P90 CR Head Modification

[thorfin]

Some additional comment on the shims--you do not need to have an expensive aftermarket chain tensioner--unless you just want it!--As far as cam tower shims are concerned, there is a relatively easy solution (since Goodson apparently doesn't supply them anymore). First of all, you don't need to worry about the headbolts being too short---- the shims go under the cam tower bolts, NOT the headbolts!--in effect they make the cam towers a little taller, and this does not affect the head or head bolt connection. Now I will tell you a fact--the BEST cam tower shim will be one solid shim that is .080 thick or thereabouts--rather than a 5 to 6 stack of thin shims--and the thickness does not have to be perfect match to the amount milled off--let me explain, the factory manual allows you to mill the head up to .030 when doing a head job-----with such light milling, the chain will just be a little more slack, and there is a chain tensioner near the crank shaft to keep this slack under control--but it has limits, and .030 is the limit--so when you mill off .080 you have to get back in range of the chain tensioner--so a range of .075 to .081 will make no or little difference--close enough!

Now another thing to keep in mind is these L6 heads are notorious for head gasket leaks and warped heads--too common--a weakness--so you need to make sure your redone head is flat on the bottom AND flat on the top--and both are parallel to each other---so it is a very good idea to have the machine shop mill the top flat-- FIRST-- by taking a skim cut--and if the head is not warped, this skim should be about .007 or so on the top--this way your cam towers base areas are going to be flat and parallel to each other--and THEN the head is flipped over to mill off the combustion chamber side--milling off the bottom say .078--then you TOTAL head thickness has shrunk in height by .085 inches--so a perfect cam tower shim is .085 inches thick to compensate--but as stated earlier .075 or .080 works fine too. Now for the shims--they must be THEN be custom made--there will be two types on the L6 head and a total of five needed --one for each cam tower--it seems like there is one of one type and four of another--total of five--you can tell by looking at your cam towers after they are unbolted from the head--BE SURE AND NUMBER MARK TOWERS #1 thru #5 BEFORE UNBOLTING THE CAM TOWERS!! --you can use the cam tower bottoms as a pattern for the shim--if you are REALLY going to do this, and want it, I have the two cam tower patterns traced on a piece of paper that I could send you--I also send one of the Goodson shims--it was leftover--do not have second type of Goodson shim for some reason--just the two pattern and one actual .015 thick shim--take the towers (or my pattern traces) to your GOOD machine shop and have them make the shims--it would work best if they got some genuine shim stock or good sheet metal that was already .075 to .080 thick--but do not get the final shims made until your head is milled and competely done--you may need it to be .090 or so because the head was warped! the exact outer shape of these shims is not critical--what counts is they are flat with no burrs or rolled edge--so that each tower is raised consistently--anyway-if you really need and want the pattern traces and sample shim, send me your address and I will mail them to you..--thorfin

[steveosupremeo]

-all 5 cam towers have one head bolt that runs through them and two cam tower bolts!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! go pop your valve cover and look for yourself. but as I stated earlier, its not enough to be an issue but they are there. thats why you have 9 short head bolts and 5 long head bolts!

[m4xwellmurd3r]

wait...but if you shave the head .080 then put .080 shims under the towers, wouldn't the overall hight between the block deck and cam tower be the same? i'm probably wrong, since I don't know the exact specifics of it all, but as far as I know, what you do is shim the cam tower back up to the stock hight, so wouldn't that mean that the bolts still grab into the block the same?

[naviathan]

wait...but if you shave the head .080 then put .080 shims under the towers, wouldn't the overall hight between the block deck and cam tower be the same? i'm probably wrong, since I don't know the exact specifics of it all, but as far as I know, what you do is shim the cam tower back up to the stock hight, so wouldn't that mean that the bolts still grab into the block the same?

I was waiting for someone to say it...Makes sense yes? Do believe he's right. The head bolts that don't run through the cam towers might actually be a bit on the long side because of the shave. Not sure how deep those threads go into the block.

[m4xwellmurd3r]

I can see the smaller bolts that thread into the head being a bit on the short side, but the ones that go through the head and into the block shouldn't be affected since you take .080 out of the head and add .080 to the cam tower.

.080-.080=0.00 right?

[thorfin]

by jimbo, steveosupremeo is right, and upon an inspection of my two shim tracings, there are three holes in each shim--two for the cam tower bolts and one for the head bolt--three total----BUT m4xwellmurd3r is also right----the total height of headafter milling and shimming is the same still about the same and thus the head bolt is not too short--in fact, most of the bolts will have a bit more bite with the slightly thinned milled head.

[steveosupremeo]

well then, never thought about the other 9 actually going deeper but since so many people have done this its obviously not a problem.

[BRAAP]

I have read time and time again about doing this setup for the P90 head and the 280 engine.

Head shims are not the correct method to compensate for the chain slop created when the head is milled this extensively.

The correct way to fix the problem is to go with the chain adjuster from Kamalari (if I spelled that right) then all of your cam spacing is not an issue any longer. You will not have to bother with shimming the towers. Also, can you even shim the cam towers that much without hitting the top of the valve cover? I don't know because I would never do this to my engine. The L series cam is long, it needs a good foundation to secure to and that many shims just is not a good way to go. Remember, the head bolts go through the cam tower, so if you shim the towers with that many shims you are losing threads in the block for the head bolts.

Spend the extra money and get the right part for the job. Also I would recommend the TOMEI adjustable cam sprocket. You can have that part in hand for about 150.00 shipped from Japan to your door. Worth every penny in my opinion.

this is the very best way to go, and you can feel confident the cam timing is not going to change after you make the adjustment.

 

 

 

Jeff,

Sorry, but I disagree with you on a couple things.

 

Tensioner;

 

1) The chain tensioner, (including the Kameari) takes up the tension on the “slack” side of the chain which has no effect on the length of the chain on the tension side between the crank and cam.

 

2) In shaving the head .080”, the cam is now .080” closer to the crank and with the tension of the timing chain still taught, that effectively causes the cam to roll, retarding the cam timing, which the chain tensioner will NOT take out because it is on the slack side of the chain, not the tension side.

 

3) If we are removing enough material from the head that we now are advancing the cam by skipping a tooth, and still able to achieve “accurate” crank to cam timing then, yes, that would old true. I have not looked into or calculated if that can be done though.

 

In short, shaving the head without shimming the cam towers back up DOES alter the cam timing and the chain tensioner does NOT affect or adjust cam timing in any manner whatsoever. If it did, I would’ve built an oil pressure actuated variable cam timing arrangement already.

 

Head Bolts/thread engagement;

 

1) 5 of the head bolts do go through the cam towers, and in removing .080” from the head, AND then using enough cam tower shims to shim the cam towers back up to the appropriate height, those 5 head bolts are now engaging the block threads the same amount as they would with an uncut stock head.

 

2) The rest of the head bolts however, could now very easily bottom out from going to deep. Adding a .080” washer under the heads of those head bolts now brings those bolts back to the same thread engagement as we had with an uncut stock head.

 

 

The valve cover clearance is definitely something to consider. Doubling up on valve cover gaskets would fix the clearance issue, though keeping it from leaking would be a trick…

[BRAAP]

... First of all, you don't need to worry about the headbolts being too short---- the shims go under the cam tower bolts, NOT the headbolts!--in effect they make the cam towers a little taller, and this does not affect the head or head bolt connection. .....

 

The cam tower shims go directly under the cam towers themselves, AND 5 of the head bolts do go through the cam towers, see the post above.

 

 

One issue will be the thread engagement of the cam tower bolts, which are already “borderline” in thread engage as it is. A possible solution would be to spot face, .080”, the cam towers where the cam tower bolts go through the cam towers to regain that thread engagement. I’ll look into that tomorrow and may even try spot facing a few on the mill to be sure it can be done.

 

The rest of your information looks accurate, thank you for your input.

[BRAAP]

Pioneer does sell the cam tower shims. The last 10 or so L-6 heads we did that required shims, I have noticed Pioneer has been having a packaging problem. They are being packaged as a 4 cylinder set in the 6 cylinder box. Our supplier is working with us on this.

 

 

So heads up you DIY head assemblers getting Pioneer cam tower shims from your local machine shop. Before you walk out the door with your box of shims for the L-6, open it up and verify that you do in-fact have all 5 shims per set. 4 L shaped and one straight.

[jeffp]

1) The chain tensioner, (including the Kameari) takes up the tension on the “slack†side of the chain which has no effect on the length of the chain on the tension side between the crank and cam.

 

2) In shaving the head .080â€, the cam is now .080†closer to the crank and with the tension of the timing chain still taught, that effectively causes the cam to roll, retarding the cam timing, which the chain tensioner will NOT take out because it is on the slack side of the chain, not the tension side.

 

This is correct, however, I also mentioned the cam sprocket fro 140.00 to do the cam timing.

Adding head bolt washers and the like is a way of doing the job, but I don't recommend it. I realize alot of you have done this modification and I really don't agree with it completed this way.

 

You guys come up with the fastest cheapest way of doing things for your beloved vehicles, why not make modifications correctly that promote reliability and longevity.

I built my engine, and I could have done a number of things to save money, and they may work. I needed a topend that I was sure would stay on the block. My cylinder pressures before firing are in the 450-500 psi range under boost. I did not want to depend on a head that has a significant amount of surface contact area removed from the head. I did not want to try to compensate for cam timing with cam tower shims either.

I bought a tensioner, that does work very well to 13,000 rpm's. I also bought the adjustable timing gear to correct for ANY offset in cam timing.

You guys always talk about performance, and do this or do that, but I NEVER, except in a few cases hear of some guy taking the time to get the actual cam timing dialed in with a DEGREE WHEEL! Performance, yea right! Shade tree mechanic type work being done all the time. Then when things go to ♥♥♥♥, you wonder what you could have done to stop the problem, bitch about how it is this or that yada yada yada.

Fact is that you short-cut proper design because of the cost. So you can give me all the reasons and excuses in the world, my answer is I don't have ANY of those challenges, and I know EXACTLY where my cam is timed because I made DAMN sure it was correct with a DEGREE WHEEL to begin with.

I completed WOT tuning of my engine last week, care to guess what power it made? I will tell you, the calculated HP at the crank is 658HP and the dyno torque figures are 509 foot pounds. In fact, if I wanted to sacrafice my 3200 RPM spool of the turbo with a .63 A/R exhaust turbin housing and went back to the standard .82 A/R exhaust turbine housing I am quite confident I could pick up another 20-25 Horse Power. That puts the engine in the 680-700 hp range! WHO ELSE HAS BONE THIS? I will tell you, Electromotive, and a couple others that I will not mention.

So you guys can debate, discuss, and theorize all you like, but the fact of the matter is, I can take most of you with 8psi of boost @ 300-350 horse power. Not bad figures I say, I doubled the hp output of the stock boost levels with my engine, and you know I did that with a STOCK TURBO INTAKE!

I NEVER heard of ANY performance builders that did not have a degree wheel handy for every build. I use to grind cams, and make valve train components back in the day of Super Shops and Sig Erson, so you could say I know a LITTLE about what is going on with these things (to quote Arnie) have fun, and if we do happen to meet on the street, I am QUITE sure I could take the majority of you with my A/C running.

Anyway, sorry if I am a little maen about the whole thing, but this is so agravating to read time and time again.

[z-ya]

1)

This is correct, however, I also mentioned the cam sprocket fro 140.00 to do the cam timing.

Adding head bolt washers and the like is a way of doing the job, but I don't recommend it. I realize alot of you have done this modification and I really don't agree with it completed this way.

 

You guys come up with the fastest cheapest way of doing things for your beloved vehicles, why not make modifications correctly that promote reliability and longevity.

I built my engine, and I could have done a number of things to save money, and they may work. I needed a topend that I was sure would stay on the block. My cylinder pressures before firing are in the 450-500 psi range under boost. I did not want to depend on a head that has a significant amount of surface contact area removed from the head. I did not want to try to compensate for cam timing with cam tower shims either.

I bought a tensioner, that does work very well to 13,000 rpm's. I also bought the adjustable timing gear to correct for ANY offset in cam timing.

You guys always talk about performance, and do this or do that, but I NEVER, except in a few cases hear of some guy taking the time to get the actual cam timing dialed in with a DEGREE WHEEL! Performance, yea right! Shade tree mechanic type work being done all the time. Then when things go to ♥♥♥♥, you wonder what you could have done to stop the problem, bitch about how it is this or that yada yada yada.

Fact is that you short-cut proper design because of the cost. So you can give me all the reasons and excuses in the world, my answer is I don't have ANY of those challenges, and I know EXACTLY where my cam is timed because I made DAMN sure it was correct with a DEGREE WHEEL to begin with.

I completed WOT tuning of my engine last week, care to guess what power it made? I will tell you, the calculated HP at the crank is 658HP and the dyno torque figures are 509 foot pounds. In fact, if I wanted to sacrafice my 3200 RPM spool of the turbo with a .63 A/R exhaust turbin housing and went back to the standard .82 A/R exhaust turbine housing I am quite confident I could pick up another 20-25 Horse Power. That puts the engine in the 680-700 hp range! WHO ELSE HAS BONE THIS? I will tell you, Electromotive, and a couple others that I will not mention.

So you guys can debate, discuss, and theorize all you like, but the fact of the matter is, I can take most of you with 8psi of boost @ 300-350 horse power. Not bad figures I say, I doubled the hp output of the stock boost levels with my engine, and you know I did that with a STOCK TURBO INTAKE!

I NEVER heard of ANY performance builders that did not have a degree wheel handy for every build. I use to grind cams, and make valve train components back in the day of Super Shops and Sig Erson, so you could say I know a LITTLE about what is going on with these things (to quote Arnie) have fun, and if we do happen to meet on the street, I am QUITE sure I could take the majority of you with my A/C running.

Anyway, sorry if I am a little maen about the whole thing, but this is so agravating to read time and time again.

 

Jeff,

 

I don't think anyone here is questioning your L6 knowledge. I for one am amazed at the amount of power you can get from a turbo L6 (we chatted at an MSA show a few years ago). But this is an open discussion forum, not a personal attack on your ability. You are correct in saying that it is important to know your cam timing, especially in a highly modified engine, otherwise you are not going to get the most out of it.

 

I tend to agree with BRAAP that the stock tensioner will work just fine in this application, but adding an adjustable cam sprocket so you can adjust cam timing should be a requirement. This of course assuming that engine RPMs won't exceed 7000RPM.

[1 fast z]

So jeff, that 658hp was "calculated crank HP"? What did it make at the wheels before the "error correction"?

[twilsonx]

Thanks for the info guys. Maybe someone should make a thread with pictures on how to do this the proper way and get it stickied by a mod.

[jeffp]

Brian, do the calculation, that is about 526Hp. I think that figure was a little higher on previous pulls. Yes the one pull I did have previously, when the car was misfiring it got 537.77 Hp the torque was 487 foot pounds.

Then the last pull that was not complete on the graph got me 509.75 foot pounds of torque. Either way, I rather get higher torque numbers and go with that in stead of the Hp numbers.

I was wondering when you were going to chime in Brian. What has your engine been able to run? I would imagine with your setup, you will be able to make better power with less stress ojn the engine and associated components.

I don't take this as a personal attack of my abilities, but there is a sticky on the cam and how you set up the cam and all of the considerations to complete the task.

The thing that really gets me is that someone (one one particular) will not take the time to get the hard line data from testing and measuring to get their answer. Seems to me that when I needed hard line data, I have always had to get the data myself. I have listen and asked a few questions of people (not mentioning names) that turns out the reply was totally incorrect when I took the time to do the testing myself.

I am not the end all bay any stretch of the imagination when it comes to the L28, in fact I get a kick out of seeing just waht this little six cylinder will do before it blows, crazy I know, but what the heck.

I have said it before and I will say it again, building an engine is simply a mathemitical calculation based on some variables. Do the math and get the answer it's just that simple. Good example: Should I build a 3.0 liter engine or should I build a 3.1 liter engine?

Do the math, and you will find there is not enough improvement, or increase, to punch the cylinder walls out so far. Questions like these are not the questions that should be asked because you can come up with hard line figures.

So anyway, hope to see all of you at the MSA show this year, and Brian, I want to know what your engine is doing. I am very curious to see how much power it will make with your cylinder head configuration.

[BRAAP]

....

I don't take this as a personal attack of my abilities, but there is a sticky on the cam and how you set up the cam and all of the considerations to complete the task.

The thing that really gets me is that someone (one one particular) will not take the time to get the hard line data from testing and measuring to get their answer. Seems to me that when I needed hard line data, I have always had to get the data myself. I have listen and asked a few questions of people (not mentioning names) that turns out the reply was totally incorrect when I took the time to do the testing myself.

I am not the end all bay any stretch of the imagination when it comes to the L28, in fact I get a kick out of seeing just waht this little six cylinder will do before it blows, crazy I know, but what the heck......

 

 

I have not personally built one of these shaved heads, though I must admit, the concept is intriguing.

 

I don’t know what ruffled your feathers Jeff, but if it was me, I didn’t mean to.

I read your post as you claiming the Kameari tensioner by itself to be the fix for the altered cam timing, and the adjustable cam sprocket just be to the icing on the cake. Both parts are mentioned at opposite ends of your post, not together going hand in hand. I apologize if I misread your post.

 

Yes degreeing the cam is important, no doubt. That stickie you are referring to is NOT the end all be all to setting a cam. A REAL tuner will know the numbers on any cam card are merely a starting point for extracting max performance and those numbers the cam manufacture printed on that card helps the builder to ensure the timing gear being used was manufactured properly and not out of tolerance. On the dyno we “verify’ the ignition timing and AFR's are what that engine wants, same goes for cam timing.

 

As for the pissing match about how fast your car is compared to everyone elses? Are you having a bad day, week, month? Sorry Jeff, I know you are more mentally mature than that, c’mon. This isn’t the grade school sand box. There are guys on this forum that have built and dyno tuned endurance race engines with over 1100 HP, (that someone is probably posting in this thread), but that doesn’t necessarily mean they don’t make mistakes or post something in error on occasion. We are all human, it is in how we deal with our mistakes and errors that makes the real difference. Not trying to beat down others. That's just immature, asinine, and a sign of a fragile inflated ego.

[JMortensen]

2) In shaving the head .080”, the cam is now .080” closer to the crank and with the tension of the timing chain still taught, that effectively causes the cam to roll, retarding the cam timing, which the chain tensioner will NOT take out because it is on the slack side of the chain, not the tension side.

 

3) If we are removing enough material from the head that we now are advancing the cam by skipping a tooth, and still able to achieve “accurate” crank to cam timing then, yes, that would old true. I have not looked into or calculated if that can be done though.

 

In short, shaving the head without shimming the cam towers back up DOES alter the cam timing and the chain tensioner does NOT affect or adjust cam timing in any manner whatsoever. If it did, I would’ve built an oil pressure actuated variable cam timing arrangement already.

This is a fair assessment of the limitations of the Kameari tensioner. BUT, add an adjustable cam gear to the whole deal and now you can shave the head and adjust the gear and get the cam timing right, and the Kameari can adjust out the slack in the chain, no problem.

Head Bolts/thread engagement;

 

1) 5 of the head bolts do go through the cam towers, and in removing .080” from the head, AND then using enough cam tower shims to shim the cam towers back up to the appropriate height, those 5 head bolts are now engaging the block threads the same amount as they would with an uncut stock head.

 

2) The rest of the head bolts however, could now very easily bottom out from going to deep. Adding a .080” washer under the heads of those head bolts now brings those bolts back to the same thread engagement as we had with an uncut stock head.

 

 

The valve cover clearance is definitely something to consider. Doubling up on valve cover gaskets would fix the clearance issue, though keeping it from leaking would be a trick…

Seems like first checking the bolts to see if they bottom and then either getting shorter bolts or cutting the existing bolts would be easy enough to do. I think you're making this part more complicated than it needs to be.

 

EDIT--Oops. Somehow I missed Jeff's response that mentioned the adjustable cam gear.

[BRAAP]

This is a fair assessment of the limitations of the Kameari tensioner. BUT, add an adjustable cam gear to the whole deal and now you can shave the head and adjust the gear and get the cam timing right, and the Kameari can adjust out the slack in the chain, no problem.

 

Seems like first checking the bolts to see if they bottom and then either getting shorter bolts or cutting the existing bolts would be easy enough to do. I think you're making this part more complicated than it needs to be.

 

EDIT--Oops. Somehow I missed Jeff's response that mentioned the adjustable cam gear.

 

 

 

Thank you for clearing that up Jon. I think that is what Jeffp was trying to say in the first place, which makes sense.

[jeffp]

I don't have a fragile whatwever in any stretch of the imagination. I realize there are a number of people on this forum that make significantly more power with their builds. I am speaking of the L28 specifically. I am quite sure there are a couple people here the really understands what it takes to build 600 + hp with the L28, not many, but a few.

So in recap of my first post:

Shaving the cylinder head to the extent that was mentioned .080 in my opinion not good for high hp and relibility. A N/A application I am sure will be fine. The thing is that you take so much of the mating surface off of the head that I for one would never consider that as an option. I would get new pistons to suit my compression requirements.

A turbo application, NO WAY is this an option for my builds. You know when you are tuning your car and people who tune daily, yes daily, engines and cars that are making three times the piower as my car start heading for the nearest cover when you do your pull there is sometning going on there.

Lance has been in the Nissan group of people since the early 80's and he has not seen the power to many times the car is making, but he is also the same guy that started stepping away from the car when I fdid my last pulls.

 

Timing on the L engine is a pain to do it correctly. You do need to use the a n adjustable timing gear to get the timing correct. (this is also correct that the timing of the cam should be finalized on the dyno to get the correct power band you want and to make best power from the cam. EVERY engine will be different) The chain tensioner is als a requirement in my opinion. Every head on the L28 had been surfaced, maybe some have not in the dark debths of someones shed. But for the most part lets say the majority of the heads have been surfaced for this discussion.

So you will need to correct for timing of the cam. There are a number of ways of doing this shims under the cam towers (but I must say 5 shims is almost funny ridiculous in my opinion) the other way is to get a cam gear that is adjustable, and for extreme cases a tensioner to correct for the change in geometry.

That is what got to me, people who try to do a change and do their best to spend chump change to complete it. This seems to be a trend in the Zcar world (don't get offended guys that have spent some good amount of money)

Example: I found a shop that did a very good 240mm clutch for me. The assembly cost me 325.00 but the clutch held at least 100 dyno pulls and at the end of the day held very well 500 foot pounds of torque. Try that with a center force, So I am all happy I found a good clutch guy and reffered him to others. I call Robin to congradulate him on his part. I thought this thing would have been toast a long time ago. I talk to Robin and he has a very bad taste in his mouth from the Nissan guys that have called him for a clutch, except one guy in the midwest I think. Robin tells me that he got the old it is to expensive, center force sells their ............ Then they have been more concerned with the color of the pressure plate then the operation of the unit. Now that makes me look bad for one, the Zcar guys are pretty much SH!! in the street with this guy, WHY because they want performance parts for cheaper then stock units. This is a perfect example of what I am talking about with the Zcar community. I have seen and read this concept over and over again, and you know after have spent upwards in the 75K range on my car I have little time for these shade tree mechanic mentality.

 

So I don't know maybe I should have said nothing on the subject and let it go like I always do.

anyway

[Mack]

If you want high compression, source a maxima N47 head. Its got a small chamber, and its a nice heart shaped combustion chamber with a high quench area. no need for all the cam tower shims or shaving the head .080". you may end up with a little TOO high compression, but if you plan on running a big cam, it shouldnt matter that much, as the big cam should lower the dynamic compression ratio a bit.