I am looking to purchase a '68 ss next year around tax time. I have started gathering parts, as I like the Yenko look and performance, so I picked up a tall deck 427 complete motor minus carburetor and starter for $300. I plan on rebuilding it and changing out the pistons, rods, camshaft, intake, and put a nice holley on top. I am also planning on putting a 4 speed behind it. What is the best transmission for me to put behind it? I plan on driving this car quite often, so regular pump gas is what it will be run on. There are several different choices for the Muncies: M20, M21, M22, and close and wide ratio.. which would work best in my application?. The car has an automatic in it now, would I also have to change out the transmission crossmember? I know I will have to change out the motor mounts, but do all big block motors have the same mounts? Until I get the engine built and transmission hooked up behind it, I will be driving the camaro as it is. I apologize if these questions are kind of "duh" to many of you, I have never performed an engine swap, and am trying to gather as much information as possible, as I don't want to have my camaro look like it was back woods thrown together by a shade tree mechanic and perform like crap because of parts that don't mesh well. Thanks for any help with these questions!

CTRSN, ***, Cody J.
USN

 

all big block chevys use the same motor mounts. to run on pump gas dont create a high compression motor because they require high octane. i think the crossmembers are the same between auto and manual but im not 100% sure. also on the trannys the M20 is the wide ratio while the M21 is the close ratio. the M22 is know as the rock crusher due the straighter cut of the gears. they make alot of nois but are very tough. the downside is that the M22 is the most sought after and most expensive muncie right now so either the 20 or 21 is good. is the current 68 a #'s matching car? is it a true ss?

 

It is supposed #'s matching. I have not crawled under the vehicle to confirm. It is in a shed, put in close quarters along with the other 3 68 and 1 67 camaro, a 65 mustang, and a 70 cuda. I planned on finding out for sure if it is indeed numbers matching when I got it home. The owner previously told me it had a TH350 behind the 350, which would make it non numbers matching, according to what I've read, they only had TH400s until 1969. I know the VIN shows it as a SS car, but whether or not the engine and trans was changed out at some point is unknown by myself at this time, and I am currently a couple states away until I go home next year. (Active duty military)

 

no the th400 were put behind factory big block cars while the th350 was behind all the small blocks. to check to see if #s matching look at the front pad on passenger side of the block where the heads bolt on. if the last 6 digits match the last 6 on the vin then its the original motor and worth alot more money with the original drivetrain.

 

The TH350 was behind the small blocks starting with the 69 model year (the year it was introduced). For 68 and earlier, the only small block automatic option was the 2-speed powerglide.

 

from what i've found, the TH400 was limited to the L35 325 hp and L34 350 hp engines in 67 and 68. In 69, the TH400 was also available with the 396 and 427 solid lifter engines.