Time to go Stage II!

[Alky V6]

Lol. It's not a fancy tool at all but it's way more accurate than what you are doing. I used to check geometry just as your doing but i checked it with the cam installed, lifters in place, using the correct length pushrods and valve springs. I would color the valve tip, roll the motor over then check the wear pattern, just as Chris described. It still isn't as accurate as t&d's stand height tool. My pattern looked good but stand height was off. I use the tool religiously now.

Well, until I come across a tool, simple or not, that can give me accurate results, I guess I'll just keep doing it the way I've always done it. I don't really find it that difficult to do without a tool.
The important thing is, where's the rocker tip at mid-lift.

 

[Alky V6]

This is Jesel's recommendation for rocker geometry. Jesel has been very successful in all forms of racing, including endurance racing such as NASCAR. There are other theorys of what the rocker arm geometry should be, but I like, and try my best to follow Jesel's theory, if the rocker system will allow it.
Some rocker systems may not allow you to get these exact results, which may force you to have to settle with the more traditional, old school geometry.

ROCKERS

What do you look for when setting roller geometry and sweep pattern?
We set our aluminum rocker arm systems with a low pivot geometry which results in the majority of the sweep pattern occurring while spring pressures are at their lower range. The majority of roller travel occurs from zero lash to half lift which results in minimum roller travel for the duration of lift when spring pressures are greatest. At zero lash, the roller should start approximately .050” behind the center of the valve stem, sweep across center and end near the center at full lift.

 

[turbojosh]

Donnie can you just write a book publish it, and I can read it please!

 

[Alky V6]

As the first exhaust event is ending (valve seating), the third exhaust event is just peaking blowdown pressure measured in that cylinder's exhaust port. According to the sim, that is about 88 psi on that exhaust port. How much of that pressure is being seen at the port of the first exhaust event?

Going back to the question of how much backpressure the first exhaust event port is seeing as that exhaust valve is closing, while another cylinder is peaking exhaust blowdown pressure at the same time in the same exhaust system.

Let's study the cylinder firing order. Two other exhaust events have started since the first exhaust event started and began going through its cycle. The first of the other two exhaust events started on the opposite cylinder bank. In a twin turbo application, that exhaust event would have no effect on the first exhaust event. On a single turbo application, it would, but the first event is still expelling gases itself, so any backpressure presented by the first of the other cylinders would have little consequence as far as valve spring pressure is involved.

Now what about the second of the other two exhaust events? This exhaust event is happening on the same cylinder bank as the very first exhaust event. This is where it gets very interesting. Are any light bulbs going off, anyone?

Remember, the exhaust port pressure AND VELOCITY on the 3rd exhaust event is peaking in its respective exhaust primary pipe just as the exhaust valve is seating on the first exhaust event. Both occurring on the same cylinder bank.
Put on the thinking caps, guys.

 

[Alky V6]

What is the primary advantage of using a tuned exhaust system that involves the use of a 'collector'?

 

[turbojosh]

What is the primary advantage of using a tuned exhaust system that involves the use of a 'collector'?

Maybe this ? http://www.epi-eng.com/piston_engine_technology/exhaust_system_technology.htm
Did not Lexus have Yamaha tune there exhaust on there super car?

 

[Alky V6]

Excellent article, turbojosh.

 

[turbojosh]

Excellent article, turbojosh.

Thank you sir! I really don't think it would help for force induction application Donnie, just because of trying to get that exhaust out . I know you have been talking so much about this build, and I feel N/A motor, yes the tuned exhaust system would help because of trying to get the most corrected tune and hp . I know that Lexus LFA depends heavily depended on this type of system Donnie!

I was told by an engineer that there is no point of touching this sytem on this car cause it's so fragile on the exhaust tune set up. I wanted to tell you to that Nelson racing engines are now using a steel for the exhaust valves called Inconel . I'm sure you know about it, and it's my fav alloy in the world. Check it out. thanks for the kind words means allot Donnie.

 

[Alky V6]

I agree, on the inconel material. It's a well known material in the turbocharged ranks. In my application, I don't feel it will be necessary. Exhaust temps with an alcohol engine is a lot different than what is seen with a turbocharged gasoline application.

 

[turbojosh]

I agree, on the inconel material. It's a well known material in the turbocharged ranks. In my application, I don't feel it will be necessary. Exhaust temps with an alcohol engine is a lot different than what is seen with a turbocharged gasoline application.

I just talked to Prasad, about this just now, and I think Nelson is using it cause of the friendly characteristics it has on a high hp street motor, but I feel it's not worth it. I'll try and ask Nelson when I talk to Larry when I have a chance cause I am curious, but I will say this stuff is a pain to machine. stuff is alien alloy. As well the goverment wants the scrap metal. There are so many pain in the arse laws on this stuff. Makes titanium look silly.

 

[Alky V6]

It was interesting, a point in the article that turbojosh linked to, about the difference in cross-sectional area between a round tube and an oval tube, even though the circumferences of the two shapes are the same. Moving from a round tube and creating an oval section at the end of the tube to provide for chassis and ground clearance, creating 77% less cross-sectional area in the oval section compared to the round section, and creating a restriction to exhaust flow at high rpm.

 

[Dusty Bradford]

Don. Here's the high tech rocker stand height tool in action. I still check pattern but only after using this first. It hasn't been wrong yet and is more accurate than the dye. Used it on a cam with .900 lift where by sight the pattern was correct but the engine kept backing off the rocker stand bolts from harmonics. This stand height tool allowed me to find the issue when my eyes told me the wear pattern was correct.

Ignore the pushrod height comment........it's not for measuring pushrod length.

http://www.circletrack.com/techarticles/ctrp_0609_pushrod_length/photo_12.html

 

[Alky V6]

Don. Here's the high tech rocker stand height tool in action. I still check pattern but only after using this first. It hasn't been wrong yet and is more accurate than the dye. Used it on a cam with .900 lift where by sight the pattern was correct but the engine kept backing off the rocker stand bolts from harmonics. This stand height tool allowed me to find the issue when my eyes told me the wear pattern was correct.

Ignore the pushrod height comment........it's not for measuring pushrod length.

http://www.circletrack.com/techarticles/ctrp_0609_pushrod_length/photo_12.html

Do you have different tools to use depending on maximum lift at the valve?

 

[Alky V6]

I used my rocker geometry on the Stage I engine with Jesel rockers and didn't have to adjust the valves for... what was it? I posted the maintenance logs for the valve adjustments in this thread. I think it was well over a year that I didn't have to change the adjustment on one single valve. Not one single valve for over a year. Inspection of the valvetrain during this latest teardown of the Stage I showed the sort of valvetrain wear that I would have expected from a street engine. It's hard to argue with results like that.
I think I'm OK without the tool. Thanks anyway, Dusty.

 

[Dusty Bradford]

Do you have different tools to use depending on maximum lift at the valve?

Yes. Different tools for different lifts. If you put the tool flush against the valve stem and have a gap, you have a simple math equation that tells you exactly how much the stand has to be shortened to get it perfect. Same if the stand is too low. You can shim and re-shim numerous times then set-up your test or you can do it once with this tool. It saves time if the stand height is off. Fortunately most of the stage 2 stuff was already set-up by nascar teams with matching rocker stands so as long as you don't change valve length, the geometry won't need to be changed.

 

[Alky V6]

Some sweep pattern measurements.
.145" wide sweep pattern from fully seated to full lift.
.100" sweep from 1/4 lift to full lift.

.095" sweep from fully seated to 1/2 lift.
.050" sweep from 1/2 lift to full lift. The pattern centered just slightly outboard from being perfectly centered on the valve tip.

The picture is of the sweep pattern from 1/2 lift to full lift. The contact starts in the middle of the valve at 1/2 lift, moves outward, then back inward as the valve lift increases, until the roller ends up back in the middle of the valve at the point of full lift. This tiny distance of sweep and this positioning of the sweep is occurring when spring pressure is highest in the valve lift cycle.

 

[Alky V6]

Yes. Different tools for different lifts. If you put the tool flush against the valve stem and have a gap, you have a simple math equation that tells you exactly how much the stand has to be shortened to get it perfect. Same if the stand is too low. You can shim and re-shim numerous times then set-up your test or you can do it once with this tool. It saves time if the stand height is off. Fortunately most of the stage 2 stuff was already set-up by nascar teams with matching rocker stands so as long as you don't change valve length, the geometry won't need to be changed.

If these new valves are the same length as what were used in these heads when they were raced by the previous owner, then it's interesting to note that they also subscribed to the Jesel style rocker geometry and not the more old school and common geometry suggested by most other companies and individuals.

 

[Alky V6]

Pushrod to rocker adjuster angularity at zero lift: 20 degrees
Angularity at max lift: 13-15 degrees.
Eyeballed against a protractor.

 

[Alky V6]

I know the popular theory is to see the rocker arm adjuster cup go perpendicular to the pushrod by 1/2 lift. I subscribe to seeing it go perpendicular somewhere between 2/3 and 3/4 lift. And that is exactly what I'm getting with this setup. In fact, it's right at 3/4 lift.

 

[Alky V6]

I mapped out the lifter bore to see how the lifter is getting its oil. The circle with the crosshatch in it is the 1/8 inch feed hole in the lifter bore supplying oil from the oil galley in the block (TA block) to the lifter. The diagram shows the lifter at zero lift and at full lift (.421" lobe lift).
The smaller hole off to the side of the lifter body is the .090" diameter edge orifice that feeds the pushrod and upper end. You can imagine that if the edge orifice had been centered, as it would be if the pushrod seat in the lifter body were centered instead of offset, the upper end might get too much oiling.