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Discussion Starter · #1 ·
Hi I got some RB26 cams and adjustable cam gears, which I fit recently,

This went into my RB25, I first pressed all the oil out of the hydraulic lifters and re fit them so that they can self adjust to the new cams.

When I put everything back together, the start up was very difficult, I had to keep the revs on 2000rpm but the car kept on dying below that.

The engine sounds like it is miss firing and it is down on power also.

I did a compression test but all the cylinders was 800kpa plus

I checked the timing mark almost 300 times already, I might have turned the engine over 200 plus times by hand to verify that the marks are dead on.

The adjustable cam gears have been set to 0 at the moment

Spark plugs is working

I do not know where to start looking next, injectors and that should be fine as I did only the cams and gears

Before


After
 

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You can't put the RB26 mechanical cams, which have their clearances set by shims, in an RB25 head, with hydraulic buckets. I am surprised that A they fit, and B you haven't done any serious damage.
 

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Discussion Starter · #3 ·
I forgot to mention that the rb25 variable vale timing thing was disabled by the previous owner, and the Rb26 exhaust cam was installed by him and the car ran like a dream, the only difference here is I changed the Intake cam and adjustable gears on his referral.

:bawling:
 

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You CANNOT run hydraulic buckets with cams with a profile for shimmed buckets. They are totally different ramp designs and are probably pumping up the lifters, or not pumping them up. Are you 100% sure the exhaust cam is an RB26 one, and not a different profile RB25 one?
 

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Someone with a more intimate knowledge of stock RB26 and atock RB25 cams may be ableto say if they have any definitive casting or part numbers on them. I have an RB25 unit with Apexi hydraulic cams in it, and they are cast with an "Apexi" name in them. Have a look at the profiles, particulary the ramp form, are they different, inlet V exhaust?
 

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As Chris says you can't put RB26 cams in a 25. The base cirlces are different for a start. RB25 being 30mm vs RB26 31mm. Your probably not allowing the hydraulic lifter to be relieved of pressure to allow it to fill with oil, and that is why the car won't run. The lifters are going flat, or the valves aren't closing fully when the engine is running.

Secondly there is no real advantage in doing so, as cam timing is in240/ex240 on RB25 and 240/236 on RB26. Think lift is higher on RB26 by 0.5mm

I would think RB26 cams have 05U cast into them.
 

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Discussion Starter · #8 ·
Ok, I put the original stuff back, the stuff that the car ran with.

Now it idles fine, but there is still that misfire behavior when the revs build.

I damaged something right? :bawling:
 

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Get a leakdown test done (NOT a basic compression test). This will show if any valves are bent, and on which cylinder. You may have just damaged some hydrauilc tappets, not sure what would happen, let us know :) Joking aside, good luck, easy mistake to make, I am surprised Nissan didn't make it so they physically wouldn't go in. Where abouts are you?
 

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Discussion Starter · #10 ·
The cased no. on the RB26 intake cam I have is 3U
The cased no. on the RB25 exhaust cam I have is 7U

So far the fault seems be a faulty triple igniter module, busy replacing it with a heavy duty, relay powered 3x TP100 igniter modules.

So holding thumbs on no engine damage :nervous:
 

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Discussion Starter · #11 ·
So, the problem was the “driver unit” from the aftermarket ECU, It had a triple igniter, and I changed it with 6 loose modules, to split the load, and whala, the car runs fine now, went for a 131km drive with the tuner to map the car very thoroughly.
I was almost certain that I did not do any damage to the engine as each time I made sure by tuning it by hand, a couple of times.
Thanks for all the advice and heads up.
 
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