73 Ventura Project

B

Barricade_Runner

I'm in the middle of making a street-running drag car out of my 73 Pontiac Ventura. It originally had the BB-350 in it which I promptly removed and I'm rebuilding a 455 for it. I've got a turbo 400 tranny to run, so I'm good up until that point.

Where I'm hitting a wall is at the rear-end. I simply don't know what's out there to use for my new rear diff. Ideally I want to get a posi unit that will fit in with a minimal amount of stress.

Anyone out there have any ideas as to what I might use and what vehicle I could find it in?
 

gtojw

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The rear end that is in there is a good starting point as it should have the 8.5 GM corporate rear end in it. This unit is nearly as tough as the Chevy 12 bolt. Get yourself a good posi for it and the right gear for your combination and you should be good to go. If you to plan on using anything other than a street tire if you drag race it, it would be a good idea to get a better set of axles too.

HTH

BTW what is are you meaning by BB 350??
 
B

Barricade_Runner

Oh, sorry, meant Big Block 350.


I think I'm going to stick with street tires for now, but I'll definitely keep your axle suggestion in mind.

So the case itself should be good, just replace the guts inside? Where could I get a good posi unit for it? Also, what kind of gear combination would be good?

I'm sorry if these questions sound really basic, but I don't know a whole lot about differentials yet as this is my first big project and I'm learning as I go.
 

gtojw

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Oh, sorry, meant Big Block 350.
Well first of all some Pontiac engine education. Presuming that you are talking a 350 Pontiac engine, there are no such things as 'big block' or 'small block' Pontiac engines when you are talking traditional Pontiac V8's which would be those made from 1955-1979, not counting the 301. The reason for this is the bore spacing, head bolt locations and block deck height is the same for ALL Pontiac V8' built during that time regardless of their displacement. The big block-small block thing is more of a Chevy-Ford-Mopar thing...

Now that I am off my soapbox,:D

Yes, the housing you have is plenty good. New posi carriers are available from places like Summit or Jegs. They did offer a posi unit from factory which with some looking you might be able to find but it is my experience that they don't have the holding power as the good aftermarket units.

As for what gear ratio is good for you will depend on a few things. Like is the car an automatic or manual, what kind of driving you plan on doing with it, if fuel mileage is any concern or not, ect. Once you figure those things out then I can help you on a few suggested gear ratios.

HTH
______________________________
 
B

Barricade_Runner

Good to know. I remember hearing something about that when I first started looking into a swap and just got used to saying big block because when you say 350 now-a-days people usually assume Chevy small-block. Kind of forgot where I was though and that people on a Pontiac forum would know better. :)

For the gear ratio:
I've got an automatic Turbo-400 Tranny for hook-up
I'm not going to be doing a lot of drag racing with it, the occasional trip out to the drag strip, and if a Honda pulls up beside me of course I'm going to smoke them.
It's a 455, so no matter what it's gonna suck fuel back. If I can get some kind of gas mileage out of it that would be nice, but not necessary. If I can get anything over 200km out of a 60L tank I'd be happy.

Cade
 

gtojw

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I have found that a nice all around ratio for a setup like yours would be something it the 3.40-3.55 range for gear ratio. You will have something that will have no problem smoking the tires off the line, especially with the torque of a 455:D:D. And if you want to take it out on the road for a trip you won't be turning the engine at crazy RPM's at highway speeds.

BTW what all are you planning on doing to the 455?
 
B

Barricade_Runner

Sounds great. I'll likely go aftermarket with the gears for a good posi unit to get me in that ballpark.

I've heard the 455's put out insane amounts of torque and I'm really looking forward to it. I've got it in the machine shop right now cleaned, magnafluxed, and ready for new parts. The current plan is to bore the block .030 over and replace the toasted crank with a stroker at a 10:1 compression ratio.

I picked up a set of 6X heads a little while ago and they passed testing, but I haven't decided whether or not to oversize the valves yet. I was going to go with a roller rocker setup (brand to be determined later), and no idea what kind of spring to use yet.

For the intake manifold and carb I was thinking about using a Edelbrock dual-carb intake manifold with 2-600cfm carbs, but figuring that would completely destroy my fuel economy I'll likely end up running a single 800cfm carb.

As for cam, I have no idea yet. I was planning on relying on my machinist for suggestions here.

No idea where I'll end up on the HP/Torque charts, but figure with a 455 under the hood I should be able to have some fun. :D
 
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