55.2-59 Help identifying driveline parts please?

[County]

Father in Law has a '55 series 2 GMC 4x4. Was all original when he got it as far as we know. The original engine was not rebuild-able, but was a 288(maybe?) v8.

So, new rebuild motor he was told is a 400sb. Can someone verify from casting? casting numbers on rear of motor, not on pad on front of head.



Please identify trans as well? 3sp or 4 sp? Seems to be only 4 gates, so thinking 3 fwd and reverse, but very jammed up and tough to move unsecured.

Old Muncie M20 maybe?







Thanks for the help identifying what we have!

-Shayne

[County]

Last part, transfer case. Please identify as well?





We're also having as issue getting a bellhousing to work between the original trans and the new motor.

Anyone have an easy solution to pair the two together please?

[1project2many]

Engine casting number comes across as a 400 smallblock, 1970-1980.
http://www.castingnumbers.info/site/search/3951509

Transmission appears to be original SM420 four speed.
http://www.novak-adapt.com/knowledge...s/manual/sm420

First gear is 7.05:1 "creeper" gear rarely used in daily driving.
https://www.advanceadapters.com/tech-vault/1-gm-sm420/

Reverse is toward the left and back. It takes some pressure to engage it.


I'm a fan of NAPCO trucks but I'm no expert.
https://historygarage.com/napco-4x4-...forgotten-4x4/

Transfer case is listed as a DANA 23:
http://www.napco4x4.org/history3.htm

There are pictures of a NAPCO conversion here:
http://67-72chevytrucks.com/vboard/s...d.php?t=529546

Welcome!

[County]

Thank you very much. Very helpful!

[County]

Anyone have a link to what kit would be required to mount the 400sbc and different bellhousing to the existing '55 please?

[burnin oil]

Before you install that 400 you need to pull the pan and check the crankshaft. 400sbc are externally balanced and the only 1st gens of the kind. Figure out if the crank is a GM unit or an aftermarket. Grab the numbers off of it and google them. This is going to be the only way to know whats inside for sure.

After market can get an internal or external balance crank setup. GM will be a cast crank thats external balanced. A regular 168 tooth flywheel will bolt up to a 400. You just need to figure out which style you have. There is a cheater weight that can be bought from places like summit that bolt to the flywheel. This option is cheap. Then you can buy a preweighted flywheel but the price goes up. The only issue is that neither is truely balanced to the motor. If you are lucky it is an aftermarket crank and you can just bolt on any old SBC flywheel.

Also look at the balancer. A factory balancer is scalloped on a 400. This means that there is a groove cut into the outer band and its not 100% round like regular SBC. If you have this it will be very obvious. You need to make sure the crank, balancer, and flywheel all match. Welcome to the redheaded stepchild of small blocks. Going by the picture of the casting number I am guessing that you have a factory crank.

One thing I didn't mention. When I had my early 60 pick up it was a factory mutt. Parts from the 50 and parts from the new body style. It had a factory hydraulic clutch and a 10.5" car flywheel. When I put the 400 in I reused the bell housing and then used a newer 168 tooth 3 bolt truck starter. This along with an appropriate flywheel (balanced externally by the machine shop) and a clutch for a 70s chevy truck. Everything bolted ride up and worked flawlessly. If that SM420 is in good shape I wouldn"t worry about breaking it. We abused one behind a torque built 350 with 5.14 gears for over a decade!

Another piece of advice is to double check all the mounting bolts holes for your engine mounts. Some times the bosses are there but they arnt drilled. I forgot on my last motor and had to drill and tap the front mount holes for the power steering pump along with the ball stud for the clutch while it was in the truck. This was in my 72.

Long story short. Confirm the flywheel wieght needed and it should bolt right back down in there with chevy parts.

[1project2many]

Anyone have a link to what kit would be required to mount the 400sbc and different bellhousing to the existing '55 please?

Hmmm... What problems are you having with the bellhousing? I don't believe you want to use a different bellhousing. The truck bell doubles as rear engine mounts. It should connect to any SBC without complication. If you use a bellhousing that doesn't bolt to the existing crossmember you'll have to install a rear crossmember and a transmission mount.

[mikebte]

Originally Posted by County

So, new rebuild motor he was told is a 400sb. Can someone verify from casting? casting numbers on rear of motor, not on pad on front of head.

Attachment 1876683

Maybe a little more info on the block. Both a 2 and 4 bolt main option was available.
Cast# 3951509....400...1970-1971...4
Cast# 3951509....400...1974-1980...2

Head looks to be a few possibilities.
462624.....1975-1986...350/400......76cc chamber, 1.72/1.5, 1.94/1.5 or 2.02/1.6 valves
OR 3998991 Cylinder head. 1972-1973, 307 or 350, 75cc chambers. Could very, need a better picture of head. Also may have a part number under the valve cover.

As mentioned, drop the pan and have a look, only way to tell what you have for part numbers and crank. Rebuilt engine could be a surprise, but that is part of the fun.

[mr48chev]

Originally Posted by County

Anyone have a link to what kit would be required to mount the 400sbc and different bellhousing to the existing '55 please?

You are going to need a cast iron 55/59 and maybe into the mid 60's V8 Chevy truck bellhousing.
It is going to look like this from the front with the pattern that matchs the back of the block


Clutch linkage shouldn't be a big issue and you may be able to use what you have.

Flywheel As They said it is best to drop the pan and make sure you have the stock 400 crank or a special crank that is internally ballanced but my bet is on stock externally ballanced crank. You should be able to look at the vibration damper and tell too as the 400 balancer is also externally balanced. The externally balanced damper has a defined cut out area on it per a photo in this link that also reinterates a lot of what they guys already mentioned. https://www.chevydiy.com/comparing-r...block-engines/