I’ll now need a stall converter upgrade. How do you know what size to get?

Engine is a 351C with 4V heads and 380ish hp.

Also, removed the old engine today. How do you know what rpm the current one is rated at as there does seem to be markings on it?

Cheers
Jase
This article helped me decide
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Jayro

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Thanks for that mate. Am I right then I’m assuming (if I’m reading my cam card right) I’ll need a 3000rpm ?
 

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Sheriff41

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Based on that excerpt you fall in the 2000 to 2400 range. Your duration at 0.050" is 234/244.
 
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I agree 2400. My experience is it’s easy to deal with a stall speed on the high side of recommended range, so no less than 2400.
Highly recommended getting a new balanced flex plate, last one i bought was a PRW through Summit. Good price and quality, I had it balanced with rotating assembly but it was balanced nicely as received.
 

Jayro

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Based on that excerpt you fall in the 2000 to 2400 range. Your duration at 0.050" is 234/244.
ah ok, I thought it was saying the Advertised Duration not 0.050?

I could certainly be wrong lol
 
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With duration at anything over 230 degrees at .050 like you have on that cam card, you will need at least a 3,000 stall converter. Advertised duration is not the same as duration at .050. The previous article from B&M can be quite confusing as they mention .050 and then they talk about advertised. Advertised duration means very little as there is no industry wide standard from where to measure advertised duration. Your advertised is 298/313, and your duration at .050 is 234/244. You always use duration at .050 as you know exactly where that measurement was taken and you can directly compare one cam to another, and you know how that cam will act in that engine. That cam company you got that cam from does not tell you where they measured the 298/313, it could have been at .006, or .004, or less or even more, The advertised duration numbers mean very little. Duration is measured from when the valve opens until it closes. A cam lobe is a circle so it is 360 degrees to go around it. Duration of 234 @.050 is measured from the point where the cam moves the lifter up .050 inch until .050 inch before the lifter is all the way back down, there are 234 degrees (out of the 360) that the valves are open . There is no standard in the industry for measuring advertised duration, many companies now use .006 but a lot do not. Advertised duration is in effect for how many degrees the valves are "off the seat", so basically from when the valves start opening to when they close. I don't believe anyone uses .001 to start measuring advertised duration, they usually take the measurement from somewhere in the .002 to .008 range. The difference between .002 and .008 can be well over 10 degrees of difference, that is why you can't use advertised duration to pick a converter, intake, headers or anything else, it varies by too much.
 

Jayro

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With duration at anything over 230 degrees at .050 like you have on that cam card, you will need at least a 3,000 stall converter. Advertised duration is not the same as duration at .050. The previous article from B&M can be quite confusing as they mention .050 and then they talk about advertised. Advertised duration means very little as there is no industry wide standard from where to measure advertised duration. Your advertised is 298/313, and your duration at .050 is 234/244. You always use duration at .050 as you know exactly where that measurement was taken and you can directly compare one cam to another, and you know how that cam will act in that engine. That cam company you got that cam from does not tell you where they measured the 298/313, it could have been at .006, or .004, or less or even more, The advertised duration numbers mean very little. Duration is measured from when the valve opens until it closes. A cam lobe is a circle so it is 360 degrees to go around it. Duration of 234 @.050 is measured from the point where the cam moves the lifter up .050 inch until .050 inch before the lifter is all the way back down, there are 234 degrees (out of the 360) that the valves are open . There is no standard in the industry for measuring advertised duration, many companies now use .006 but a lot do not. Advertised duration is in effect for how many degrees the valves are "off the seat", so basically from when the valves start opening to when they close. I don't believe anyone uses .001 to start measuring advertised duration, they usually take the measurement from somewhere in the .002 to .008 range. The difference between .002 and .008 can be well over 10 degrees of difference, that is why you can't use advertised duration to pick a converter, intake, headers or anything else, it varies by too much.
Ah that’s is great info thanks mate. I appreciate that.
 

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Thanks for that mate. Am I right then I’m assuming (if I’m reading my cam card right) I’ll need a 3000rpm ?

It depends on much more than just the cam for optimum performance. If you're simply building a cruiser, then an off the shelf 2800rpm converter will be fine. If you're expecting more, then I'd talk to a converter manufacturer. You haven't stated which transmission you have - C4, C6 or FMX.
 

Sheriff41

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With duration at anything over 230 degrees at .050 like you have on that cam card, you will need at least a 3,000 stall converter. Advertised duration is not the same as duration at .050. The previous article from B&M can be quite confusing as they mention .050 and then they talk about advertised. Advertised duration means very little as there is no industry wide standard from where to measure advertised duration. Your advertised is 298/313, and your duration at .050 is 234/244. You always use duration at .050 as you know exactly where that measurement was taken and you can directly compare one cam to another, and you know how that cam will act in that engine. That cam company you got that cam from does not tell you where they measured the 298/313, it could have been at .006, or .004, or less or even more, The advertised duration numbers mean very little. Duration is measured from when the valve opens until it closes. A cam lobe is a circle so it is 360 degrees to go around it. Duration of 234 @.050 is measured from the point where the cam moves the lifter up .050 inch until .050 inch before the lifter is all the way back down, there are 234 degrees (out of the 360) that the valves are open . There is no standard in the industry for measuring advertised duration, many companies now use .006 but a lot do not. Advertised duration is in effect for how many degrees the valves are "off the seat", so basically from when the valves start opening to when they close. I don't believe anyone uses .001 to start measuring advertised duration, they usually take the measurement from somewhere in the .002 to .008 range. The difference between .002 and .008 can be well over 10 degrees of difference, that is why you can't use advertised duration to pick a converter, intake, headers or anything else, it varies by too much.
Damn! That switch to advertised duration caught me. You are correct and please disregard my previous reply.
 

Paul M

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Hey guys,

Bit the bullet and got a fresh built engine. So it’s considerably my hp and more cam that my previous. I’m told I’ll now need a stall converter upgrade. How do you know what size to get?

Engine is a 351C with 4V heads and 380ish hp.

Also, removed the old engine today. How do you know what rpm the current one is rated at as there does seem to be markings on it?

Cheers
Jase
What ever you decide, the flywheel you use will have to be balanced with the rotating assy. The stock C6 flywheels are too flimsy. The Cobra jet ones are better quality, unfortunately you are stuck with a odd 9 1/2" bolt circle, that 98% of the aftermarket torque converters won't fit. The rare ones that will are $. The CJ converters are slightly smaller in diameter considered a 10" and measure @ 10 3/4" They have @ 2600 stall, which fell short for my cam, so I sent it out to broader performance to have it cut in 1/2 and re-stalled. Hughes also does this mod. I've got @ 3000 now. They did this for 250.00. Hughes gets a lil more.
 

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Jayro

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It depends on much more than just the cam for optimum performance. If you're simply building a cruiser, then an off the shelf 2800rpm converter will be fine. If you're expecting more, then I'd talk to a converter manufacturer. You haven't stated which transmission you have - C4, C6 or FMX.
Running a C4 tranny mate. Thanks for that info
 

machphil

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Thanks for that mate. Am I right then I’m assuming (if I’m reading my cam card right) I’ll need a 3000rpm ?
Your cam spec card indicates you can stay with the 2400 according to the previous article. I have a '73 CJ with the 10" factory converter and I hate the fact that I have to rev the engine to that rpm to get real movement. It kills the mileage too. Ford did that in '73 because the compression was only 8.0 to 1 and they retarded the CJ cam for emissions. A retarded cam moves the compression and power higher in the rpm. So to give the Mach decent takeoff they used the 10" converter. You could convert your trans to the 4R70? transmission which gives you a lower first gear, an overdrive, and lockup capability.
 
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Your cam spec card indicates you can stay with the 2400 according to the previous article. I have a '73 CJ with the 10" factory converter and I hate the fact that I have to rev the engine to that rpm to get real movement. It kills the mileage too. Ford did that in '73 because the compression was only 8.0 to 1 and they retarded the CJ cam for emissions. A retarded cam moves the compression and power higher in the rpm. So to give the Mach decent takeoff they used the 10" converter. You could convert your trans to the 4R70? transmission which gives you a lower first gear, an overdrive, and lockup capability.
Read the B&M article again, you are confusing advertised duration with duration at .050. A 2400 stall converter with a 234 at .050 cam will be a dog off the line unless you have 4.56 gears, and even then it won't be optimal. The best advice was given by a previous poster, just choose a converter company you like, call them up, give them the specs of the car and let them tell you what they recommend. There is so much that goes into torque converters that it is almost a science. An advertised 3,000 RPM converter will probably never stall at 3,000 RPM's. Too many variables change the stall speed of a converter. The more torque an engine makes the higher the stall speed, the heavier the car, the higher the stall speed, lower gears less stall, higher gears more stall, and the opposite is also true, so the lighter the car the lower the stall speed and the less power/torque you make the lower the stall speed. The advertised stall speeds are usually based on your average car, a 3,500 pound car with a 400 HP small block. If your car fall right there the advertised stall will be close, but if it is outside of those parameters, it could be way off. Say you have a 23T bucket with a high winding 289 that makes 350 HP and you need a 3,000 stall converter to make your cam work. You buy an off the shelf 3,000 RPM converter and you may get lucky to stall at 2,200. Your 1500 pound car with a lower torque engine that your average 350 SBC 400 HP engine means that you will not be even close to where you need to be. You may need something that a converter company sells as a 4,000 RPM stall to get the 3,000 you need on your 289 23 T.

I do understand the issue of the high stall converter and the slipping at low engine RPM's and the crappy gas mileage. I have driven many a car with high stall torque converters on the street and it kinda sucks, until you mash the go pedal and the engine flashes to 3,200 rpms and the thing goes sideways doing its best imitation of a old school early 60's top fuel car, when tire technology had not arrived yet, and those things just smoked the tires the whole 1/4 mile. It all about compromises, you want high RPM power with a lot of cam, either use a manual trans or you have to live with the slipping converter. We still do not have V-Tec system for our cars that can automatically change the cam timing at higher RPM to make more power...
 

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