The Stovebolt Site Forums The Shop Area Engine Shop 250 I-6 questions, and rockwell ??

Hi all,
I have a late 60's (68-70) 250 with 4spd and rockwell transfer case.
The 250 has sat since about 2000. I got it running with fresh gas and a fresh battery. The valve cover is leaking a fair bit, and running onto the exhaust. THe 4 speed seems to shift hard, but don't know why. I have the body off right now, and really don't want to rebuild, just minor repairs, and get to driving this truck.
Are there any recomendations out there?
Also the upper rear cover plate on the rockwell transfer case is cracked, and has been "RTV'd" to stop the leaking. Anyone know where I can find another cover for a rockwell transfer case? Or what a good replacement is for the rockwell behind the 4spd?
Thanks, Garry
1965 IHC w/ Chevy 250, 4spd, rockwell

Valve cover leaks are a pain on the 250. Remove and clean the cover, then straighten the lip and be sure to smooth out around the bolt holes. Also get the mating surface on the head clean enough to eat on. Get a cork gasket and a tube of yellow weatherstrip adhesive. It will need to be applied to both sides of the gasket and both mating surfaces, then allowed to cure per the label. I will usually do the head side first, and after the gasket is on the head then apply to the cover and top of the gasket. install the cover and torque to the manufacturers recommendation. I use an acid brush to apply the adhesive to the head, it allows you to reach everything.

For the transfer case, try placing an ad in the swap meet here. You can also try some of the 4x4 forums, hopefully someone here can recommend one. You can also try the 67-72 parts board there are a few 4 wheelers there.

Your tranny, if it's original, should be the SM420, reverse is to the left and down. Very tough tranny, preferred by the rock crawlers. It could just need an oil change. When I had mine out of the truck I drained the oil, filled it with kerosene and let it set a few days, rocking it every once in a while. Then I drained and put in new oil.

The SM420 4 speed was used through 1967; the SM465 replaced it in 1968. The SM420 was a good transmission, not quite as beefy as the 465, but plenty strong for a light truck. Along with its lower first gear, the case is a little shorter than the 465. If you change out to a later trans, be sure to get the bellhousing as most of the 465s use a larger bearing retainer.

1968 was the last year for the Rockwell transfer case; it was replaced by the NP205 in 1969. The NP205 is a much superior transfer case, and quite plentiful. You may want to strongly consider replacing the Rockwell with an NP205. If you keep your eyes open, SM465/NP205 combos show up on ebay.