Checking Rod Side Clearance - Don't Assume !!!

[Indycars]

I saw this procedure in the book below, but don't assume it will work in all cases !!!

When checkingrod side clearance you can place two rods together and measure their width. Below is
exactly how they had them lined up. I'm using the clamps so I can take the picture.
You can see the light coming thru because the small end of the rod is wider than the big
end causing the gap. When I measured this way, I got a measurement that was 0.018" wider. Maybe this
works for stock rods.

one factor to keep in mind is that rods typically have a side that rides against its matched companion and a side thats BEVELED for clearance on the crank journals radias EXAMPLE

notice the top rods non-beveled side that faces the matching rod is up, but on the lower rod the the beveled side that faces the crank counter weight is up on the lower rod
BTW, I did make sure the sides with the biggest bevel were facing to the outside.

Scat Forged Rods
Part Number: 2-ICR6000-7/16 -- Bushed, ARP 8740 7/16” x 1.400 cap screws for stroker clearance

 

[grumpyvette]

you usually measure rod side clearance at 12, 0'clock 3 0'clock,6 0'clock,and 9 0'clock with a tappet gauge,between the paired connecting rods after torquing the matched connecting rods on their respective crank journals, on or near one side of the block rail in the crank rotation, then as far over to the other sweep extreme as you can reach, because the rods may not set at exactly the same angles or parallel and the journal may not have an exactly even, or have a concentric bevel on the journal/counter weight contact area, and the rods may also be machined so clearances stack up, doing the measurement on the journal you generally see clearances change slightly as the crank rotates but a bit loose is better than a bit to tight in most cases, if it falls in the .Rod side clearance: 0.014-0.020 inch range your good to go in most cases, and I would not panic if it was a thousandth or so larger or tighter, IDEALLY YOULL USE A pair of feeler gauges AS THAT WAY IT does not cock the rods to one side LIKE WHEN ONLY ONE FEELER OR TAPPET GAUGE IS USED, and you’ll generally see a slightly tighter clearance when using two feeler gauges rather than one. You also may have heard that tighter rod side clearance will help reduce oil windage, but that’s not really true. The gallons of oil per minute that escapes past the rods is determined by the bearing clearance, oil viscosity and oil temperature – not by the rod side clearance. So the larger end of the range on rod side clearances are acceptable – and a bit safer than tight clearances.

some connecting rods are DESIGNED to have non-parallel mating surfaces, or small grouves with a bit more clearance on the up facing side so oil leaving the bearings is directed, bye design to exit up-ward on the cylinder walls and cam to help lube and cool those components

VERIFYING CLEARANCES GREATLY REDUCES WEAR AND DURABILITY ISSUES

your going to need decent feeler gauges

 

[Indycars]

some connecting rods are DESIGNED to have non-parallel mating surfaces, or small grooves with a bit more clearance on the up facing side so oil leaving the bearings is directed, bye design to exit up-ward on the cylinder walls and cam to help lube and cool those components

Now that's one I've never heard before, hence the reason for measuring in 4 places around the rod. This is one of
those cases where it is better to measure in place instead of on the bench.

 

[grumpyvette]

"HEY GRUMPYVETTE< I MEASURED MY ROD SIDE CLEARANCE AND GET,
journal 7,8; .016
journal 5,6; .013
journal 3,4; .017
journal 1,2; .020
WILL THAT BE OK?"

Its always best to maximize the consistency in clearances between connecting rods if you can, if you have the correct micrometers and feeler gauges you might try piston and rod #2 with #6 OR #5 and #1 as it might result in a more consistent rod side clearance, both the piston and connecting rod needs to face the correct direction during engine assembly, don,t forget to check bearing clearances with plasti gauge also
http://www.small-block-chevy.com/assemblyspec.html

Common assembly clearances

(ALWAYS consult your piston manufacturer for recommended clearances. Many pistons require a tighter bore)

Piston to bore 0.0055 - 0.0065" ( measured at centerline of wrist pin, perpendicular to pin)


Piston ring gap MINIMUM end clearances Top 0.022"
2nd 0.016"
Oil 0.016"

Wrist pin 0.0006 - 0.0008" in piston, 0.0008 - 0.0010" in rod for full floating pin (End play 0.0 - 0.005"

Rod bearings 0.002 - 0.025" , side clearance 0.010 - 0.020" TRY FOR .014- .016

Main bearings 0.002 - 0.003" , 0.005 - 0.007 crankshaft end play

Piston to head clearance 0.038 MINIMUM including gasket (steel rods), 0.060" MINIMUM aluminum rods

Valve to piston clearance BARE MINIMUM 0.080" exhaust , 0..080" intake NO VALVE FLOAT
Recommended: 0.100 PLUS intake, 0.100 PLUS Exhaust (steel rods) 0.120 intake, 0.120 Exhaust aluminum rods

notice the top rods non-beveled side that faces the matching rod is up, but on the lower rod the the beveled side that faces the crank counter weight is up on the lower rod
notice how one side of the bearing holding section has a radias (left)(GOES TOWARD CRANK COUNTER WEIGHT) but the opposite sides flush (right) (FACES MATCHED ROD)

related info

viewtopic.php?f=53&t=2726&p=7077&hilit=plastigauge#p7077

viewtopic.php?f=53&t=247

viewtopic.php?f=53&t=852

viewtopic.php?f=53&t=3897

viewtopic.php?f=53&t=5478

viewtopic.php?f=53&t=4630

viewtopic.php?f=53&t=509

viewtopic.php?f=53&t=4419

viewtopic.php?f=53&t=3449&p=10012&hilit=assembly+lube+moly#p10012

 

[Indycars]

Its always best to maximize the consistency in clearances between connecting rods if you can, if you have the correct micrometers and feeler gauges you might try piston and rod #2 with #6 OR #5 and #1 as it might result in a more consistent rod side clearance, both the piston and connecting rod needs to face the correct direction during engine assembly, don,t forget to check bearing clearances with plasti gauge also

Valve to piston clearance MINIMUM 0.020" exhaust , 0.010" intake NO VALVE FLOAT
Recommended: 0.080 intake, 0.100 Exhaust (steel rods) 0.100 intake, 0.120 Exhaust aluminum rods

Very timely post for me, I'm checking rod side clearances right now. I had forgotten to check at 4 positions.....12-3-6-9 o'clock. I also didn't think torquing would make any difference, I just hand tightened to about 25 lb ft. But I went back and torqued all the rods and check in 4 places. I'll post my clearances over in my build thread.

About those Piston-to-Valve clearances, I can't say I've ever read any close to .020"-Exhaust and .010"-Intake. I've always seen more like the recommended clearances above as minimum.

 

[grumpyvette]

"Valve to piston clearance MINIMUM 0.080" exhaust , 0.080" intake NO VALVE FLOAT
Recommended: 0.080 intake, 0.100 Exhaust (steel rods) 0.100 intake, 0.120 Exhaust aluminum rods "

as far as IM concerned that first sentence is a huge mistake or typo that I cut & pasted from here,
http://www.small-block-chevy.com/assemblyspec.html
sorry I didn,t correct that before this I have now