408 and large hp/tq owners

nvrstuk · Jan 19, 2017

5001Craig- The "this" link doesn't work...takes you to "some place like Summit link". Interested in reading about that TC. Can you repost it? thanks...

Walls-
I was talked into a 2200 rpm TC and I think it's too low. I spent a lot of time asking manufacturers but they all showed concern about heat build up when rock crawling like in the Rubicon when you crawl for hours at a time without stopping... I have a 4r70W and can lock in the TC so that helps...

If this was a car it'd be changed by now...potential reward vrs money spent on trying a different converter vrs weekend swapping it out... be nice to ride in someone else's similarly equipped rig and see what the differences might be...

If it wasn't such a PITA to pull drivetrain or engine, I'd try a 3-3500rpm converter and see how it changes my performance. I would think on snowy/icy surfaces it might be a bit sketchy...don't know, nobody local runs something similar... can't try it out.

EricLar80 · Jan 19, 2017

High torque motors will provide a higher stall than specified because the stall speed is dependent on the input (engine) torque. So, gotta be careful putting too high of stall with a big motor. I currently have a converter specified as 1600-1800rpm in my setup and it works well.

For reference, I have the FM69L converter shown in this document. Even though it works, I could see there being benefits of moving to a higher stall speed.
https://www.transtar1.com/TranstarIndustries/media/Transtar1/technical/bulletins/TLT-TC-018.pdf

But, I completely agree, I have made the mistake of putting pairing the wrong cam and converter together and it can make a huge difference in how the engine performs. I think it was mostly a wrong choice in the cam in my case, but that's besides the point.

Eric

EricLar80 · Jan 19, 2017

nvrstuk said:
5001Craig- The "this" link doesn't work...takes you to "some place like Summit link". Interested in reading about that TC. Can you repost it? thanks...

Use this link instead. Direct summit links never work for some reason...
http://tinyurl.com/hdkwd4k

5001craig · Jan 19, 2017

EricLar80 said:
Use this link instead. Direct summit links never work for some reason...
http://tinyurl.com/hdkwd4k

Huh... Yep--that's the one. 42-30HD.

I was told the converter stall is solely based on the cam. Not sure if this is true but that's what I was told by the torque converter guys. Makes sense. Too low and it's trying to go through a stoplight due to idle. Mine's a bit lumpy.

68stang73 · Jan 19, 2017

Yeah this is some good info and nice to hear others experience. We haven't talked about tq converters yet but we willl.

EricLar80 · Jan 19, 2017

The torque converter constant, called "K factor", is what determines how a converter will function. K factor is driven by the design - how may vanes and their shape, the clearances, etc. The stall speed can be determined using the convert K factor and engine torque according to this equation:

stall rpm = K*sqrt{torque}
see this reference

So, increasing engine torque will increase the effective stall rpm. Conversely, installing a converter will a lower K factor will lower the stall speed.

What I found with my cam/converter mismatch was that converter was coupling at a lower rpm than the cam was ready for. So, it was a complete dog off idle but ran great up above. I went to more of a torque/RV cam but kept the same converter and it ran awesome at all rpms. Looking back, I probably could have changed the converter stall speed (k-factor) instead of the cam.

walls · Jan 20, 2017

When you are ready for the proper torque converter call layne at ptc torque converters. Tell him what you have, what you do with it, answer his questions and hang up the phone. Let him take care of the rest, you will not be disapointed. I have had 5 converters from them for different applications from trucks to 7 sec race cars and they usually are right on the money first shot. If not they will adjust it for free to your liking 1 time for free.

EricLar80 · Jan 20, 2017

About what do they charge for a converter for our application?

walls · Jan 20, 2017

EricLar80 said:
About what do they charge for , converter for our application?

All depends. I have paid 175.00 for a rv tow converter, in the mid 3s for a nice c4 converter and 1200 for race converter going behind a 900 hp sbf in a drag car so its all different. Converter for my 4r70w is coming soon. No idea what that is going to cost, from what I hear a nice lock up converter is a bit pricey but you get what you pay for. For me a converter is not the place to chince out.

68stang73 · Jan 21, 2017

Yeah I'll see where we are once it is done and talk to the builder and then tq coverter guys.

bmc69 · Jan 21, 2017

The 408 I built for my old trail rig had peak torque of 496 ftlbs at 2900 rpm. Hp was something like 342 at...don't remember...mid 3000 range anyway. It was a truly fantastic crawling engine and was fine for the very limited street use it saw. But it was all done by 4000 rpm too. I'm building another one..going for a more balanced engine so it will be equally happy on street and trails

68ford · Jan 21, 2017

Not sure if it was stated, but what is the cams lobe separation?

68stang73 · Jan 21, 2017

For my build it will be a custom cam. Prolly close to this one on this spread sheet. All I know is it will be close if I remember correctly hence good vacuum in the 14" range.

408 and large hp/tq owners

nvrstuk

Just a Bronco driver for over 50 yrs!

EricLar80

Bronco Guru

EricLar80

Bronco Guru

5001craig

Bronco Guru

68stang73

Sr. Member

EricLar80

Bronco Guru

walls

Full Member

EricLar80

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walls

Full Member

68stang73

Sr. Member

bmc69

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68ford

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68stang73

Sr. Member

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