The Stovebolt Site Forums The Shop Area Engine Shop 235 crankshaft in a 216 engine

Since most people believe the old 216 is nothing but a boat anchor, there are lots of them available, either cheap or sometimes "free if you haul it away". That's mostly because us old geezers who know how to rebuild them are slowly "achieving room temperature" as the late great Rush Limbaugh used to say. There's also the little problem of the main bearings getting scarce, and/or horrendously expensive.

Here's an alternative to scrapping that old 216- - - -put a pressure lubricated 235 crankshaft and connecting rods into it. No, it's not a "drop-in" fit, but with a little creative metal butchering, it's definitely doable. You'll encounter two small obstacles- - - -the 216 block is 1/8" shorter than the 235, which would make the pistons stick out of the top, and the #3 main bearing web of the 216 is about 1/4" wider than the 235 crankshaft thrust faces. The main bearing diameter is the same on both cranks, however. It's a fairly simple machining process to narrow the main bearing web, so the 235 bearings can be used in the 216 block, and it's also possible to fit the much more available and less expensive 1955-63 235 main bearings to the 216 block in the process. The pressure lubed 235 rods and replaceable bearings also work instead of dealing with spray-oiled Babbit ones.

Now- - - -how about that pesky "too short block" problem? Buick 215 V8 pistons (Silv-O-Lite #1718) are the same bore size as a 216 (3.5 inches) and are available up to .060" oversize. That gives displacements from 227 up to 235 cubic inches, depending on the overbore. The compression height comes out correct, and the 235 connecting rod small end only needs to be reamed .010" to fit the Buick wrist pin. They're also lighter weight than the cast iron 216 pistons. A 1953-55 Melling M-29 oil pump for a 235 is a bolt-in swap for the 216 oil pump, and provides sufficient oil volume to lube the pressurized crankshaft. The rest of the 216 oil system functions as designed, after plugging the oil passage that formerly fed the oil pan spray nozzles.

I've probably just cut off my supply of freebie 216's, but I've got more of them stockplled than I'll ever be able to build, anyway!
Jerry

Hot Rod Lincoln's Crate Engines coming soon??

1) I’d like to know more about narrowing of the #3 web.
2) Does the 216 block also need some sort of align-bore procedure to accept the 235 crank?
3) Is the Buick wrist pin a press fit design or something else?

Fun fact: the Buick 215-based design was used into fairly modern times in Land Rovers. Might be an alternative source for pistons and such there. I’d have to go do some reading to understand what all they changed through the years to test that theory. Perhaps HRL already knows.

Edit:

* Here is a site that has many different iterations of the Rover pistons for sale. They don’t list compression height to verify that matches the Buick.
https://rimmerbros.com/Item--i-GRID800016

* A good overview of the Buick/Olds V8 use in the Rover line and various revisions into the 90s. Might be some other bore size possibilities᠁
https://www.hemmings.com/stories/article/buick-215-cu-in-v-8-rover-3-5l

Since the stovebolt connecting rod has a pinch bolt in the top end, the wrist pin only has to be rough centered in the pin bosses- - - - -no end clips in the pistons are needed. According to my Silvolite catalog, the #1718 piston has a compression height of 1.843" and a wrist pin diameter of 0.875". The stovebolt wrist pin is a 0.865" diameter, with a 2.060" compression height. The compression height of the 215 piston is just enough shorter to compensate for the longer stroke and shorter deck height, while keeping the piston top close enough to the top of the block to maintain good compression pressure. The Buick piston also has a shallow recess, which could be used to adjust the deck height by machining the top of the piston a little if necessary. The only downside is the wrist pin offset- - - -the 215 piston is on center, and the stovebolt piston has a slight offset. That MIGHT result in a slight piston slap, depending on where the ignition timing is set. Fitting the pistons with a fairly tight skirt clearance would tend to minimize that problem.

I'm in the process of fabricating a milling fixture that centers up in the #3 main bearing bore and can be used in a floor mount drill press to do the main web narrowing- - - -line boring should not be necessary. It uses a 3 1/2" diameter shell milling cutter to machine an equal amount of material from both sides of the thrust face of the block and main bearing cap. However, I do have a portable line bore machine if I decide to do the full bottom end rehab.
Jerry

Does the 216 block have more cylinder “meat” than the 235? Such that it could accommodate a significant overbore?

Not likely- - - -either one can probably handle 80 over, but 60 is more likely to be longer lasting and have less of a possible problem with overheating. A 60 over 216 with a 235 crankshaft results in 235 cubic inches in a 216-appearing block. The lightweight aluminum pistons will really wake up an engine that once had cast iron ones! Quicker acceleration, and higher RPM. I'm also working on a radically modified 216 with a stroker crankshaft that will have 258 cubic inches, H-beam connecting rods, roller valve lifters and stud-mounted roller rocker arms.
Jerry