Valve clearances

[VIPERGTSR01]

my valve train is getting alittle noisy on my R33 RB25DET, i am going to check the clearances so does anyone know the clearance?, i know the R32 RB26DETT is 0.05mm

thanx in advance

[the phantom]

Your R33 RB25DET has hydraulic lash adjusters and as such cant be 'adjusted'. You may have to get new ones...

[VIPERGTSR01]

Oh, the R32 RB26DETT uses shims to adjust the gap so i wrongly assumed that the RB25DET would be the same. So does this mean i would have to buy a new set of RB25DET lifters if thats the problem?, if so where would i buy them from?....nissan? they would charge a packet

[the phantom]

Ring Unley Nissan Spare parts and find out...oh yeah, and make sure you're sitting down...there are 24 of them

[JimX]

The reason why RB26 has shims is because it has solid lifters. As already said, RB25 uses hydraulic and are self-adjusting.

Valve noise *could* mean they're worn out, it could also mean one or more are partially blocked with gunk. Try an engine flush and oil change, followed up with some valve lube additive. I had a lifter problem which seems to have been solved by doing the aforementioned. I don't know how long the solution will last though, but the alternative of replacing all the lifters @$100 each plus labour just didn't appeal to me.

Thicker oil should also help reduce the noise.

[Warpspeed]

I am driving a Ford Laser at the moment, but had a similar situation, with a noisy cylinder head.

If it is just one hydraulic lifter that ticks, it may be stuffed, and replacing it the only option. But I doubt if they are all faulty. Anyhow, the lifters should all pump up and remove all clearance from the valve train, and it should run quiet.

BUT this assumes the cam is not bouncing around in worn cam bearing journals. When I checked the cam bearing clearances they were huge, like fifteen thou on some bearings. They should be more like one and a half to two thou. So even if the lifters are perfect, it is going to rattle something shocking.

Now your mechanic is going to tell you the only way to fix it is to get a new cylinder head, because the cam runs straight in the aluminium casting without replaceable bearing shells. His eyes will light up as he tells you this is going to cost really big dollars, and be a lot of work.

If you think about it, the valve springs are all pushing upwards, and all the wear is going to be in the bearing saddles, not the actual head.

Now if you are adventurous, it is possible to take out the cam, remove the twelve lifters (from each side) and after degreasing everything, put the cam back in. Measure the cam bearing clearances with plastigauge by tightening down the saddles. You must remove the lifters and clean everything up first though, to get a true reading.

You can then tighten up the clearances by rubbing the saddles on very fine wet and dry abrasive paper. Be very careful about this though. It is possible to get the cam bearing clearances back to factory specs. It will cost zero, and all the noise will then go away.

Do not attempt this if you are not completely confident in being able to do it right. It certainly worked for me. I did it about a year ago on my Laser, and it has remained quiet. Just remember the saddles are very soft, and it is easy to remove too much material. Then you are stuffed. So go very easy and take your time.

I know this is going to horrify some people, but it does work.

[VIPERGTSR01]

i did a oil change and that didnt fix it, when you listen closely it seems to only be coming from one lifter (maybe two seeing as they are close together), i was thinking of replacing it but then i know i must take out the cam, and then i will notice wear and it will probably turn into a big progect

not a bad idea warpspeed, i could do it myself but for now i think i will put up with the light ticking noise

BTW i dont do all work on my cars myself i never let a mechanic try and talk me into some crap i dont need

[the phantom]

Hi,

what warpspeed suggested is a hands on approach to what a line bore/hone in a crank tunnel achieves. I would guess something like this process could also be done on the head with a machine, if anyone isn't game enough to try the manual method! I dont know how common small diameter tools on such machines are however...

Early on I also had a slight ticking, more prevelant when the engine just started and was cold. After various excercises I ended up having the head cleaned up. This included a seat regrind, which must have moved the valves up just a little bit and ever since I have had no more issues...that was 55k km ago... I'm not sure why the lifters weren't pumping up to compensate, but I guess that there is a limit to how much they can take up. I didn't really do anything else to the lifters other than taking them out cleaning them (on the outside) and putting them back in.