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Discussion Starter #1
Rear end question for all the experts!

I have a '66 Galaxie with a stock 352, Edelbrock performer 2105 intake, Holley 600 cfm carb and FPA headers. C6 trans and a 9" rear. Exhaust is 2 1/4" pipe, H style with flowmaster super 44's, which sounds outstanding. I put the 352 back in the car since it only had less than 80,000 original miles and ran like a champ (still does). Plan to put a bigger motor in later but for right now, just running this 352.

It currently has 18" rims with Pirelli 275/45/18 27.8" tires. While it is fairly fast on the open road, it seems ALOT slower off the line than what I would like it to be or expected. The vast majority of my driving is within the city but some of those drives would be like driving highways since I live in a big city and can drive for up to an hour at higher speeds.

My goal is to get MORE acceleration off the line, but keep the car driveable. The car currently has a 3:0 gear. Would a 3:25 make enough of a difference or should I go with the 3:50?

Since I don't have an RPM gauge (yet) I checked an online RPM calculator, it shows my current RPM at 70mph with my 3.00 and 27.8" tires is 2538. 3:25 would be 2750 and a 3:50 around 2961.

It already "seems and sounds" to be screaming at 70mph. I'm assuming that would only "seem and sound" worse going with a higher gear. I'm posting this question obviously because I don't know and ask for your opinion on how to best achieve better acceleration off the line. I'm not too worried about fuel consumption or MPG either. Just looking for some more punch!
 

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Are you sure you have 3.00 rear end currently? My suggestion would be to hook up a tachometer, esp. if you are considering one for the future as they are an easy install and not too expensive. That and a GPS receiver will show you where you are now. The speedometer could be off or have the wrong gear, etc. Rear gearing is always a tradeoff between acceleration and high speed cruising. My first car as a kid was 64 Galaxie with a 390 and 4.11 rear end (4 speed). It was pretty loud at 70 but at 16 it didn't bother me.

Pat
 

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Discussion Starter #3
Are you sure you have 3.00 rear end currently? My suggestion would be to hook up a tachometer, esp. if you are considering one for the future as they are an easy install and not too expensive. That and a GPS receiver will show you where you are now. The speedometer could be off or have the wrong gear, etc. Rear gearing is always a tradeoff between acceleration and high speed cruising. My first car as a kid was 64 Galaxie with a 390 and 4.11 rear end (4 speed). It was pretty loud at 70 but at 16 it didn't bother me.

Pat
Yes, definately a 3:00. Ordered it new myself.
 

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Have you done any work to the distributor? Sounds crazy given your question, but for part throttle performance, in traffic, you have done 2 of the most important things for an FE but not the third. 1 - headers, 2 - properly sized 4 barre and intake, but equally (if not more important) is a distributor recurve. I would have it done to get 36 degrees total at 2800 rpm, with initial set at 12-14 (so 22-24 mechanical), then I would run ported vacuum advance. That will create a heck of a drivability improvement

Ford set up ingition curves, slow and huge to counter low initial numbers so that it would run on any kind of swill people pumped into the tank. Recurving makes a huge difference, more so the lower your compression is.

Then, I think if you want more power than that, a 3.25 isn't worth it, go 3.50, spinning at 3 grand at 70 won't hurt it and you'll get used to it. In fact, the reverberation of a noise cancelling muffler like a Flowmaster is probably why it sounds like it's screaming. You will lose highway gas mileage, but you likely will gain in town mileage (if you keep your foot out of it)
 

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Have you done any work to the distributor? Sounds crazy given your question, but for part throttle performance, in traffic, you have done 2 of the most important things for an FE but not the third. 1 - headers, 2 - properly sized 4 barre and intake, but equally (if not more important) is a distributor recurve. I would have it done to get 36 degrees total at 2800 rpm, with initial set at 12-14 (so 22-24 mechanical), then I would run ported vacuum advance. That will create a heck of a drivability improvement

Ford set up ingition curves, slow and huge to counter low initial numbers so that it would run on any kind of swill people pumped into the tank. Recurving makes a huge difference, more so the lower your compression is.

Then, I think if you want more power than that, a 3.25 isn't worth it, go 3.50, spinning at 3 grand at 70 won't hurt it and you'll get used to it. In fact, the reverberation of a noise cancelling muffler like a Flowmaster is probably why it sounds like it's screaming. You will lose highway gas mileage, but you likely will gain in town mileage (if you keep your foot out of it)
+1

The biggest problem with your combination (352, C6 and 9") is a trifecta of inefficiencies and low initial power. The '66 352 was a low torque and horsepower engine, couple that to a C6, which in stock form is a big energy vampire and so is a Ford 9" with its long tooth sliding engagement. You can approach this from a number of different angles; try to increase engine low end torque (as My427stang suggested with the recurve), switch rear end gearing and settle for tradeoff's, and/or reduce the parasitic drag in the C6 and 9" to free up lost horsepower.

In my opinion I do not like revving an engine if I don't have to. I put 3.25's in one of my big block cars and I do not care for the 75MPH can you hear me scream engine. The only time I would do that now is if I had overdrive of which is that plan for that car. With that here are some alternative suggestions for your consideration:

1.) Rollerize the C6 and replace 1st gear with a higher ratio gear set, this not only frees up extra power but increases off the line initial grunt, I think they have a 2nd gear ratio change as well. This gives you more of what you want without revving the engine in 3rd as you have with a higher rear end gear set. Basically you are converting to a wide ratio transmission such as the Ford 4R70W, or the GM 700R4/4L60/4L60E, but without the overdrive obviously.

2.) There are gear vendors that will micro polish your gear set in the 9" to reduce friction and free up horsepower, aside from fancy lubricants this is the only way to economize a 9"

3.) Aside from the distributor recurve you could change other things on your 352. You didn't mention if the internals were OEM stock parts or not. Possibilities are using the Edlebrock aluminum heads, with a cam change. I know Edelbrock says their common FE CJ head will not fit 352 only 390's, but I did experiment with one fitment wise on a 352. Turns out you're just limited to valve lift before the valves whack the cylinder wall. You could also convert to a roller camshaft and with its higher ramp rates than a flat tappet cam, depending on the grind chosen, it could boost your low end torque and help you there.

Cheers
 

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Discussion Starter #6
Have you done any work to the distributor? Sounds crazy given your question, but for part throttle performance, in traffic, you have done 2 of the most important things for an FE but not the third. 1 - headers, 2 - properly sized 4 barre and intake, but equally (if not more important) is a distributor recurve.
Thanks for the input My427stang!
Do you happen to know the recurve kit information for a stock distributor?
 

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Discussion Starter #7 (Edited)
+1

The biggest problem with your combination (352, C6 and 9") is a trifecta of inefficiencies and low initial power. The '66 352 was a low torque and horsepower engine, couple that to a C6, which in stock form is a big energy vampire and so is a Ford 9" with its long tooth sliding engagement. You can approach this from a number of different angles; try to increase engine low end torque (as My427stang suggested with the recurve), switch rear end gearing and settle for tradeoff's, and/or reduce the parasitic drag in the C6 and 9" to free up lost horsepower.

In my opinion I do not like revving an engine if I don't have to. I put 3.25's in one of my big block cars and I do not care for the 75MPH can you hear me scream engine. The only time I would do that now is if I had overdrive of which is that plan for that car.

Cheers
Thanks DesertXL!

At this point, I think I'll start by recurving the distributor and try a 3:50 gear to start. BUT, by your response, do you think I wont like the 3:50 gear? Can you explain for me?

I probably won't be doing any internal altering of the transmission but it was recommended by a friend to adjust the screw on the vacuum modulator 3 turns clockwise as a general starting point and that this would increase the shift points, giving me higher RPM's. Was instructed to take it for a test drive prior to the adjustment, put it in drive and get on it through out all of the gears, making note of what RPM's it shifts at. Then make any adjustments and do it again and I would notice the change. I'm just unsure at what RPM's I should be adjusting it too or if I'm looking for it to shift earlier or later. Any input on this recommendation?
 

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Expensive solution....

Install 3.70 gears (or even 4.11's) in the diff, and a Gear Vendors Overdrive behind the C6.
You get punch off the line from the diff gears, and lowered cruise rpm with the overdrive.

.
 

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Thanks DesertXL!

At this point, I think I'll start by recurving the distributor and try a 3:50 gear to start. BUT, by your response, do you think I wont like the 3:50 gear? Can you explain for me?

I probably won't be doing any internal altering of the transmission but it was recommended by a friend to adjust the screw on the vacuum modulator 3 turns clockwise as a general starting point and that this would increase the shift points, giving me higher RPM's. Was instructed to take it for a test drive prior to the adjustment, put it in drive and get on it through out all of the gears, making note of what RPM's it shifts at. Then make any adjustments and do it again and I would notice the change. I'm just unsure at what RPM's I should be adjusting it too or if I'm looking for it to shift earlier or later. Any input on this recommendation?
Hello mvannote,

All I meant is that I do not like high ratio (> 3.00) rear end gears as I don't like spinning an engine unnecessarily, it just wears things out faster and engines aren't cheap to build up. I put a 3.25 in my 1973 Caprice Classic. It was originally a 2.73 so it was a step up, seemed like a good idea at first, but my car is a daily driver and since we live out in the country there's plenty of interstate driving where the speed limit is 75 MPH. At 75 - 85 MPH the 454 is just screaming and I don't care for it. But that's just me.

Let me give you another example of one of our cars. The wifey's '96 Impala SS. It's a ~4300 lb car, with its wheezy original little 350 small block LT1. It has the factory 3.08 rear gear in its axle, but it has the 4L60E tranny with a high ratio first and second gear. As a result it feels very spry off the line. Don't get me wrong it's still a mid 15 second in the quarter mile but the 1st gear ratio really gets that heavy little car moving off the line.

For example the ratios for a C6 are:
1st = 2.46
2nd = 1.46
3rd = 1.00

The 4L60E:
1st = 3.059
2nd = 1.625
3rd = 1
4th = 0.696

Like galaxiex suggested you can also add a bolt on overdrive (still will not have lockup) and increase the rear axle ratio. As the adage goes there is more than one way to skin a cat.

A note on adjusting the vacuum modulator. You'll want to adjust the shift points at or just before the peak in the power band. If your 352 has the stock camshaft, it's a relatively narrow power band as I've modeled that engine and if you drag out the shifts past peak power the car will effectively start slowing down again before it shifts. That obviously will make it even slower getting up to speed. Every part of the drivetrain needs to be tuned together.

Hope that helps a little.

I know you just are now enjoying the car, but maybe you should think about either obtaining another C6 and building that up the way you want it, then just swap it in so down time is minimized. Either that or go the full monty and buy an adapter plate and put a 4R70W or a 4R100 with a wide ratio gear set in it and now the car has an overdrive with lockup. This is more involved however.

Just ideas.

Cheers
 

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Agree with these guys. I put 3.90’s in one of my cars behind a 4 speed. That was great for around town driving.
I since moved to a very rural area where towns are miles apart and no stoplights. The 3.90’s SUCK for this! I have put a deposit on a 5 speed. That way I can still get good acceleration off the line, but drop it in 5th on the open road.
 

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Rear end question for all the experts!

I have a '66 Galaxie with a stock 352, Edelbrock performer 2105 intake, Holley 600 cfm carb and FPA headers. C6 trans and a 9" rear. Exhaust is 2 1/4" pipe, H style with flowmaster super 44's, which sounds outstanding. I put the 352 back in the car since it only had less than 80,000 original miles and ran like a champ (still does). Plan to put a bigger motor in later but for right now, just running this 352.

It currently has 18" rims with Pirelli 275/45/18 27.8" tires. While it is fairly fast on the open road, it seems ALOT slower off the line than what I would like it to be or expected. The vast majority of my driving is within the city but some of those drives would be like driving highways since I live in a big city and can drive for up to an hour at higher speeds.

My goal is to get MORE acceleration off the line, but keep the car driveable. The car currently has a 3:0 gear. Would a 3:25 make enough of a difference or should I go with the 3:50?

Since I don't have an RPM gauge (yet) I checked an online RPM calculator, it shows my current RPM at 70mph with my 3.00 and 27.8" tires is 2538. 3:25 would be 2750 and a 3:50 around 2961.

It already "seems and sounds" to be screaming at 70mph. I'm assuming that would only "seem and sound" worse going with a higher gear. I'm posting this question obviously because I don't know and ask for your opinion on how to best achieve better acceleration off the line. I'm not too worried about fuel consumption or MPG either. Just looking for some more punch!
I started with a 352, it was reliable and kept running when I wanted it to. It'll last forever (other than the timing chain) if you change the oil and don't overheat it. But with that short stroke, etc. it doesn't have a lot of power. Since then I had a 390 for a brief time on one car, and 428's in a couple cars for a while, but I have hundreds of thousands of miles and decades with 427's, toploaders and C-6's with rear ends from about 2.5 for high speed, to 3.5 for the city. I didn't do a calculation but sounds like those tires are taller than the original. I'll assume they are the same. if you rarely go on the highway, and when you do, it's not for too long, I'd go with the 3.5 It'll be a lot quicker. 3.25 might be the sweet spot too, it'll be noticeably quicker in the city. The good news is that the 352 has such a short stroke, if it's got good oil, etc. spinning it on the highway over 3k won't hurt it, it'll just burn more gas.
 

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Expensive solution....

Install 3.70 gears (or even 4.11's) in the diff, and a Gear Vendors Overdrive behind the C6.
You get punch off the line from the diff gears, and lowered cruise rpm with the overdrive.

.
I have a gear venders with a built up C-6, a slippery torque converter, and a 482ci all aluminum Sideoiler 427 with a relatively mild cam and massive amounts of torque. I chose a 3.25 posi rear end. That engine has so much torque if I had to do it over I might think about a 3.0 or even higher. Keep in mind, it's not a 4th gear, it's a 3.5 gear. Technically it's a 6 speed, but in the real world, or a race, you'd only use the normal 3 and the overdrive 3.5 On a drag strip however, I'd use 1, 1.5, 2.5 which takes me over 100 mph.
 

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Hello mvannote,

All I meant is that I do not like high ratio (> 3.00) rear end gears as I don't like spinning an engine unnecessarily, it just wears things out faster and engines aren't cheap to build up. I put a 3.25 in my 1973 Caprice Classic. It was originally a 2.73 so it was a step up, seemed like a good idea at first, but my car is a daily driver and since we live out in the country there's plenty of interstate driving where the speed limit is 75 MPH. At 75 - 85 MPH the 454 is just screaming and I don't care for it. But that's just me.

Let me give you another example of one of our cars. The wifey's '96 Impala SS. It's a ~4300 lb car, with its wheezy original little 350 small block LT1. It has the factory 3.08 rear gear in its axle, but it has the 4L60E tranny with a high ratio first and second gear. As a result it feels very spry off the line. Don't get me wrong it's still a mid 15 second in the quarter mile but the 1st gear ratio really gets that heavy little car moving off the line.

For example the ratios for a C6 are:
1st = 2.46
2nd = 1.46
3rd = 1.00

The 4L60E:
1st = 3.059
2nd = 1.625
3rd = 1
4th = 0.696

Like galaxiex suggested you can also add a bolt on overdrive (still will not have lockup) and increase the rear axle ratio. As the adage goes there is more than one way to skin a cat.

A note on adjusting the vacuum modulator. You'll want to adjust the shift points at or just before the peak in the power band. If your 352 has the stock camshaft, it's a relatively narrow power band as I've modeled that engine and if you drag out the shifts past peak power the car will effectively start slowing down again before it shifts. That obviously will make it even slower getting up to speed. Every part of the drivetrain needs to be tuned together.

Hope that helps a little.

I know you just are now enjoying the car, but maybe you should think about either obtaining another C6 and building that up the way you want it, then just swap it in so down time is minimized. Either that or go the full monty and buy an adapter plate and put a 4R70W or a 4R100 with a wide ratio gear set in it and now the car has an overdrive with lockup. This is more involved however.

Just ideas.

Cheers
Just running a small block but love the wide range 4r70w with a 3.0 rear. It will roast up a one wheeler squealer or shift smooth and be in OD at 40mph.

If you have deep enough pockets, there are outfits that can build a 4r70w for FE block.

Always have to figure out if the juice is worth the squeeze and there is always something to spend some $$ on.
 

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If you do put the 3.5 in, will you report on the difference.
I replaced my 352 with a 390 and honestly could barely notice the difference. I have a spare 3.5 and I've been thinking of replacing my 3.0 but I want to know if the experience would be the same.
 

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Just running a small block but love the wide range 4r70w with a 3.0 rear. It will roast up a one wheeler squealer or shift smooth and be in OD at 40mph.

If you have deep enough pockets, there are outfits that can build a 4r70w for FE block.

Always have to figure out if the juice is worth the squeeze and there is always something to spend some $$ on.
Hello Mercury4me,

That's brilliant! I wonder if they would just machine the case of the 4R70W and old FX/MX/FMX bell housing so they would mate. I would want to build the transmission myself. I was always leery about using an adapter plate.

Thank you for the idea and sharing the link.

Cheers
 

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Discussion Starter #16
If you do put the 3.5 in, will you report on the difference.
I replaced my 352 with a 390 and honestly could barely notice the difference. I have a spare 3.5 and I've been thinking of replacing my 3.0 but I want to know if the experience would be the same.
Will do puttster.

I'm doing some additions soon. First, I'm going to get my distributor recurved, set my timing and fine tune my Holley AGAIN. Then I'm going to install either a 2000 or 2400 TCI stall converter in my C6. If all goes as I expect, I'll then be installing a 3:50 gear.

That combo should get me where I want to be.

My 352 has lower miles and runs strong. I was thinking of swapping my 352 for a 390 as well but have heard the same responses from others so I'm keeping my 352 for now.
 
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