Moparchat - Home of MOPAR enthusiasts worldwide!



Go Back   Moparchat - Home of MOPAR enthusiasts worldwide! > Technical Forums > Performance Talk

Click here to search for Mopar cars and parts for sale.


Reply
 
Thread Tools Display Modes
  #1  
Old 01-19-2003, 01:43 AM
bouncer bouncer is offline
Inactive User
 
Join Date: Sep 2002
Location: victoria
Posts: 47
Default torque conv. and rear end

Could someone possibly reference me a site or shed some light on torque converters and rear ends, mainly at what point they need to be changed during a performance build up.

318 motor, will roughly run 300 hp.
Reply With Quote
  #2  
Old 01-19-2003, 01:56 AM
pishta's Avatar
pishta pishta is offline
Senior Member
 
Join Date: Aug 1999
Location: Tustin, CA
Age: 55
Posts: 3,987
Default

torque convertor ratrings usually are used to get the most torque transmitted to the rear at a point where the motor starts making the most torque. If you put in a stout cam that makes power from 3000 to 6500, then you want a convertor that starts to transmit the most torque at around 3000 or close. Some of the drag guys are running 5500 RPM stall speed convertors! They do so to get the most power to the rear wheels starting at those high RPMS, right where their monster cams make the ponys. Their cars are dogs at 1700 RPM so they dont want alot of torque to the rear wheels, it would do them no good. Conversly the 1800 stall is great behind a stocker because that is where most of their torque is needed, right out of the hole.
As for rear ends, the 7.25 rear is a lightweight unit not really designed for any performance applications. The bigger you can get the better the strength. 8.75 is a great performance rear, the 8.25 is a close second if you dont want to go the mega buck DANA route.
Reply With Quote
  #3  
Old 01-19-2003, 02:28 AM
bouncer bouncer is offline
Inactive User
 
Join Date: Sep 2002
Location: victoria
Posts: 47
Default

so since my application is street, 1500-5500 rpms, a stock conv. in a 904 will do me fine correct?
Reply With Quote
  #4  
Old 01-19-2003, 02:57 AM
440cj's Avatar
440cj 440cj is offline
Inactive User
 
Join Date: Mar 2002
Location: Ft. Worth, Texas
Age: 67
Posts: 187
Cool

Going on what info you have given so far....YUP! 440cj
Reply With Quote
  #5  
Old 01-19-2003, 09:52 AM
dirty dan's Avatar
dirty dan dirty dan is offline
Inactive User
 
Join Date: May 2002
Location: Rockingham,nc
Posts: 1,027
Default convertor

Quote:
Originally posted by bouncer
so since my application is street, 1500-5500 rpms, a stock conv. in a 904 will do me fine correct?
Hey Bouncer
Pishta has given you an acurate over view of how it works.
However regaurdless of street or strip use.
There are a couple of questions that must be asked.
What cam shaft are you going to use?
And what gear ratio?
How heavy is the car?
These are the determineing factors.
When decideing what is required.
Reply With Quote
  #6  
Old 01-19-2003, 12:20 PM
thecudaguy's Avatar
thecudaguy thecudaguy is offline
Inactive User
 
Join Date: Oct 2001
Location: Eastern Canada
Age: 58
Posts: 109
Default

This artical was originally published in a Pontiac mag. Ouch... it hurt saying that! Anyway, it's a great piece.

http://www.boyleworks.com/ta400/psp/Twisting.html
Reply With Quote
  #7  
Old 01-19-2003, 05:39 PM
John Kunkel John Kunkel is offline
Registered User
 
Join Date: Nov 2001
Location: NorCal
Age: 80
Posts: 10,059
Default

Here's a more general article on converter operation and selection:
http://www.tciauto.com/tech_info/tor..._explained.htm
Reply With Quote
  #8  
Old 01-19-2003, 05:58 PM
dave571's Avatar
dave571 dave571 is offline
Inactive User
 
Join Date: Feb 2001
Location: carstairs,alberta,canada
Posts: 2,809
Default

I would think that a 300 horse 318 would have to have, a fairly aggressive cam in it.

I'm not sure how high a Stall I would use, but I don't think a stock one will be right for the job. Dan's questions are important ones. An agressive cam is necessary for the power you want. It is important to remember, that when a more aggressive cam is used, low end torque is sacrificed. Your "stock" converter is probably more set up for nice smooth starts(down low) This will have a very negative effect on performance.

Somewhere from 2500 to 3500 is more like what you'll want.

If youve got an 8 1/4 or better. it will probably be strong enough. Gear selection is another issue. Same concept as the converter. The 300 horse engine is meant to breathe. If the gear ratio doesn't allow this (lugs the motor instead) performance is also hurt.

Not paying attention to these two factors, when building a street car, are the leading causes of dissapointment. Equally, when accounted for properly, these are factors that can make an engine perform better than one would think it could.
Reply With Quote
  #9  
Old 01-19-2003, 07:13 PM
6 packin's Avatar
6 packin 6 packin is offline
This account disabled due to bad email address!
 
Join Date: Apr 2002
Location: Under my car!
Age: 48
Posts: 1,551
Default

Dave 571 is right! A looser converter will help take off big time! A 300 horse 318 can be had fairly easy, with 1- a set of heads that outflow a stock 318 head everywere in the lift range. 2-a camshaft that will take advantage of high rpm. A cam with maybe 225-235 dur@.050 and a 2800-3000 converter, along with 3.91 gears and free flowing exhuast and headers will be a screamer. Oh yea dont forget a good intake (Edelbrock air gap RPM) and a good 4 barrel carb somwere along the 650 cfm range. Dont over cam it or to big a carb and it will be a pig of the line.
__________________
68 Coronet
69 Super Bee......new 500 cid comin soon!
73 Duster witha missing 440/727
Reply With Quote
  #10  
Old 01-19-2003, 08:02 PM
bouncer bouncer is offline
Inactive User
 
Join Date: Sep 2002
Location: victoria
Posts: 47
Default

6 packin, yup, pretty much hit my combo on the head. Cam will be a replacement 340. I have the 8 1/4 rear end, the gears are still a mystery to me, im gonna measure them next time I can hoist the truck up.

Thanks for the links and info as well, appreciated.
Reply With Quote
  #11  
Old 01-20-2003, 11:04 AM
cuda66273's Avatar
cuda66273 cuda66273 is offline
Banned
 
Join Date: Dec 2001
Location: Beaverton Oregon
Age: 71
Posts: 3,685
Default

Truck? did you say truck?

Wieght is going to be the main factor here, you need to call Jim at Racer Brown and have him select the correct cam for you and he will be able to recommend a convertor stall to make it perform correctly.

You might say I've done a little research on 318's and I think you'll be disappointed if you use the 340 Mopar replacement cam in your combo...a Racer Brown custom cam will run you about $40.00 more...and run circles around that 340 bump stick.

When you get to your 8.25 rear end your going to find about a 2.72 ratio. Most rear end shops will tell you that a 3.91 gear set won't fit...don't believe it....I've done it, it takes a patient and determined machinist and a few tool bit's but it will fit and handle nearly 400 HP hammering on it through a 4000 stall Dynamic convertor with 3500 studder box launches...I have since replaced it (after 200 runs) with a spooled Dana 60/4.56, it's now in a 67 Cuda 360 street car and after 2 years it's still spining the tires all over town.
Reply With Quote
  #12  
Old 01-20-2003, 07:37 PM
bouncer bouncer is offline
Inactive User
 
Join Date: Sep 2002
Location: victoria
Posts: 47
Default

Ok, few more questions though, thanks cuda.

So a higher set of gears, say 3.91, will take longer to run through correct? And a higher rpm converter should just be matched to my higher engine speed/weight as well?

Also, is there a relation between advertised duration and lift, and duration at .05 tappet lift? Reason being is that when I compare different cams, some manufacterers only display one set of numbers, so there is no way to tell them different.

And by the way,
GO BUCS!
Reply With Quote
  #13  
Old 01-20-2003, 08:47 PM
6 packin's Avatar
6 packin 6 packin is offline
This account disabled due to bad email address!
 
Join Date: Apr 2002
Location: Under my car!
Age: 48
Posts: 1,551
Default

I posted this a few days ago about the relation ship between advertised and duration@.050 valve lift.

I normaly try not to look at advertised dur at all.....just my preferance. About all the major manufactors have different ways of calculating there advertised duration. Thats why is just advertised, When ya look at it a .050 lift there can be no misleading info. For that reason that why they will give you a reading at .050 lift which will give you a better understanding of the cam profile. Just compare Comps Cams to Mopar Performance Cams.

Comps Cam for Big Mopars part # 21-213-4
Advertised Duration is 260
Duration@ .050 lift is 212

Mopar performace Cam for Big Mopars part # P4286675
Also advertised at 260 Duration
Duration@ .050 lift is 221

So you can see that the Mopar cam is much bigger Even though the advertised duration is the same.

To calculate Mopar Performance Cams at .050 lift Mutiply adverised duration by .850

On your gearing Q's!

Higher the numerical value of the gear ratio, the lower the gearing will be. So a 4.10 gear ratio will like speeds below and up to 100 MPH for a average car or engine. Any thing above this is winding the engine tight or at a High RPM value. (rear tire size is a factor but will not go there) With a 4.10 gear the car will accelerate very quickly. Ok with a 2.76 ratio it will act the very opposite. To get the car to say 6000 rpms like the 4.10 gear at 100 mph, the 2,76 gears in the same car may not see that rpm speed till maybe 150+ mph. This just a example.....
It is very important that you match your camshaft,weight of car,rpm level and gearing togather for the besy performance! Along with that a good exhaust, intake, and carb matched to take full advantage of the performance of the car..or truck. A enigne with just a big cam and carb alone will run poorly than it did stock in some cases. You heard about the boy who runs the Chebby camaro, thats puts a big cam,intake and carb on his 350....and it wont pull it self to the junk yard. Mismatched parts can kill a engine, its better to pick the right parts the first time.
__________________
68 Coronet
69 Super Bee......new 500 cid comin soon!
73 Duster witha missing 440/727
Reply With Quote
  #14  
Old 01-20-2003, 08:54 PM
rumblefish360's Avatar
rumblefish360 rumblefish360 is offline
Moparchat Bronze member
 
Join Date: May 2000
Location: C
Age: 57
Posts: 11,120
Default

These guys have been writin up in MoPar mags a plenty. He can help ya out. Have your info ready about your truck.
http://www.dynamicconverters.com/
Reply With Quote
  #15  
Old 01-20-2003, 09:28 PM
cuda66273's Avatar
cuda66273 cuda66273 is offline
Banned
 
Join Date: Dec 2001
Location: Beaverton Oregon
Age: 71
Posts: 3,685
Default

Ya...what those Guy's said....
Reply With Quote
  #16  
Old 01-20-2003, 09:34 PM
bouncer bouncer is offline
Inactive User
 
Join Date: Sep 2002
Location: victoria
Posts: 47
Default

Gotcha, thanks.
Reply With Quote
  #17  
Old 01-20-2003, 09:53 PM
thecudaguy's Avatar
thecudaguy thecudaguy is offline
Inactive User
 
Join Date: Oct 2001
Location: Eastern Canada
Age: 58
Posts: 109
Default On the same topic...sorta

My tq. is matched to my combo. Or at least I think it is. The stall on it is 3500 but it will flash to 3800. Is it trying to tell me something? The cam range goes from 2800 - 6400.
Reply With Quote
  #18  
Old 01-21-2003, 09:51 AM
cuda66273's Avatar
cuda66273 cuda66273 is offline
Banned
 
Join Date: Dec 2001
Location: Beaverton Oregon
Age: 71
Posts: 3,685
Default

First of all everyone thinks their convertor is good because they can flash it and it does what it's supposed too...3800 in your case.

Not that I'm suggesting that there's anything wrong with your convertor or anyone else's but, the real test of convertor efficiency is at the other end of the track and it's the relationship between engine speed and tire speed, the difference being the slippage of the convertor calculated as a percentage.

Rocket science? no not really it's actually a very simple calculation.

Here's an example:

Car runs 120 MPH and the the tach at the stripe is reading 6800. We know that the tranny is in high gear so it's a 1:1 ratio, the rear gears are 4.56:1 and the tire diameter is 30".

So now go to
http://www.prestage.com/carmath/calc_gears.asp

Check the box that says "RPM" enter the numbers and the mathmatical calculation shows the engine should be turning 6129 RPM...so what happened to the other 600+ RPM?...unless you were spinning the tires it was lost in the slippage of the convertor in this case about 10%.

Dynamic will tell you that your convertor should slip no more than 6% anything else is lost power and slow ET's. Not even accounting the excessive heat it building in the tranny trying to melt down the clutches.

Here's the test on my Cuda with a Dynamic convertor:
29" tire, 110 MPH at 6150 RPM...calculations show 5812 RPM doing the math you'll see that it equates to 5.5% slippage...this is very good and typical for a Dynamic.

I've done this test a 100 times at the track for guy's and most of convertors fail this test. I have found that Coen, Continental and A&A's are really good but the numbers from Dynamic and A&A (Reboxed Dynamic) are about the best.

No need to slam the post with a 100 comments about how good you MP or GER or whatever your running is...this is the proper way to test the efficiency of your convertor....the proof is in the math.

You may also want to do this test at different temperatures and see how it performs when the oil is hot and cold...this is why you might think about running a tranny temp guage..it's a dial-in thing.

Doing this calculation on a Buddy's 73/440 Charger showed 18% slippage...he bought a Dynamic and cut his ET by 3/10ths, picked up 6 MPH and reduced the stripe RPM by almost 700...now he's buying smaller diameter tires.....just an example.
Reply With Quote
  #19  
Old 01-21-2003, 06:21 PM
thecudaguy's Avatar
thecudaguy thecudaguy is offline
Inactive User
 
Join Date: Oct 2001
Location: Eastern Canada
Age: 58
Posts: 109
Default

My tranny temp NEVER goes above 175*. Thanks to the monster cooler and synthetic tranny fluid. But there is a difference in the figures you have shared with me via the formula. It pulls hard in 1-2 so why would it slip in 3?

This is not good. I paid $900 for that thing. It is supposed to be one of the best. It's a TCS converter. Is it crap... Apparently so?
My buddy talked me into getting it there. What is cheaper A&A or Dynamic and how much approx.?

It is starting to make sense now...
Everyone at my home track says when I leave the line and hit second gear it sounds like I am doing 100 mph. What causes this and can I fix the one I've got?
Reply With Quote
  #20  
Old 01-21-2003, 11:47 PM
bouncer bouncer is offline
Inactive User
 
Join Date: Sep 2002
Location: victoria
Posts: 47
Default

Thats awesome cuda, thanks, makes some more sense.

As for the rear gears... When I cruise down the highway at 120 km/hr or so, my rpms are already high, if I get larger gears in the back, isnt highway driving gonna be very high rpms?
Reply With Quote
  #21  
Old 01-22-2003, 01:45 PM
cuda66273's Avatar
cuda66273 cuda66273 is offline
Banned
 
Join Date: Dec 2001
Location: Beaverton Oregon
Age: 71
Posts: 3,685
Default

cudaguy: Is your convertor crap? I don't know did you do the calculations? what did it show you?

If it's eating up the engine RPM in high gear it's probably worse in 1st and 2nd just because of the tork multiplyer to the rear wheels with the tranny gear ratio, but we don't have any way to really measure this unless maybe if you shift after the 1/8 mile and can get your tach reading and MPH at the 660 and do the calculation using 1.45 for example for 2nd gear on a 727.

Can it be fixed?...depends on how they got the stall in it...some shops just cut them open and with a pair of pliers bent the fin tips and weld them back together..this brings the stall way up but raises hell with the oil under a hard load reducing the efficiency, cavatating the oil and heating it way up. Your synthetic oil is probably keeping the temp down in the tranny..that's amazing stuff!

Whenever someone recommends a product or change on your car you should be able to find a mathmatical formula to determine whether it will work or not...or ask me I'll check the chrystal pentastar and see what the Genie has to say about it....or I'll look at my old reciepts and tell you how long it lasted before I broke it

Bouncer: That is correct the higher the number the higher the RPM for a given MPH, you can use a % formula as in 3.55/4.10=13.5% so if your turning 3500 with a 3.55 at 120km/hr you'll be turning 3500 x 113.55 =3972 with the new gears at the same speed.

Of course the tork mutiplyer of a lower Gear set (Higher number) will make it jump hard out of hole but on normal driving will cause it to run constantly higher RPM which is RP mile and the engine will wear out quicker...but who cares I'll take the tork anyday rings and bearings are cheap. If you want to get 200,000 miles out of it better go look at a Geo

Change the gear and "Drive it like you stole it"
Reply With Quote
  #22  
Old 01-22-2003, 07:53 PM
thecudaguy's Avatar
thecudaguy thecudaguy is offline
Inactive User
 
Join Date: Oct 2001
Location: Eastern Canada
Age: 58
Posts: 109
Default

The loss % is 10.31. Thats not good. Are you familiar with TCS. That is where I got it. Their site is:

http://www.tcsproducts.com/products/...?product_cat=2

Think I'll get a dynamic before spring hits!
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
torque conv ss/tmall Trucks - Parts for Sale 0 11-21-2004 12:52 AM
What kind of torque conv. for my 360? FARGO318 Performance Talk 14 04-19-2003 07:32 PM
1973 340 Torque Conv. on a 360?? PINK71T/A Performance Talk 4 06-26-2001 11:54 PM
torque conv. lockup ??? Checkmate Ram Truck Chat 9 05-24-2001 07:25 PM
360 balancer /torque conv KLR65FISH Performance Talk 3 01-27-2000 05:31 AM




All times are GMT -4. The time now is 05:12 PM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
. . . . .