RB26 cams in RB20 didnt work :-(

[Sydneykid]

Hi Steve,

You have worked on more RB's than I have, what do you think the problem is?

[lukevl]

I am very interested to see how you go with the GTR cams SK. If you like, send me the cams and I will do a cam dr on them for you for free and give you the spec sheet (They should be the same as the solid profile posted before) I would really like to know how it goes.

God I wish you weren't in the southern part of our country so i could see it with my own eyes. Got a video cam????

[Roy]

I am very interested to see how you go with the GTR cams SK. If you like, send me the cams and I will do a cam dr on them for you for free and give you the spec sheet (They should be the same as the solid profile posted before) I would really like to know how it goes.  

So does that mean you think that in the real world some of the theory of solid v hydraulic gets lost in application?

[aRCH]

Eek! Interested to hear how the R34 cam testing goes SK. I've just bought a set of cams with the intent of fitting them to a future engine.. (current RB20 isn't feeling too good, lol)

Good luck with it!

[lukevl]

Roy - No I don't. I am being polite as I don't want to fall into the whole 'I give you x amount of cash if it actually works' again.

Put it this way, if it works, I know a LOT of people in the camshaft industry who would be very surprised.

[ylwgtr2]

so luke...apart from the front drive...whats the diffrence in the 34 GTR to 33 GTR cams...

[jnr32r]

SK: I can guarantee that the RB26 cams i have are 0.1mm thicker at the heel of the lobe than the std RB20 cams hence they would push on the lifters 0.05mm more than the std ones.

Dont you think there is a need to bleed all the lifters before fitting the RB26 cams?

We actually tried blowing out the oil out of one lifter and there was ~0.05mm difference in height.

I can also guarantee 99% that the install was right. Its actually quite easy as there is alignment marks everywhere (crank gear, pulleys, backing plates, belt)...

[bbenny]

yeah i beleive you did it right jnr32r.

as i had the exact same problem when i tried it, yet when i replaced the standard ones back (installing exactly the same way as the GTR cams) everything started perfectly and is still going great... so i dont beleive it is an installment issue.

as everyone attempting it themselves has had the exact same problems, yet when returning to the standard items, everything is fine. so i think the mechanical skills of the ppl attempting this mod is not the issue.

[lukevl]

You boys seem to be more than equipped with the skills to do the conversion. I promise you that is not the problem. But then again, everyone already knows how I feel.

jnr32r - What do you mean by 0.1mm thicker? Do you mean the base circle diameter is larger by 0.1mm? If so, this is because when measured with a mic, you actually measure part of the ramps too.

[lukevl]

so luke...apart from the front drive...whats the diffrence in the 34 GTR to 33 GTR cams...

Profile (I think I really should check that), and the shaft diameter (That is the un machined casting surface) is larger on the R34 GTR cams. I don't have any R34 ones here atm, but if someone puts up a pic you will see what I mean. Its that noticeable, as soon as I picked one up I could feel it and was like 'Whats going on here?'

[jnr32r]

You boys seem to be more than equipped with the skills to do the conversion. I promise you that is not the problem. But then again, everyone already knows how I feel.

jnr32r - What do you mean by 0.1mm thicker? Do you mean the base circle diameter is larger by 0.1mm? If so, this is because when measured with a mic, you actually measure part of the ramps too.

Its possible but we measured a few times and at slightly different angles and it was pretty consistant....

You know what i rekon !! I rekon we should all get together have a BBQ and get SydneyKid to install a set on someones car... What do you say ????????

If theres 10 of us it should be a 20min job.... LOL

[lukevl]

Yeah but I'll have to join in via satellite! I'll post some sausages down lol

[Ahh32]

so i dont beleive it is an installment issue.

as everyone attempting it themselves has had the exact same problems, yet when returning to the standard items, everything is fine. so i think the mechanical skills of the ppl attempting this mod is not the issue.

They worked when i did them. i used 33 GTR cams.

i blew the oil out of the lifters then soaked them in oil for 2 hours before installing them in. This was done during a full rebuild, and it ran fine until sunday night when it spun number 6 bearing. so know i have to pull it apart again and i will check the condition out

[jnr32r]

They worked when i did them. i used 33 GTR cams.

i blew the oil out of the lifters then soaked them in oil for 2 hours before installing them in. This was done during a full rebuild, and it ran fine until sunday night when it spun number 6 bearing. so know i have to pull it apart again and i will check the condition out

Whats the reasoning behind soaking them in oil??

[omp]

I WAS very keen on trying some RB26 cams for my RB20, I also have a set of adjustable cam gears here which are yet to be fitted. With these adj. cam gears in would the RB26 cams work then or is it the whole "ramp on the cam lobe thing" that throws everything out of wack? If so what cams would be recommended? I have a std rebuilt RB20 (apart from Trust headgasket

[ylwgtr2]

Whats the reasoning behind soaking them in oil??

Id like to know also because usually if you put a new lifter in any engine without doing this it just rattles its tits off....so i could only see that doing this would have no effect on the outcome....possibly even make it worse as the unit is fully extended and full of oil alowing it to hydraulic lock....but i have never played with lifter equipped RB heads so i could be wrong....

[WazR32GTSt]

so that makes 2 people (excluding sydneykid because he's a god not a person) which have done the conversion with R33 GTR cams into their rb20...

do you have any comments based on this lukevl?

do you have a technical explanation for how it could have worked seeing as it obviously can be done...

Waz.

[mabru]

After failing at this conversion myself, I asked a friend of mine who runs a shop here ( he works on RB's constantly, skylines are like ****roaches in Japan). He says that they'll work but you NEED adjustable gears on both sides to time them right. I, of course did not have adjustable gears when I attempted it.

I had mine idling well for a little while, but we discovered that the exhaust cam was about a tooth off and there was no power above the mid-range. It did sound mean as hell while they were in hehe.

-Matt

[jnr32r]

After failing at this conversion myself, I asked a friend of mine who runs a shop here ( he works on RB's constantly, skylines are like ****roaches in Japan). He says that they'll work but you NEED adjustable gears on both sides to time them right.  I, of course did not have adjustable gears when I attempted it.  

I had mine idling well for a little while, but we discovered that the exhaust cam was about a tooth off and there was no power above the mid-range.  It did sound mean as hell while they were in hehe.

-Matt

Actually Matt, i did install adj. cam gears at the same time and tried setting them at 2 degrees advanced on the inlet and 3 degrees retard on the exhaust without succes... so i dunno

[lukevl]

do you have any comments based on this lukevl?

do you have a technical explanation for how it could have worked seeing as it obviously can be done...

Waz.

How do you know they used GTR camshafts? You can't tell by looking at them so I am intruiged to find out where the verification was.

Think about this - Lobe centre lines are the crankshaft position at maximum lift (essentially for a symmetrical lobe). This varies from a minimum (tight lobe centres) of about 100 degrees before/after TDC to a maximum of 120 degrees if its a stock V6 holden. For the RBs you wouldn't want to go out of the 102 - 114 range. Thats a total movement of 12 degrees.

The ramps are in the viscinity of 80 degrees long total. How can 12 degrees compensate for such large ramps?

HERE WE GO -

Hydraulic lifters.

The theoretical operation of hydraulic lifters is that they can increase their height (tip of valve to cam rubbing face) but can not reduce their height. They use a one way valve to let oil in and not out. This means that no matter how you prepare the lifters for installation, they will end up being the right height so they just touch the base circle (smallest radius on the lobe) after a minute or less depending on how good the lifters are. This means that they run ZERO tappet clearance hence no need for ramps. The lifters adjust their height accordingly to suit valve growth.

So if you give your car a big over-rev and get valve bounce, the lifters will adjust to a point where the valves are slightly open and the car will run like a wrx for a minute or so until the lifters settle back down. Yes they leak oil, but only slowly. Anti pump up lifters (old school) leak fast and this is their purpose.

I said theoretically because they do squash, but only by the amount i mentioned earlier as specified by the SAE. I dare say it is actually less because those figures are old and relevant to pushrod lifters which run higher spring pressure.

So in short, how you prepare the lifters makes no difference to the cam operation. If you put too much oil in the lifters, they have a chance of snapping the cams. I have seen a few broken RB cams from installation. I prefer to only put a small amount of oil in because the oil pressure will take up the clearance quick enough anyway.

Wow, i can't believe i got back into this arguement. Pardon my spelling, I didn't proof read it.