Connecting Rod and Cap Fitment

[roadrunnerh]

While installing my piston rings, I noticed the little number stamp on each rod and cap where they meet. I know this 1968 383 has never been opened up, so this must have been factory. I read here and elsewhere that others have noticed this as well, but not all 383/440s have the little stamp.

Is this Rod Cap installed correctly?

The original bearings have a hole on the end where the oil channel squirts out oil to the other rods and the cam, oil hole faces inward.
So when I order new rod bearings: https://www.summitracing.com/parts/cle-cb527p/
I noticed these don't have a hole opposite of the end where the tangs meet. Doesn't this render those little channels in the rods caps non-functional?

 

[1 Wild R/T]

Every 383/440 OE rod I've ever worked on has had the cylinder ID numbers stamped into them... The oil passage has been found to ne be needed & it lowers oil pressure at the rod bearing where it's good to keep all he oil pressure you can....

 

[roadrunnerh]

Thanks for the reply. Should I install the bearings and rod caps as the punched cylinder numbers meet? I am only OCD level "concerned" I may have turned a cap around. It seems the cap can ONLY go on one way, and if the tangs meet on the same side, you're good to go. No?

 

[1 Wild R/T]

Thanks for the reply. Should I install the bearings and rod caps as the punched cylinder numbers meet? I am only OCD level "concerned" I may have turned a cap around. It seems the cap can ONLY go on one way, and if the tangs meet on the same side, you're good to go. No?

Correct, the caps need to be installed correctly, lock tangs together, stamped numbers together....

 

[Beekeeper]

I’ve always assembled the caps back exactly as they were disassembled. Never checked but would think
They would not be sized correctly otherwise.

 

[Cranky]

Do you have any machinist measuring tools? If you mic the big end, you should mic at 10, 12 and 2 o'clock. If you go across at the parting line, they will usually measure bigger.....but that's not a big deal as long as it's not excessive.

 

[roadrunnerh]

I own a Starrett 124 inside mic. I don't understand the reason or relationship to cap orientation.

 

[1 Wild R/T]

I own a Starrett 124 inside mic. I don't understand the reason or relationship to cap orientation.

It's because when you resize a rod you remove material for the cap & rod at the parting line.. So the hole gets smaller in one direction.. Then you hone the bore on the rod resizer to get it back to the original I/D... You don't want to remove more metal from the cap/rod at the parting line to reduce the side dimension.. You would do more harm than good..

 

[roadrunnerh]

Got it, thanks!

 

[493 Mike]

When the cap bolts are torqued the bearings are designed to "crush" at the ends (parting line) this holds the bearing in position.
Mike

 

[Challenger340]

Connecting Rod big ends should be straight & round the entire diameter within +/- a ten-thousandth or two... that's it... that's all. (.0001" to .0002"), even at the parting lines.
It is the Bearings themselves that provide the amount of eccentricity, change in Bearing Thickness middle over to parting lines, and conform to the perfectly round(see above) Rod Big Ends under the applied Torque.


And here are the quick Notes the average NAPA machinist has no clue about.... information generally reserved within Race oriented Machining, Race Engine Builder's.
ALL Bearing halves are thickest in the middle.... and taper(become thinner) as you move closer to the parting Lines.

This is called Bearing ECCENTRICITY.... the "amount" of change in Bearing Thickness from the middle over to the Parting Lines, and the Bearing Material construction, denoted by the Bearing SUFFIX ie:
"P" bearings, "H" bearings, "V" bearings", "M" Bearings.... etc., etc.
We'll leave "where & when" to use each Bearing eccentricity as too long winded for here.... my point being, Rods themselves should be straight & round their entire circumference.

 

[wyrmrider]

Straight means no taper or bell or hourglass across the faces
NO ANGLE CUT CAPS buts tremendous strain on the bolts
some builders angle cut to pull the sides of the rod in so they can get a round hole
as said above if you cut the caps then bore or hone you end up just touching the sides at the parting line and removing material from the top and bottom
makes your rod shorter so you can use the bushing to restore length or set length to max allowed by the rules
measuring rods on the dial bore gauge is an ART to find taper, bell, hourgalss

 

[Cranky]

Connecting Rod big ends should be straight & round the entire diameter within +/- a ten-thousandth or two... that's it... that's all. (.0001" to .0002"), even at the parting lines.
It is the Bearings themselves that provide the amount of eccentricity, change in Bearing Thickness middle over to parting lines, and conform to the perfectly round(see above) Rod Big Ends under the applied Torque.


And here are the quick Notes the average NAPA machinist has no clue about.... information generally reserved within Race oriented Machining, Race Engine Builder's.
ALL Bearing halves are thickest in the middle.... and taper(become thinner) as you move closer to the parting Lines.

This is called Bearing ECCENTRICITY.... the "amount" of change in Bearing Thickness from the middle over to the Parting Lines, and the Bearing Material construction, denoted by the Bearing SUFFIX ie:
"P" bearings, "H" bearings, "V" bearings", "M" Bearings.... etc., etc.
We'll leave "where & when" to use each Bearing eccentricity as too long winded for here.... my point being, Rods themselves should be straight & round their entire circumference.

Yep, my bad about saying the rod is wider at the parting line. It shows up with the bearing IN the rod.....

 

[wyrmrider]

Cranky
sometimes the rod does end up bigger at the parting line
if the rod is wide you might have to cut the rod or cap too much in order to get it narrower
example from a spun bearing
a little wide hurts nothing, but have plenty of crunch/ crush
sometimes a rod core is just not available

 

[Challenger340]

Straight means no taper or bell or hourglass across the faces
NO ANGLE CUT CAPS buts tremendous strain on the bolts
some builders angle cut to pull the sides of the rod in so they can get a round hole
as said above if you cut the caps then bore or hone you end up just touching the sides at the parting line and removing material from the top and bottom
makes your rod shorter so you can use the bushing to restore length or set length to max allowed by the rules
measuring rods on the dial bore gauge is an ART to find taper, bell, hourgalss

NO cap cutter can cut perfectly perpendicular, close but no cigar... hence why it's so important to cut BOTH the Cap and the Rod with the tang to the same side so they offset any angle the cap cutter may leave once mated back together.
We personally would never purposely "angle" cut a Rod or Cap to bring it back within range over at the parting lines ? there are other methods to accomplish that without butchering anything.

The only way I know of to restore C/C length on a Rod is with a Tobin Arp Machine ? maybe it could be done with a Mill.... but I think that would take some time ?

 

[roadrunnerh]

You guys are getting deep!

 

[Cranky]

A lot of people think that machining parts is a cure all but it's not. After over 25 years of machining parts, I 'learnt' that machining ain't perfect. You can sometimes be perfect but it's not that easy.

 

[miller]

The original bearings have a hole on the end where the oil channel squirts out oil to the other rods and the cam, oil hole faces inward.

I cringe every time I hear that. So, my two cents on it. I'm full-blown old school, been around engines most of my life . And, anyone can dis-agree with me. I build mine how I want, you build your's how you want.

Yeah, the rod bearings I bought, no squirt holes. I cut my own. Vee filed a notch, to line up with the notch in the rods.

Those squirt holes do NOT oil the cam, or the rods...well maybe a little mist. The way I've always understood it, their for providing a little oil spray, for the cylinder walls, piston skirts, and piston rings. It sure don't come from oil splash!!

Anyway...done biting my lip...

 

[roadrunnerh]

Miller, just so I'm clear, you feel it's a mistake to use rod bearings without the oil hole? I understand that without the "v" or semi-circle cutout on the bearing, the oil groove/channel in the rod cap serves no purpose.

 

[miller]

I understand that without the "v" or semi-circle cutout on the bearing, the oil groove/channel in the rod cap serves no purpose.

That is correct. The hole has been corked. So...how does the cylinders/pistons get lubed. Somebody going to tell me, it's NOT needed. Sorry, not this catfish.

To answer your question, yes, I believe it's a mistake...maybe the bearing makers cutting out a step, saving time. Don't know, don't care. I've been fooling with these things for 50 years. So, yeah, I'll admit, I'm set in my ways. (I'm 70 year's old, worked many V8s, many radial engines.)

But, to be clear...it's builder's choice. Pick your poison.
I actually used a small triangle file, to cut my notches. If you don't know what your doing, please don't! It must be done right. After filing the notches, the filed edges need to be de-burred. Even half the size of the rod notches, are good.
When I 'play' with my bearings, I never touch the bearing surface. Only handle the bearing edges.

Now...I'll wait for all the dis-agrees...