RB26 cam swap into an RB20

[DriftingisLame]

I just installed some rb26 cams into my rb20, swap was pretty interesting.. I learned a lot, quite fun actually.

I cant seem to get solid specs on both of these cams, everyone has a different opinion on what is supposed to be "facts"

Here is what I came up with:

RB20 intake - 240 degree duration 7.8mm liftRB20 exhaust - 232 degree duration 7.3mm lift

RB26 intake - 248 degree duration 8.6mm liftRB26 exhaust - 240 or 248 degree duration 8.6mm lift

I marked the piss out of the timing belt to make damn sure everything went back together properly.. And it did.. So I think.

When it first fired up (first try) the idle was so bad! I was so exited that my car had such a horribly awesome cam idle... Reminds me of my friends c5 LS1!

Now I'm starting to think the idle is just plain unhealthy, and although it shouldnt be as smooth as stock, it should idle better than this...a lot better. It wants to die coming to a stop, and 90% of the time wants to die instead of idle anyway. I lost a lot of low end, which was expected.. But now it seems as though the car takes longer to get to redline, and doesnt feel any faster top end, maybe even slower. Now I did have some correction with my SAFC before (8%-12% less fuel across the board), which I reset to stock. The timing feels retarded, but I cant get it timed properly with my bad idle... I *think* its timed properly, but I just cant be sure...

I replaced my O2 sensor and spark plugs while the car was apart, with a sensor from an 84 200sx turbo. I believe I found that cross reference on this board. The sensor end is different from the sensor I pulled out of my car, so I'll try swapping back to my old sensor... its a long shot, but maybe thats causing a poor idle.

Anyone have any suggestions, or done this cam upgrade themselves?

Video: http://www.youtube.com/watch?v=VQW1AAPi4tc

Thanks!-Max

[mello88]

Did you replace both intake and exhaust cams?

Looking forward to some more info on this subject.

[SeVa-S13]

Edit: lol, coming back to this thread now I realized I this reply was meant for another thread. =\

Good luck.

[Darius]

I'm assuming you reset your timing to stock settings, right? When I installed my HKS cams, it idled like a V8 until I turned the timing back to stock. It smoothed out instantly and even moreso when I installed the PFC.

[gawdzilla]

what timing are you running? RB20 stock timing or RB26 stock timing?

If you bump the timing to RB26 timing it might help your idle/powerband.

[DriftingisLame]

Darius - I am trying to set my timing to stock, and I believe I set it to 16 degrees. The thing is, the idle only stays steady for a few seconds, so I have to adjust it before it drops, and I have to rev it to keep it alive.. That helps a lot though, now that I know once I can get the car to at least stay at a constant rpm, and adjust the timing, my rough idle can be corrected... for the most part.

Seva - I'm not sure what means

Mello - Yes I did both. Some aussie dudes claim 10-15 rwkw from 4-7k rpm, with a peak of around 10 rwkw on a stock RB20. Power is supposed to not drop off as bad in the early 6k rpm range.. I made peak power, 219 hp, at like 6100 and then steadily dropped all the way to 200 at redline... So I'm hoping it will at least sustain the power up till redline.

If I can work out this problem, I'd highly suggest this upgrade to rb20 owners, as the duration is not as extreme as aftermarket (not a total loss of low end), but the extra lift really makes the midrange and top end rip. Plus I bought these from a nico member for about 1/5 the cost of aftermarket cams.

If anyone is interested I'll give the information I can about how the swap went, tips/things to watch out for/etc.

Thanks for the replys-Max

[DriftingisLame]

Gawdzilla - I'll go try that as soon as I get my old o2 sensor back in.

Isnt stock rb26 timing 20 degrees?

[gawdzilla]

this is a pretty interesting and budget swap props for doing it

yea, rb26 timing is 20 btdc. what are the other guys doing this mod doing? keeping rb20 timing? it would make sense to me to run the timing to match the cams. i would try running 20 btdc and keeping an eye on your knock

[DriftingisLame]

Thanks man

Yeah theres not a lot of solid info on this cam swap, just many claims.. So I'm not exactly sure. I've tried to get some more info on it but no one reply's...

I'll try 20 degrees, but I dont have a knock sensor.. I have a digital safc 1 with no knock sensor readout. I was thinking about getting some 100 octane just to be safe, this stuff is sketchin me out!

Thanks again!-Max

[Yellow4g63]

Why not start over. Put the motor to BTDC and get the cam timing right? I have installed cams off a few teeth and the car idled and ran like crap. Just a thought since it won't be so hard to do since you did it once already.

[DriftingisLame]

now, to get to TDC, I set the dots on the cam gears to the marks on the back of the timing cover correct? I'm not sure what I'm looking for here..

The way I did this to begin with was marking the belt and the gear on each gear, these marks were aligned with the marks on the back of the timing chain cover. I put them back perfectly and never moved the crank pulley.

[Sil240]

HeyQuick question??Did you change to the RB26 solid lifter????You do know that they are both hardened and menat to work together. Becarefull you may tear up the cam and lifters.

Good luck!!!!When you get it, do a write up on it.

[DriftingisLame]

Nope, its been done before with stock lifters retained.

I'm not sure how hydraulic lifters differ from solid lifters once they are pressurized anyway. It seems as though they would both do the same thing.

Yes its probably not ideal, but not the end of the world. A few mechanics at my work say that using hydro lifters on a cam thats made to run with solid lifters was a really bad thing to do on older v8's because the lifter design sucked sufficiently, and they would leak.. Once a solid lifter cam was put in a hydro lifter motor, they would leak even worse and thats mostly where the big fuss came about..

I'd do a writeup, but I am still but a newb to this myself. I wouldnt want to claim false evidence as truth purely because I'm inexperienced at engine building. Besides, I only took before pics.

[Darius]

This is a stupid question, but you made sure to line up the timing belt with the dot on the crank and count the number of "valleys" up to the dot on the cam gear, which is aligned with the mark on the rear timing cover, right? I'd hate to be something as simple as that, but as big of a PITA to correct.

[Yellow4g63]

now, to get to TDC, I set the dots on the cam gears to the marks on the back of the timing cover correct? I'm not sure what I'm looking for here..

The way I did this to begin with was marking the belt and the gear on each gear, these marks were aligned with the marks on the back of the timing chain cover. I put them back perfectly and never moved the crank pulley.

I'm not 100% sure on how to set the rb to btdc. Someone showed me once but I forgot.

[Carl H]

this trick only works with r32 gtr cams, 33 and 34 have slightly diffrent profiles but they are diffrent enough to cause the car to not run right.easiest way to set the motor to tdc with the cams out is to take the plugs out, put a REALLY long 3/8" extention down plug 1's bores and turn the motor till it goes up at its peak.rb20det cam specs are roughtly 240/7.5mm intake and 248/7.5mm exh.

[ISUJinX]

I know that some hotrod guys use hydro lifters to simulate a higher duration cam, because the spring in the hydro lifter keeps the valve at top lift for longer.... but that wouldn't cuase the bad idle problem. I think youre off a few teeth on the install, or the timing is off *shrug* I'm tired and probably not thinking straight

[Chaos the Xile]

Hey this would make a killer write up, take some pics so we can see what you are doing! Sounds like a cool idea loved to see more of what your working with man.

[gawdzilla]

If you have doubts that your timing belt is set correctly, DEFINITELY fix that first. If its off a tooth at all it will run like crap if at all.

I was going off the assumption that you properly installed the timing belt. If so, the next step i would say is to play with the ignition timing and run 20 degrees btdc, by rotating the CAS and using a timing gun. I think the procedure is to unplug the TPS and the IACV but i forget now. I cheat and use PFC to see my timing to compare it against the gun.

[DriftingisLame]

If you have doubts that your timing belt is set correctly, DEFINITELY fix that first. If its off a tooth at all it will run like crap if at all.

I was going off the assumption that you properly installed the timing belt. If so, the next step i would say is to play with the ignition timing and run 20 degrees btdc, by rotating the CAS and using a timing gun. I think the procedure is to unplug the TPS and the IACV but i forget now. I cheat and use PFC to see my timing to compare it against the gun.

Oh man a PFC would come in handy right now! lol.

I believe I lined up my marks properly and my cam timing is correct..

The reason I believe this is because the car acts entirely normal after idle. Normal yet slightly low on power... I feel i've lost 15 rwhp across the board, and a lot of torque down low (duhh).

I finally got my timing set to what I think is 20 degrees. The car was idling like crap again when I went to time it, but it evened out just long enough for me to get a solid look at the marks and line up the CAS. I kept watching the marks and after I set it to 20 degrees it stayed pretty constant even when the idle would fluctuate slightly. I'm going to check it again today to be sure.

Honestly my car's had ignition problems since the day I fired up the RB, I'm beginning to think the bad idle also has something to do with an ignition miss, yet everythings normal past 1500 rpm.. I'll check that.

My new theory on why my car is slow, now that I'm confident with my timing, is a flipping BOOST leak.. Thats right, my intercooler piping is way janky, fitment wise, and I messed with a lot of it doing these cams.. Thats on my list for today.

Thanks for the help and support guys, if you think a writeup is necessary I'll get my pictures together and photoshop them, and write up a step by step kind of thing... Yes I only have before pics, but if you can tell the 8 degree and +1 mm lift difference between cams, props to you, but theres not much of a visible difference. I'm pretty confident I could make a good one now.

Thanks again-Max

[mello88]

From the specs you provided above.. It seems like a guy could do a "poor-mans" KA Style cam swap and run two RB20 intake cams?
Modified by mello88 at 3:45 PM 1/18/2007

[nuts510]

it's been my experience if you install a cam designed for solid lifters and use hydraulic lifters this causes the duration of the cam to change it increases it when you take away the Clarence the hydraulic lifters will do. The result is a very rough bottom in performance, and not too hot a performance in the high RPM's. What you install the solid lifters? I'll be honest I haven't messed with RB matters a whole lot but everything else I've worked with which is all whole lot are cars you can't mix a solid cam with hydraulic lifters. I hope this helps

[Sil240]

If you can get your hands on some solid lifters go for it.You'll be able to rev the piss outta it, if need be. Plus you wont have to worry about it also.

[DriftingisLame]

What lifters would I use? RB26 or aftermarket?

I'll check up on prices, and see if the wallet agrees.

[mello88]

I haven't researched this yet, but in your reading did you see anything about running two RB20 intake cams?

Sorry I can't help on the lifters.

[DriftingisLame]

That is not possible. The rb20 intake cam has no CAS drive, the exhaust cam does.

Great success! I had a few major boost leaks like I thought, I fixed them and didnt notice much of a change.. Now that I've driven the car for about 50 miles I notice I have much more low end torque, still less than before, but much better.. The mid/top end feels a lot healthier as well.. I think this upgrade is finally coming together now that I have the bugs worked out for the most part.

I'll post some solid results once I can get the car on a dyno.. Btw, I dont even have a wideband yet, so the car is set to stock fuel maps.

-Max

[mello88]

D'oh! Forgot about our friend the CAS. Do you have the specs for RB25 cams? Were the 25/26 cam specs changed throughout the years, r32/33/34?

Sounds like your project is coming together... I think with some tuning to take advantage of your cams you'll see some gains on the top. Update the thread after the dyno!

[Shahee1]

WOW!!! U have researched the same swap on aussie forums and could not get a straight answer from sydneykid who nailed the swap ... you need to do a nice lil writeup ... I have a set of RB26 cams from r34 that I have not used since there was all claims and no final resolve.

[DriftingisLame]

WOW!!! U have researched the same swap on aussie forums and could not get a straight answer from sydneykid who nailed the swap ...

Yeah I'm not sure what you mean there.. SydneyKid says he's done 4 and raves about how good of a swap it is.. Everyone else is very unsure, and really wants to know if it provides any worthwhile gains.

One thing's for sure, SAU has no pictures, no video, no dyno graphs, etc.. Just claims.

[DriftingisLame]

For what its worth... My 200,000 km+ rb20 made it from eugene, OR, to phoenix, AZ (24 hour drive?). Never got hot, never had to stop to fix anything... Developed a miss about an hour before I arrived, but I think I know where a loose connection is.

RB FTW