Rb 25 Lifter/oil Problem

[r33_racer]

I will be surprised if that is the issue lol.

Unless you are running larger studs and the machine shop didn't drill out the head stud holes big enough....

[Dobz]

Did you put the ARP studs in when you put the second hand head on?

[KiwiRS4T]

In your opinion the oil is not the problem. It may or may not be be but a change could be the solution. I am getting the impression that there are at least two problems - dirty lifters and wrong oil. Short of disassembling the lifters and cleaning them you could try a very thin diesel rated oil. Put some km on it (not on a track) in the hope it will clean things up a little. Then replace it with a quality synthetic lower than 10W 60.

[nemesis-dk]

Got around to pulling the four studs, arp studs are 11mm std bolts are 10mm and the channel is 11,5mm so there has only been 0,25mm around the arp stud to feed oil to the lifters ..... in my book not much... i have hammered the engine and slaugthered a set of tires ,,,, you know what ..... no ticking at all ! So much work and money for gaskets, oil, filters, oilpump and head wasted because of stud opgrade ........

Btw i cant run a racecar on the streets here in DK. Even if it could be fun

ive used 24L of oil in the last couple of month and gotten 3 track laps out of it .... oil might not be dirty ;-)

if you cant do it right dont do it at all and dont quick fix .... it will end in tears !

so now im sending my head to the machine shop to have the channels bored up

[Dobz]

This doesn't make sense to me, if the problem was due to using ARP head studs then pretty much every person with an RB25 using them would be having this problem.

EDIT: I thought i would do some calculations on cross sectional area according to your measurements.

Two stock 2mm oil restrictors (which i assume you have) have a total cross section of 6.28mm2 and from your 11mm stud in 11.5mm hole measurment the total cross section of area for oil for both studs is 17.66mm2. It doesn't add up.

Edited May 19, 2012 by Dobz

[dampachi]

This doesn't make sense to me, if the problem was due to using ARP head studs then pretty much every person with an RB25 using them would be having this problem.

Spot on mate.

[r33_racer]

Factory RB25 headbolts have a M11 thread on them, though they do have a reduced shank (down to 10mm), though from memory the ARP studs are also slightly reduced, I dont think they are bang on 11mm OD. Even being 0.1-0.2mm undersize is going to increase the CSA substantially and also the supply oil flow potential, however it seems the block restrictors are the biggest inhibitor of flow, not your head stud hole clearance.