I'm going to start a project car soon. '69 fastback, pro-street/drag-car. Its going to have a 460 block, bored .030 over with a 4.5" stroke making it a 545. It will have p-51 heads with flat top pistons. Should have 13.7:1 compression. Single plane 1500-6500 rpm power band manifold. 750 cfm carb. I'm using a c6 trans with a 3000 stall torque converter and a ford 9 inch. What kind of gears should i use in the diff (what ratio)? thanks.

 

What will the torque and horsepower numbers look like for this? I hope you are putting in some serious chassis mods. I am running about 500ft*lbs of peak torque in my '69 small block and have trashed pretty much everything once. I think I could turn my car into a pretzel with a big block.

The torque is going to shred your drive train and when you get it hooked, it is going to twist the car pretty good. A tube chassis or at least a really good roll cage with sub-frame connectors should help. A stock leaf spring setup is going to be hard to get to hook. You will need traction bars to have a prayer. A link rearend would be better.

The lower rear gear you put in, the harder it is going to be to get the car to hook because you will be putting more torque to the wheels. What size and type of tires are you going to run?

The mustang drag packs from '69 and '70 came with 3.91 and 4.30 rearends. Either of those will put you close to redline at the trap which is good, but it may create too much torque for you to plant. I run a 3.50 with 26x11.50R15 MT ET Street Radials and they will barely hook up with a limited slip and CE Slide-A-Links. I have to slip the clutch a little or it just goes into tire shake and hop at the launch. With a trans brake you will have the same issue.

 

Thanks, and I'm lovin your mach 1.
Yes, i was planning on doing some MAJOR suspension upgrades. Probably an 8 point cage. I'm hoping to push 650-700 horses. The rear end is gunna be shortened to fit 275 drag radials but im open to change anything. I'm making the list right now and finding parts so anything is still possible.

 

Thank you.

I would plan on some if not all of the following:
Four link rearend like TCP G-Bar
Rear anti-sway bar with matching front bar
Sub-frame connectors with cross brace piece (TCP)
Roll cage welded through the floor to the frame
Possible front suspension upgrade to Opentracker control arms, UCA drop, roller spring perches, etc.
Possible Borgson integrated power steering upgrade
35 spline 9" axles with detroit locker
Drive Shaft loops
1350 U joints
Bad Ars (not a brand name) drive shaft
Bad Ars C6
Front Export brace
Monte Carlo bar
Aeromotive fuel system with tank sump
Wilwood disc brakes front and rear
SFI bellhousing like Lakewood
SFI flywheel and balancer

Gosh, that just gets you started. That does not touch the engine or interior. Hope this helps. If you do not know why I recommended something, just fire back.

 

awesome, thanks for the helpful advice

 

Selecting the correct rear gear ratio is really not that hard. Are you going to be cruising the city streets? Or the highway? Planning on drage racing the 1/4 mile? Or the 8th mile?

Essentially, you want the engine to be maxed out at the end of your drag strip run. On the street, you only want it in the mid to low range of the power band while cruising.

 

for sure not highway. its mainly a drag strip car (1/4 mile) but i still want to be able to drive it in rural areas to goto car shows and stuff.

 

Either a 3.55 or 3.73 is probably your best bet. The big block will produce plenty of torque to give you a good start, and even with a hydraulic valve ttrain you won't run out of gear at the top end.

If you go too low - like 4.11 or 4.56 - you'll produce so much torque you'll have a tough time hooking up. Rememeber that a torque converter will multiply your low end torque a bit.

Plus, that will provide a nice street ride.

 

I ran 3.50 gears with no stall to begain with in a 89 Mustang with a 9.1to1 460 that weighed 3200lbs with me in it and I drove it everywhere. It ran consistent 12.20's, Then I went to 4.11's with 3200 stall and went 11.50's spinning the first 10 to 20 feet on sticky street tires at the track. This was back in 1990. For driving on the street I liked the 3.50 gears better. The thing you have to remember when you are driving it on the street with a stall converter, you want the converter to be locked up at cruising speed. If it is not you will burn the trany up, Because it will be slipping all the time. That is what I was told from TCI and B&M.
I was running a 28.5 inch tall tire.
The only reason I sold my Anglia is I got tired of buying a barrel of fuel just to drive it around town and to car shows. Even thougth I trailered it into the town the car show was in. With that kind of compression you just can not pull up to the gas pump and fill up.
That is why this time with my 33 ****** I am going to go twin turbo on a 4.6 DOHC.

 

Thanks bob and angilagasser for the info. do you think a 4.11 would work better with a 3000 stall? also i'm gunna be using maybe 275 drag radials or Nitto NT05R's rather than slicks.