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Rb30/26 Hks Step 1 Cam Timing Please Help

leeroy_25

By leeroy_25,
in Engines & Forced Induction

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leeroy_25 Community Regular

leeroy_25

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Posted

Hi Guy's I am really hoping someone can give me some help here or eve a few peoples opinions so I can get an average!

I recently finished putting my engine back together. While doing so I thought I would time my cams (HKS Step1 264) using the lift at TDC method. I am running a Holset turbo which can work with slightly different timing to a garret type turbo but the overall picture should be roughly the same. I was given some timing to try by a tuner in Europe who has supplied a lot of Holset turbo's for various builds. He aid try 1.3mm lift @ TDC for inlet and 0.7mm Lift for exhaust.

I initially had my pullies set at 0deg when it went back together although I do not know how accurate this is to the stock lift setting recommendation. For a start I cannot find a listing for HKS cams in mm @TDC? Anyway 0degs on the pullies equated to about 2.1mm lift Inlet and 1.9mm lift exhaust. After adjusting as suggested It gives an equivalent adjustment of 8deg Inlet (retarded is that right?) and 10degs Exhaust (advanced?).. I thought this was excessive so dropped the exhaust back to about 8degs also.

Anyway.. As recommended this should bring my boost on lower? Also note I am trying to bring the power band lower down a I am running a stock RB30 bottom end and revving to 7000 redline. I believe this adjustment is pretty much opposite to normal?

Anyway.. previously before adjusting I would make my boost by 4250rpm.. Now it seems I am around 5000rpm t reach the same boost with no other changes?!

So clearly something is not quite right with my recommended adjustment or I have done something wrong?

Please let me know your thoughts guy's so I can get this somewhere near right prior to going to the dyno!

Cheers

Lee

P.S.

Can someone help with e-mail notifications? I am not getting them any more but all my notification settings are on! And I have checked my junk too!

Thank you

Lee

rob82 Mentor

rob82

Posted
Posted

I would suggest around 2.2mm lift @TDC inlet and 0.8mm lift @TDC exh as a start point. HKS cams work great on STD centers - pretty sure they have moved the center lines forward so they work just by dropping them in and setting them to zero. For more low end try more ad on the inlet(clockwise rotation) and slightly retard on the exh to increase overlap. But too much overlap will kill top end especially if back pressure is an issue.

leeroy_25 Community Regular

leeroy_25

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Posted

Hi Rob,

Just to be sure I was working this correctly in my head.. if I started with 2.1lift inlet and 1.9 lift exhaust you have suggested I Advance the inlet a touch to 2.2mm lift which is the opposite to what I have done so far but makes sense with what I have read before. With the exhaust I need to advance it also on my standard lift measurement to 0.8mm? I have to say I am not convinced the pulley aligns correctly with the timing mark on the back plate for the exhaust side so this may be out to start with? As I said I have not reference as to what '0' marks would normally relate to lift wise for the cams? As I have read normally the exhaust timing is retarded to increase spool up? This would laso lead me to believe my start point is incorrect.

So in fact the measurements you have stated are not a million miles out fomr what i have. I actually set my exhaust to aout 0.9mm in the end when I did it as it seemed a hugh adjustment in degrees!?

I don't envisage back pressure being an issue as I have quite a large turbo and downpipe! I presume I can monitor this with EGT's?

If you can give me an idea what mm@TDC settings would normally be on zero that woul dbe great.. I am wondering if there is a slight difference in my inlet and exhaust cam pullies that I did not notice and have them on back to front? I guess it does not matter much if they are adjusted right now?

Cheers

Lee

leeroy_25 Community Regular

leeroy_25

Posted
  • Author
Posted

Come one guys' some one surely can shed a bit of light on this?? Even if you can give me base settings for another mild aftermarket cam or standard Nissan ones that would probably give me a pretty good idea as to what I am working with.. Just need the factory base setting for mm of lift at TDC (non-firing) for each cam please.

Thank you

Lee

T04GTR Grand Master

T04GTR

Posted
Posted

one way to be sure is to instal the standard cams and se where they are at. ie how far out the cam timing is with the conversion. that is if you have the standard @tdc lift figures.

another thing that can change them is the valve clearance.

i would get out the degree wheel and do it that way. only way to get it in the ball park

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