Rear axle

Blish

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Does anyone know how much power the stock axles can take? Is it a 8 1/4 or a 8 3/4? I plan on either building an engine or swapping in a 6 pack 440 sometime in the future. I would like to be more confident in the gearing. It is a 2.76 ratio axle. 77 Newport 400-4.

-Paul
 
For that car, it probably is a 9.25" 2.71 gear ratio.

You will also probably need some better brake friction materials as well as some sort of rear spring "anti-windup" traction-related items, too. Maybe even some stronger u-joints?

Save the 6bbl induction for a B/E-body. A single 4bbl can get similar power without all of the 6bbl's troubles.

Also chase down a 3.21 or similar rear axle gear set. Plus a good SureGrip unit and a 10.75" higher-stall torque converter ('68 Road Runner spec).

For best results, a stock rebuild with a 400/440HP cam, 9.0-9.5 compression ratio, better under-car dual exhaust system. Past that, costs rise almost exponentially.

Regards,
CBODY67
 
I was thinking more like this
1276-020 pistons
milled 452 heads mild port and polish stock valves
shorty headers dual exhaust
weiand action plus
thermoquad
comp cam (not sure but probably something in the 210 degree range @.050)
1800 stall converter
3.55 gears.

Thats if i build a 400. If i do a 440 itll either be a 6 pack or a dual 4 barrel. Its got the cool factor.
Or maybe a carbed Viper motor with a manual swap, wouldnt that be butchery! haha

If it has a 9.25 i would be extremely happy, as i know where i can get a yukon limited slip and a yukon gear set for the 9.25 on the cheap. Idk the ratio id have to count. But given it was going in his d100 street truck id say its a pretty decent sized gear.
 
I'm going to say it's probably an 8.25" rear.

That's what my '76 Newport 400 4bbl had.

Best to just take a look under the car instead of speculating. The 8.25 and 9.25 look totally different.

Here's a guide that I stole from one of C Body Bob's posts:

img_4682-jpg.jpg


Jeff
 
I'm going to say it's probably an 8.25" rear.

That's what my '76 Newport 400 4bbl had.

Best to just take a look under the car instead of speculating. The 8.25 and 9.25 look totally different.

Here's a guide that I stole from one of C Body Bob's posts:

View attachment 478013

Jeff

this was helpful! it is an 8.25 rear

would it hold to the power of a mild 400 or 440? looking at about 300-400 horses hopefully, depending which route i go.
 
Remember that if you mill the 452s enough to get decent compression increase, you'll also need to consult "the experts"/chart to see how much you'll need to also mill the intake manifold sides so they all fit together well. THEN, the intake manifold and heads become a "matched set", so to speak. Just a normal "surface/true" cut, no worries, generally.

That "cool factor" can be a good bit of work to keep it all working "as designed", which the magazines don't usually mention. Plus expense! Especially when the engine might spit-back when starting, which then means a new power valve in that center carb. But if you desire to learn about these things . . .

Enjoy!
CBODY67
 
Remember that if you mill the 452s enough to get decent compression increase, you'll also need to consult "the experts"/chart to see how much you'll need to also mill the intake manifold sides so they all fit together well. THEN, the intake manifold and heads become a "matched set", so to speak. Just a normal "surface/true" cut, no worries, generally.

That "cool factor" can be a good bit of work to keep it all working "as designed", which the magazines don't usually mention. Plus expense! Especially when the engine might spit-back when starting, which then means a new power valve in that center carb. But if you desire to learn about these things . . .

Enjoy!
CBODY67
I've been reading for every .010 on the heads you need to go .012 or so on the intake to get it lined up properly. I figure if I go about .050 this should bring my compression up 2 points with the 1276-020 pistons. 9.61 to be exact. But most engine builder's would say thats a 9.5:1 engine.

I'm looking at 350-400 horse and probably 500+ ft lb torque. Forgot if I've already mentioned that. I'm not going super agressive with whatever I build.
 
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