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Advice On Correct Cam Timing

urtwhistle
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urtwhistle Proficient

urtwhistle

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Posted

Hello,

firstly I want to say yes I have searched and posted this more then once before in the RB30DET thread with no response.

I was hoping I may be able to get some advice regarding setting up standard Neo cams on a bastardized RB30DET that I have recently built. When I built the motor I had a momentary lapse of reason and never fitted my adjustable cam gear. My timing is clearly out, but all timing marks line up and the VCT is working also (marks on cover appear dodgy and I don't trust them).

I therefore intend on dialing the cams in properly once and for all with a mag base dial indicator but to do that I need to know the correct positioning for a RB25 Neo.

standard RB25DET NEO Camshaft duration 236°in, 232°ex lift: 8.4mm in, 8.7mm ex

Does any 1 know what degree's in relation to TDC the intake cam is set to or @ 0.040" of lift? Either should get me the correct position and then I can move the exhaust position while sitting on the dyno.

The manual tells me to match up to the timing cover marks and also mentions that the cam shaft dowl pins are 14 deg from horizontal. Is that at TDC?

Thanks in advance.

Chris

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KiwiRS4T Grand Master

KiwiRS4T

Posted
Posted

The manual tells me to match up to the timing cover marks and also mentions that the cam shaft dowl pins are 14 deg from horizontal. Is that at TDC?

Thanks in advance.

Chris

Yes TDC - have a look at this thread in case it helps:

http://www.skylinesaustralia.com/forums/Ca...m-B-t73824.html

rob82 Mentor

rob82

Posted
Posted
Hello,

firstly I want to say yes I have searched and posted this more then once before in the RB30DET thread with no response.

I was hoping I may be able to get some advice regarding setting up standard Neo cams on a bastardized RB30DET that I have recently built. When I built the motor I had a momentary lapse of reason and never fitted my adjustable cam gear. My timing is clearly out, but all timing marks line up and the VCT is working also (marks on cover appear dodgy and I don't trust them).

I therefore intend on dialing the cams in properly once and for all with a mag base dial indicator but to do that I need to know the correct positioning for a RB25 Neo.

standard RB25DET NEO Camshaft duration 236°in, 232°ex lift: 8.4mm in, 8.7mm ex

Does any 1 know what degree's in relation to TDC the intake cam is set to or @ 0.040" of lift? Either should get me the correct position and then I can move the exhaust position while sitting on the dyno.

The manual tells me to match up to the timing cover marks and also mentions that the cam shaft dowl pins are 14 deg from horizontal. Is that at TDC?

Thanks in advance.

Chris

Good luck finding lift at TDC specs on these thing nobody seems to keep these specs. The factory manuals have valve opening and closing times. Time to get the cam degree wheel out. Your lucky with the NEO as there is no hydraulic lifters so just throw a dial gauge straight on top of the bucket and away you go.

urtwhistle Proficient

urtwhistle

Posted
  • Author
Posted

cheers for the link.

ok I opened up the old RB30DET Howto for an unrelated reason and spotted this under cams

Cam Duration (IN) Cam Duration(EX) Cam liftIN(mm) Cam liftEX(mm) Lobe centreangle (IN) Lobe centre angle (EX) NVCSrange(rpm)

236° 232° 8.40 8.70 119° 115° below 5400

Therefore when I have the dial gauge and degree wheel setup correctly. In theory at full valve lift the timing should be at 119 degree's.

regards

Chris

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