3. Nissan SR20DE, DET
? The venerable SR20 has powered many a race car and drift car over the years and is a relatively sturdy engine, but it still has plenty of quirks that can really affect its reliability for performance use.
Yes, we are going to pick on the good, old SR20. We feel that we can, as just about every MotoIQ staffer has raced with SR20’s at one time or another, and we are well aware of its somewhat odd and fatal quirks.
The SR20 uses a finger follower valvetrain with rockers that are prone to fly off at high rpm, any over rev, even just slightly overreving the engine like hitting the stock rev limiter really hard for a long period of time, can make this happen. A lot of this is due to a combination of valve float and the stock hydraulic lash adjusters pumping up.
One of the biggest weak points of the SR20 engine are the finger follower rocker arms. They are not really constrained and fall off with the slightest overrev. Even bouncing on the stock rev limiter can cause them to fall off. Every person who races or drifts with one of these engines has had the rocker arms fall off at least once.
One of the aftermarket “cures” for the rocker arm falling off issue is these rocker stoppers which click the fulcrum end of the rocker to the fulcrum. Do not use these. The rockers will still fall off just a few hundred RPM later and when they do, now that the rocker arm is constrained and held near the valves and cam lobes, the cam lobe will smash the crooked rocker, breaking it and bending valves and other carnage in the process. Without the rocker stopper, most of the time the rocker will just fling away and not get damaged. An easy fix.
Some tuners use rocker stoppers to help keep the rockers in place by clipping the pivot end of the rocker to the hydraulic lash adjuster. This still results in the rockers falling off, but now the damage is worse because the dislodged rocker is smashed by the cam lobes, breaking them into pieces and bending the valves.
Rocker blockers in place.
With conversion to a mechanical cam, good valvesprings and using lash caps with retaining grooves, an SR20 valvetrain can be stable to over 9000 rpm, maybe.
To make the SR20 valvetrain as bulletproof as possible, switch to a mechanical cam and get rid of the hydraulic lash adjusters. Running guide-type lash caps on both valves as shown here helps keep the rocker from slipping off as well. The SR20 in stock form only has a guide cap on one of the two valves.
Perhaps the worst thing about the SR20 is its cooling system. The water pump cavitates easily and just about stops flowing at 6600 rpm. The engine has a wonky coolant flow path and the cylinder head has small water passages and a lot of core shift in the water jackets. In addition, the programing of the ECU’s in B13 Sentra SE-R’s leads to thermal runaways to where the engine gets hotter and hotter until it self-destructs with even mild track use. Even when you do stuff to address the water pump and coolant flow issues, the SR20 requires about twice the coolant heat exchanger area of other engines of equivalent power.
To keep the water pump from cavitating, an underdrive front pulley is essential. It is also important to partially restrict the water flow in the external passage to the thermostat housing or a lot of water will just go around and around in the head, not flowing to the radiator!
A larger water pump pulley is needed as well to further slow the water pump.
Finally, the SR20 has inadequate oil flow to the rod bearings. This makes them prone to spin on the rods at higher rpm and load which usually ends up as total destruction of a lot of expensive parts. This can be cured with the wider GTI-R 54C variant rod and main bearings, grooving the main saddles of the block for more oil flow to the rods and running the VE or 54C higher capacity oil pump.
Grooving the main saddles in the block helps improve rod bearing oiling. SR20’s tend to spin rod bearings.
The 54C Pulsar GTI-R SR20DET variant uses wider rod bearings and main bearings with these additional oiling holes. When combined with the grooved block saddles, rod oiling and load capacity is greatly improved.
To top it off, the SR20 has a tiny oil capacity from the factory, which really cooks the oil in short order with little reserve for burning any on the track, but that is easily fixed with many of the available aftermarket oil pans.