Part of the cleaning process as soon as assembling a brand-new engine build is ensuring all the thread holes are in good condition and clear of gunk and also crusty develop up. We have found that simply washing them or offering them a scrub with pipe cleaners is not sufficient to rerelocate points prefer rust, scorched oil and also grime. The just means to really clean the threads is to run a thcheck out chaser or incredibly very closely a thcheck out cutting tap.

Why Clean the Threads?

Just like the rest of the motor you want to minimize and also minimize the amount of pwrite-ups and debris that get right into the fresh engine in the time of the build procedure. Trapped dirt and grime deserve to hide internally within the various engine threads and come out when the vibration starts and also the warm oil begins to circulation.

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More importantly you want to make certain the threads are in excellent condition and clear to encertain you don’t cross thread or strip out any type of of the bolt holes. You also want to make sure you obtain the ideal torque worths when assembling and tightening all the various engine components together to ensure also clamping pressure.


Tools and Equipment:

Engine Block

Cylinder Head

Engine Components

Brake Cleaner

Automatic Transmission Fluid (ATF)

Safety Glasses

Powder Free Nitrile Gloves

Threview Chaser

Thread Cutting Taps Various Sizes

Paper Towels

Coffee Filters

Lint Free Cloths

Threads Sizes on the Nissan / Datsunlight Engine

The Datsunlight L-Series motors were made in Japan so use metric thread sizes but there are likewise a few specialty Japanese threview sizes. Such as Japanese Industrial Standard (JIS) Tapered Pipe thread forms uncovered on some of the intake fittings. The JIS Tapered Pipe Thread is rather interchangeable via British standard pipe threads. Here are a bunch of the various threview sizes and also pitch for the Engine Block, Cylinder Head and also components on the L-Series engines.

Camshaft Tower right into Cylinder Head M8 x 1.25

Camshaft Tower Spray Bar Mounting Holes M6 x 1.00

Camshaft Front Block Off Plate M6 x 1.00

Camshaft Snout M16 x 2.00

Crankshaft Flywheel Bolt Holes M12 x 1.25

Crankshaft Snout M16 x 1.50

Key Bearing Caps M10 x 1.50

Main Cap Top Holes for Removal M8 x 1.25

Oil Pump Mounting M8 x 1.25

Oil Pick Up M8 x 1.25

Oil Pan Bolts M6 x 1.00

Cranksituation Vent Cover Bolts M6 x 1.00

Front Cover Bolts M6 x 1.00 / M8 x 1.25

Water Pump Mount M6 x 1.00 / M8 x 1.25

Motor Mounts Into Block M10 x 1.50

Alternator Mount Into Block M10 x 1.50

Smog Equipment Mounts M10 x 1.50

Cylinder Head Bolts into the Engine Block M10 x 1.50

Cylinder Head Intake/Exhaust Mounting Studs M8 x 1.25

Cylinder Head Spark Plug Thread M14 x 1.25

SU Intake Mounting Stud M8 x 1.25

SU Intake Heat Shield Mount Holes M6 x 1.00

Here is a list of thread taps or chasers that you will certainly find valuable once rebuilding your L-Series motor.

M6 x 1.00

M8 x 1.25

M10 x 1.50

M12 x 1.25

M14 x 1.25

M16 x 1.50

M16 x 2.00

Cleaning Rusty Threads

The threads on the cast iron engine block are regularly full of rust or dried out oil and also grime. Depending on the condition you can begin by spraying brake cleaner in the threaded holes to loosen and break up the grime.


Use lint complimentary cloths, paper towels or coffee filters to clean out whatever the brake cleaner has broken up or disinserted.

We then fill the holes via Automatic Transmission Fluid (ATF) to act as a lubricant for the threview cutting tap or chaser and also also for trapping any grit and also dirt the tap removes from the threads.


For actors Iron blocks we tfinish to usage thcheck out cutting taps over chasers as they seem better able to reduced through and also rerelocate any kind of old rust that has actually occurred on the threads.

Almethods start the cutting tap by hand also to encertain that you carry out not cross thread the tap. Continue to twist the tap into the block (clockwise) a couple of transforms till you begin to feel it lightly snag on the grime.

Then twist it back the various other way (counter clockwise) to aid clear any type of dirt rerelocated. The clearing flutes on the tap assist move the dirty product out of the method. Continue this process working the tap earlier and also forth in the block to clear the rust, baked on oil and grime.


As you run the tap into the block the ATF will press up out of the hole dislocation by the tap and also likewise bring the dirt and debris up out of the hole.

Be patient and take the procedure progressively working the tap earlier and forth to rerelocate all the dirty material. The whole procedure will take some time but it will be worth the outcomes.


Use a lint complimentary towel or paper towels to wipe ameans the ATF and debris. Sometime you will need to run the tap or thread chaser via the block multiple times to really clear it out.

Here you can see some of the dirt and also debris left over by running the tap via the threaded holes.

Different threaded taps will certainly be essential relying on the location in the block and the dimension of the hole. Notice just how dirty the rags obtain from just a couple of holes. All of this grime and also dirt might be floating approximately inside your oil or freshly built engine.

Also make sure to clean out the threads on the exterior of the block. It will make the assembly process a lot simpler insituation you find an worry. Much less complicated to deal with any type of threaded holes now than in the future as soon as you currently have the engine parts cleaned out and partly assembled.

We cleaned out every one of the threaded holes on the block even the ones we might not use for mounting. We wanted to get rid of any rust or dirt and then cover over the unprovided holes through a fresh coat of paint once prepping the engine block.

We uncovered it simpler to fill all the holes on one side at a time via ATF. This means we could store track of which threads had actually been cleaned also if we acquired interrupted or had actually to soptimal part method through the process.

You likewise desire to encertain the primary cap holes are clean for correct torquing and even clamping of the primary caps. We safeguarded the primary surdeals with and also oil feeds from debris using some masking tap.

Make certain to use well positioned towels to collect and also prevent any kind of of the grit and also debris from scratching the surdeals with or acquiring right into the oil galleries.

Use the very same procedure through the aluminum components on the engine. You might be much better suited utilizing a thread chaser here to prevent destroying the soft metal threads.

We didn’t have any kind of threview chasers at the time so incredibly very closely supplied the thread cutting taps. Only begin the taps by hand also. Be exceptionally careful when you begin to encertain you execute not cross threview or sexpedition out the soft aluminum. Here you have the right to check out us cleaning out the threaded holes of the front cover for the oil pump drive.

Cleaning out all the the front cover holes, make sure to obtain all the debris out of the threaded holes. We discovered a couple of threaded holes that had viewed much better days damaged or absupplied that required us to extremely cautious and also gradually run the cutting tap through to straighten or recut the threads. Hopetotally you don’t find any that poor and also you can conveniently acquire your engine components prepared for assembly.

Here you can see an older video of us clearing out the intake and exhaust stud threads on the Datsun Cylinder head.

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Continue the process for all the various engine components. After running the chasers or thcheck out cutting taps via make certain to thoaround clean the all engine components and also particularly the threaded holes.