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View Full Version : SR20 - Rocker arm to Camshaft Clearance at Rest


mastaflash05
04-11-2010, 09:21 PM
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i have HKS solid lifters with my setup, and i need to go about leveling the rocker arms, and shimming the lifters. i understand the process of reshimming the rocker arms so that they set level across the valves, thats no problem.

what i am wondering though, is do i need to adjust the shims inside the solid lifters to adjust the clearance between the camshaft, and the rocker arm? with everything installed as it comes from the box, there seems to be a high clearance, which if im thinking correctly, would reduce actual valve lift.

with HKS solid lifters, are they adjustable for cam to rocker clearance? if it needs shims, are these available anywhere or am i looking at having to make something custom?

i have been running the car like this and havent had any mechanical problems, but my dyno results were lower than expected, and i wonder if this could have something to do with it.

midnight_rex
04-11-2010, 09:29 PM
there is a certain way on shimming solid lifters with rockers. if ur planning to rev high then solid lifters is your best route. just remember re-shimming is mandatory on this kind of valve train setup. here is a write up a guy did a while back...

How to Build a 9000-rpm SR20DET Head (http://www.nicoclub.com/archives/how-to-build-a-9000-rpm-sr20det-head.html)

mastaflash05
04-12-2010, 09:03 PM
that is a good source of information, but i am using hks lifters, and that thread was showing how to set up tomei lifters.

jspaeth
04-12-2010, 09:34 PM
there is a certain way on shimming solid lifters with rockers. if ur planning to rev high then solid lifters is your best route. just remember re-shimming is mandatory on this kind of valve train setup. here is a write up a guy did a while back...

How to Build a 9000-rpm SR20DET Head (http://www.nicoclub.com/archives/how-to-build-a-9000-rpm-sr20det-head.html)

That's a good link, but you didn't really try to answer his question....

Hopefully someone will chime in on this.....it's a very good question, and like you said, it seems like it can effect the max valve lift.

IIRC, the guides only come in a single thickness, right?


Also, IIRC from reading the above link, that guy sent the rockers to be machined, because the actual tips of the rocker arms needed to have different angles...

Did you do that to yours?

jspaeth
04-12-2010, 09:37 PM
Also, I just went back and reread that article....not sure if it matters, but which cams are you using?

Tomei ProCams? I am wondering if it matters which cams you use with the solid lifters.....

mastaflash05
04-12-2010, 10:32 PM
i have hks step 3 272 intake and exhaust. i did not machine my rockers, but im not sure that you have to with the hks lifters. i have never had the chance to inspect the tomei style lifters so i dont know the differences.

i compared the hks and oem lifters tonight to try to get more understanding of whats going on. i noticed that the height of the hks solid vs. the rest height of the oem is significantly different. i will try to get actual measurments and some pictures tomorrow.

i am going to try to call hks tech tomorrow to see if they can provide me with any more detail on setup procedures. hopefuly they can help me, but im not getting my hopes up.

also, because the rocker is essentialy sitting further away from the cam the valve opens later and closes sooner, as well as doesnt open as far. now, the cam could be built to overcome this, but it doesnt explain the large cam to rocker clearance at rest.

jspaeth
04-12-2010, 10:37 PM
There really are a lot of variable here. You essentially have to just measure everything by hand.


Also, the reason for tipping the rocker arms appears to be that perhaps the lift is so much that you get to the point where the corner edge of the rocker is pushing on the shim/guide, rather than the flat bottom surface....

I think you should just measure everything by hand to be honest.

midnight_rex
04-13-2010, 02:24 PM
sorry i didnt answer your question myself. i dont have experience with solid lifters but that article clearly gives you a heads up. in that article there was no problem with the way the solid lifters sit in the pots. maybe you got a bad batch of lifters. or maybe you do need to machine the rocker arms.

if hks did design them to sit higher then oem specs then i think thats a stupid idea. they should meet oem measurements. hope you get it right :)

mastaflash05
04-13-2010, 04:52 PM
the hks lifters are essentialy modified oem lifters. after taking an oem lifter apart i realized that oem lifters can easily be modified to be hks lifters exactly.

no solid lifter can match a hydraulic lifters height because it is variable. also, mine seem to sit lower than oem, not higher.

i called hks today for further instructions, and they told me that the installation is as printed in the oem service manual. i asked about any available shim kits, or individual shims and she told me they are available through nissan. she was refering to the rocker leveling shims though.

i would still like to have some input from anyone else who has setup this type of lifter.

jspaeth
04-13-2010, 05:30 PM
if hks did design them to sit higher then oem specs then i think thats a stupid idea. they should meet oem measurements. hope you get it right :)

Not really true, because if you are talking about extremely high lift cams and want to build the head to rev to 9000 RPM, not all of the specs are going to be the same as the original OEM setup.

the hks lifters are essentialy modified oem lifters. after taking an oem lifter apart i realized that oem lifters can easily be modified to be hks lifters exactly.

no solid lifter can match a hydraulic lifters height because it is variable. also, mine seem to sit lower than oem, not higher.

i called hks today for further instructions, and they told me that the installation is as printed in the oem service manual. i asked about any available shim kits, or individual shims and she told me they are available through nissan. she was refering to the rocker leveling shims though.

i would still like to have some input from anyone else who has setup this type of lifter.

How much did the lifters alone cost? I would definitely be careful with this if I were you and take my time and get in touch with someone with this kind of setup did.

i think Ray (fliprayzin240sx) has a solid head, IIRC

army240
04-13-2010, 06:46 PM
Ok, I didn't went throught everything, but in the link to build a 9000-RPM head, there is a link to Tomei English Manual that says "Nissan Motor Recommends clearance of: 0.14~0.17mm (when cold)". Here's the link to the PDF Document!

http://www-personal.umich.edu/~taesoo/SRHead/Tomei%20Manual/TomeiManualEnglish.pdf (http://www-personal.umich.edu/%7Etaesoo/SRHead/Tomei%20Manual/TomeiManualEnglish.pdf)

I know this is for Tomei, but I'm pretty sure the Rocker to Cam Clearance should be the same for HKS ;)

Also, I was about to ask the same question, so I guess it's a nice thing! haha

EDIT : Jspaeth, you are right about guides coming in only one size from nissan, but some companies make different ones!

Frank

jspaeth
04-13-2010, 07:26 PM
Other question is this:

SHOULD the clearance between rocker and cam the same?

Do we know if the distance from the cam surface to the center of the rotational axis is the same for this aftermarket cam and the OEM cam?

(as measured on the side of the cam opposite of where the lobe is....)

army240
04-13-2010, 08:56 PM
Other question is this:

SHOULD the clearance between rocker and cam the same?

Do we know if the distance from the cam surface to the center of the rotational axis is the same for this aftermarket cam and the OEM cam?

(as measured on the side of the cam opposite of where the lobe is....)

I'd say yes... Cam clearance is cam clearance... I guess that "Cams Designers" don't change that too much, or it will affect lift and duration... I can check tomorrow between BC 272's and stock cam for that info!

Frank

army240
04-14-2010, 05:27 PM
Ok guys, I've got the answer. I've talked to a friend who's an engine builder.

The distance you are talking about is called "the base circle". Yes, every maker use their own base circle... he told me that in some american big block, the base circle of some cams have .040" more than stock one!

Here's a nice link talking about that : The Science Behind Camshaft Design - Circle Track Magazine (http://www.circletrack.com/techarticles/ctrp_0701_camshaft_design_science/index.html)

I wasn't able to check the base circle of stock cams and BC stage 3 thought...

Frank

jspaeth
04-14-2010, 05:43 PM
Ok guys, I've got the answer. I've talked to a friend who's an engine builder.

The distance you are talking about is called "the base circle". Yes, every maker use their own base circle... he told me that in some american big block, the base circle of some cams have .040" more than stock one!

Here's a nice link talking about that : The Science Behind Camshaft Design - Circle Track Magazine (http://www.circletrack.com/techarticles/ctrp_0701_camshaft_design_science/index.html)

I wasn't able to check the base circle of stock cams and BC stage 3 thought...

Frank

Yes!

This morning I started writing a response and was going to talk about this, but I couldn't think of the right words to use.

Now that you mention it, I DO remember hearing the word "base circle".


So NO, cam clearance IS NOT cam clearance, because if the base circles are different, you need to take that into account!

army240
04-14-2010, 06:19 PM
Haha it's exactly the same for me! As soon as he said "Base Circle" I remembered it too! So you are right, you need to take this into account! ;)

Frank

mastaflash05
04-19-2010, 07:31 PM
well i may be closer to spec than i thought. i measured with a set of feeler gauges on one rocker on the intake cam and came up with a measurement of 0.203mm. its on the high side, but i have not checked the level of the rocker yet.

i was unable to check any others because i have the exhaust cam out, and was not able to rotate the cam/engine.