No shims shaved N42

[JohnH]

I have be searching around trying to find some definate answers. I'm replacing a head on a F54 flat top N/A setup. The N42 head that I'm putting on has been milled 80 thou. I have a Kameari twin gear chain tensioner with a relatively new chain (under 5K). If I do not run the shims under the cam towers can I advance the cam sprocket to the second position so the cam timing would be correct. Would the stock cam sprocket 2nd position be enough or too much advance or would an adjustable cam spocket like Tomei help. The Kameari tensioner will take up the dreaded slack in the chain so I'm not worried about that. Its the cam timing I'm concerned with if I do not shim the towers.

 

I found a couple of threads which have vague references.

 

This one but the orginal question was ignored & not responded directly to.

 

http://forums.hybridz.org/index.php/topic/92848-head-shaving-question/page__p__876461__hl__%2Bshaving+%2Bhead__fromsearch__1#entry876461

 

and this one which has a vague reference

 

http://forums.hybridz.org/index.php/topic/96300-can-you-remove-links-in-the-cam-chain-to-reduce-slack/page__p__905027__hl__%2Bshaving+%2Bhead__fromsearch__1#entry905027

Edited May 7, 2012 by JohnH

[JohnH]

Let me put it a different way "How much cam retard does milling a head 80 thou cause while using a perfectly good timing chain?"

[ctc]

I have be searching around trying to find some definate answers. I'm replacing a head on a F54 flat top N/A setup. The N42 head that I'm putting on has been milled 80 thou. I have a Kameari twin gear chain tensioner with a relatively new chain (under 5K). If I do not run the shims under the cam towers can I advance the cam sprocket to the second position so the cam timing would be correct. Would the stock cam sprocket 2nd position be enough or too much advance or would an adjustable cam spocket like Tomei help. The Kameari tensioner will take up the dreaded slack in the chain so I'm not worried about that. Its the cam timing I'm concerned with if I do not shim the towers.

 

I found a couple of threads which have vague references.

 

This one but the orginal question was ignored & not responded directly to.

 

http://forums.hybridz.org/index.php/topic/92848-head-shaving-question/page__p__876461__hl__%2Bshaving+%2Bhead__fromsearch__1#entry876461

 

and this one which has a vague reference

 

http://forums.hybridz.org/index.php/topic/96300-can-you-remove-links-in-the-cam-chain-to-reduce-slack/page__p__905027__hl__%2Bshaving+%2Bhead__fromsearch__1#entry905027

 

Pardon my ignorance, but wouldn't you install the cam with zero timing advance? The big advantage of the Kameari part is to take up the extra slack created when shaving the head. With the cam dialed into zero advance and the crank at TDC, the relative location of links on the timing chain are irrelevant because the chain will maintaing the relative position of the cam and the crank.

 

Am I wrong?

[Leon]

You can easily figure this out using the arc length forumla, S=R*theta, where S is the arc length, R is radius of cam sprocket and theta is cam retard (in radians). Your arc length would be the .080" and you'd have to measure the cam sprocket radius, in inches.

 

Solve for theta:

theta=S/R

 

Plug in your numbers (I'll plug in an educated guess for R):

theta=.080/2

theta=.040 rad

 

Convert radians to degrees:

theta=.040*(180/pi)

theta=2.3deg

 

Plug in your measured value for R, and that should get you close to what you should expect if you were to actually degree the cam before/after.

 

Of course, nothing beats actually degreeing your cam.

Edited May 9, 2012 by Leon

[clarkspeed]

Set up cam with degree wheel. It's the only way to know what you have and get close to cam specs. If its a new build, I will also check piston to valve clearance at multiple cam angles so I will have no fear of trying different cam settings on the dyno. Often you can get by with stock sproket so save your money unless your measurements say you need it.

[JohnH]

Pardon my ignorance, but wouldn't you install the cam with zero timing advance? The big advantage of the Kameari part is to take up the extra slack created when shaving the head. With the cam dialed into zero advance and the crank at TDC, the relative location of links on the timing chain are irrelevant because the chain will maintaing the relative position of the cam and the crank.

 

Am I wrong?

 

The Kameari twin gear tensioner can be adjusted for chain slack. However that chain slack is only on the slack side of the chain path (passenger side of engine). The drive side or constant tensioned side if you like is always a fixed distance from the crankshaft timing chain drive to the cam sprocket. If you use the stock cam sprocket in its # 1 position & don't shim the cam towers after the head is milled the cam timing will be retarded by the amount milled as the distance between the cam center line & the crankshaft center line has now been shortened. This is of course when timing from TDC from the shiny chain marks (42 links between cam mark & crankshaft gear mark) which begs the question if one can advance the cam by one tooth on the cam sprocket & how much is that in degrees as oppose to the 4 degrees advance of the #2 cam sprocket position.

[ctc]

This is of course when timing from TDC from the shiny chain marks (42 links between cam mark & crankshaft gear mark) which begs the question if one can advance the cam by one tooth on the cam sprocket & how much is that in degrees as oppose to the 4 degrees advance of the #2 cam sprocket position.

 

This is what I was getting at, if you degree the cam you know exactly how much you need to move the timing and would most likely need the Tomei or Kameari adjustable cam gear. As for slipping a tooth, I would assume since there are 40 teeth and 360 degrees that each tooth is 9 deg off on the cam or 4.518 deg crank (see below). Sounds like you should run the shims or an adjustable gear.

Edited May 9, 2012 by ctc

[NewZed]

which begs the question if one can advance the cam by one tooth on the cam sprocket & how much is that in degrees

 

One tooth divided by the total number of teeth times 720? Just a quick guess...

[Leon]

This is what I was getting at, if you degree the cam you know exactly how much you need to move the timing and would most likely need the Tomei or Kameari adjustable cam gear. As for slipping a tooth, I would assume since there are 40 teeth and 360 degrees that each tooth is 9 deg off on the cam or 4.5 crank. Sounds like you should run the shims or an adjustable gear.

9 cam degrees is 18 crank degrees. However, 9 degrees is the relevant number in this discussion, and that is correct.

 

One tooth divided by the total number of teeth times 720? Just a quick guess...

Correct, but only if you're referring to crank degrees. Cam degrees are more pertinent when talking about cam timing.

 

OP, perform the calculation that I've laid out. That will let you know how much the cam will be retarded. You can then leave it retarded for some more top end, advance for more low end, or test both conditions and see what you like best. Don't skip teeth, there is not enough resolution there.

 

An adjustable cam sprocket and a degree wheel is the better solution. I'm somewhat perplexed as to why an engine with a Kameari chain tensioner would have a stock cam sprocket. If I dropped that much dough to be able to take up slack in a timing chain, you bet I'd get an adjustable sprocket as well.

Edited May 9, 2012 by Leon

[NewZed]

According to the FSM, the four degrees described per cam shaft sprocket adjustment hole, is in crankshaft degrees. #2 is four degrees, #3 is eight.

 

The sprocket has 40 teeth, so 1/40 is .025 or 2.5% of one camshaft rotation, 5% of one crankshaft rotation since the crank moves at double camshaft speed. .05 times 360 = 18 degrees. Or 1/40*720.

 

 

So you can have 4 or 8 degrees of advance with the stock chain/camshaft configuration or retard the timing one tooth and use the adjustment holes to move forward to get 18-8 (the #3 hole) for 10 degrees advance, or 18-4 (the 2 hole) for 12 degrees. 4, 8, 10, 12. Weird how that worked out so evenly.

 

Sticking with the stock chain and sprocket configuration and using the #2 hole seems like the most likely option, if you can avoid the chain slack issue, and are on a budget.

 

 

BUT, isn't rocker arm angle and wear patterns the other problem with the milled head? The other, maybe the main, reason for the shims?

[Leon]

According to the FSM, the four degrees described per cam shaft sprocket adjustment hole, is in crankshaft degrees. #2 is four degrees, #3 is eight.

 

The sprocket has 40 teeth, so 1/40 is .025 or 2.5% of one camshaft rotation, 5% of one crankshaft rotation since the crank moves at double camshaft speed. .05 times 360 = 18 degrees. Or 1/40*720.

 

 

So you can have 4 or 8 degrees of advance with the stock chain/camshaft configuration or retard the timing one tooth and use the adjustment holes to move forward to get 18-8 (the #3 hole) for 10 degrees advance, or 18-4 (the 2 hole) for 12 degrees. 4, 8, 10, 12. Weird how that worked out so evenly.

 

Sticking with the stock chain and sprocket configuration and using the #2 hole seems like the most likely option, if you can avoid the chain slack issue, and are on a budget.

 

 

BUT, isn't rocker arm angle and wear patterns the other problem with the milled head? The other, maybe the main, reason for the shims?

Whoops, looks like I'm off today. I need more sleep. Yes, crank degrees is the important number.

 

As for your last statement, you've got that one backwards. Rocker arm wear patterns change because of shimming the cam towers, not milling the head. That's when you get into needing different lash pads, since cam-to-rocker distance changes.

[NewZed]

Backwards I was. So, there are advantages to avoiding the shims.

 

Your 2.3 camshaft degree estimate (4.6 crank degrees) suggests that the #2 hole would give 0.6 crank degrees retarded with the .080" missing. Seems within the bounds of the range suggested by the FSM's before and after pictures.

 

Also, since the notch is relative to the cam, you could pre-assemble and check the notch position per the FSM procedure to see if it's right.

[JohnH]

Thanks guys. I do have a Nismo multi hole cam sprocket somewhere around but I think I might go with a Tomei or Kameari slide adjustable sprocket & degree the cam in sans cam tower shims.

Edited May 10, 2012 by JohnH

[Tennesseejed]

I have be searching around trying to find some definate answers. I'm replacing a head on a F54 flat top N/A setup. The N42 head that I'm putting on has been milled 80 thou. I have a Kameari twin gear chain tensioner with a relatively new chain (under 5K). If I do not run the shims under the cam towers can I advance the cam sprocket to the second position so the cam timing would be correct. Would the stock cam sprocket 2nd position be enough or too much advance or would an adjustable cam spocket like Tomei help. The Kameari tensioner will take up the dreaded slack in the chain so I'm not worried about that. Its the cam timing I'm concerned with if I do not shim the towers.

 

I found a couple of threads which have vague references.

 

This one but the orginal question was ignored & not responded directly to.

 

http://forums.hybridz.org/index.php/topic/92848-head-shaving-question/page__p__876461__hl__%2Bshaving+%2Bhead__fromsearch__1#entry876461

 

and this one which has a vague reference

 

http://forums.hybridz.org/index.php/topic/96300-can-you-remove-links-in-the-cam-chain-to-reduce-slack/page__p__905027__hl__%2Bshaving+%2Bhead__fromsearch__1#entry905027

 

Good thought, but advancing your cam timing does not solve issues related to extra timing chain slack.

 

Except, possibly, when your engine is decelerating quickly and the velocity of the camshaft exceeds the speed of the crankshaft, there will never be slack on the 'down' side of you timing chain. Instead, all of the slack will exist on the 'up' side of the chain which is why the stock chain tensioner is where it is. If that makes sense.

 

Advancing your cam timing does not effectively split the difference of the timing chain slack in actual operation. If you advance your cam timing, as another poster stated, you are lowering the powerband designed into you cam.

 

I don't believe the stock tensioner can handle the extra slack you propose. Not having any experience with the Kameari tensioner, I'd call them and ask. If they have doubts, get the cam towers.

 

Cutting .080 off the P90 head and installing N42 valves is a pretty popular mod for Z car owners. Somebody probably makes them. JMO, but I'd get the shims and have the designed cam timing geometry.

 

Good luck with your project.

[Leon]

Good thought, but advancing your cam timing does not solve issues related to extra timing chain slack.

 

Except, possibly, when your engine is decelerating quickly and the velocity of the camshaft exceeds the speed of the crankshaft, there will never be slack on the 'down' side of you timing chain. Instead, all of the slack will exist on the 'up' side of the chain which is why the stock chain tensioner is where it is. If that makes sense.

 

Advancing your cam timing does not effectively split the difference of the timing chain slack in actual operation. If you advance your cam timing, as another poster stated, you are lowering the powerband designed into you cam.

 

I don't believe the stock tensioner can handle the extra slack you propose. Not having any experience with the Kameari tensioner, I'd call them and ask. If they have doubts, get the cam towers.

 

Cutting .080 off the P90 head and installing N42 valves is a pretty popular mod for Z car owners. Somebody probably makes them. JMO, but I'd get the shims and have the designed cam timing geometry.

 

Good luck with your project.

That's the point of the gear tensioner, you don't need tower shims since the idler takes all the slack out. It's a matter of adjusting the cam to where you want it.

 

http://www.kameariusa.com/L6_Twin_Idler_Gear.php

[Tennesseejed]

That's the point of the gear tensioner, you don't need tower shims since the idler takes all the slack out. It's a matter of adjusting the cam to where you want it.

 

http://www.kameariusa.com/L6_Twin_Idler_Gear.php

 

Yes, but the orginal question was whether the OP should change his cam timing to compensate for the additional chain slack. I'm saying he should time his cam normally. And that I don't know how much slack the Kameari can accomdate so he might consider asking the source. That's all.

[Leon]

Yes, but the orginal question was whether the OP should change his cam timing to compensate for the additional chain slack. I'm saying he should time his cam normally. And that I don't know how much slack the Kameari can accomdate so he might consider asking the source. That's all.

This is why I linked the Kameari web site in my previous post. This is straight from the manufacturer:

 

The head space can be adjusted between 0-4mm so the cam spacer is unnecessary. (L4 is 0-3mm)

4mm equates to .157". 'Nuf said.

 

Re-read the original question, you've misinterpreted it.

 

The reason for the question is that with the head shaved .080", no cam shims, and the gear chain tensioner your cam timing will be retarded because of a shorter relative distance between cam and crank centerlines. OP was interested in using the stock cam sprocket (for whatever reason). In order to account for this, you must know how much the timing has been thrown off, knowing that the stock sprocket allows for 4 degree intervals of adjustment.

 

I mathematically approximated the cam timing to be retarded by 4.6 crank degrees (please, do not rely on this number). Therefore, when using the second hole in the stock sprocket, the cam would be 0.6 degrees retarded or close to "straight up" when using a stock cam. This answers this original question, although I strongly recommend actually measuring the cam sprocket diameter and redoing the calc.

 

As I and others have recommended, using a sprocket with more adjustment would be much more beneficial especially under the assumption that if you spend $800 on a chain tensioner, then you'd be fine with dropping some more for an adjustable sprocket. As the OP realized, using an adjustable sprocket and a degree wheel to actually degree the cam is a much better idea than approximating timing change due to machining and trying to use a stock sprocket to make up for it.

[Tony D]

Everybody is obsessing on how "much" the cam is "retarded" by the milling, and has been unable to see the forest because of all the trees when someone answers "degree the cam as you normally would, and move on"...

 

With the KEW tensioner, one makes the assumption that it's not some amatuer stock rebuild, where they are thinking "stick it in the hole and fagadboudit"---one makes the assumption that you will degree the cam, see where it lies, and install "straight up" to give camshaft grinders projected performance.

 

Stuffing it on an arbitrary hole on a stock or even multi-holed sprocket (calculations notwithstanding) is at best a compromised guess.

 

Use the Tomei sprocket, set up your indicator Znd set the cam where it's supposed to be, not approximately, not 'as best as I can get from my calculations'---EXACTLY where it's supposed to be.

 

No, you don't need the shims. Degree the cam as you normally would. If you want to do calculations, do them. Won't change the fact that if the cam is ground 1/2 a degree off the profile you STILL need to degree it and set it 'straight up' for your dyno baseline, then make your pulls to determine which relative position (exact amount of advance or retard necessary) to give best power under the curve.

 

The problem with calculations is they don't remove the reason you do degreeing in the first place: chain stretch or cam grinder errors.

[Leon]

Everybody is obsessing on how "much" the cam is "retarded" by the milling, and has been unable to see the forest because of all the trees when someone answers "degree the cam as you normally would, and move on"...

 

With the KEW tensioner, one makes the assumption that it's not some amatuer stock rebuild, where they are thinking "stick it in the hole and fagadboudit"---one makes the assumption that you will degree the cam, see where it lies, and install "straight up" to give camshaft grinders projected performance.

 

Stuffing it on an arbitrary hole on a stock or even multi-holed sprocket (calculations notwithstanding) is at best a compromised guess.

 

Use the Tomei sprocket, set up your indicator Znd set the cam where it's supposed to be, not approximately, not 'as best as I can get from my calculations'---EXACTLY where it's supposed to be.

 

No, you don't need the shims. Degree the cam as you normally would. If you want to do calculations, do them. Won't change the fact that if the cam is ground 1/2 a degree off the profile you STILL need to degree it and set it 'straight up' for your dyno baseline, then make your pulls to determine which relative position (exact amount of advance or retard necessary) to give best power under the curve.

 

The problem with calculations is they don't remove the reason you do degreeing in the first place: chain stretch or cam grinder errors.

Couldn't have said it better myself!

 

I will admit to enjoying mathematical exercises, though.