360 combo for '69 notchback using tall gears?

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DusterKrazy

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Okay, I will be basing most of the combo on what I have laying around. The car is a '69 notchback Barracuda with a 360. I will be replacing the 7.25 for an 8.25 SureGrip rear with 2.45 gears. I figure the fairly light weight car with a torque heavy small block will be fun even with the high gears. I have no intention of making a drag car out it. Think of a really nice effortless highway cruiser or road rocket?? lololol..Headers for the win for sure!!

The basics are of a course, a 360 with a 904 auto. I do have a Coan 2800 rpm stall converter that could be used. I am aiming for 9.1 compression to try and get it pump gas friendly. Dual plane intake and I do have a Demonsizzler Thermoquad as well to throw into the mix. I have a stock cast iron intake as of now but will be looking for a good aluminum replacement soon. I know the Weiand Stealth and the Edelbrock RPM Air Gap are both really good intakes. I guess I will use what I can find or afford. Lots of hate for them but I love the Offenhauser's...

My biggest choice as of now for the combination is what cam to use??? Any other advice is appreciated. Thanks..
 
try 2.92, or 3.08 gears. Cam, something with a tighter lobe separation for lower rpm torque. That torque converter stall speed would be better suited for at least 3.23 up to 3.73
 
i had 2.45 gears in my car with the 318 eddy carb 2 1/2 ex with 235 70s 3000 rpm was like 95 or 100 mph made it to vegas in 7 hours from livermore, and we stopped to eat.100 mph all the way!with a 360 a 268 cam 650 dp holley it would pull real good from about 60 mph . thats why i need low rear gears.
 
bad440 said:
i had 2.45 gears in my car with the 318 eddy carb 2 1/2 ex with 235 70s 3000 rpm was like 95 or 100 mph made it to vegas in 7 hours from livermore, and we stopped to eat.100 mph all the way!with a 360 a 268 cam 650 dp holley it would pull real good from about 60 mph . thats why i need low rear gears.
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268 cam..Do you mean a Comp? Or is there something similar??
 
racerdan80 said:
try 2.92, or 3.08 gears. Cam, something with a tighter lobe separation for lower rpm torque. That torque converter stall speed would be better suited for at least 3.23 up to 3.73
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That car will be a dog with 2.45 gears. 2.73 is the lowest I go with 2.9 being my pick, you will be using short tires, around 25 inch I am guessing.

If you really really want 2.45, well the heck with getting the rpm, etc intakes, what is a point? Those are for mid to upper rpm range power.

Why even try to floor it with 2.45 gears?

Get on a bicycle and see how big a difference the gearing can make
Sure the factory used 2.45 gears with some cars with 27 inch tires and they were getting 23 mpg highway they claimed. It has its good points but plan on hanging out with the GM Volts taking off from any traffic light, lol
 
bad440 said:
i had 2.45 gears in my car with the 318 eddy carb 2 1/2 ex with 235 70s 3000 rpm was like 95 or 100 mph made it to vegas in 7 hours from livermore, and we stopped to eat.100 mph all the way!with a 360 a 268 cam 650 dp holley it would pull real good from about 60 mph . thats why i need low rear gears.
Click to expand...


Oh, well you still can do 100 mph all day long with even 3.55 gears, just burn lots of fuel.

I;m tryin to explain what is the point of building a more powerful engine when a gear change would be the most help? The lower the gears the MORE stress you will place on the engine when flooring it. You going to lug the heck out of that little motor. The converter is what saved the combo last time around.

Now if you just want to coast up to 100 mph, sure the 2.45 gears are great.
 
I'm doing the math

100 mph with 2.45 gears and 25 inch tires, gives the motor 4,800 rpm in 2ND gear ! See, so why get the rpm intake when still the motor will be under 5,000 rpm?

You know what I would get for that combo, an old Holley single plane Street Dominator intake, those had small short ports and were great at 4,500 rpm and you might get BETTER mpg. I know I got a smoother idle with that intake compare to the rpm, yes the rpm felt a bit better from the light but I swear at 5,000 rpm and up that little Holley intake was better

Yep, more math, at 130 mph in 2ND gear once again, gives 6,200 rpm.
 
The shorter runner of the intake should dictate a higher RPM useage. Right?

Getting better mileage with a single plane intake should be possible since the air and fuel should have an easier time getting to the cylinder, atomize more since theres no or little turns or bends making the engine breath easier.

D-Krazy, your in the mist's of a mis-match of parts. And a doggie fuel drinking soggie runner it'll be. The 2.45's can not afford you much cam at all. I'll be dead honest with ya, IF a cam change or need to have one is gonna happen,then I would not go but a few degree's (Less than 5*'s) more than a dead stock cam and I would go with a split duration with about 8* - 10* more on the exhaust on not less than a 110.

The intake would be the OE cast iron since the aluminum units have a elevated rpm range (Except the Performer) that will not help your efforts, loose you the valued torque of the little engine and drop your mileage like an old wore out shoe into the trash.

Also, loose the converter. It stalls way to high for the gears and will not help.

OR, up your gear ratio like mentioned above.
 
If you plan on staying with the thermoquad your intake choices are limited, the best being modifying a LD340 but theres nothing really wrong with the stock iron piece
 
From what I've seen super tall gears like that can even lower your in town fuel mileage cause it lugs the engine. If you do plan on using them use the shortest tire you can run and you might use a little looser than stock converter but I wouldn't use the one you mentioned. Even with today's good converter technology their not designed to work with 2.45 gears.
 
dodge freak said:
I'm doing the math

100 mph with 2.45 gears and 25 inch tires, gives the motor 4,800 rpm in 2ND gear ! See, so why get the rpm intake when still the motor will be under 5,000 rpm?

You know what I would get for that combo, an old Holley single plane Street Dominator intake, those had small short ports and were great at 4,500 rpm and you might get BETTER mpg. I know I got a smoother idle with that intake compare to the rpm, yes the rpm felt a bit better from the light but I swear at 5,000 rpm and up that little Holley intake was better

Yep, more math, at 130 mph in 2ND gear once again, gives 6,200 rpm.
Click to expand...
just said air gap because the reg performer isnt as good as a factory cast iron intake,i agree the holley manifold would be better.i only had 245s because my 8 3/4 wasn't ready and it needed somthing 75 bucks let us go to mopars at the strip.i really only like very low gears for my personal cars highway gears get me in trouble.
 
just so you know the 2.20 and 2.45 cased 8.25's cant be changed...

they will only take those gears...

so if you plan on trying different gears or just going to 2.9's or something you need a different housing
 
805moparkid said:
just so you know the 2.20 and 2.45 cased 8.25's cant be changed...

they will only take those gears...

so if you plan on trying different gears or just going to 2.9's or something you need a different housing
Click to expand...

Thanks Moparkid, I have learned about the interchange or lack of between the super high geared 8.25 rears.

To respond to other posts..

I already have the 2.45 8.25 rear with a Sure Grip. I am out of work and have very little to no money. I am basing the combination on what I have already and it's not set in stone.

I am not really worried to much about blistering launches because I have three other old Mopars set up to get my speed fix :D. I am not setting up the '69 Barracuda to drag race.

I know not to go big on the cam because of the gearing but was wondering if anybody has made any combo to work with tall gearing. My buddy has an '84 Diplomat police car with a 318 and 2.24 gears and honestly- I am impressed with how it runs! That's a heavy car and it's only mods are a Weiand Action+ intake a 500cfm Edelbrock carb. There's dual exhaust to of course.

Thanks for all the replies. I will ponder of the combination some more...
 
Years ago I ran a Vega converter behind a 327/350motor in a 62 Impala with 3.08 gears. If it had had some street manners I would have kept it in but with the tall gears it slipped all the time and kept the tranny fluid hot even with a cooler. If yours has some street manners like a "street fighter" which only slips a little till you hammer it then it might work for you . If it is loose you will need a big cooler if you want to preserve your tranny.
 
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