Torque converter recommendations

[ds440]

Hey guys,
I'm looking for opinions on torque converters on my brother's '69.   I've done several searches on the site and it seems like there are a lot of factors that go into choosing the right converter.  ANY help is appreciated.

Some background: The original engine builder has fallen seriously ill and is understandably unable to help us (for at least awhile).  The motor is a 400 block stroked to 500ci, with Edlebrock aluminum heads.  The engine was dyno'd and produced 484 hp @ 5300 rpm, with 588 lbs @ 3500 rpm at the flywheel.  After the dyno, the engine builder said he would 'tune the engine back a bit' so that it was more streetable.  We assumed that meant timing and carb jetting.

Since the car has been finished, it seems to be a bit down on power and lacks the 'grunt' that we think a car with 588 lbs of torque should have.  He hasn't even really chirped the tires.  Several people have suggested that it may have the wrong torque converter for the car.  So I thought I'd reach out the experts to get any opinions you guys might have.

Here's the stats:
- Strictly a street car, with a 727 Torqueflite automatic that was rebuilt to "hemi spec's."  (Hemi specs?)   
- Current converter is a 'heavy duty' 2500 stall.
- Rear-end: 3.23.
- Rear tire height: 24" high.  (285/40/R17)
- Car weight: mostly stock '69.  Aluminum heads, intake on the engine.  Hotchkis suspension.  Guessing 3800 lbs?
- Cam specs:
     - Comp Cams XEHL #23-227-4
     - Intake duration @ .050" = 231 degrees.
     - Exhaust duration @ .050" = 237 degrees.
     - Intake installed at centerline = 106 degrees straight up.
     - Lobe separation angle = 110 degrees.
     - Intake lobe lift = 0.3510 / .525 @ 1.5 rocker
     - Exhaust lobe lift = 0.3510 / .525 @ 1.5 rocker
     - Intake valve to piston clearance @ 10 degrees ATDC = .360
     - Exhaust valve to piston clearance @ 10 degrees ATDC = .395
     - Intake valve lash = 0.00 HYD
     - Exhaust valve lash = 0.00 HYD

Is a 2500 stall within a good range for a street car?  Any recommendations are greatly appreciated.

[c00nhunterjoe]

The "hemi" trans is essentially the same thing as a regular 727 as far as driveability is concerned. A few less clutch drum springs and an extra friction here and there, but saying "hemi spec" just sounds cool. Without certain modifications, you cant "upgrade" a "regular" 727, but thats a whole other conversation...

    A stock heavy duty hemi converter will not flash at 2500 rpm behind a 500 inch stroker making almost 600 lb ft at 3500 rpm. That converter should easily stall at 3000+ if the tires would hold it. There are alot of things that are not adding up.

Low profile 17" tires should not be capable of holding this engine as described. It should fry them from a dig, it should fry them on a 2-1 downshift. It should spin from a roll. You say it wont even chirp them??? 

   I suggest putting a timing light on it 1st and see where this "detuning" has it set at. I would suggest putting it at 36 to 38 total to start.  What fuel pump are you running? Have you verified fuel pressure?

[cdr]

The "hemi" trans is essentially the same thing as a regular 727 as far as driveability is concerned. A few less clutch drum springs and an extra friction here and there, but saying "hemi spec" just sounds cool. Without certain modifications, you cant "upgrade" a "regular" 727, but thats a whole other conversation...

    A stock heavy duty hemi converter will not flash at 2500 rpm behind a 500 inch stroker making almost 600 lb ft at 3500 rpm. That converter should easily stall at 3000+ if the tires would hold it. There are alot of things that are not adding up.

Low profile 17" tires should not be capable of holding this engine as described. It should fry them from a dig, it should fry them on a 2-1 downshift. It should spin from a roll. You say it wont even chirp them??? 

   I suggest putting a timing light on it 1st and see where this "detuning" has it set at. I would suggest putting it at 36 to 38 total to start.  What fuel pump are you running? Have you verified fuel pressure?

    That car should be violent & scary with those tires.

[justcruisin]

I have basicly the same set up in a stock stroke 440 - same heads same cam, I run a 11" converter, it will flash to 3200. It boils the hides with no problems, I would guess you should be making good power below 2000 RPM with the stroker crank and that cam, you should be able to fry the tires even with a stock 12" converter. I would be checking the basics first - timing, fuel, brakes if the car has been sitting. There would be no need to de-tune the engine for street use with that set up unless the compression is too high, what is the cranking compression?

[ds440]

Thanks guys!
Yeah, I figured the 'Hemi spec' comment was just a line for the most part.  Like when you hear non-Mopar people mention things like "Hemi side mirrors" or "Hemi interior trim."

The engine performs acceptably - it doesn't stutter, cough, or choke out.  But when he gets on it from a roll and it doesn't even chirp the tires.  With dyno numbers like that, we thought for sure this thing would be terrifying.  But so did the engine builder, and he made several comments about how scary this engine would be.  We think he was legitimately scared for our well-being (or maybe the car's well-being   ) and detuned everything to ensure that the car didn't get away from us.  However....the car isn't launching like it should.

He originally had an Edlebrock mechanical fuel pump, but it chewed through the pushrod in less than 300 miles.  So instead of getting a new hardened pushrod, he upgraded to an Holley HP Billet electric fuel pump (#12-800).  There is a fuel pressure gauge by the carb that reads 6-8lbs of pressure (if memory serves me).

The compression is 10.5:1, I believe.  Maybe 10.25:1 ...I don't have the build sheet in front of me at the moment.  It runs on pump gas with no problems. 

One thing to note as well - we think the car is running rich (Proform 850cfm).  The exhaust is really thick with a fuel smell.  So clearly, it's not yet fine tuned.  The car only has a total of 600 miles and we are chasing a series of new-resto-teething gremlins (electrical issues, the aforementioned fuel pump problem, rear main seal leaking, etc).

We'll throw a timing light on it, see where it's set at and move from there.  Thanks for all your feedback.  We're novices at this and, like I said, several people have mentioned the torque converter as a potential issue.  We really appreciate you guys taking the time to help!

[c00nhunterjoe]

Fuel sounds good at idle. Double check full throttle after a full pull in 1st and part way into 2nd just to he safe. Timing next.

[cdr]

also check & make sure when pushing the gas pedal that the carb is WIDE OPEN.

[c00nhunterjoe]

  a dollar for everytime that was the problem and i could retire...

[ds440]

Great advice - thanks guys! 

[firefighter3931]

DS440,

Does the preform carb have the throttle adapter installed. When using a Holley/Proform carb you must install the Holley 20-7 throttle adapter which is a Mopar specific part. If the adapter is not installed you will not be able to get wide open throttle with the pedal on the floor. You absolutely need this part. 


As for timing ; this engine will want at least 16* at idle with 35-36* total timing all in by 2500 rpm. 


Ron

[ds440]

DS440,

Does the preform carb have the throttle adapter installed. When using a Holley/Proform carb you must install the Holley 20-7 throttle adapter which is a Mopar specific part. If the adapter is not installed you will not be able to get wide open throttle with the pedal on the floor. You absolutely need this part. 


As for timing ; this engine will want at least 16* at idle with 35-36* total timing all in by 2500 rpm. 


Ron

Ah - great to know!  I'm not sure if that adapter has been fitted to the car or not.  But I will definitely double check.

We've yet to get the chance to put a timing light on it yet....but when we do, we appreciate the starting point!  Thanks-a-million, Ron!!!

[firefighter3931]

DS440,

Does the preform carb have the throttle adapter installed. When using a Holley/Proform carb you must install the Holley 20-7 throttle adapter which is a Mopar specific part. If the adapter is not installed you will not be able to get wide open throttle with the pedal on the floor. You absolutely need this part. 


As for timing ; this engine will want at least 16* at idle with 35-36* total timing all in by 2500 rpm. 


Ron

Ah - great to know!  I'm not sure if that adapter has been fitted to the car or not.  But I will definitely double check.

We've yet to get the chance to put a timing light on it yet....but when we do, we appreciate the starting point!  Thanks-a-million, Ron!!!

Hey Dave,

Here is a pic of the Holley 20-7 Mopar adapter as well as an installed pic on a ProForm double pumper carb with the auto trans kickdown linkage properly installed. 


Ron

[ds440]

Hey thanks, Ron!

This is the current linkage set up on the car - these are pics from the restoration.  To my untrained eye it looks like a different set-up from the picture you've attached.     I guess that would make sense: the engine pulls hard on the dyno, but then once in the car, it struggles because it's only pulling half-throttle because of a linkage goof.  We still have to double-check the timing as well.

My brother is currently out of town on vacation (thus the delay on setting the timing as well), so this will be the first thing we'll tackle when he gets back. 

I really, truly appreciate the help!

[firefighter3931]

Hey thanks, Ron!

This is the current linkage set up on the car - these are pics from the restoration.  To my untrained eye it looks like a different set-up from the picture you've attached.     I guess that would make sense: the engine pulls hard on the dyno, but then once in the car, it struggles because it's only pulling half-throttle because of a linkage goof.  We still have to double-check the timing as well.

My brother is currently out of town on vacation (thus the delay on setting the timing as well), so this will be the first thing we'll tackle when he gets back. 

I really, truly appreciate the help!

Hi Dave,

I see two things wrong ;

(1) The 20-7 adapter is not installed. Without it you will never get proper operation of the carburetor....the pedal ratio will be off.

(2) The kickdown linkage is not properly adjusted and the tension springs that hold the lever against the stud are missing. This will affect transmission shifting and internal line pressure. That also needs to be rectified.


Ron

[ds440]

Hi Dave,

I see two things wrong ;

(1) The 20-7 adapter is not installed. Without it you will never get proper operation of the carburetor....the pedal ratio will be off.

(2) The kickdown linkage is not properly adjusted and the tension springs that hold the lever against the stud are missing. This will affect transmission shifting and internal line pressure. That also needs to be rectified.


Ron

Thanks Ron!!! 
These pictures were taken while the car was being assembled (the windows weren't in yet, the interior was missing, etc), but I'm 99.9% sure the 20-7 adapter has not been installed since.  The kickdown linkage I'm 50/50 unsure about.  It may have been adjusted since these pictures were taken.   

Regardless, I'll see if I can get a few recent pictures uploaded to verify.  I can't even begin to tell you how much you've helped us and how thankful we are!   

[ds440]

Below are some images of the throttle linkage as it currently sits.  It appears that the transmission kickdown has been adjusted, but I still don't know if this is acceptable (?).

I'm not seeing the 20-7 adapter installed on there.  Or the set-up is different from the picture that Ron posted. 

Thanks in advance for any input!

[firefighter3931]

Hi Dave,

The first thing you need to do is install the 20-7 throttle adapter and adjust the cable so that it's getting wide open throttle with the gas pedal on the floor. The way it's set up now is incorrect and it's only opening the throttle blades partially.

After the cable is set up with the 20-7 adapter you can adjust the kickdown lever. The way to adjust that is to open the throttle wide open and adjust the threaded rod so that it is fully syncronized with the the throttle blade opening at wide open. Then reattach the tension spring to pull the slotted lever tight against the stud.


Ron

[ds440]

Thanks Ron!  You're input has been invaluable!!!

The 20-7 adapter has been ordered and should be arriving shortly.  We really appreciate you taking the time to help us.

I'll keep you posted!