Hot Rod Forum banner

21 - 36 of 36 Posts

·
'23 T-Bucket Pickup
Joined
·
1,738 Posts
Let's remember guys, this is an El Camino, not a full size work truck. The 489 is built with STREET in mind, not drag racing.
After much debate I feel the 3.08s will serve my needs quite well. Combine all this with a proper "tight" stall convertor and the grin factor should be huge.
And hopefully without killing me on fuel.
I believe that you will be pleased with that setup. I have a couple of friends with 454 Monte Carlos that came with 2:73 ratio rear gears. The 3;08 is a great ratio also. An 1800 rpm stall should be just about right. Could even go 1500 if the cam would permit. The camshaft manufacturer can recommend the proper stall speed converter if in doubt. Playing with the size of the primary jets in the carb can make a significant difference in fuel mileage. I kept going smaller until I ended up with a flat spot and then went up one size. I put another 100,000 miles on my truck with the refreshed engine before I traded it. It was still running great and had never had any problems with the engine or carburetor. Running too rich of a fuel mixture will shorten engine life due to the washing of cylinder walls. Hopefully this helps.
 

·
Rod...from a Chrysler?
Joined
·
5,322 Posts
Use the smaller cam for mileage and torque down low.
 
  • Like
Reactions: adantessr

·
Registered
Joined
·
357 Posts
You’ll be fine with 3.08’s. My car has 3.08’s, same motor you’re having built, just a hair smaller cam 225/235, you can get yourself in trouble, but it’s not undriveable at all.

Hate to burst your bubble on mileage, you have to fill those cylinders with something and it ain’t air alone.
 

·
'23 T-Bucket Pickup
Joined
·
1,738 Posts
You’ll be fine with 3.08’s. My car has 3.08’s, same motor you’re having built, just a hair smaller cam 225/235, you can get yourself in trouble, but it’s not undriveable at all.

Hate to burst your bubble on mileage, you have to fill those cylinders with something and it ain’t air alone.
I used to get 24 mpg with my 75 Nova SS. Had a stock 350 with a three speed on the floor. I got 21 mpg with the factory 2bbl carb. When the warranty expired at 12,000 miles I put on a Quadrajet carb and manifold and headers. I could hear the engine note change when the distributor reached full advance. As long as I kept my engine rpm at that rpm or above I got the great fuel mileage. I don’t remember that I had a tachometer but the sweet spot came at 60 mph which meant that I had to speed to get my best fuel mileage. No interstate highways in the upper peninsula of Michigan so speed limit was 55. I always got a shade over 24 when I’d travel I-75 @ 70 mph in lower Michigan. Good fuel mileage should be obtainable with the right combination of pistons, heads, camshaft, intake and carburetor along with some judicious tuning. FWIW I brought the fuel mileage on a buddy’s 76 mustang II V-6 from 17 mpg to 26 without changing any components. But that is an entirely different story.
 

·
Registered
Joined
·
887 Posts
What you really need is an OD trans and that will work with 3.42 or 3.55 or even 3.73 rear gears. Click below to calculate Eng RPM for different combinations. I'm running a 3.55 rear gear with 28" tires and .67 overdrive and turn 2000 RPM @ 70 MPH. This is with a Tremec 5 Speed Manual trans. I love it. I had a 3.73 rear but I get on the highway a lot and the first 4 gears are great around town.

 

·
Registered
Joined
·
257 Posts
Discussion Starter · #26 ·
You’ll be fine with 3.08’s. My car has 3.08’s, same motor you’re having built, just a hair smaller cam 225/235, you can get yourself in trouble, but it’s not undriveable at all.

Hate to burst your bubble on mileage, you have to fill those cylinders with something and it ain’t air alone.
What does your ride weigh and what stall are you running? Just curious about how you set your car up.
 

·
Registered
Joined
·
30 Posts
You are hoping that someone is going to tell you that your performance won't suffer, or won't suffer much. Its just not going to happen. Recently I watched an Episode of Road Kill garage or one of the shows that Friberger does. He had 3.43 (?)gears in a 383 roadrunner and wanted to swap them for some 2.70s so he could cruise at 70/80 mph on the California freeways. He ended the show by showing what a "turd" the car had become. That was his choice of words. The logical thing to do is to sell your transmission and just put the money from it and the cost of a gear swap into the purchase of a 4L80 transmission. Its basically a Turbo 400 with overdrive. Why build a screaming hot motor and then tie its hands with the rear gear ratio. It will never perform like you want and you'll probably get embarassed on occasion by some quick little smallblocks that are running overdrive. It may not be what you would like to hear, but the reality is that cars aren't driving 55 mph on the freeways like they did in the heyday of 3 speed automatics........and one of the most important things (as you have already discovered) is keeping engine rpms down when you do drive somewhere. The reality today is that an overdrive is the best choice. You can turn your head away and refuse to accept that, but thats the reality for todays high speed expressways. Again, I know this isn't what you want to hear, but years of experience have taught me that non-overdrive transmission are only for dragstrips and in town cruises. If you want your car to be an all around enjoyable performance vehicle, you just have to be realistic about what works best. Very seldom will you ever hear anyone who is disappointed with choosing an overdrive .
 

·
Rod...from a Chrysler?
Joined
·
5,322 Posts
Agree with overdrive.
I'm going so far as adding a Gear Vendors behind a 4L80e.
 

·
Registered
Joined
·
257 Posts
Discussion Starter · #29 ·
You are hoping that someone is going to tell you that your performance won't suffer, or won't suffer much. Its just not going to happen. Recently I watched an Episode of Road Kill garage or one of the shows that Friberger does. He had 3.43 (?)gears in a 383 roadrunner and wanted to swap them for some 2.70s so he could cruise at 70/80 mph on the California freeways. He ended the show by showing what a "turd" the car had become. That was his choice of words. The logical thing to do is to sell your transmission and just put the money from it and the cost of a gear swap into the purchase of a 4L80 transmission. Its basically a Turbo 400 with overdrive. Why build a screaming hot motor and then tie its hands with the rear gear ratio. It will never perform like you want and you'll probably get embarassed on occasion by some quick little smallblocks that are running overdrive. It may not be what you would like to hear, but the reality is that cars aren't driving 55 mph on the freeways like they did in the heyday of 3 speed automatics........and one of the most important things (as you have already discovered) is keeping engine rpms down when you do drive somewhere. The reality today is that an overdrive is the best choice. You can turn your head away and refuse to accept that, but thats the reality for todays high speed expressways. Again, I know this isn't what you want to hear, but years of experience have taught me that non-overdrive transmission are only for dragstrips and in town cruises. If you want your car to be an all around enjoyable performance vehicle, you just have to be realistic about what works best. Very seldom will you ever hear anyone who is disappointed with choosing an overdrive .
Wow, that's a pretty blunt statement, lol! Here's the thing: my guess is that 383 was pretty high strung and when he put the 2.70s in he was out of the cam's powerband which would have resulted in the car being a "turd". You don't just throw gears in and hope, it all has to be part of a package. Also, don't forget I will have 106 more cubic inches than Freiburger.
My origional car, an Olds Cutlass, 1984, had a 408 BBC and 3.42 gears. The car weighed almost 4000 lbs with me in it and stabbing the gas at a stoplight resulted in instant tire smoke for 2 gears.
I am now building a 489 for an El Camino which is 200 pounds lighter. There should be 100 ftlbs more torque on tap compared to the 408, so I feel, after much research, going to a 3.08 gear will be a non-issue. The engine should also be quite happy at 80 mph, or loafing along at 45 mph. It's all in the package.
Overdrive transmissions are indeed great, but they too come with compromises. If you have an engine that doesn't "come on the cam" till 2500rpms and your overdrive cruising rpms are 1800rpms, your engine probably won't be happy. Then, if you gear it to make the cruise rpm higher, odds are pretty good you just made 1st gear completely worthless.
When you have to modulate the gas pedal to keep from breaking the tires loose then numerically lower gears are also pointless. There is far more to this discussion than watching a tv show and thinking it's that way for all vehicles lol.
 

·
Registered
Joined
·
3,757 Posts
more power means you don't have to crutch it with gear, but the difference is only 10%.
I find that most people can't tell a 10% in rear gear ratio---would drop your cruise RPM by a couple hundred and probably can't be ready off a regular tach. OD takes your 3.73 gear and makes it a 2.70
 

·
Registered
Joined
·
357 Posts
What does your ride weigh and what stall are you running? Just curious about how you set your car up.
Around 3400lbs, 3000 stall converter.

Th400’s don’t have lockup converters, that’s a benefit if you have a big cam. Add in higher stall and it calms down the bad low rpm manners, which with the cam you picked, low rpm manners are not an issue. Higher stall converters soak that stuff up, you know immediately who has a 4 speed with a ostrich egg lobe cam, they rev up to pull out, where as automatics just pull away.

You have 489ci, with a mid range cam, mid range in a 427 or 454, 489 drives it toward lower mid range, dual plane intake, oval port heads, which drives it even more lower mid range because intake charge velocity is up vs rectangles and a single plane, which means lower torque peak, which means torque comes on quicker, which means highway friendly gears like 3.08 are just fine to use.

So, unless you want to spend a bunch on an od trans, and rob the rear gears out of grandpa’s farmall, put 3.08’s in, or leave the 3.42’s you have now, the back tires are screwed either way, just a little less exhaust noise cruising is what you’ll have.

It’s your car and your wallet, only you can decide what’s best for you, we’re all just giving our opinions. I hate to tell you, but that 408 will seem anemic.
 

·
Registered
Joined
·
30 Posts
When you talk about a package, that also has to include tires and suspension capable of handing the power available. When you use numerically lower rear end gears, you not only change the ratio in first gear but in all gears, and you need more power to overcome that. The result will be a slower accelerating vehicle. The spread between the gears will be wider at the final ratio . Technology has proven the value of having more gears available so that the spread between the gears allows an engine to be kept in its best power range. You have to look at how the lower ratio affects the final drive ratio the engine is working against. The thing a hot rodder has to concern himself with is not ultimate HP at a kazillion rpms, but the average torque/HP produced while accelerating. Think of it as being the actual power produced measured in 1/10 of a second steps. If everything else is equal the car producing the most total HP over time will win the race. Now remember that this power needs to be measured where it is being applied........at the rear wheels. So what you are doing is changing the leverage which is equivalent to just giving away a bunch of that HP. You figure to overcome that by starting at a higher rpm. If that was all there was to consider, then cars at drag strips would not need numerically high gears....they could just increase rpms at the start. No, its not that simple if you really want the car to perform well. The logical question is why should you give away HP after you just spent a bunch of money to acquire it? With an overdrive you don't give any of that power away and you still get the benefit of lower rpms and better gas mileage along with an equally strong transmission. You also have a higher stall speed and may have to use a less than optimal tire size . A much smaller engine with optimal gearing will most likely put a hole shot on you because they have not compromised their engines abilities. I think you are committed to doing it the way you stated and just wanted agreement to support your decision. Sorry that I don't think thats a good choice after already spending a lot of money to create HP. You ask for opinions and mine is meant to help you, not to insult you. Best of luck however you proceed.
 

·
Registered
Joined
·
257 Posts
Discussion Starter · #33 ·
When you talk about a package, that also has to include tires and suspension capable of handing the power available. When you use numerically lower rear end gears, you not only change the ratio in first gear but in all gears, and you need more power to overcome that. The result will be a slower accelerating vehicle. The spread between the gears will be wider at the final ratio . Technology has proven the value of having more gears available so that the spread between the gears allows an engine to be kept in its best power range. You have to look at how the lower ratio affects the final drive ratio the engine is working against. The thing a hot rodder has to concern himself with is not ultimate HP at a kazillion rpms, but the average torque/HP produced while accelerating. Think of it as being the actual power produced measured in 1/10 of a second steps. If everything else is equal the car producing the most total HP over time will win the race. Now remember that this power needs to be measured where it is being applied........at the rear wheels. So what you are doing is changing the leverage which is equivalent to just giving away a bunch of that HP. You figure to overcome that by starting at a higher rpm. If that was all there was to consider, then cars at drag strips would not need numerically high gears....they could just increase rpms at the start. No, its not that simple if you really want the car to perform well. The logical question is why should you give away HP after you just spent a bunch of money to acquire it? With an overdrive you don't give any of that power away and you still get the benefit of lower rpms and better gas mileage along with an equally strong transmission. You also have a higher stall speed and may have to use a less than optimal tire size . A much smaller engine with optimal gearing will most likely put a hole shot on you because they have not compromised their engines abilities. I think you are committed to doing it the way you stated and just wanted agreement to support your decision. Sorry that I don't think thats a good choice after already spending a lot of money to create HP. You ask for opinions and mine is meant to help you, not to insult you. Best of luck however you proceed.
I gotta hand it to ya, you make a very compelling argument. Everything you have said makes a lot of sense so I have done some digging. My local salvage yard has a 4l80 that needs to be rebuilt. I can pick it up for just the core charge of 100 bucks. A few hundred more for fresh guts and I'll have a new transmission.

I want to thank you for your persistence in explaining the benefits of an OD trans. I know it's been said many times on other threads how great overdrives are, but I guess it took your explanation to get me to check into it. Now I gotta figure gears for the other end of the spectrum lol. Any Ideas?
 

·
Registered
Joined
·
257 Posts
Discussion Starter · #34 ·
Around 3400lbs, 3000 stall converter.

Th400’s don’t have lockup converters, that’s a benefit if you have a big cam. Add in higher stall and it calms down the bad low rpm manners, which with the cam you picked, low rpm manners are not an issue. Higher stall converters soak that stuff up, you know immediately who has a 4 speed with a ostrich egg lobe cam, they rev up to pull out, where as automatics just pull away.

You have 489ci, with a mid range cam, mid range in a 427 or 454, 489 drives it toward lower mid range, dual plane intake, oval port heads, which drives it even more lower mid range because intake charge velocity is up vs rectangles and a single plane, which means lower torque peak, which means torque comes on quicker, which means highway friendly gears like 3.08 are just fine to use.

So, unless you want to spend a bunch on an od trans, and rob the rear gears out of grandpa’s farmall, put 3.08’s in, or leave the 3.42’s you have now, the back tires are screwed either way, just a little less exhaust noise cruising is what you’ll have.

It’s your car and your wallet, only you can decide what’s best for you, we’re all just giving our opinions. I hate to tell you, but that 408 will seem anemic.
Thank you for he information. Just found out today my crankshaft will be delayed till June, so I'm messing with other stuff. I just found a 4l80 core at my local salvage yard for a 100 bucks. Shoot, a few hundred for fresh guts and I'm in business.
Isn't it amazing how you have a set path for a build, then out of nowhere everything changes on a dime? I've never owned a muscle car with an overdrive, so this will be a new experience for me.
At least the good thing is I haven't even started working on the El Camino. Right now it runs and drives as is so I can just sit back and collect parts, then do major surgery all at once instead of switching directions half way through the project.
 

·
Registered
Joined
·
30 Posts
I gotta hand it to ya, you make a very compelling argument. Everything you have said makes a lot of sense so I have done some digging. My local salvage yard has a 4l80 that needs to be rebuilt. I can pick it up for just the core charge of 100 bucks. A few hundred more for fresh guts and I'll have a new transmission.

I want to thank you for your persistence in explaining the benefits of an OD trans. I know it's been said many times on other threads how great overdrives are, but I guess it took your explanation to get me to check into it. Now I gotta figure gears for the other end of the spectrum lol. Any Ideas?
I appreciate that you put some thought into what I was saying and decided to change your plans. I probably came off a little too strong, and I apologize if I did. There are two versions of the 4L80. One is just 4L80 and the other is 4L80E which is an electronic version and needs a controller or computer. You want the non-computer version. $100 for a 4L80 core is very cheap. I bought a new one at the Street Rod Nationls in Louisville from a company called Performance Automatic. They give a lifetime guarantee on it. You need to get someone to rebuild it that has experience with them and you know they will be there if there is a problem. Like all transmissions, there are upgrades available that make them even more durable. As for your rear gears, I would just leave what you have in place till you get the car running, and you will probably be happy with them. You can find the rpm/speed calculators on line to see what your tire size will give you when cruising at 70/80 miles per hour, but I think you will find that you made a much better choice when you get it all together. I'll say this.....If you hang on to your 400 till after you get the car up and running........then if you decide you are not happier with the OD trans, you can always revert to your original idea and sell the OD. It will bring a good price and you will have direct experience for any future builds. Good Luck with it!

One more thing, Gas Prices keep rising. Was buying regular for $2.15 a year ago and its $3.20 today. Premium is going to be a lot more than that.
 

·
Rod...from a Chrysler?
Joined
·
5,322 Posts
I appreciate that you put some thought into what I was saying and decided to change your plans. I probably came off a little too strong, and I apologize if I did. There are two versions of the 4L80. One is just 4L80 and the other is 4L80E which is an electronic version and needs a controller or computer. You want the non-computer version. $100 for a 4L80 core is very cheap. I bought a new one at the Street Rod Nationls in Louisville from a company called Performance Automatic. They give a lifetime guarantee on it. You need to get someone to rebuild it that has experience with them and you know they will be there if there is a problem. Like all transmissions, there are upgrades available that make them even more durable. As for your rear gears, I would just leave what you have in place till you get the car running, and you will probably be happy with them. You can find the rpm/speed calculators on line to see what your tire size will give you when cruising at 70/80 miles per hour, but I think you will find that you made a much better choice when you get it all together. I'll say this.....If you hang on to your 400 till after you get the car up and running........then if you decide you are not happier with the OD trans, you can always revert to your original idea and sell the OD. It will bring a good price and you will have direct experience for any future builds. Good Luck with it!

One more thing, Gas Prices keep rising. Was buying regular for $2.15 a year ago and its $3.20 today. Premium is going to be a lot more than that.

I believe you are mixing up the 4L60 (700r4) and the 4L60e. All 4L80's are electronic. There was the 3L80 which is a TH400. A manual valve body can take away electronics.
 
21 - 36 of 36 Posts
Top