The Stovebolt Site Forums The Shop Area Engine Shop 216 upgrade news flash- - - - - - -

For those of you who are considering retrofitting a 235 crankshaft to a 216 engine- - - - -I just made a very important discovery. The #3 main bearing cap- - - -the one that needs to be narrowed on a 216 for a 235 main bearing set and crankshaft to fit- - - -has exactly the same bolt spacing and inside diameter as a 54-63 235 engine. If anyone has a "junk" 235 block- - - - -PLEASE DO NOT DISCARD THE MAIN BEARING CAPS! The 216 block web still has to be machined, but by installing a 235 bearing cap, half the work has already been done for you, and the fore/aft spacing of the main bearing won't be altered, which keeps the timing gears aligned properly. Also, if anyone has some 235 main caps in your parts stash, I'll be glad to buy them, or cover shipping. PM me, please!

BTW- - - -216 and spray-oiler 235 connecting rods can be machined to accept the 235 replaceable rod bearings. The oil hole in the bottom of the rod cap doesn't prevent the later model bearing from fitting properly, with a little TLC by a competent machinist!
Jerry

Machining the 216 cap separately from the block to match the 235 would be pretty easy, as well. You don't have to work around the block. Also, installing the narrower cap to do the machining would let you cut the block web till the cutter just "kisses" the narrow cap. Using the 216 cap should also mean you wouldn't have to line bore it to match the block, as that would already be taken care of if it was the one that was originally on the engine.

One thing about stovebolt main bearing caps- - - -they "float". There's no dowel pins, or other means of holding them in perfect alignment with the block, so as long as the inside diameter of the block/cap interface is correct, line boring just might not be necessary. As the bolts are snugged up while installing the crankshaft, the cap (and the lower main bearing) tends to self-align with the crankshaft. That's particularly true if brass shims are being used to adjust the oil clearance.
Jerry

Jerry, I was just going by your comment to another bolter about needing to line bore if the cap were swapped between engines. If they don't need line boring, all the better.

It all depends on how well the block (and the different cap) were machined in the first place. On the blocks that I'm going to convert to small block 400 main bearings with reducer bushings in the block and the caps, I'm pretty sure I'll need to rough out the new dimensions with a line bore, and then line hone the finish diameter. I just spent $3K on a line hone mandrel about 4 feet long to do the finish sizing. The end result will be all four main bearings the same diameter, and readily available bearings that cost around $50.00 a set. I'll also be able to salvage "worn out" crankshafts that have been ground way undersize without welding on journals.
Jerry

This is very excited, and I just so happened to have those caps! Can’t wait to get this engine built.

Also here’s a Video on YouTube of me disassembling the 55 235. Lessons we’re learned since I was being lazy and didn’t take off the top end up get out the crank.

I was wondering if you were able to get the crank gear out thru the front plate. Looks like it worked out, but with a bit of fiddling around to get it thru the hole. I had to pull the crank gear on mine, because the pistons were frozen up and I couldn't get to the oil pump retainer pin until I could turn the crank a bit. I didn't catch on your video what size the rod bearings were. My 235 crank will probably need to be reground, so thinking about having it ground offset to increase the stroke just a bit. A standard crank could be ground 0.040 undersize on the rod journals, which would put the top of the Buick pistons 0.020 closer to the top of the deck on the 216. Without an offset ground, my calcs say the piston tops will be 0.06 below the deck. Offset grinding would increase the compression ratio just a bit.