You're probably right - that would even it out a bit, but if I do that, I need to check the remaining 2 cylinders on that side to make sure it isn't just one rocker arm.

Frank

Checking the other ones is a pi <img src="/forums/images/graemlins/butwiggle.gif" alt="" />, well maybe not that bad. But 8 deg is a bit off. Especially when you can just change a bushing. You have been this thorough, at least put it within a degree or two of the leading cam.

I've chewed on it a bit and decided to spend some time figuring out what's wrong. I'll first swap in another rocker arm as a check against the first. If the rocker is bad.... end of KNOWN problem. If I get the same result, I'll check the other cylinders and then decide. I can always split the difference if the numbers vary on that side.

What concerns me is the geometry that could be screwed up from a prior valve job. The side that's off required a thinner feeler shim for zero lash - could be the rocker, but it could be the valve stem. The issue could be at least partially caused by a difference in valve grind and/or recession and I won't know until I check the rocker and at least one more cylinder on that side.

6-8 degrees bothers me a lot, too. If I ever build another one of these engines, it'll be completely blueprinted.... the variances are very surprising to me.

Frank

The cams are now as good as I can get them, but that's the toughest job I've tried on a 3.0L. <img src="/forums/images/graemlins/scared.gif" alt="" /> It's MUCH more work than it should be to dial in the cams. I've installed the lead cam at 0* and rolled the trailing cam 5* advanced. Everything appears to be on the open/close numbers, and surprisingly, the dots on the sprockets are dead on the timing marks. <img src="/forums/images/graemlins/kewl.gif" alt="" /> The lead cam is at 114.5* C/L and the trailing cam is at 115* C/L. <img src="/forums/images/graemlins/kewl.gif" alt="" />

I did check another rocker and found the first one to be fine. The issue is with the shimming system I tried to use with a hydraulic lifter rack. I used a feeler gauge to take up slack between the jerry-rigged now-solid lifter and the cam lobe. With a shim too thin, the dial indicator reads late-opening/early closing.... as expected. With a shim slightly too thick, the reading goes whacky - usually close to the correct opening point, but very late closing. The big issue is the difference made by only .0005" - and I don't have a set of .0005" differential feeler gauges. I finally realized that if the opening was 4* late and the closing was 4* early.... and the next .001" shim caused the readings to go crazy, the points would likely be very close to spec if a 'tweener shim was used to take up the last .0005" of slack. It's amazing how much difference a very slight amount of slack can make in the readings.

It would be a little easier with a solid lifter adjustable rack - and I suppose the hydraulic system was never designed to to be checked like I did, but it's about as good as I can get it. I even found a difference in the readings when the weather dropped 20* overnight. <img src="/forums/images/graemlins/scared.gif" alt="" />

Frank

Three places to look at a cam....

The very start of the ramp for the lobe. That section has a gradual acceleration to load up the system. The lift per degree of cam rotation is low.

At .050" lift: Your well into the acceleration part of the cam profile. This is a prefered section for rating cams by most aftermarket cam grinders.

To either side of the cams nose just before the dwell section at the nose.

To get a good understanding of a cam I plot the entire lobe out out for lift VS crank rotation and make a graph of it.

It helps make sense of what the valve is really doing. Also in my experiance getting withing 2? on either cam is as close as you practicly need. Closer is beter but not worth killing yourself over.

Basicly if I was testing a cam at the track and I advanced it 2? it would be very heard to tell any thing had changed. At 4? you can measure a differance in performance.

When I was testing cams in my 340 Dodge I would start with the cam straight up and even lash on the intake and exhaust. Then open up the intake lash to see how less duration affected it. Close the intake lash down and open the exhaust up.

Advance the cam and re run the test.... Four cams later.

Every cam got its lobes profiled. You can find some interesting differances in the lobes from cam company to cam company.

One change is on flat tappet cams many after market Mopar cams were ground with a Chevy profile. What does tha mean? Chevy small blocks have a smaller tappet and could only take so many degrees of lift per degree of cam rotation at the start of the lobe.

Since getting the valve off the seat quickly is critical to making the most power for a given cam duration this is not the right direction.

Roller cams I bought had the same lame profile!

Once I changed cam vendors I got a bit more agressive profile and better performance.

What is the point of this? Getting the lobe profile for your cam is great information and I would like to do the same for the non roller cam in the 2.6 and the 3.0.

I want to get a feel for what Mitsubishi was using for cam profiles in its motors. It is possible to get the cams reground and it helps to know the starting points.

Would you be up for plotting a couple of cam lobes?

Kevin

Kevin -

I took readings on the lobes of both cams at opening/closing plus both sides of the lobe @ .050"/.100"/.200"/.300" to get an idea of what was happening, but I didn't save the readings on a plot - just used them to see if the points were the same at a given lift for both ramps..... they appeared to be equal on both sides of C/L. I can do a plot on another engine, but I've already installed all of the valves and springs in these heads.

I *think* I have these about as close as they can be and was very surprised by the difficulty of doing this on a hydraulic lifter assembly. The problem I see with trying to set the opening point of the lobe is the necessity (and difficulty) to get to exactly zero lash.... fairly easy with adjustable rockers, but near impossible with the hydraulic rack. Also, with a forced induction engine, I felt that it it is more important to not close the inlet valve too early than to set the opening point early and have the valve also close early. I'm concerned that allowing the valve to close early will raise the dynamic CR and cause detonation.

To make the job easier, I need to figure out a better method than a feeler gauge because the gauge doesn't follow the curvature of the lifter nose or the cam lobe..... there's always a little stiffness in the gauge that can throw off the reading. If anyone has a solution, I'd like to hear it.

You want the profiles for a 3.0L cam?

Frank

Frank,

I am interested in using a mild roller profile on the 2.6 engine. Since I can have a cam grinder re grind a cam for me a 3.0 profile is an option, its a roller profile, so I'm interested.

I like the idea of a late intake closing and a pressurized intake...

Also even if the valve never hits the seat just zero your indicator to the lowest lift point. That will give you the correct starting point of the cam. The error comes in if the lash adjuster changes height during a reading. Once your solid all you need is to start at the cams base circle.

Kevin

Not really.... it depends on what you mean by "solid" <img src="/forums/images/graemlins/lol.gif" alt="" /> There's "almost solid", "solid" and "too solid". I got different readings from all 3 measurements. It wasn't easy on this engine. <img src="/forums/images/graemlins/scared.gif" alt="" />

After I get this engine running, I'll get the profile on the Montero cams for you. I do need to make a better fixture for the dial indicator, though - that was part of what took so long. The magnetic base wasn't stable enough on the uneven knock sensor bracket. I need to make something that screws onto a head stud.

Frank

Notice in this picture, after swapping pistons and rods to get the least deck clearance variance, 2 pistons are on the wrong side. Unfortunately, the machine shop didn't set them up as full-floating pins and they can't be changed without risking piston damage. <img src="/forums/images/graemlins/angry.gif" alt="" /> I was able to do another round of swapping and got everything within .001", so it's still good, but I'll be looking for a new machine shop.


The engine's ready to go in the bay - Brendan plans to come help with the install this weekend:



325cc/min @ 3bar injectors are on the way.... hope they're enough - should be good for 240HP+..... along with a new NPW fan clutch and a set of NGK plugs 2 ranges colder than OE... depending on what engine <img src="/forums/images/graemlins/lol.gif" alt="" /> The standard Montero plug is a heat range 5, the Diamante 10:1 CR is a heat range 6.... I ordered heat range 7.

Frank

That looks good!

Just wondering, did you put the part on to hook the (engine) oil cooler lines into?