Drive train not quite right

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70 Duster Herb

70 Duster Herb

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1970 Duster. 318 built but not extreme, don’t know the cam but it has a performance cam(15 psi vacuum at idle). I know very little about the engine but it does very well out to 5500ish rpm. Trans 1969 HD van 727 (every spring for clutch is there like 15.) Again this performs and shifts great. 83/4 sure grip 489 case b body axle rebuilt has 3:23 gears.
as stated it preforms very well from 2500 ish to 5500 ish shifts-well and pulls hard.
So the low end idle to 2500 ish pretty sluggish. Can’t roast the tires at all. I can feel them turn a little but not enough for me to feel all hps hitting ground. Oh tire size 295 55 on 15x10 rim. Power braking… NAH! Ain’t having it. Revs to 1500-1800 and just sits there or pushes through the front brakes.
I think the gears aren’t right or torque converter is too low a stall. I’ve tested it I think I’m 1500-1800 most likely stock from the van.
Theory is if it can’t get to power band until 2500 ish I should put a 2500 stall converter in or should I change gears to get to power band quicker.
I need a drive train person to give me a little schooling. I’m actually tired of reading all the torque converter threads that just don’t apply. Thanks for the yer knowledge.

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Lets not over think this. What is the initial timing? Do you run a vacuum advance? What distributer? My first impression is that you need quicker RPM.
 
70 Duster Herb said:
1970 Duster. 318 built but not extreme, don’t know the cam but it has a performance cam(15 psi vacuum at idle). I know very little about the engine but it does very well out to 5500ish rpm. Trans 1969 HD van 727 (every spring for clutch is there like 15.) Again this performs and shifts great. 83/4 sure grip 489 case b body axle rebuilt has 3:23 gears.
as stated it preforms very well from 2500 ish to 5500 ish shifts-well and pulls hard.
So the low end idle to 2500 ish pretty sluggish. Can’t roast the tires at all. I can feel them turn a little but not enough for me to feel all hps hitting ground. Oh tire size 295 55 on 15x10 rim. Power braking… NAH! Ain’t having it. Revs to 1500-1800 and just sits there or pushes through the front brakes.
I think the gears aren’t right or torque converter is too low a stall. I’ve tested it I think I’m 1500-1800 most likely stock from the van.
Theory is if it can’t get to power band until 2500 ish I should put a 2500 stall converter in or should I change gears to get to power band quicker.
I need a drive train person to give me a little schooling. I’m actually tired of reading all the torque converter threads that just don’t apply. Thanks for the yer knowledge.

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That is a lot of tire you're trying to turn with a 3.23. I have a 3.23 SG that I am going to replace soon. I have a 408 going to a 727 w/3500 9.5 converter turning 28" tires (275/60-15's). I have no problems turning my tires if I get on it but I have a massive amount of torque to do so. If your engine is tuned properly, you are making power but a different converter sure would help that bottom end a lot! You should give the folks at PTC (or others) a call to see what they recommend for stall.
 
Yep get a good converter. Makes all the difference in the world. 3.23 gear? I'd say a 3000 stall but you never know until you put in there and see how she feels. Maybe a tight 3500?
 
I've got a 72 Duster. Stock 318 with a 272 454 Summit cam, dual plane intake, headers , 904, 3.23s , 275/60-15, etc,etc. Stock converter flashed to about 2000. Called PTC and had them make me a 9.5 street/strip converter. He asked me what stall I wanted and I said, "about 3500 I guess". I got the converter about a month later and spent a Saturday evening installing it. Guess what it flashes to? About 3500. So, I would say they hit it right on the mark. Launch is much improved. Now I just need to get back to the track. I've got a Dynamic 9.5 in my Satellite and I almost ordered from them again but decided to give PTC a try.
 
forphorty said:
I've got a 72 Duster. Stock 318 with a 272 454 Summit cam, dual plane intake, headers , 904, 3.23s , 275/60-15, etc,etc. Stock converter flashed to about 2000. Called PTC and had them make me a 9.5 street/strip converter. He asked me what stall I wanted and I said, "about 3500 I guess". I got the converter about a month later and spent a Saturday evening installing it. Guess what it flashes to? About 3500. So, I would say they hit it right on the mark. Launch is much improved. Now I just need to get back to the track. I've got a Dynamic 9.5 in my Satellite and I almost ordered from them again but decided to give PTC a try.
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Flash stall is always higher then brake stall. My converter brake stalled a 5400 and flashed at 5800-6000 depending on trans temp. I had a 5500 tight.
 
The stall of a 904 converter that came in most of those cars was a lot higher than a 727 converter out of a heavy van. There were a few heavy Dodge vehicles that had hi-stall converters, but they also had low geared rearends. This situation you have is a common occurrence when switching to a 727; if the trans is from a heavier vehicle; low end suffers from decreased stall; giving the 727 a bad rep for "parasitic loss"...
 
Agreed on the convertor. It will make a world of difference. My only advice is to spend a little more $$ and invest in a quality unit. For this car, a solid 9.5" or 10" TC will be A-Okay. No need to get an 8".

Sweet ride, btw
 
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