now my head is starting to spin, information overload!! seriously though, thanks again for the info...
My experience is vacuum advance will add more than 1 mpg... unless you have a very heavy right foot. Probably closer to 3-4. And as has been said, changing just the rear axle ratio will just move the problem.
Without all the rocket science, your thinking is right on the money. With the camshaft that your running, anything below 2400 rpm its not going to be happy. With the combo you have either lower your OD ratio or your Diff ratio. 4.11 rear or .73 od sounds about right. Millage will improve and performance will be better through out the RPM range. Steve
P.S. I'd prefer to drop the rear to a 4.11 ratio. She would monster stop light to stop light and an angel in OD on the highway. Just my 2 cents. Sounds like a pretty good combo. Aint bench racing fun!! Steve
I think if you go to a shorter tire, it would help. I run Michelin 7.50R16s on my 74 F350 ramp truck, and they are 32" tall. And I don`t agree about 4.10s with a T5 making first gear "useless" I don`t know what the 1rst gear ratio in a Camaro T5 is, but I ran a 3.35 low gear T5 in my Mustang with 4.88s, and for acceleration, it was great. Yeah, in normal street driving, you will likely be shifting into 2nd 1/2 way thru the intersection, so what? The off the line grunt is well worth it to me.
If this were Consumer Reports forum, yeah, I'd agree with you. But damn...how about building a traditional hot rod?
Come on guys, inefficiency, and outright wasting fuel and money is traditional. Get with the program!
Hey I agree but times are a changing! Gas price, house expense, babies, college funds, retirement, lower income jobs. Don't get me going Jim. If I had kept the M20 4 speed in my car I would never had been able to drive the chevy to California from Toronto, Ontario Canada! I would never had been able to afford the gas man! I think that the 5 speed is the best of both worlds! 1st-4th is a handful with my set-up. It sure is nice to be able to slip into fifth and cruise the hwy and not kill my bank account! Besides to look inside my car it would take a trained eye to see that it is a Tremec. I kept the 4 speed ball just for the naysayers! lololol Jay
My Falcon has a 5-speed. My Model A has a 6-speed. Both can get 30MPG if driven conservatively, and the A has a V8. Putting a 4-speed, or even a 3-speed in either would not make either more fun to drive, just more expensive. Each is "dressed" above the floor, to appear no different from a period transmission. There is no gain in fewer gears, only loss. Oh, and the Falcon will be getting a 6-speed, fronted by a common-rail, direct-injected intercooled-turbo-diesel, as soon as I finish gathering hardware. Yeah, I will be no longer able to talk about it here, but performance will increase, and the MPG should be at or about 60MPG, at 65MPH.
4 speed is traditional? In the 60's my Olds powered 32 had a Cad-Lasalle, no crappy 4 speed Of course premium was 36 cents (2.03 in todays dollars) Tradition means different things to different folks, I'd say a 324 trumps the 5 speed.
i check the RPM's with the GPS on my phone... 4th gear @2300 rpm is 60 mph- 4th gear should show about 57 MPH @ 2300 RPM. Something is not reading correctly, or the rear ratio is wrong, as squirrel already mentioned. [/QUOTE]
turning the engine 1 full rotation gets me around 1.25 on the driveshaft. 10 rotations gets me 17.7 ish... tire height is 30.5 how do i translate this info into what OD ratio i have??
double checked rpm's with a gps.. pretty much the same- 1 st- 3000 @ 26 2nd-3000 @38 3rd- 3000 @ 52 4th- 3000@ 74 5th-1800 @ 80 the engine started to ping in 5th, so i backed off pretty quickly.. i realize this points to timing / tuneup situation.. i'll be dealing with all that in the next week or so. including installing a vacuum advance-
So it's a .59. with a 3.70 that's a 2.18 in 5th. Call it 15 inch loaded radius you are looking at 1709 RPM at 70 MPH. With a .72 OD gear you would be at 2085.
This is a model of your car, shifting at 5500. It slows down when you hit 5th. Blue = RPM, Red MPH, White = Accell G oh and
Hoop, mullskull, This is almost exactly where I ended up with my setup after changing from the .5 something to the .72 OD. Only difference is I have a 3:55 rear. 30-1/2" tire. Right at 2000 in 5th at 70. 2400 pound roadster with 327 and comp XE268 cam. I wish I could figure out how to post the excell spread sheet I used.
Highlight the cells and "copy". Open MSPAint Paste, save as jpeg. Use advanced under post, manage attachments, browse to file and upload it.
Yep it looks like you got a .59 od. A .72 should be about perfect for 3.70 R&P with 30 inch ish tall tire. Now time your cams power range to your gearing and dial in your ignition and you'll be good to go.
The good news is that T5 5th gear sets are a separate unit, and can be swapped for other ones, without ditching the whole trans. You will, of course, have to figure out which main to counter-shaft ratio you have, and then figure out what gearset you need from there. Alternately, post the transmission tag number, and I will see if I can get an answer for you. It is probably the Mustang 2.95 gear set. Numerous and various 5th gear sets are often on that auction site that shall not be named.
Unfortunately I don't think that the trans has a id tag... I'm gunna call the guy who built the trans, hopefully he keeps good records- If not what's the alternative.. Take the trans apart to find out what gearset I'll need?? Posted using the Full Custom H.A.M.B. App!
The Jalopy Journal
