You may remember our report on the lifters a few weeks ago https://www.speed-industries.ch/wordpress/?p=2147. The same engine is really being used on drift events and not being babied, with the rpm limit set to 8000. The RB25 cylinder head is heard to be strong enough to rev to that rpm level. What we didn’t take into account, is the fact, that in drifting applications, the limiter is hit quite often and for a lot longer time than under normal race conditions.
The result from the January event in Monza was a slight ticking noise from the cylinder head. The above pictures shows, what we found when removing the rocker covers and cams. The strange noise already came up about three hours before the end of the event and we didn’t bother too much as it could as well have been a dirty lifter. So either we have been amazingly lucky or the valve setup in the RB25 is ridiculously strong, being able to be reved around 6000-8000rpm for a few hours with a broken retainer.
Either way we had to get a decent upgrade kit to keep going. There are a bunch of nice kits out there, but the Supertech one had a great reputation and is comparably low-priced.
The kit basically consists of stronger valves and titanium retainers. These two upgrades adress the weaknesses of the stock parts directly. In high rpm conditions, the valves can start to „float“. This means they begin to move radially (bend to a certain point). The reason for this phenomena is the valve spring not being up to the job anymore. Increasing the spring pressure solves the problem. Secondly the stock retainers also have their load limit, the Supertech titanium retainers are stronger and weight approx. 50% of the stock ones.
Together with the kit, you should also order new valve keepers, once you disassemble all the s*** anyways. Those are the little fuckers that keep the retainer to the valve and are therefore quite important. Although on an RB25 that means ordering 24 pairs, it’s quite cheap (approx. 3.- per pair).
Now don’t even think of trying to disassemble the valve train without the proper tools. With the cylinder head staying on the block, this is a serious job. There are numerous universal tools on the market, but you can never be sure, that they fit the RB head.
We decided to fabricate our own tool kit, for the perfect fit and ease of operation. It is not too difficult and you have the great advantage, that the tools are made for the definite application.
As the valve pouch is very narrow on the Nissan head, the crown of the „depressor“ has to be precisely made.
The bridge, where the depressor can get hold on, was made adaptable to a certain point, so it could be used for the whole cylinder head by relocating the flanges.
Be aware, before you begin depressing the valve springs, that each cylinder has to be pressurized. Otherwise the valve will drop into it. And you don’t want that, believe me… 🙂
So get a comp air adapter for the spark plug thread and attacht your air compressor to it.
Now you can press down the valve retainers and get out the keepers with a gripper or a magnet. Ideally, the retainer declines and the valve stays erected. Some of the valves may be tilt, they decline together with the retainer (maybe the keepers are stuck). In this case, put a suitable wrench nut on the retainer and hit it with a reasonable strike by a hammer. Now try it again with your depressor.
The new springs are longer, generating more spring pressure when mounted.
This is what a broken retainer looks like. Unbelievable this thing, broken in two parts, held the valve to the spring a few million times until disassembled.
Having placed the new spring and retainer and depressing it with our tool, this is when the nasty part comes into play. First, you got to have 4 hands, so get a friend to help you. Second, you need the patience of about 150 Buddha monks combined in one person. Tryin‘ to get the two halfs (valve keepers) into the tiny hole between the retainer and the valve, while lacking space and angle for any spiky tools can blow your mind! Be sure, the keepers will play tricks on you. They will do their best not to get into the tiny hole and let you perish in despair…
This will be your doom for exactly 24 times. With the pain in the ass quickly gaining intensity the more you move further back towards the firewall of the engine bay. For the last 8 valves, you will be kneeling on the engine, f***** up your back. The picture above shows the result of the epic trials.
This is what you will have on the bench when finished, it will make you completely happy. Now your valvetrain has become strong and rigid.
On top, don’t cheap out on a upgraded timing belt. The valvetrain is a lot stiffer now and this means a lot more stress on the belt.
Your RB25 is now able to cope with 8000rpm all day long. We mapped the car for 8400rpm at race conditions and 8000 for drift events. We’ll see what the setup will bring and if it proves to be reliable.
Give us a call or drop an email, if you need parts!
-Chris
You may remember our report on the lifters a few weeks ago https://www.speed-industries.ch/wordpress/?p=2147. The same engine is really being used on drift events and not being babied, with the rpm limit set to 8000. The RB25 cylinder head is heard to be strong enough to rev to that rpm level. What we didn’t take into account, is the fact, that in drifting applications, the limiter is hit quite often and for a lot longer time than under normal race conditions.
The result from the January event in Monza was a slight ticking noise from the cylinder head. The above pictures shows, what we found when removing the rocker covers and cams. The strange noise already came up about three hours before the end of the event and we didn’t bother too much as it could as well have been a dirty lifter. So either we have been amazingly lucky or the valve setup in the RB25 is ridiculously strong, being able to be reved around 6000-8000rpm for a few hours with a broken retainer.
Either way we had to get a decent upgrade kit to keep going. There are a bunch of nice kits out there, but the Supertech one had a great reputation and is comparably low-priced.
The kit basically consists of stronger valves and titanium retainers. These two upgrades adress the weaknesses of the stock parts directly. In high rpm conditions, the valves can start to „float“. This means they begin to move radially (bend to a certain point). The reason for this phenomena is the valve spring not being up to the job anymore. Increasing the spring pressure solves the problem. Secondly the stock retainers also have their load limit, the Supertech titanium retainers are stronger and weight approx. 50% of the stock ones.
Together with the kit, you should also order new valve keepers, once you disassemble all the s*** anyways. Those are the little fuckers that keep the retainer to the valve and are therefore quite important. Although on an RB25 that means ordering 24 pairs, it’s quite cheap (approx. 3.- per pair).
Now don’t even think of trying to disassemble the valve train without the proper tools. With the cylinder head staying on the block, this is a serious job. There are numerous universal tools on the market, but you can never be sure, that they fit the RB head.
We decided to fabricate our own tool kit, for the perfect fit and ease of operation. It is not too difficult and you have the great advantage, that the tools are made for the definite application.
As the valve pouch is very narrow on the Nissan head, the crown of the „depressor“ has to be precisely made.
The bridge, where the depressor can get hold on, was made adaptable to a certain point, so it could be used for the whole cylinder head by relocating the flanges.
Be aware, before you begin depressing the valve springs, that each cylinder has to be pressurized. Otherwise the valve will drop into it. And you don’t want that, believe me… 🙂
So get a comp air adapter for the spark plug thread and attacht your air compressor to it.
Now you can press down the valve retainers and get out the keepers with a gripper or a magnet. Ideally, the retainer declines and the valve stays erected. Some of the valves may be tilt, they decline together with the retainer (maybe the keepers are stuck). In this case, put a suitable wrench nut on the retainer and hit it with a reasonable strike by a hammer. Now try it again with your depressor.
The new springs are longer, generating more spring pressure when mounted.
This is what a broken retainer looks like. Unbelievable this thing, broken in two parts, held the valve to the spring a few million times until disassembled.
Having placed the new spring and retainer and depressing it with our tool, this is when the nasty part comes into play. First, you got to have 4 hands, so get a friend to help you. Second, you need the patience of about 150 Buddha monks combined in one person. Tryin‘ to get the two halfs (valve keepers) into the tiny hole between the retainer and the valve, while lacking space and angle for any spiky tools can blow your mind! Be sure, the keepers will play tricks on you. They will do their best not to get into the tiny hole and let you perish in despair…
This will be your doom for exactly 24 times. With the pain in the ass quickly gaining intensity the more you move further back towards the firewall of the engine bay. For the last 8 valves, you will be kneeling on the engine, f***** up your back. The picture above shows the result of the epic trials.
This is what you will have on the bench when finished, it will make you completely happy. Now your valvetrain has become strong and rigid.
On top, don’t cheap out on a upgraded timing belt. The valvetrain is a lot stiffer now and this means a lot more stress on the belt.
Your RB25 is now able to cope with 8000rpm all day long. We mapped the car for 8400rpm at race conditions and 8000 for drift events. We’ll see what the setup will bring and if it proves to be reliable.
Give us a call or drop an email, if you need parts!
-Chris