hi guys,
ok im not trying start another debate or war here but just need some advise please.
as you know im building up a 388 c.i 4 bolt roller, high compression forged race motor with a 8 t/b i.r intake.
my car is a 6 speed with dana 44 with 3.45 ratio currently.
this car is not a daily driver,just a weekend cruiser toy.
more for cruising and traffic light racing to kick some a#ss over these holden commondores and fart can jap crap cars!!
im hoping to gain about 500 rwhp for this engine combo im building up.
so ok which ratrio do i go with ??
3.73,3.90 or 4.10 ratio please ??
i heard that the 8 throttle body indivdual runner cross ram intake manifold intakes produce huge gain in all round performance power even loads of low end poewer!!
i still want to keep some top end speed though and thought might just go 3.90 ratio over 3.73 or 4.10!
so im not sure .
i just want to get all round performance if possible basically!!
any ideas thoughts guys please.
thanks very much
cheers
glen

Given the cam you'll probably be using to obtain that HP level, I don't think the 4.10s would be too much at all. It's probably the only way you'd ever be able to use 6th gear comfortably at anywhere near legal highway speeds.

Do you have a photo of this motor?

4.10 is about as big as a Dana 44 casing will accept and even then a little machining is recommended.

With that said, that much motor can accept that much gear.

hi there guys,
thanks for your replies so far.
yeah so im thinking i will buy the 4.10 viper gear set then!
iv been qouted $500 aus to fit the rear gears and clutch pack.
thanks
glen

Good luck with traction. First and second will be useless.

hi jeffvette,
so what would you reccomend then please ??
may be 3.73 max then ??
im sure 3.73 for example would be a improvement over 3.45 ratio what i have now ??
i have heard about that r.e traction problems with going 4.10 actually!!
btw, i have 315 mm wide rear tyres ,would that help with traction much at all though??
traction is important especially if you want to take off quick from the lights
thanks
glen

Depends abit on the tires more so than just the width Glen, as well as what size wheels youve got them mounted to. There are some 315s that are cheaper in price that wont hold as well as some of the top end 275s and 285s, it will depend on what youve gone with, what wheels youve got, how agressive you are with the clutch, how agressive you are with the throttle, and also the surface youre trying to launch from.

By the same token, you dont want them to stick that well that they tear the diff or drive train to shreads either, cause that would be alot more embarasing than spinning the tires!!

hi case,
the new tyres im getting soon will be the 17" diameter bfgoodrich g-force kd range 315 mm size.
they have a nice wide stance tread pattern,much better than those sh#it summatamos tyres that i have that have rounded dumb corner side walls!!
so do you reackon 3.73 or 3.90 ratio might be better casey instead of 4.10 ratio ??
thanks
glen

HP is useless.

Tell me what powerband it'll run in, what RPM you'll be shifting at, and what MPH you'll be trapping.

Quote:
The Sumitomos are rubish mate yes, i had 2 of them on my 94 when i got it, they didnt last worth a damn and didnt grip real good either.

Im not familiar with your engine package and where its going to make its power, so i wouldnt like to recomend anything myself, but Central Coaster will have a better idea. Id personally go with 3.73, but then i dont know if that is the best you could have for it.

Quote:

hi centralCoaster,
thanks for your reply!!
well i will have a guess at it mate,
powerband i would say would be from 2,200 - 6,200 rpm range, as that is the cam specs when it starts to kick in at and finish at,
shifting at 4,000-5,000 rpm i dare say and mph i will be trapping i have no idea.
hope that may help some.
cheers
glen

I will be curious if that cross ram proves to be that wide on the power band... I have heard they are very peaky.

Super cool to look at, just not all that user friendly.

The BFGs should be a-ok.

hi bogus,
how are ya!
thanks also for the reply,
the power band i mentioned mate was what the cam spec card says the cam operates in,2,200 rpm-6,200 rpm ,not the intake manifold.
but from what iv heard from "boschvette" who has the same intake he said he gained all round power from this intake.
thanks
cheers
glen

Theoretically it should provide a more even power across the board, cause all 8 runners are exactly the same length from the throttle body to the intake valve.

What sort of HP are you expecting? I can surmise a trap speed from that and figure out a good starting point for your gear ratio. You'll be surprised that it's taller than you'd expect.

hi there guys again,
thanks for your keen interest and help!
much appreciated.
from the mods i have for this engine and seen on other engines with simialr mods,im expecting around the 460 -500 rear wheel horsepower !!
thanks guys
cheers
glen

So you'll be trapping about 122 mph. I don't know what engine combo you're running, but unless it's a diesel, I seriously doubt you'll be shifting under 5000 rpm with that sort of power.

Here's your trap RPM with a 26" tire. Unless you feel like putting down 500 hp in overdrive (bad idea). If you're shifting somewhere in between two ratios, pick the next size taller. But you won't have a clue about your shift points until you get your engine dyno'd and have someone that knows what they're looking for to check it out. You didn't think it'd be easy would it?

4.11:1 = 6500 rpm
3.90:1 = 6150 rpm
3.73:1 = 5900 rpm
3.54:1 = 5600 rpm
3.45:1 = 5400 rpm
3.33:1 = 5250 rpm
3.07:1 = 4850 rpm

hi centralcoaster,
thanks very much for your table guides.
looks like if i want to keep the revs down a little i had better stick with my standrd 3.45 ratio then,lol!!
my engine combo mods list is on the other thread i posted in tech section about royal purple synthetic oil!!
cheers mate
glen

C4, I have an LT-4, running a 4.09 final drive ratio. The acceleration will flatten your eyeballs, and at 2000 RPM in 6th gear it cruses at about 75 MPH.

However…with the price of petrol in this country, I’m considering going up to a 3.90 final drive. With all the torque I have, I don’t think it will matter much to the kid in the Mustang.

Mine is a weekend toy, set up to go around corners, but I’ve been playing with various ratios…even in the gear box.
The formula goes like this:

RPM
X Gear Ratio
÷ Final Drive Ratio
X Tyre circumference (inches)
÷ 63360 (inches per mile)
X 60 (minutes per hour)
= MPH

I made an xl spreadsheet, so I could just plug in different ratios to compare the results. I'll e-mail it to you if you wish.

CentralCoaster’s right…It wouldn’t be fun if it was easy.

Have fun!

Instead of stuffing around with all that jargon, how about you just use this: http://www.f-body.org/gears/

Quote:

My vote is to stay with the OEM 3.45:1 until the rest of the drivetrain is
built and has some time on it.

.

hi there guys,
thanks for the extra replies on which ratio to run!
much appreciated guys!!
yeah im thinking guys that i will just run with the 3.45 ratio i have for the moment and see how it handles/performs then upgrade if needed!
cheers
glen