Milwaukee Midget

[Stan Back]

"One per exhaust port is my understanding . . . "

Thats the official Whitworth formula, rite?

[Milwaukee Midget]

"One per exhaust port is my understanding . . . "

Thats the official Whitworth formula, rite?

Sorry, Stan - one needs to be MI-5 or higher to access the Whitworth files.

[Milwaukee Midget]

Well, it mics up okay - everything reads smack dab in the middle of specs, consistent from journal to journal, but that consistency has me thinking two things -

1 - I haven't checked my mics against a Jo block in years

2 - If my mics are indeed accurate, I might want to have the crank touched up a tad to take it to bottom tolerance.

I'll start the dry build this weekend and see what the plastigauge tells me.

[Milwaukee Midget]

Once again, I appear before the greatest brain trust in racing, seeking wisdom.

Started the dry build.  New billet crank, new thrust washers.  I know a generous radius is a good thing for a crankshaft . . .



BUT . . .
The radius appears to be interfering with the inside arc of the thrust bearing.  It’s a little tough to see, but notice the inside arc of the bearing – shiny after a few turns of the crank by hand . . .



I had zero end play.  .002 -.003 is where it should be.

Now I COULD send the crank that I’ve been waiting for since the day after Christmas back and have him put a smaller radius on it.  But I can’t think of a reason why I couldn’t simply relieve the inside arc of the thrust bearing. 

Am I missing something?

[grumm441]

I wouldn't ruin a perfectly good crank, that you have waited, and waited, and waited for
Take it out of the thrust bearings. After all if you stuff them up, how long do you have wait for a new pair
G

[Koncretekid]

MM,
I'm probably not the right person to answer your question, but a good man on a Bridgeport milling machine could clamp the thrust bearings down to a block of aluminum on a rotary table (or a programmable mill) and use a radius tool to put a nice radius on the inside edge of those thrust bearings.
Tom

[AJR192]

Take it out of the bearings. They have plenty of material and the engine will never notice. On the other hand, those big fillets on that crank are where it is getting it's strength and is the reason you waited 8 months and spent a wad of cash for a billet crank, right?

[jdincau]

Before narrow inserts became available off the shelf it was standard practice to cut a chamfer on standard width connecting rod bearings for use on large radius cranks in drag race motors.

[Milwaukee Midget]

Thanks, guys - I appreciate the insights.

I've worked on engines before, but I've never attempted anything this extreme.  You can do your homework, read articles, sift through tech sheets, and have everything plotted out, but until you start screwing it together and looking at it critically, you just don't know what kind of questions will pop up.

This is an issue I never even gave a thought to.

Again, thank you.

Chris

[Milwaukee Midget]

Another question answered.  Not a bull’s-eye, but at least a double 20.



I’m only about .013 shy on the deck height.  I’m grateful it’s coming off of the block and not the pistons.  I can send the pistons out for coating while the block is getting machined and fitted with cam bearings.

One other issue – comparing the stock crank with the new one indicates the gap between the front and back thrust surfaces on the new crank are about .003 narrower than the old stocker.  I’ll see what my results are after I chamfer the inside arc of the thrust bearings, but I may have to give the back of the thrust bearings a shave and a haircut.

[AJR192]

You can take it to your local machine shop with a crank grinder and have them bump the thrust surface to open it up. Most can do that while you wait.

[Milwaukee Midget]

You can take it to your local machine shop with a crank grinder and have them bump the thrust surface to open it up. Most can do that while you wait.

True - that would be the most correct way of doing it.  And I am making an assumption that the old crank I'm comparing it to is in spec - truth is, I don't know that for sure.  A bit of research is in order. 

Or, as I'm taking the block in anyway, I could have the faces touched up. 

But I'm only looking at .0015 on either side, the bearing is a steel stamping with a bronze alloy bearing face, its .0925 thick, and if it gets screwed up, I can get replacements at NAPA overnight.

The trick would be setting up the bearings to be skimmed on the back sides.

I've got the old ones from disassembly - I'm thinking I'll try an experiment and see if I can evenly take them down with a piece of emery on a flat steel plate.

[38flattie]

Chris, you get everything figured out?

[Milwaukee Midget]

Chris, you get everything figured out?

Everything? 

Well, just enough to know that next time, I'll take a very long, hard look at building a small block Chevy. 

Nah - just kidding - my dad would kill me.

Well, after chasing down a new battery for my dial indicator, jostling around rod-piston combinations, and allowing for ceramic coating, I'm thinking that .010 is the magic number for the block shave - I'll drop it off on Tuesday before I fly out to SLC.

I was able to put a chamfer on the thrust bearings with my Dremel - came out nice - all those years of building model cars and working in a hobby shop are starting to pay off - but they're still a tad thick, so I'll try my emery cloth idea tomorrow.

Buddy - I'll introduce myself to you in a week.  Don't break, go fast, be safe, have fun.   

[hitz]

Chris,
You might try a fine file on those thrust brgs. Emery may leave embeded particles in the soft bearing material. When you get that end play right, you're golden. Good luck.

Harvey

PS 1" mic check at 0