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Discussion Starter · #1 ·
First, start by installing 4 valves into your test head with the lightest valve spring you have. In my case, I used the inner valve springs only from the Skunk2 Pro series valve springs. This keeps the amount of tension you have to keep in the chain to a minimum. Less tension in the chain makes things easier to turn.

Then, you need to rig up something like this to keep the cams in time relative to one another. With a little ingenuity, you can make it happen. Note that I have the intake cam gear pinned at 50deg. I have a custom cam gear that allows me to check clearances at individual cam angles, but that's currently for my eyes only. :p

Here's a shot of the intake valves at full lift.

The exhaust valves at full lift.

Now we start to measure valve to valve (v2v) clearance. I started with the lash set at .010". I didn't have feeler gauges thick enough, so I just stacked two together.

The v2v on my Skunk2 stage II cams, VTEC lobe @ 50deg intake advance and -5 marks on the exhaust cam gear.

Now we re-check at 0 lash.

As you can see, the v2v goes WAY down with valve lash. Let this be a warning to you people out there that like to lash things ultra tight on big cams.


Tomorrow, I should have pictures up from claying the motor. :up:
 

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Discussion Starter · #2 ·
Just got back in from claying the motor. Came up with some interesting results. But first, I realized that yesterday I did not have my exhaust rocker assembly properly lashed. I used a new rocker assembly on the exhaust side. Therefore, I repeated the v2v measurements.

This time the v2v clearance was more in line with what I expected. This was at .010" lash. Quite a different result from last night.

Just for kicks, I checked the v2v at .011" lash. .001" of lash gained .002" of clearance.

Now, on to the claying. The process is very simple, cut out strips of clay, and lay it out on your piston in the following areas. Lock your rockers in VTEC and set your cams to the max settings you think you can get away with. Then assemble the head to the motor. Some people will spray down the combustion chamber roof with WD40 to keep the clay from sticking to the head, but I've found that it's a crapshoot on whether the clay will stick to the piston or the head no matter how much WD you spray on.

Once the head is on the motor, turn the engine over so that the valves make their impression on the clay. Then take it apart to inspect. As you can see below, there is plenty of clearance between the piston domes and the head. The exhaust v2p measured out to .125". I didn't even need to measure to know that the intake v2p is insufficient. The intake v2p measured out to .015". This is one reason why you use old valves when claying a motor. If things do touch, you don't want to trash a new valve.


The conclusion is that the Skunk2 stage II cams are NOT 50deg safe in my motor. I always suspected this. Back when I did the cam test, the skunk2 stage II's (and the IPS k2's) had an insane knock count anytime I'd advance to 50deg on the VTEC lobe, no matter what rpm. My suspicions that I'd have clearance issues at 50deg were cemented when the v2v clearances came up so small with the exhaust rocker lashed correctly. For reference, I have shelf stock CP 12.5:1 pistons with Eagle rods.

One curious note regarding my engine is that TDC occurs well before the factory mark on the crank pulley and cam gears. I've long suspected this, but was able to verify it with a travel gauge. Finding the true TDC point of your motor is a simple affair with the head off and a travel gauge. You setup the gauge perpendicular to the piston and turn the crank while watching the gauge. When the needle reverses directions, you've found your TDC. You can do the same thing with the head on the car, but you'll need a long extension for your travel gauge.


Typically, knowing the "true" TDC of the motor is not necessary, but in my case, I'm degreeing the cams in so I need to know exactly where my TDC occurs. Once I know where TDC is, I can set my exhaust cam centerline accordingly. Oh, and to degree cams, you need to be able to measure the angular travel of the crank. So I made this little thing.


The true TDC was found with the travel gauge and then marked using a pointer. In my case, a steel rule + magnet. It was tough to get the camera in at the right angle, but it was marking zero.


Now, the crank is turned to the desired centerline of 107 BTDC. So 360 - 107 = 253. Again, it looks off, but it's b/c I couldn't get the camera at the perfect angle in the fender well.


Once the crank is set to the desired centerline, setup a travel gauge on one of the rockers or retainers. Loosen the set screws on the cam gear and slowly advance/retard the cam and look for where the rocker arm reaches it's maximum travel. Lock the set screws. You can double check now by actually rotating the crank. If you assume a symmetric ramp rate, you can turn the crank to slightly before the location of the centerline, and zero out the travel gauge. Turn the crank, passing the centerline until the travel gauge hits zero again. Subtract the starting crank angle from the finishing crank angle, and divide by two. Then add to the starting crank angle. That is the location of your centerline. I verified my centerline about 3x over and found that I only needed to retard the exhaust cam 1.25 marks, or 5 crank degrees.


I aslo checked my pistons to see how far out of the hole they are. came out to be .009"


So the moral of the story here is, if you're building a motor with big cams like the skunk2 stage II's or IPS k2's and using an after market rod/piston setup, CHECK YOUR CLEARANCES!!!. It's best to KNOW what you're getting into. I've been told all sorts of things regarding what is safe for my motor and what kind of cam gear settings I should run etc. The reality of the situation was that my motor didn't follow the rules. Now I know my engine's mechanical limits and I can dial it in and hopefully make the most power that it is capable of.

Hope you guys enjoyed this brief tour. :)
 

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nice job chunky...

If you get some time maybe do a quick list of tools/parts needed for each process...
 

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Chunky, I'm confused. How where you able to take picture of the bottom of the head while rotating the chain? How where you also able to check clearance with a feeler gauge while rotating the chain?
 

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Chunky, I'm confused. How where you able to take picture of the bottom of the head while rotating the chain? How where you also able to check clearance with a feeler gauge while rotating the chain?
Look at the second picture.
 

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Look at the second picture.
What about the second picture? How can he see or even take a pictre of the valves in motion inside the combustion chamber, when the head is bolted on the block? Did he install a borescope inside the spark plug hole?
 

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Discussion Starter · #10 ·
that looks like a pretty neat set-up.

you might even want to only set-up 1 intake and 1 exhaust valve to further reduce the spring forces
I thought about doing that, but I wanted to see both valves moving. Even with 4 valvesprings in place, the motion of the cams is very easy to control with a 17mm wrench on the intake cam gear bolt.

Also, I updated with pics of the claying process. :)
 

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Great info,for you to run those cams at 50 deg what would you have to do?
custom pistons i assume :confused:
 

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Discussion Starter · #12 ·
Great info,for you to run those cams at 50 deg what would you have to do?
custom pistons i assume :confused:
In my case I'd have two options.

1) have the valve reliefs on the piston deepened.
2) run a modded cam gear to limit travel to 45deg.

My bottom end is assembled and is not coming apart for this. Plus, I wouldn't want to lose compression just to gain 5deg of cam timing. My engine hits TDC "sooner" relative to the markings, so the extra 5deg of travel probably wouldn't afford me much power. 50deg is only utilized in the lower RPM anyhow.

Since I already have cam gears made that can limit VTC travel to whatever I want (with the option to easily change in the future) that's the route I will use.
 

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just having the inner valve springs installed doesn't affect the outcome of this experiment at all? i would think that with only one cylinder's set of valves installed you could still get pretty precise with measurements.
 

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Discussion Starter · #14 ·
just having the inner valve springs installed doesn't affect the outcome of this experiment at all? i would think that with only one cylinder's set of valves installed you could still get pretty precise with measurements.
The additional spring pressure is not needed. Since you can assume that the metal parts are all inelastic, the only concern is that the spring has enough force to keep the valve from dropping.
 

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If we retard the exhaust cam at 10deg. with the use of an adjustable cam gear, that will equate to 20deg at the crank. Now does that mean that if your VTC was set at 50deg that would actually mean that k-pro will actually set it at 30 deg since we played with the exhaust side by 20deg?

Does that mean that the max degrees the VTC can now see is 30deg and not 50deg?
 

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Discussion Starter · #18 ·
If we retard the exhaust cam at 10deg. with the use of an adjustable cam gear, that will equate to 20deg at the crank. Now does that mean that if your VTC was set at 50deg that would actually mean that k-pro will actually set it at 30 deg since we played with the exhaust side by 20deg?

Does that mean that the max degrees the VTC can now see is 30deg and not 50deg?
You're confusing yourself. The exhaust cam phase and intake cam phase are controlled separately. It is, after all, a DOHC motor. The timing of each cam does not affect the other.
 

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You're confusing yourself. The exhaust cam phase and intake cam phase are controlled separately. It is, after all, a DOHC motor. The timing of each cam does not affect the other.
I'm not making this up, Hondata has stated this.

Mechanically you're right, but the VTC is controlled electronically via the ECU.
 

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Discussion Starter · #20 ·
I'm not making this up, Hondata has stated this.

Mechanically you're right, but the VTC is controlled electronically via the ECU.
Can you link me to where hondata has stated this? As far as I know, everything in a k-series is referenced from the crank position sensor, that includes intake cam phase and ignition timing. Increasing the phase gap of the exhaust cam via an adjustable exhaust cam gear may cause you to throw a code (which you can disable via k-pro) but it doesn't happen with the skunk2 gear retarded all the way.

Anyhow, I'm quite certain that even with a retarded exhaust cam gear, the ecu can, and will, fully advance the intake cam gear.
 
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