The Nissan RB25DET is one of the most sought after Japanese Domestic Market (JDM) engines of all time. This is part 2 of our How To Rebuild your RB25DET Guide, and if you have this engine imported in, it’s a good idea to tear it down because of the length of time that most of these engines can sit. Combine that with being exposed to the elements (mostly sea air)it’s always a good idea to tear down your imported engine swap before installing it into your car.

Today I’ll be showing you how to service RB25 valvetrain by giving you step by step directions on how to test and check each component. This guide assumes you already have your cylinder head removed, if you don’t check out our How To Change Your RB25 Headgasket article.

We’ll begin with the RB25DET camshafts and measuring these for runout as well as checking the camshaft runout while the camshaft is still in your car. The RB25DET features two camshafts, which are the exhaust and intake cams, you will require a micrometer to check the tolerances in your RB25 cylinder head.

How To Check RB25 camshaft runout

Place your RB25 camshaft on a V block or similar device that will allow you to rotate the camshaft while mounting a dial gauge. Set the dial gauge to the #4 journal on your RB25DET camshaft.

While rotating the camshaft in question, check the runout of the camshaft using the dial gauge. While rotating the camshaft, the camshaft should not vary more than 0.02mm, while 0.05 is the service limit.

Check both the intake and exhaust camshafts, with the cam gears removed. If you are modifying your vehicle, it might be a good time for upgraded cam gears in your RB25DET to allow for overlap adjustment. Check out our How To Install RB25 Cam Gears article here.

Measuring the RB25DET Cam Nose

The next step is to measure each individual cam lobe and what we are looking for here is specifically the butt to nose measurement of the cam. The “nose” of the cam refers to the crest of the lobe, you are in essence measuring the complete lobe to see if your camshaft is within spec.

Using a micrometer measure the lobes of the intake and exhaust camshaft separately. The standard specification for the exhaust camshaft is between 39.70 – 39.89 mm for each lobe on your RB exhaust cam. The intake camshaft should measure between 39.705 – 39.895 for the cam nose measurement.

The service limit for the RB25 cam nose is 0.05 mm, if you find either of your camshafts out of round or past the service limit, replace them immediately.

Inspect your Hydraulic Lifters

To check your hydraulic lifters, inspect for any visible damage to the top of the lifter or the sides of the cylinder head walls.

If there is any scorching, scratching or damage replace these components immediately. To measure the lifter clearance, you will need to remove the lifter itself.

Remove the lifter by gently pulling it out and examine the sides for any nicks or scarring. With this unit removed, check the walls for further damage.

Using your micrometer measure the outside circumference of this lifter to check for runout or any warping.

The measurement you are looking for here is 30.955 mm – 30.965 mm, try to rotate the lifter to see if the diameter varies any. This lifter should slide in and out of your cylinder head freely. Now flip your micrometer around or attach inner diameter measuring arms to determine the inner diameter of the lifter.

The inside diameter should read between 31.0 mm to 31.020 mm, anything outside of these two readings and you will need to replace one of the lifters. Remove all your lifters and measure to test if they are still good or not. Never store them with the flat face downward, always place them safely where they can sit as they do inside the engine.

That does it for our how to service RB25 valvetrain article, for more on the RB25 check out our How Tos and DIY sections!