Another underpowered 307 and badly geared gbody

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Mattyp77

Not-quite-so-new-guy
Nov 20, 2014
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Hey guys I guess it's official I am definitely a gbody guy now cause I'm now on my second. It's a 1987 Buick regal. It's just a shame that such great looking cars can be so underpowered. I may try to do some little things over time to increase the power of the 307 but for now I think the best thing that can be done to gain some acceleration is do something about the gears in the back. I haven't checked for sure what's back there but I think it's safe to say it's that awful 2.41 it whatever. I know it's definitely the 7.5 10 bolt housing. Any suggestions on what to do to help this thing along a little? A good gear ratio for this drivetrain?
 

TURNA

Rocket Powered Basset Hound
Jul 24, 2009
10,941
19,990
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Easiest thing would be to find a GN 3:42 or Hurst/442 3:73 8.5 rear

Simple direct bolt in just cut your driveshaft 1 inch
 

MrSony

Geezer
Nov 15, 2014
6,793
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Des Moines, Iowa
Tried and true field tested swap:
GN 3.42s
Auto trans with good shift kit.
300+hp Buick 350. :p

Or since you got a 307 any olds engine will swap in with little to no mods.
 

bracketchev1221

Royal Smart Person
Jan 18, 2018
1,386
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I would go with an 3.42 gear for an upgrade. I would love to find an 8.5" rear for mine, but they are next to impossible to find and expensive if you do find one.
 
Oct 14, 2008
8,806
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Melville,Saskatchewan
Everyone who had the swirl port 307 complained of the lack of power back when they were on the road. Hopefully it has the OD trans, then add 3.73 gears. Add the Thornton manifolds, shorty heads or Hedman full length headers with dual exhaust. The whole factory exhaust is horrible from those tubular manifolds all the way back. Those two upgrades alone will make it perform and sound better.
 
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Yav8

Master Mechanic
Aug 19, 2014
275
114
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Manitowoc wis.
Looking for a simple gear swap and CHEAP to boot. If you are staying with the 26spline axels then the early S10s or GMC will have the gears you want. Something with a auto will have the 3.42s and most 4 cyl and stick will have the 3.73 or the 4.10s. Also most of the 4 wheel drive will likley come with a gove lock posi. Not haveing a lot of power they will work just fine. If you want to go to the 28 spline axels then just order the axels from summit or jegs for the GN and then look up the 90 and newer Gm stable of S10 comaro firebirds and the rest that came with the 7.5 10 bolt. They are all the same.
 

Turbo Zach

Comic Book Super Hero
Sep 8, 2015
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If you have overdrive? I would keep a eye out for a Monte Carlo SS rearend. They go pretty cheep and have 3:73 gears. I have a 8.5 with 3:42 gears and a three speed automatic. It twists pretty high RPM's at 70 mph. A 3:08 gears might be better for you? I plan to build a 200r4 sometime soon, so the 3:42 is not a big deal to me. Hands down the best thing you can do for performance though.
 
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MrSony

Geezer
Nov 15, 2014
6,793
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Des Moines, Iowa
If you have overdrive? I would keep a eye out for a Monte Carlo SS rearend. They go pretty cheep and have 3:73 gears. I have a 8.5 with 3:42 gears and a three speed automatic. It twists pretty high RPM's at 70 mph. A 3:08 gears might be better for you? I plan to build a 200r4 sometime soon, so the 3:42 is not a big deal to me. Hands down the best thing you can do for performance though.
Agree. I gotta get a good 200r4 too. 3.42s are pretty buzzy with a 3 speed.
 
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