Dialling In Hks Cams (rb25)

[PM-R33]

We installed the new cams last week along with a timing belt, water pump etc. They are HKS 256/8.8 on the intake and HKS 264/9.0 on the exhaust. The cams were dialled in with the factory marks on the standard gears for top dead centre (same as the factory cams). Now the car ran fine.....

Today it went in for the tune and once on the dyno we could see the power graph was all over the place with not much power and we couldn't put any timing into it without it pinging. Obviously the cams aren't dialled in correctly.

Now since the intake cam is made for the VCT this should be in the correct position as you can't put an aftermarket cam gear in without losing the VCT.

So it all points to the exhaust cam needing an aftermarket cam gear and dialling it in correctly, would this assumption be correct?

If it does need an adjustable cam gear, does any one with these cams have a rough idea on what they should be dialled in to be correct?

Your help would be greatly appreciated as i wanna get this car running ASAP and i need to know wether to buy an adjustable cam gear.

Thanks guys

Edited June 5, 2008 by PM-R33

[Sydneykid]

We installed the new cams last week along with a timing belt, water pump etc. They are HKS 256/8.8 on the intake and HKS 264/9.0 on the exhaust. The cams were dialled in with the factory marks on the standard gears for top dead centre (same as the factory cams). Now the car ran fine.....

Today it went in for the tune and once on the dyno we could see the power graph was all over the place with not much power and we couldn't put any timing into it without it pinging. Obviously the cams aren't dialled in correctly.

Now since the intake cam is made for the VCT this should be in the correct position as you can't put an aftermarket cam gear in without losing the VCT.

So it all points to the exhaust cam needing an aftermarket cam gear and dialling it in correctly, would this assumption be correct?

If it does need an adjustable cam gear, does any one with these cams have a rough idea on what they should be dialled in to be correct?

Your help would be greatly appreciated as i wanna get this car running ASAP and i need to know wether to buy an adjustable cam gear.

Thanks guys

I assume that these are RB25 HKS cams, not RB26?

If you have truly installed and timed the cams correctly with the standard pulleys, then there is something else wrong.

Cheers

Gary

[PM-R33]

Yeah Rb25 Gary.

Hmm thats what i've been thinking the more i look at it, surely a small adjustment on a pulley couldn't be causing it to run bad. Ill pull all the covers off again and check everything but when it was put together the intake cam, exhaust cam and harmonic balancer were all lined up with the marks on the timing belt. Unless it has some how slipped a tooth or two now that it's been run in but i doubt that.

Edited June 5, 2008 by PM-R33

[PM-R33]

Picked the car up just then and gonna take the timing belt cover off to again check the timing belt marks but im pretty sure they are spot on.

After talking to my tuner for a while he's starting to think that maybe its a problems with the standard valves/springs either staying open or something....

Could this have something to do with it? We can't run any more then 2 degrees timing in it without it pinging and thats at 12.1 air/fuel ratios and its making bugger all power throughout the rev range on 20psi boost. Therefore something is definetely wrong. Maybe im going to have to take the head off and replace the valvetrain gear and while im at it clean up the head and aim for 300kw@wheels....

God these problems never end with cars

Edited June 5, 2008 by PM-R33

[joeyjoejoejuniorshabadoo]

300 rwkw on your GT-RS?

[PM-R33]

Well 255kw was on 17psi with no cams or head work and not much advanced timing cause it was summer. Surely with 20-21psi, the cams, head work, oversized valves, springs etc and a bit of timing i reckon 290+ should be achievable. Hell i'd love to do it just to see if it can be done.

Back on topic though, I checked the cams last night and all timing marks are 100% on TDC, therefore its not an installation problem. So what the hell is going on with the car, it's driving me crazy. I'm going to do a compression test on it this arvo to see if maybe the valves aren't sealing properly.

Could this really be because they are standard springs?!?! Theres heaps of people on here using standard springs on HKS cams and they run fine.

Please help some one Sydneykid?

[rev210]

You should get some cam gears. Asuming this 'drop in' cam mentality isn't smart. Why did you think you could drop them in?

I am pretty confident the cam gears will help a fair bit.

Also, did you just whack the boost to 20-21 psi or did you start at the old 17psi?

With the bigger cams you ought to start with less everything and work up. Start the tune at 14psi and work up. With larger cams you will make more power with less boost and rpm than before.

Left of field is the potential of having a blocked injector, going lean on one pot. Have a look at the plugs.

[PM-R33]

We tried 14psi all the way up to 21psi. On 14psi it was barely making over 200kw on 21psi barely 230kw.

Well the inlet cam gear can't be changed because i want to retain the VCT so only the exhaust cam gear could be changed. But i seriously doubt it would change that much, maybe it will but why? I've spent a lot of time reading over the threads on SAU from people with 256/264 cams and nearly all are set at TDC. The inlet cam is made for VCT so it is made to stay at TDC. So everything points at the exhaust cam.

[rev210]

We tried 14psi all the way up to 21psi. On 14psi it was barely making over 200kw on 21psi barely 230kw.

Well the inlet cam gear can't be changed because i want to retain the VCT so only the exhaust cam gear could be changed. But i seriously doubt it would change that much, maybe it will but why? I've spent a lot of time reading over the threads on SAU from people with 256/264 cams and nearly all are set at TDC. The inlet cam is made for VCT so it is made to stay at TDC. So everything points at the exhaust cam.

Do the easy things first like check the plugs for mixture issues on one pot. Hopefully it's not a valvetrain issue or somthing worse.

[PM-R33]

Yeah that's whats worrying me, wether the increase in lift on the exhaust side is causing a bad seating problem with the valves or something. It's only 9mm lift though which i've read is ment to be fine on the stock head.

Ill take the plugs out tonight to do the compression test so ill try to elimante all that.

[rev210]

boost and rpm play a part in whether it can handle things also what sort of condition they were in before you popped the cams in.

[PM-R33]

Ok did the compression test and everything seems fine, all 6 around 135-140psi. Spark plugs and tops of pistons all seem fine.

The photos show that its all at TDC. The only other thing i can think of is when I installed the microtech ages ago I had to lock the timing and set it to 10BTDC. Since the belt and cams have been changed wether this has altered something, because when i put the timing light on the car last night it was no where near 10BTDC and i couldn't even adjust it so it got near 10BTDC. This might have something to do with it....

This has really stumped me, im nearly up to the point of ripping the cams out and putting the standard ones in there

Edited June 9, 2008 by PM-R33

[rev210]

Sounds like the timing is completely out of whack. How does the CAS drive look?

[PM-R33]

Well what do you know, you might have solved it. Took the CAS out and it had bits of metal shavings in it and the half moon was snapped inside of it and it feals really rough to spin the drive. Replaced it with a mates CAS as nissan wasnts $1200 for new one (f**k that) and it seems to drive a lot better. Putting it back on the dyno tomorrow to see if this could have been the culprit. God i hope that was the problem all along.

Thanks a lot man

[rev210]

too easy dude , glad you found the issue. Now you can get that power up

[PM-R33]

Car spent a few days at the tuner and its still extremely down on power compared to what it was. 20psi 230rwkw, 14psi 200rwkw. No clue what is causing it but i give up, im chucking the standard camshafts back in.

Ok i just double checked one thing, the exhaust camshaft that i got off of slide is a 2202-RN175 however nengun lists the exhaust cam for a series II R33 a a 2202-RN176. Says one is pre 97 and the after 97, what the hell is the difference between them. Mine is a 96 model so im assuming it is the correct cam?

EDIT: My bad, i forgot about the different CAS on the later model R33's having the R34 CAS. So yeah definetely the right cams.

Edited June 18, 2008 by PM-R33

[33drifter]

i can confirm they are the right ones, my mechanic gave me the same part number. im interested to see what what the out come of this is, as i am about to purchase some for myself, (maybe yours, haha)

[PM-R33]

Its just so f***ing annoying not knowing what it is. I don't know wether to a) pull these cams out and put the standard ones back in and hope that it goes back to the way it was or b) if its a spring or valve problem rip the head off and work the head and again hope that it fixes it. If i do that i might aswell get it port/polished, 3 angle valve job, new springs, 1mm oversized valves, headgasket etc etc. But then there is 3-4grand. I just have no clue where to start

[nizmonut]

did you gap down your spark plugs? also what fuel are you running?

sounds to me like the pistons or some area of the combustion chamber has got hot points in it, (areas with sharp edges that can cause pre ignition)

run some av gas or methanol through with the fuel to help clean all the carbon out.

[PM-R33]

Plugs are BKR7E so 0.8mm gap, same ones i have always used. Only fuel i have used is BP Ultimate or Shell V Power.

Hmm interesting theory, havn't heard of that before. There is something definetely wrong in the combustion chamber that is causing it to lose so much power and the fact we cant run anymore than 2 degrees advanved ignition timing without it pinging is the most bizare thing.