Man, I would have never even thought the timing would be an issue. I have much to study up on. Thanks!
Easy (?) OD Auto Install
- Thread starter Topless69
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Man, I would have never even thought the timing would be an issue. I have much to study up on. Thanks!
My 79 Diplomat and my Dad's 79 St Regis both had that 904 lock up. Lots of them were swapped out back then because of torque converter shudder when locking up.
No one knew what the problem was at first since Chrysler was the first to use the lockup of the big 3.
RussellSullivan
Well-Known Member
I had a 74 Dart that had one. Not sure if they came factory that year or if I swapped it in. I remember it would shudder pretty hard if I was in third and just let off the gas. If I accelerated again, the shudder would ease up/go away entirely.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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The only complaint I had with mine was that it liked to occasionally go from Second straight to Third-LU
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So I was trying to accomplish the same this as the OP with the least amount of headache. The car is a 70 Dart with a moderately build 318 and a 904 that I am building for long distance road trips. After I did a bunch of research, I contacted Rick at A&A transmission in St. Louis. We came up with this: in the 1980s Chrysler was trying to chase gas mileage in their V-8 cars and the rear end ratios got down to 2.45:1. Which was fine on the highway, but a real dog around town. So they changed the internal 1st and second gear ratios from the old 2.45, 1.45, 1.00 to the new 2.74, 1.54, 1.00 making 1st and second gear act like it had a lower (numerically higher ) gear ratio. They also came up with lock up converters - first using hydraulics in the trans with serious problems and then with electronics connected to a computer. What A&A is going to build me is a 904 with the new ratios and a lock up manually actuated with a switch (and some fail safes to keep me from dying at a light because I forgot). I'm going with 2.94 rear gears which in 1st would be like the old trans with 3.28 rear gears, 2nd would be like 3.10 gears and 3rd would be 2.94 and lock up on the open road which should be worth another 2-300 rpm drop at 65. Like I said this is all in process, but no new drive shaft, not tunnel cutting, run some extra wires and off we go (theoretically).
famous bob
mopar misfit
Put taller tires on it , 3 :55 aint that terrible .
RussellSullivan
Well-Known Member
The rear gears even got as ridiculous as 2.2. I have a set that I swapped for 3.21s in my Diplomat's 8 1/4. I was able to cruise over 100mph without going over 2800rpm. My 0-60 times could be recorded with a sun dial
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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The Cruise timing is only an issue if you want to squeak out some fuel economy.
It has happened that after installing an overdrive, the engine actually loses fuel economy, because the new rpm is too low for the cam, and or the engine is NOT getting the ignition advance it needs.
I my experience, cruising at 2240 for years and years with my overdrive, I know that my engine likes timing deep into the 50s. Your results will vary. With the previous cam it was Ok with less.
Here are the Advertised durations of my two Hughes Cams, first the previous HE2430AL, then
the current HE3038AL;
1) 270/116/111/276/110+1/53,52Effective/Ica of64*
2) 276/116/103/286/110+4/61,58Effective/Ica of64*
Intake/compression/power/exhaust/ LSA/ovrlap/Ica
Cam 1 made fantastic fuel mileage, that Cam 2 couldn't touch.
Notice the colored numbers.
Cam 1, has 7.8% more degrees spent in power extraction, and has 8* or less overlap, or 89.6% as much.
I can tell if a cam is likely to make good fuel mileage by adding the compression and extraction degrees together. Cam 1 has 227, and cam 2 has only 219. No matter where you time the cam; you can trade a few degrees this way and that with cam-timing; but the totals will always add up to 227 and 219.
One might not think that such a small change would be a big deal, but when you factor in the overlap, that's when if goes to heck.
With Cam 1)
I could run a final drive of 3.23 x .71 x.78= 1.79, which is 65=1460, I mean the engine had no problems pulling that; but I could not get the timing up. She wanted 60 degrees, which consistently allowed the smallest throttle opening. My power curve had been established at .78* per 100 from 1200 to 2800, and 14* initial. So at 2000rpm, that came to 24*. To that, my Vcan was adding 20, for a total of 44*. So I was still 16* short. But at 1460 there was just no way to satisfy it.
So I went and got me a standalone timing delay box with a range of 15*, for a total of 59*@2000 rpm , but 2000 rpm was 90 mph! So I had to do something!.
I ditched the OD box, and replaced it with a Commando box, and got 65=2060; badaboom. And that is how I get fantastic fuel mileage with cam 1.
With Cam 2)
I chose a cruise speed of 65=2240 (manual trans); now using 3.55s and the .78 GVod for a final drive of 2.77
1) any slower and reversion was an issue and I couldn't control the AFR., and
2) it is the lowest rpm I could get the cruise timing up close to where it needed to be
3) but with the extraction reduced to 103 from 111, and the rpm up a bit; 2240 versus 2060, there was no way she would give me the mileage that I had been enjoying for the previous 4 years. So since 2005, I have been waiting for Cam 2 to die ...... but she's like the Energizer bunny...........
My car was a DD for years, racking up around 120,000 miles in less than 10 years, so to me, fuel economy was a really big deal.
But if you don't care about fuel economy.... then optimum cruise-timing is meaningless.
Man, yeah that’s a lot. And well over my head. I drive under 1,000 miles a year. So the cost isn’t a big factor. Just don’t enjoy 3k+ rpms on the highway lol
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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I hear ya. I got the overdrive partly because with 3.55s and small tires, my combo was doing 56=2600, and even 2600 was taxing in my daily one-way commute of ~30 minutes.
Oh for sure. Yeah I’d be going that route too with that many miles.
the question is how much surgery are you up for
A fair amount is alright.
512Stroker
We are all here because we are not all there.
Have you ever considered a 727 with a hydraulic lock up convertor?
No overdrive but, zero convertor slip while cruz'n.
Should be a drop in no sheet metal surgery.
No. I'd really like a A500/42 trans. for this one.
SleeperDart505
Stock wheels, Stock Paint, 505" Stroker, Full Cage
Awesome! Thanks for posting this info. This looks like the least intrusive way to get an OD tranny into an A body. Now, the only thing left is to ask the hard question.............roughly how much did this cost? Cost is less important to me than how much fabrication I have to do. But cost is pretty high up on the wife's list of questions to ask!!!
SleeperDart505
Stock wheels, Stock Paint, 505" Stroker, Full Cage
I'm not sure how much of that I understood but it was cool to read.
Would any of that matter with a 505" stroker 440 and a newly installed O.D. tranny or Gear Venders unit? I'm worried now that if I get the RPM's down TOO MUCH that I'll start having timing issues and my MPG's won't go up as much as I thought they might. I'm running down the road in the slow lane trying to keep up with traffic (70/75 MPH?) and turning about 4000 RPM currently. Something's gotta give, right? I have a 3.73 gear and 25.5" tall tires. I know I can go to taller tires and make a difference in the right direction but I don't think it'll be enough. I just bought this car so this was all done before I got it. I may have made a few different decisions if I built the car.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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Yeah, I agree; 75@4000 is too much for me. 3000 is even barely tolerable.
I have very limited experience with BBs and zero with anything over 440 cubes.
With your stated combo, the math goes to 75=3688@zero slip, could be|
up to 3800 @3% slip on the tach.
4000 would be 8.5% slip,
which points to; a slipping/loose convertor, a tach-error, or 3.91s actually being back there........
The 200R4 has ratios of 2.78-1.57-1.00-.67od
The A727 has ratios of; 2.45-1.45-1.00
So, with the 200R, your Zero-slip@75mph comes down to 2470. Adding 3%slip for a tighter GM convertor, that comes to 2545, which is high enough to be able optimize the timing for, using a factory Mopar type distributor, especially if you have alloy heads, which in my modest experience with my 367, don't need quite as much timing advance as iron open chambers.
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My 367 with alloy heads cruises best at a higher coolant temp. I surmised that was because the alloy heads were extracting heat out of the chambers even as it was being produced. So I painted my heads in an effort to keep the heat in, and jacked the minimum coolant temp up to 205*F, and shazzam, with optimized timing, she was up in the mid 20s mpgUs @65mph, which is the speed limit everywhere in Manitoba, except the TransCanada hiway.
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But I gotta ask you something;
You have a lightweight Dart, with a Monster motor, and stock narrow wheels, with, I assume tiny tires; that should roast any tires right up to cruising speed.
Have you thought about just running less rear gear?
I mean, 3.73 x .67= 2.50 equivalent. and/or 27inch tires over 25.5, is the equivalent .66 gear reduction.
Say you keep the 25.5s, and get a tighter convertor that cruises at 3% slip.
To cruise at 75=2550@3% slip, would now require a rear gear of 2.50..
>> 2.94s, 25.5s, and your current loose convertor would get you 75=~3130
Your starter gear would be 2.94 x 2.45= 7.20, but at zero mph, that number could easily be multiplied inside the convertor by say 1.8; so then, 7.20 becomes 12.97, which is killer. This will ramp down automatically over the next second or so at WOT, to become something like 7.2 x 1.4(estimated.)= 10.08 at the top of first gear, which is still a killer number. Second gear becomes around 1.45 x 2.94 x 1.3(est) in the convertor= 5.55ratio; Which will get you ;
6000@ around 103 mph with 25.5"tires. (still in second gear).
For a lightweight streeter, with skinny tires, and a stockish back-half, these are very nice numbers; and that BIG engine should have no trouble pulling this combo.
EVEN if you mini-tubbed that Dart, and kept the current loose convertor; you would still need a better rear suspension to keep from blowing the tires away.
How much is a 2.94/SG pumpkin gonna cost you?
Unless you run a potent traction-aide back there, you can even stick a small-pinion chunk back there. I mean guys used to give those away.
For a lil more money; 3.23s, 27s, and a tighter converter, would get you
75= ~2900; and at that rpm, you can easily tune the ignition system to optimize the cruise timing, to optimize your mpgs.
Altho,
with 505 cubes,
not sure it will make that much of a difference, lol
_______________________________________
Now, if I had 505 cubes in a stock-tubbed, street-Dart;
I would think about putting a tiny 228ish cam in it, and gear it with a Loc-Up overdrive, to cruise 75@ say 1700
which would take that 200R4, and 27s, and 2.76 gears. BUT
I might put a bit of stall in her, just for a bit of, off-the-line fun.
With 2.76s, and 27s, and a 2.78 low gear ;
first gear will go to 50mph @ 5200ish/ 60@6250ish; Bam!
I have very limited experience with BBs and zero with anything over 440 cubes.
With your stated combo, the math goes to 75=3688@zero slip, could be|
up to 3800 @3% slip on the tach.
4000 would be 8.5% slip,
which points to; a slipping/loose convertor, a tach-error, or 3.91s actually being back there........
The 200R4 has ratios of 2.78-1.57-1.00-.67od
The A727 has ratios of; 2.45-1.45-1.00
So, with the 200R, your Zero-slip@75mph comes down to 2470. Adding 3%slip for a tighter GM convertor, that comes to 2545, which is high enough to be able optimize the timing for, using a factory Mopar type distributor, especially if you have alloy heads, which in my modest experience with my 367, don't need quite as much timing advance as iron open chambers.
______________________________________
My 367 with alloy heads cruises best at a higher coolant temp. I surmised that was because the alloy heads were extracting heat out of the chambers even as it was being produced. So I painted my heads in an effort to keep the heat in, and jacked the minimum coolant temp up to 205*F, and shazzam, with optimized timing, she was up in the mid 20s mpgUs @65mph, which is the speed limit everywhere in Manitoba, except the TransCanada hiway.
_______________________________________
But I gotta ask you something;
You have a lightweight Dart, with a Monster motor, and stock narrow wheels, with, I assume tiny tires; that should roast any tires right up to cruising speed.
Have you thought about just running less rear gear?
I mean, 3.73 x .67= 2.50 equivalent. and/or 27inch tires over 25.5, is the equivalent .66 gear reduction.
Say you keep the 25.5s, and get a tighter convertor that cruises at 3% slip.
To cruise at 75=2550@3% slip, would now require a rear gear of 2.50..
>> 2.94s, 25.5s, and your current loose convertor would get you 75=~3130
Your starter gear would be 2.94 x 2.45= 7.20, but at zero mph, that number could easily be multiplied inside the convertor by say 1.8; so then, 7.20 becomes 12.97, which is killer. This will ramp down automatically over the next second or so at WOT, to become something like 7.2 x 1.4(estimated.)= 10.08 at the top of first gear, which is still a killer number. Second gear becomes around 1.45 x 2.94 x 1.3(est) in the convertor= 5.55ratio; Which will get you ;
6000@ around 103 mph with 25.5"tires. (still in second gear).
For a lightweight streeter, with skinny tires, and a stockish back-half, these are very nice numbers; and that BIG engine should have no trouble pulling this combo.
EVEN if you mini-tubbed that Dart, and kept the current loose convertor; you would still need a better rear suspension to keep from blowing the tires away.
How much is a 2.94/SG pumpkin gonna cost you?
Unless you run a potent traction-aide back there, you can even stick a small-pinion chunk back there. I mean guys used to give those away.
For a lil more money; 3.23s, 27s, and a tighter converter, would get you
75= ~2900; and at that rpm, you can easily tune the ignition system to optimize the cruise timing, to optimize your mpgs.
Altho,
with 505 cubes,
not sure it will make that much of a difference, lol
_______________________________________
Now, if I had 505 cubes in a stock-tubbed, street-Dart;
I would think about putting a tiny 228ish cam in it, and gear it with a Loc-Up overdrive, to cruise 75@ say 1700
which would take that 200R4, and 27s, and 2.76 gears. BUT
I might put a bit of stall in her, just for a bit of, off-the-line fun.
With 2.76s, and 27s, and a 2.78 low gear ;
first gear will go to 50mph @ 5200ish/ 60@6250ish; Bam!
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