Plastic gauge specs for 79 l20b

[smokin joe]

Hello. Im new to the ratsun forum. Thans for the good info, and stories. Im putting together a 79 l20b and wanted to use plastic gauge to check my clearances. Any idea what it should read on the rod and main bearings? Smokin Joe

[datzenmike]

Plastic gauge is good enough for home build (looking for gross errors) and will point out any really bad clearances. For a performance build, proper mechanical gauges should be used.

 

L20B clearances...

Main bearing......... 0.0008" to 0.002.4" roughly 1 to 2 1/2 thousandths.

Rod bearing.......... 0.001" to 0.0022" or 1 to 2.2 thousandths.

 

[Stoffregen Motorsports]

.001" is too tight for the mains. Typically, .002" to .003" is expected, though the .003" is about as loose as you'd ever want to go. That loose may require thicker oil to maintain good oil pressure.

 

.0018" to .0022" on the rods is the "good" range.

[smokin joe]

Hey. Thanks for the info.I am having a machine shop grind the crank and size the rods for me. I wanted to use the plastic gauge to check there work.

[banzai510(hainz)]

be honest I had 2 L motor blocks done and none needed to be reground. on the crank and rod bearings

My 510 had 190k on this L16 motor   Bores was different had new bigger pistons in

 

I had Autosport Seattle do it.

 

 

just hop he aint doing to as a make $$$ work project if the bearings are still std size

 

maybe longer stroke motor of L20 might have more issues I dont know but Datsun, the  cranks are fucking rock solid Forged!!!!!!!!

 

 

most times the L20 has cracks in the water passage near the center pistons.

 

get ARP rod bolts

Edited September 8, 2023 by banzai510(hainz)

[datzenmike]

Only reason for crank grinding is if you spin a main or rod bearing but not long enough to window the block. Measure the crankshaft mains.

 

Mains are between 59.942-59.955mm or (for Americans) 2.3599" to 2.3604"

Rod journals 49.961mm to 49.974mm or 1.9670" to 1.9675" 

 

If within these specks save your money on the grinding and finding over size bearings.

[smokin joe]

The crank had some pretty deep grooves. Then have already ground it, and just took their recommendation.