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Discussion Starter #1
Hey all, it's been a while since I've been on here mainly because the Nova's been mothballed. Well it's time to get it back out and I'm considering changing the transmission and rear gear in an attempt to get more use out of the car.

I was orginally thinking about using a 200-4R but it's more money and there is more to change to install it. So I started looking at the T350 and it seems like when you do the math I should get roughly the same performance as the PG if I use 1&2 for racing and have a more sane highway rpm in 3rd.

Here is the current combo that has gone a best of 11.62 @ 118 with a 1.6 60'.

327 .030" over
stock block, crank, rods
forged flat tops with 2 valve reliefs
461 casting ported heads
252/260 @ 106 .540 int, .547 ex at the valve
380 ft lb from 4500 to 6000
435 HP at 6750
shift at 7000 and going through the lights at 7000
The converter flashes to 4400 off idle

PG
Manual valve body
turbo spline

9" with 4.56 gears

6 pt cage
frame connectors
cal tracs
stock monoleaf
235/60-15 hoosier quick time

The only change I want to make is to go with the Turbo 350 and 3.25 rear gear and slightly taller 255/60-15 while using the same converter. Another factor here is that the rear end is howling and needs a rebuild so if I'm going to make a change now would be the time to do it.

At this point I am not concerned with all out performance but have good performance with the ability to drive the car to the track 40 miles away rather than towing or running 3800 @ 60 mph.

Here is the math on the comparison.

starting line ratio
PG - 1.76 x 4.56 = 8.02
T350 - 2.52 x 3.25 = 8.19

rpm drop 1st to 2nd
T350 = 7200/4343
PG = 7200/4019

Using 1 & 2 - 1.52 x 3.25 = 4.94 final drive and 27" tire =
7500 RPM 122.71 MPH
7000 RPM 114.53 MPH

using 3rd on the highway
2500 RPM 62.17 MPH

It seems like if I use the T350:
- cheaper than 200-4R
- less weight than 200-4R
- similiar results using 1&2 as with the PG
- use same converter from the PG
- still have a reasonable highway rpm

What am I missing or does this actually make sense?

Thanks in advance and sorry for the long post.

PB
 

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id say change the rear gears to 4.11s so you can still run in the elevens i dont know too much with the trans gearing i have a 63 nova with a 3000 converter and 3.73s and i drive it all over the place havent been down the freeway yet but i will be changing my converter to a 4000 so i can 60 ft like you
 

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You may be a bit optimistic on your rpm at freeway speed. Have you accounted for converter slippage? I have a 3.50 gear, TH350, 27" tire and run about 3200 rpm at 65 mph. Still reasonable for freeway driving. :yes: I drive 85 miles to the track, run low 12's and then drive it home. But I also have a 383 with peak HP just under 6000. At any rate, I think your idea of going to a freeway gear is the way to go.
 

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Discussion Starter #4
You may be a bit optimistic on your rpm at freeway speed. Have you accounted for converter slippage? QUOTE]

No I didn't. The number was just a straight calculation from one of the tools on Wallace Racing.com.
However that is one of the things I'm wondering about along with the flash stall. I believe the converter is fairly efficient in the current combo I think it was like 3% if memory serves or my calculations were correct.

I was hoping I could get away without having to redo the converter but I'll probably have to and I'm thinking it will probably cost me a little et.

Thanks for the input.
 

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id say change the rear gears to 4.11s so you can still run in the elevens i dont know too much with the trans gearing i have a 63 nova with a 3000 converter and 3.73s and i drive it all over the place havent been down the freeway yet but i will be changing my converter to a 4000 so i can 60 ft like you
No I didn't. The number was just a straight calculation from one of the tools on Wallace Racing.com.
However that is one of the things I'm wondering about along with the flash stall. I believe the converter is fairly efficient in the current combo I think it was like 3% if memory serves or my calculations were correct.

I was hoping I could get away without having to redo the converter but I'll probably have to and I'm thinking it will probably cost me a little et.

Thanks for the input.
Sounds to me like you two need to trade converters :yes:
 

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I have a calculator I built in a spreadsheet.
It also does not allow for converter slippage.
I come up with 69 MPH in first gear at 7,000 MPH and 114 MPH in second gear at 7,000 MPH.

I guess the question is at the point that you have hit 7,000 RPM, have you covered the quarter mile?

That is a little tougher to figure out, but even if you have to shift into third, what would be the problem be with that?

I will say that if you put in a good 2004R, you won't be disappointed.

I am running 3.73s and 2,000 rpm is about 63 mph.
 

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...that is one of the things I'm wondering about along with the flash stall. I believe the converter is fairly efficient in the current combo I think it was like 3% if memory serves or my calculations were correct.

Slippage of 3% would be VERY efficient!:yes: I think 7-8% is more typical, which is what mine is at freeway speed. My converter is supposed to be 3000stall speed, but is probably closer to 2500. I still get decent 60 ft times even at that, but again I have a 383 with a mild (low rpm) build. Your motor needs a lot more rpm to get the same HP.
 

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I think 7-8% is more typical, which is what mine is at freeway speed
Hey Bob,
Now I ain't no mathmagician, but I get closer to 12% slippage for your combo!
Whose converter are you running? Maybe you should look into a new one, you might be leaving a lot on the table.


As for going from 4.56's with a Glide, to 3.25's with a TH-350 and taller tires, I think you are going to lose some performance, but it's hard to say. It looks like you have a pretty well matched combo to be going that quick!
 

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Hey Bob,
Now I ain't no mathmagician, but I get closer to 12% slippage for your combo!
Whose converter are you running? Maybe you should look into a new one, you might be leaving a lot on the table.

Mike, you may be right. I haven't checked it lately, was going from memory and that can be dangerous! :eek: I have a question for you about your converter. As I recall your stall is about 4800 (again, going from memory:eek:) and you have stated several times a good converter will have less slippage even if it has a high stall speed. I assume you are talking about steady state cruising at freeway speed. So my question relates to stop and go driving: with higher stall speed doesn't the converter slip more as you go from a stop to say 40 mph? Once at a steady speed I can see how the slippage would drop, but even with low acceleration rates, it seems there has to be some trade off for a street car as stall speed increases. Otherwise, why wouldn't everyone just go with a 5000 stall speed and have the best of both? Just curious.
 

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Discussion Starter #10
you have stated several times a good converter will have less slippage even if it has a high stall speed. I assume you are talking about steady state cruising at freeway speed
.

Znova, I guess that's where I'm going with this and the question is do I need to adjust the stall on my converter since my freeway rpm will be so much lower than with the 4.56's.
I think:confused:, the converter as it is may work fine at the track since the starting line ratio and rpm drops are similiar but will it operate acceptably on the freeway?
 

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My converter is 6000+ depending on which engine I'm running. When I drove the car to Nashville, in regular, flat cruising you wouldn't know much difference. When climbing a steep grade that requires more throttle input, you are going to see more slippage. In stop and go traffic there will also be more slippage, but you learn to control your foot so it's not too bad--I really don't notice it much because I've had it more many years.
I run 4.30's, but I know a guy that ran a converter like mine with 3.08's--he used the coil thing off the back of a refrigerator as a trans cooler--it covered a large area under the car so there was a lot of fluid circulating from there to another big cooler up front.
 

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Discussion Starter #12
I know a guy that ran a converter like mine with 3.08's--he used the coil thing off the back of a refrigerator as a trans cooler--it covered a large area under the car so there was a lot of fluid circulating from there to another big cooler up front
Okay, so heat is the issue then. I have a trans temp gauge in the car and I was planning on using a deep pan like I did on the PG. I never saw over 180F in the PG. Are there any other issues assuming you can keep the fluid cool?

Thanks everyone for your input.
 

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.

Znova, I guess that's where I'm going with this and the question is do I need to adjust the stall on my converter since my freeway rpm will be so much lower than with the 4.56's.
I think:confused:, the converter as it is may work fine at the track since the starting line ratio and rpm drops are similiar but will it operate acceptably on the freeway?

I agree, I think your 4400 stall converter will work fine on the freeway if you change gears. You should check slippage by comparing your calculated rpm vs. actual at freeway speed. If it is 8% or less, I'd say you are good to go. In fact when I change converters, I plan to go to a slightly higher stall speed and live with slightly more slippage in stop/go driving. As Mike points out, slippage at steady speed on flat ground is independent of stall speed. And yes, heat is critical so as long as you have adequate cooling you should be fine.
 

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ok i have one of them b&m super coolers on mine am going to change to a 4500 converter and 4.11s soon it is mounted in front of radiator right now im using a mech fan with shroud will be changing over to a proform electric water pump , a 16'' electric fan with shroud as well will this be adiquit cooling for me also i have a 2'' deep sump aluminum trans pan too just want to make sure i dont burn up also in the near future i may go with a gear venders unit so i wont have to worry about rear gears or converter although its still going to slip a litte
 

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I would think that your slippage in high gear with 3.25 gears would be greater than with 4.11 gears, even with the same converter. The 3.25 gears would present greater resistance, so I would think it would slip more.
 
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