I have 2 engines w/casting numbers 3914678 & 3782870 and a Muncy 4 speed trasnmission. I would like to get rid of but not sure what GM cars they belong to.

www.mortec.com

I couldn't get the link to work, but I have a PERA (Production Engine Rebuilder's Association) handbook that lists the first number as an "early" 350 Chevy (circa '72-'78, but it isn't real specific). The second one is a small-journal 327. Pull the pan on the 350. It has about a 75% chance of being a 4-bolt.

All Muncie 4-speeds have an aluminum case and 7 bolts holding the side cover on. Saginaws are iron cases and Borg Warners have 10 or 11 bolts holding the side cover.

If the Muncie has the speedo gear go into the driver's side, it's a Pontiac or Olds/Buick. If it goes into the passenger's side, it's a Chevy. There are three basic "flavors" of Muncie. The M-20 is a "wide ratio" (deep 1st gear, about 2.56:1) with the coarse spline input and small output. M-21 is similar but usually "close" ratio (2.20:1 1st). M-22 has the large output shaft (same size as TH400). M-22s may or may not be "coarse spline" input. Many of the last version were "fine spline" (26 splines instead of 11, I think).

There's a 4th Muncie, but very rare. It's M-37. It has the 1 1/4" input shaft (as opposed to the 1 1/16" on the others) and large output. 1st gear is "spur cut" (teeth are straight, not "helical"). This is the infamous "Rock Crusher ", found only in '67 Corvette ZL-1 cars (production), but MANY were sold over the counter for racing. It's a common misconception that any Muncie is considered a "Rock Crusher"... The noise 1st gear made due to the gears is where the nickname came from. Very loud whine, like a cement mixer...

Jim