The Stovebolt Site Forums The Shop Area Engine Shop 216 rebuilders- - - - -got a question

Back in the dark ages when I learned to rebuild engines (mid-1950's) the oldtime mechanics from the 20's and 30's who were my mentors had a procedure for adjusting rod bearing clearances that included shoeshine-polishing the crankshaft journals with super-fine grit emery cloth and scrape-fitting the bearing material using Prussian Blue and a triangular file ground into a razor-sharp fitting tool. The procedure involved spreading a thin layer of blue onto the bearing surfaces, lightly clamping the rod onto the shaft without shims, turning the crank one revolution, and gently scraping away any bright streaks in the blue that indicate high spots. Recoat/repeat until the bluing gets a smooth smear with no shiny spots, then use a 1/8" wide piece of .002" shim stock between the crank and the rod cap and shim the cap until turning the crank gives a slight drag with the rod bolts torqued. Move on to the next rod, and repeat. Then Plastigauge came along and made the clearance-checking phase a little easier.

Does anyone else fit bearings before checking oil clearance? BTW, I'll be doing the same thing on a Model A Ford engine soon with poured rod and main bearings. Fun and games!
Jerry

Jerry, You are probably the only one on here that knows how to scrape bearing for clearance. Kind of a lost art with inserts anymore. Be a skill that would be nice to know though......

John

There is a web site called practicalmachinist.com that organizes scraping classes two or three times a year. Not very expensive to attend. The guy that runs them will also go on site to teach small groups, but its kinda spendy.

Scraping is still done all the time. If you pour a bearing you gotta scrape it.

Bearing fitting is job one on any 216 rebuild, and it really needs to be done when rod clearances are adjusted- - - -I was just wondering if anybody else bothers to do it. That's probably why 216's get a bad rap about being fragile and/or unreliable.
Jerry

On main bearings they talk about having them line bored. Rods generally have shims don't they?

John

The very early 216's had a "semi-finished" insert main bearing that had to be line bored after it was installed in the block. Later 216/early 235 mains needed final clearance adjustment with shims even though they were supposedly "precision" bearings. The rods on all 216's and low-pressure 235's were Babbit-lined and had to match the crankshaft diameter- - - -when a crank was ground undersize a corresponding-diameter set of reconditioned rods had to be installed. The rebuilders that did a really top-notch job did the Prussian blue/scrape-fit procedure to assure a perfect match between the crankshaft and the rod bearings, then set the oil clearance with shims.
Jerry

so Jerry......

When do you say that you wanted to come teach a young pup how to rebuild a 216? I would love to have even a small portion of the knowledge that you have about these engines.

Chris

If you can find a copy of it, the old Lindsay book seller had a few good books on scraping and babbiting.

http://www.youroldtimebookstore.com/product-p/22440.htm

Pouring babbit is still widely done. I'm surprised that no one has recreated the centrifugal babbit process used by Chevy. That would save a ton of work and money.

I'm thinking Jerry's videos on various engine and drivetrain building tips....

John

It seems to me that babbit scraping would only be necessary with new bearing material. If you are re-using the babbit rods, then theoretically, there are no high spots to scrap off and you just need to check/adjust clearances. This is what I did. If your babbit is gone, it would be best to convert to inserts IMHO.

See it done on a large scale in "The Train".
Burt Lancaster pours and scrapes the inserts for his seized steam locomotive rod, then uses an overhead crane to put the rod back.

Excellent movie, if you haven't seen it.

I remember a story I heard from my father,talking about watching his father using a piece of thread and a micrometer to check clearances. Imagine torquing down the cap and mic ing the thread. I have no idea if this actually happened or worked. I heard the story in the mid 60's

Waxed cotton thread. Precursor to Plastigage.

And you certainly didn't crank down on the ratchet of your micrometer to read it.

Don't forget all that industrial equipment with bearings where you can't just go out and buy a set of Clevites. As someone said; still a lot of applications for fitting bearings.

That movie was just on television last week or so.
John

I think I know the answer to my own question. The rods are the same length in a 216 and a 235? I was wondering if the pin in a 235 piston is in the same location as the 216, but I'm think "NO". I seen in my book where they bored out a 216 engine 1/8" to a 3 5/8" bore making it a 232 engine.

John

The pin diameter and location is the same on a 216 and 235 piston.
In fact you can bore a 216 .0625" over and use standard size 235 pistons in it.

So the rods are different lengths or is the block 3/32" taller on a 235??

John

The 235 block is taller.

Hmmmm- - - -so a 216 becomes a 224 with 235 standard-bore pistons in it! Good to know!
Jerry

You can end up with an almost square engine bore vs stroke....

John