Quote:
Originally Posted by JBates
Hi everyone I recently posted a thread requesting recommendations on a hydraulic flat tappet cam for my engine build. Based on the responses I now have a pretty good idea of what would be suitable. In the process I found out I have a 2.56 Rear End. Based on my build and intended use I’ve been advised I’ll need to go with 3.42 or 3.55 gears.
After doing some more digging it looks like I have a oldsmobile 12 bolt cove / 10 bolt carrier on my car. One of the prior owners swapped out the original engine with a ’73 400 and 4x low compression heads. In the process they must have replaced the rear end and went with the lazy 2.56 rear end.
Checking to see if I can get some feedback on the most feasible way to to get my desired rear end. Should I look into getting a complete different rear end or is it possible to get rebuild kit for the 12 bolt oldsmobile rear end with 3.42 or 3.55 gears.
I’m hoping to avoid any wheel spacing offsets so ideally it would be nice if I can find a 1966 Pontiac GTO rear end. Are there any good alternatives? Any feedback is greatly appreciated.
1966 Pontiac GTO
-‘73 400 ci block going to be bored out 0.30 over from 4.12 to 4.15
-Tri Power Carbs
-‘68 #16 heads 2.11/1.77 valve heads (72-75cc)
-14cc dish pistons
-CAM Crower 60243 or Voodoo 703
-Ram Air Exhaust Manifolds
-2.5" Exhaust
-4 Speed Muncie M20
Thank you
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If you want to drive the car for any length of time faster than 55 or 60 mph, stay away from the 3.55-3.42 gears. 3.23 are about the perfect gear for a 4 speed A body, and 3.36 are decent too. I had the 3.55's removed from my '65 GTO (389/tripower/M20) and had 3.36 gears installed and that moved my cruise speed from 60 to 70 mph. Not much on paper, but the car got a whole lot more drivable. 3.55's suck at any speed over 60 mph for more than 5 miles.