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Discussion Starter · #1 ·
Hey guys, new to VMF have tried to spend several months reading before posting out of respect for previous posts especially from the more knowledgeable contributors. So thank you ! I’ve learned a lot and while still inexperienced I am hopefully better positioned to keep from asking STUPID questions.

Recently purchased a 66 C Code Vert 289 with what I believe to be the original 4 speed manual transmission. My goal for the car is a well performing DD. And for this car I am more interested in modernization than originality. Besides my myriad of questions regarding susp, wheel and brake upgrades I wanted to address the highway RPM issue. There is no tack on the car but the RPMs are just too high for my preferences at highway speeds (and gas pocket) not to mention the engine noise with headers.

I know I can invest in a T5 and would like to eventually anyway just for the modern shifting but am wondering if there are some initial, less costly steps that can be taken ie. differential ratio mods. Not sure of the current ratio. I know the car stumbles a bit from idle. It already seems to lack power a low revs, especially from idle and wants to stall out without excessive goosing which is harder on the clutch. In any case you get the idea.

Any direction would be massively appreciated!

Best

RudeMan.
 

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Sounds like a tuneup is the first step. Try to work through the stumbling and lack of power before messing with gears or transmission. You will probably improve your gas mileage too.

Once you get through that..... An axle gear swap is cheaper than a T5 swap, but you want to make sure your gear will play well with the T5 too.
 

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Agree with Pollock, tune it up and adjust the carb to get rid of your off idle stumble. May be as simple as an accelerator pump or float level adjustment.

Get a tach and determine what your highway RPMs actually are. These cars don't putt along at 1800 like many modern V8 cars, and will turn up towards 3000rpm even with a 2.83 rear gear to keep up with todays traffic. A T-5 will definitely make a difference and bring it into the low 2000s. Something else to consider is the cooling fan. The factory fixed units make a lot of noise. Switching to a clutched unit, or going electric will reduce much of the engine noise.
 

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First off...Ford designed these engines to run just fine at the RPMs they turn at highway speeds. An example for you...about 7 years ago I bought a Miata, at the time I was used to turning about 2900 RPM on the highway...the Miata of course had a much higher ratio and turned about 4100 RPM or so on the highway @75mph. This was outside my comfort range...but in the end it didn't matter how I felt about it, the car performed just how it was designed...it got 30mpg while spinning 4100 RPM and was right in its powerband for passing when it needed to be.

The point I am making is that spinning higher than you like doesn't mean anything at all, engines are generally designed to be able to spin that fast without any issue. A louder exhaust note is an issue with running a loud exhaust and points toward correcting the exhaust to be a more reasonable note.

Yes, of course you can change the trans to get an overdrive gear(or 2) and change the rear end gearing to a higher(numerically lower) ratio to reduce the RPM...but the ratio of the rear end is a torque multiplier...you lose acceleration for the "privilege" of consuming less gas and a quieter ride...but the answer here is that you are far better off changing the trans than the rear end gearing, at least with the trans you are able to choose when you want fuel economy instead of gutting the acceleration 100% of the time like a rear end gear change. You can also run larger diameter tires to reduce RPM if you want an easily reversible mod...it can make a difference of a few hundred RPM.


here is a calculator that allows you to play around with all your options to choose what is right for you.

If I were you, I would not change the trans to get a quieter note or to save gas though....a far better option is buy a beater car that gets 40mpg to do your high speed commuting and leave the mustang to cruising. I am not saying don't daily drive the car....I am going to quote Curt Kobain here "Take your time, hurry up, Choice is yours, don't be late " IE...leave earlier and drive at a slower speed when driving the mustang. Of course I am not in the same position...I only hit a max of 60mph on my way to work, but choosing to drive the mustang I wouldn't mind leaving earlier for work.

First thing to do is determine your RPM(any performance car needs a tach), your tire size, your gear ratios, and your rear end ratio so you have some information to work off of.
 

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Discussion Starter · #5 ·
Guys thanks for the thoughtful replies. Im going to get a tack and confirm my current rear end ratio and will likely circle back. Thank you for the calculator ! Perhaps I’ll be thinking about RPMs in a new light given wicked93’s post. I guess I’m realizing that the engine noise and swiftly moving gas gauge is bugging me more that I thought. And maybe the first step besides figuring out the slight choking off the line is is to attack the engine noise issue via exhaust upgrades/ changes. If you’ll indulge the conversation a little bit further I have two remaining questions:

1)why would a radiator fan upgrade reduce engine noise ?

2) is there any value in switching back from headers to stock exhaust manifolds in terms of engine noise reduction.

thanks so much.

RudeMan
 

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I have a 66 with a wide ratio Toploader, 3.55 gears and 215/60/15 tires. I was driving at 80 mph for a while turning 3800-4000 rpm. The sweet spot seems to be around 65 mph. As far as T5's most people use the production version with a 3.35 first and .60 fifth. Then they'll put in something like 4.10's and say how great the OD is on the highway. Ok but now first gear is so low, you're shifting into second gear right away. Many times they start off in 2nd gear and they'll tell you how nice it works. So basically you're now using 4 of the 5 gears. At that, you have a big jump between 4-5. I was just having a discussion with a guy this morning on exactly this. With a 3.35 T5 and 4.10's compared to a wide ratio Toploader with 3.00 gears. Over all final drive ratio in a T5 starting off in second it's 7.87:1 and fifth gear final drive is 2.46:1. Now look at the Toploader. In first gear final drive is a lower 8.34:1 and final drive ratio in forth is 3.00:1. With the Toploader you also have all four gear ratios evenly spread that you do not have in the T5. So is it worth the expense to install a T5 and low gears to take advantage of OD compared to the Toploader. On the highway the Toploader is only going to be a out 200-250 rpm more. Plus it'll take anything you can dish out to it.

If you ran 2.80 gears in the Toploader, it now more closely matches the T5 with 4.10's when comparing both 2nd gear to first gear and 5th gear to the Toploader 4th gear on the highway.
 

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1966 289 3-speed
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Guys thanks for the thoughtful replies. Im going to get a tack and confirm my current rear end ratio and will likely circle back. Thank you for the calculator ! Perhaps I’ll be thinking about RPMs in a new light given wicked93’s post. I guess I’m realizing that the engine noise and swiftly moving gas gauge is bugging me more that I thought. And maybe the first step besides figuring out the slight choking off the line is is to attack the engine noise issue via exhaust upgrades/ changes. If you’ll indulge the conversation a little bit further I have two remaining questions:

1)why would a radiator fan upgrade reduce engine noise ?

2) is there any value in switching back from headers to stock exhaust manifolds in terms of engine noise reduction.

thanks so much.

RudeMan
Welcome RudeMan! Just my personal experience but I had an electric fan on a previous 66 car that was annoyingly loud. Much more so than the stock fan. Maybe I just had a crappy one, but it'd be leery of doing that conversion just for noise sake.
 

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1)why would a radiator fan upgrade reduce engine noise ?
Fixed fans rotate at engine speed - always. Some of the "performance" fans are horrendously noisy. A thermostatic clutch fan will rotate only at a percentage of engine speed when it's not needed, like on the highway when airflow through the radiator provides the needed cooling. Electric fans set up with a thermostatic controller operate the same way.

2) is there any value in switching back from headers to stock exhaust manifolds in terms of engine noise reduction.
Yes, but it's probably best to determine which mufflers your car has. A high quality turbo style muffler, such as a DynoMax Super Turbo is about the quietest performance muffler available.
 

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Discussion Starter · #9 ·
Welcome RudeMan! Just my personal experience but I had an electric fan on a previous 66 car that was annoyingly loud. Much more so than the stock fan. Maybe I just had a crappy one, but it'd be leery of doing that conversion just for noise sake.
thanks for the welcome and the fan advice. It’s definitely largely combustion noise. Which I’m sure many would say leave it as is. If I can tone it down with the right mufflers and some floor insulation I’ll be more than satisfied. I’ve presently got the heater pulled out of the car and there is a 6 inch round hole under the rug. So that’s not helping LOL !
Nice coup and GT BTW !
 

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thanks for the welcome and the fan advice. It’s definitely largely combustion noise. Which I’m sure many would say leave it as is. If I can tone it down with the right mufflers and some floor insulation I’ll be more than satisfied. I’ve presently got the heater pulled out of the car and there is a 6 inch round hole under the rug. So that’s not helping LOL !
Nice coup and GT BTW !
Sounds like you just need to tone down your exhaust. Take some pics and post what you're running. You may be happy with a simple muffler swap.
 

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I have a 66 with a wide ratio Toploader, 3.55 gears and 215/60/15 tires. I was driving at 80 mph for a while turning 3800-4000 rpm. The sweet spot seems to be around 65 mph. As far as T5's most people use the production version with a 3.35 first and .60 fifth. Then they'll put in something like 4.10's and say how great the OD is on the highway. Ok but now first gear is so low, you're shifting into second gear right away. Many times they start off in 2nd gear and they'll tell you how nice it works. So basically you're now using 4 of the 5 gears. At that, you have a big jump between 4-5. I was just having a discussion with a guy this morning on exactly this. With a 3.35 T5 and 4.10's compared to a wide ratio Toploader with 3.00 gears. Over all final drive ratio in a T5 starting off in second it's 7.87:1 and fifth gear final drive is 2.46:1. Now look at the Toploader. In first gear final drive is a lower 8.34:1 and final drive ratio in forth is 3.00:1. With the Toploader you also have all four gear ratios evenly spread that you do not have in the T5. So is it worth the expense to install a T5 and low gears to take advantage of OD compared to the Toploader. On the highway the Toploader is only going to be a out 200-250 rpm more. Plus it'll take anything you can dish out to it.

If you ran 2.80 gears in the Toploader, it now more closely matches the T5 with 4.10's when comparing both 2nd gear to first gear and 5th gear to the Toploader 4th gear on the highway.
This subject is actually pretty hillarious. I have the MT82 6 speed for my swap...not because I have any desire whatsoever for a 6 speed since 6th is around .70, its really no better than a 5 speed in that regard...I just have the MT82 because it was a lot easier for me to just stick with it than the PITA it would be to convert to a T4 or T5(not that I could find a T4 for a decent price anyway).

There is a whole idea going around that the more gears you have the better...a 5 speed is better than a 4 speed, a 6 speed is better than a 5 speed, etc...but the whole idea is garbage spread by people who don't understand transmissions at all. As you mentioned, many 1st gears are near worthless these days. My gears for instance are
4.232.531.661.231.000.70

Now, I have a v6 that is going to have significantly less torque than a v8...but even so a 4.23 1st is still a granny gear to the extreme....and since I rarely hit the interstate 6th is meh...so the trans itself is really a 5 speed + overdrive....but in reality the gears I am using 90% of the time are pretty close a wide ratio T4 and in effect on a daily basis if I had a T4 I would see nearly no difference. One thing the gears would allow me to do is run a lower rear end ratio...but running something like 4.10s is self-defeating because that will in effect shorten all the gears...and the thing no one ever mentions is that more(and shorter) gears you have, the more time you lose having to shift...even in NA applications. In turbocharged or supercharged applications it becomes even worse because every time you shift you lose boost pressure...so when I look at a car turbocharged from the factory with 6 gears I just laugh because they have in effect made the car slower to pander to the whole more-gears-is-better thing....that might be true if we lived in a world where the speed limit on the interstate was 120MPH, but not in the real world.

If you have ever driven a large diesel truck you know very well that more gears does not make you faster, quite the opposite. There are now a few cars out there with 7 speed manual tranmissions(exotics mainly) it makes me wonder how many of their customers ever drive more than 150MPH(which is the only conceivable reason to have 7 gears)
 

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1)why would a radiator fan upgrade reduce engine noise ?
Just like the propeller on an airplane, a fixed fan makes noise. Other types, especially a thermal clutch fan, make far less nose.

2) is there any value in switching back from headers to stock exhaust manifolds in terms of engine noise reduction.
Sure- It'll get much quieter both under the hood and at the tailpipe, at the expense of engine power, mainly at higher rpm's.
 

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1)why would a radiator fan upgrade reduce engine noise ?
Just like the propeller on an airplane, a fixed fan makes noise. Other types, especially a thermal clutch fan, make far less nose.

2) is there any value in switching back from headers to stock exhaust manifolds in terms of engine noise reduction.
Sure- It'll get much quieter both under the hood and at the tailpipe, at the expense of engine power, mainly at higher rpm's.
Don't forget cast iron manifolds will also be much COOLER under the hood. Headers are hot, and heat does bad things to hoses and the like in the engine bay...most people don't wrap their headers...they seem to think they are show pieces.

As far as fan noise...the biggest difference is going to be highway speeds...and electric fan(wired properly) will never be on at interstate speeds, mechanical fans are always spinning


One thing of note here though on the whole subject.....we are spoiled by modern cars and so expect when daily driving a classic that they will be somewhat quiet....but the reality is that classic cars will always be louder and in general more primitive in every aspect. Its not a bad thing, its the nature of the beast. We get warped expectations of what we expect from a daily driver. For that matter...by the standards of the vehicles I learned to drive on, a classic mustang would be the lap of luxury...old international trucks and VW bugs....those are some rattle-can noisy vehicles.
 

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Discussion Starter · #14 ·
Ok great. I’m up in Asheville NC for the week so I’ll attach some muffler pics when I get back. That might be the easiest and most cost effective step toward engine noise reduction besides some floor installation. (Right now I’ve got a large sponge stuffed in the heater blower motor whole while I rebuild the heating system - the sound absorption properties of a good sponge are surprising) Mufflers, Who would have thought mufflers had anything to do with engine noise ? Duh!

So the other half of this conversation was surrounding high revs and fuel consumption. I know, if you want a highway cruiser and fuel economy then don’t drive around in a 55 year old car with the original V8. I get it. But I live in coastal SC and you can’t go anywhere on the grand strand without getting on Rt 17 - a badly designed two lane excuse of a highway where everyone is driving an SUV and averaging 65 to 70. The tranny replies have officially gone over my head so I’m going to re read them and make sure my next post includes some numbers. I can see now that’s it’s not necessarily about just throwing in an expensive T5. That might be the answer in the end but now I have more questions than when I started which is the whole reason and purpose of this forum. So thanks !

RudeMan
 

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Discussion Starter · #15 ·
Don't forget cast iron manifolds will also be much COOLER under the hood. Headers are hot, and heat does bad things to hoses and the like in the engine bay...most people don't wrap their headers...they seem to think they are show pieces.

As far as fan noise...the biggest difference is going to be highway speeds...and electric fan(wired properly) will never be on at interstate speeds, mechanical fans are always spinning


One thing of note here though on the whole subject.....we are spoiled by modern cars and so expect when daily driving a classic that they will be somewhat quiet....but the reality is that classic cars will always be louder and in general more primitive in every aspect. Its not a bad thing, its the nature of the beast. We get warped expectations of what we expect from a daily driver. For that matter...by the standards of the vehicles I learned to drive on, a classic mustang would be the lap of luxury...old international trucks and VW bugs....those are some rattle-can noisy vehicles.
 

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Discussion Starter · #16 ·
Appreciate the headers comment. Great point regarding engine compartment heat. And totally agree with your comments regarding being spoiled with modern vehicles. I guess if I was flush with cash or I had a wife who’s opinion I didn’t care about, I’d have two mustangs, vintage and modern. I used to drive around in a 69 karmann Ghia and had to hold the door closed when taking a right turn. That car was was a rattle box !
 

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The other thing about running 4.10s with a .60 OD vs direct 4th with something like 2.80 or 3.00 is driveshaft speed and heat generated in the axle
 

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Discussion Starter · #18 ·
Thanks. Never would have thought of that ! While Ive got the community helping me reducing my revs, engine noise and engine compartment heat, can anyone suggest a good header wrap for both sound and heat insulation ? Or is it bad VMF form to intro another subject on this thread ?
 

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Thanks. Never would have thought of that ! While Ive got the community helping me reducing my revs, engine noise and engine compartment heat, can anyone suggest a good header wrap for both sound and heat insulation ? Or is it bad VMF form to intro another subject on this thread ?
By rights it should be a new thread, but... I had my headers ceramic coated to reduce heat. Course that does nothing for sound.
 

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Drove my 68 Cougar XR7 with a 302 C4 on the highway at 70 mph in 1973-74 for 2 years to Community College. That car had a 3.0 rear gear. It turned 3000 RPM at that speed, never gave it a second thought.
 
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