Pushrods, and valvetrain geometry Options

[MattR]

Im sitting in my apartment right now about 45 miles from my car and trying to think of EVERYTHING that can (and will) go wrong with my 914 when I try to start it up this weekend. I started thinking about the pushrods and valvetrain geometry. I used stock pushrods, but the heads have been flycut by Rimco and Im using a web 494 cam. From what Ive read online, proper valvetrain geometry is set by measuring the rocker arm to be perpendicular to the ground at half the duration of the cam. My questions:

This is a 2056 with webber 40s and is meant to be a driver. Should I eyeball it? Or do I really have to setup a jig with a dial indicator to get the proper geometry?

If I do have to get new pushrods for the geometry to be correct, should I go with chromoly? They will expand differently then stock aluminum, right? How do I account for that on the valve adjust?

[SLITS]

If they took a nominal flycut for cleanup, it should not be a great problem. Generally, you would cut the pushrod the same amount as the head was flycut to maintain the factory geometry. The three worst problems are:

1.) Side loading the valve, wearing the guide sooner

2.) Adjustor screws hitting the rocker box cover

3.) Not having enough screw length to compensate before pushrod bottoms into rocker.

#1 is prolly the only "problem" you would face under your described conditions.

Oh, I forgot....engineering student? (IMG:http://www.914world.com/bbs2/html/emoticons/lol2.gif)

[MattR]

QUOTE (SLITS @ Jun 29 2005, 02:06 PM)

Oh, I forgot....engineering student? (IMG:http://www.914world.com/bbs2/html/emoticons/lol2.gif)

i need slides (IMG:http://www.914world.com/bbs2/html/emoticons/rolleyes.gif)

thanks ron, I'll check that out.

[john rogers]

I'd call the cam company and see what they say to do. For example, when I had my stroker 4 race engine, Crower said since I had a very high lift cam, type one lifters, cromo steel push rods and roller rockers to set the lash with the engine HOT and just enough clearance so you could spin the push rods. The push rods were all custom cut and the rockers were set by dial indicator I believe? If you are off the best case is some lost power due to bad valve adjustments, worst case is the valves hit the pistons! I'd say be as conservative as possible with the assembly. Good luck.

[Demick]

You can put shims under the rocker assemblies to compensate for the flycut heads. I put ~.035" spacers (shims) under the rockers assemblies to get proper valve train geometry.

Demick

[nebreitling]

yup, i shimmed up my rockers ala demick and just eyeballed it. if you have a good eye, you can do it w/out a dial indicator.

[MattR]

Alrighty. Thanks guys! I'll take pictures when my car is on the road (IMG:http://www.914world.com/bbs2/html/emoticons/cool.gif)

[JoeSharp]

Matt: Sorry about not replying to your PM, I've been perty bussy. I have an adjustable push rod for measuring the lenght of the push rod.
:PERMAGRIN: Joe

[McMark]

The more work you do now, the more headache you'll save later. It just depends on what kind of rebuild you have going. Looking for lots of miles or just a quick and dirty rebuild. Eyeballing will work. A dial indicator, adjustable pushrod, and a set of rocker shims will set you up with a longer lasting engine.

[Type 4 Unleashed]

The push rods, have no bearing on the rocker arm Geo, the push rod length, only has to do with where the adjusters are set.

The Cam, Rocker Ratio, Valve length, and how much the seats have been cut , are what change Rocker Geo.

A dial indicator is needed, to find 1/2 lift, you can eye ball it or use a straight edge (Like one of those little 6" machinist rulers) once you find 1/2 lift.

After you set the rocker geo, is when you cut your push rods, leaving the adjusters enough room to adjust.

[Jake Raby]

QUOTE

The push rods, have no bearing on the rocker arm Geo, the push rod length, only has to do with where the adjusters are set. The Cam, Valve length and how much the seats have been cut , are what change Rocker Geo.

I don't think I have ever read a ststement that I disagree with more than this one But what the hell do I know-

Proper geometry is attained through adjuster position, the relationship of the rocker shaft assembly to the head (impacted by valve installed height greatly) and overall pushrod length.

Pushrod length is the biggest part of correctly setting rocker geometry- Without the proper length pushrod you will not attain optimum net valve lift and more than likely your geometry will never be effectively set.

[Type 4 Unleashed]

QUOTE (Jake Raby @ Jun 29 2005, 10:45 PM)

QUOTE The push rods, have no bearing on the rocker arm Geo, the push rod length, only has to do with where the adjusters are set. The Cam, Valve length and how much the seats have been cut , are what change Rocker Geo. I don't think I have ever read a ststement that I disagree with more than this one But what the hell do I know- Proper geometry is attained through adjuster position, the relationship of the rocker shaft assembly to the head (impacted by valve installed height greatly) and overall pushrod length. Pushrod length is the biggest part of correctly setting rocker geometry- Without the proper length pushrod you will not attain optimum net valve lift and more than likely your geometry will never be effectively set.

Here is a copy of the instruction sheet for Pauter Type lV Ratio Rockers, they seem to think that pushrod length has no effect on the rocker geo, but what do they know?

But I did forget to include lash caps as something else that effects rocker geo.

Let me try this way, with the Pauter rockers, the adjusters are on the pusrods, at 1/2 lift the the geo is set, the adjuster is 2 to 3 turns out from bottoming out in the rocker as recommended, your pushrod is at X length. Now lets shorten the pusrod by X -.500, and make up the pushrod shortage in the adjuster by adjusting it out 1/2". The pushrods were shortened 1/2" but the rocker geo setting WAS NOT CHANGED. The end may bind up now fully closed, but the geo was not changed.

[Dave_Darling]

QUOTE (V6914 @ Jun 30 2005, 12:03 AM)

Let me try this way, with the Pauter rockers, the adjusters are on the pusrods...

I think that's what's got you. The Pauter rockers are very different--the fact that the adjusters are on the pushrod side means that you can just lengthen the distance between the rocker and the pushrod if you shorten the pushrod. And you can shorten that distance if you lengthen the pushrod.

The stock rockers have the adjusters at the valve end, of course. So when you change the pushrod length, you are (effectively) rotating the rocker arm. This does change the geometry.

Pauter rockers == apples
Stock rockers == oranges

--DD

[Jake Raby]

The sheet that you received from Pauter is not accurate for anything OTHER than their rockers- Their adjusting screw is on the bottom and the rockers have a roller tip so the characteristics of setting geometry changes drastically over what most people will experience here on this forum.


The roller tip drastically effects the "push" effect of the valve during the opening event...

BTW- They must not know everything- The camshafts they provide to match their rocker arms do not have correct ramp speeds and their rockers are not self oilers- That means if you are not screaming around at 5K RPM your valve guides, springs and the like are getting very minimal oil.

I avoid these rockers for street engines, no matter the displacement...... Camshafts that have the proper ramp speeds for them generally don't have over .430 lift anyway.

It amazes me what people can misconstrue from reading directions- I write my own.

[Type 4 Unleashed]

Here is an article out of the 2002 VW Trends

Where it says that varying the length of the pushrods is used to achieve maximum cam lift, and shimming the rocker pads to achieve the correct geo, and it also says both of these vary depending on the cam size and the valve installed heights.

This guy in the article is also named Jake (IMG:http://www.914world.com/bbs2/html/emoticons/happy11.gif)

[914werke]

QUOTE

That means if you are not screaming around at 5K RPM your valve guides, springs and the like are getting very minimal oil.

Jake not to be agrumenitive but I thought the opposite was true? That drainback to the sump was a challenge because so MUCH oil was trapped atop the heads (im lazy or id go a searchin in a earlyer post that showed how much in a windowed valve cover?) (IMG:http://www.914world.com/bbs2/html/emoticons/wacko.gif)

[Type 4 Unleashed]

QUOTE (rdauenhauer @ Jun 30 2005, 10:49 PM)

QUOTE That means if you are not screaming around at 5K RPM your valve guides, springs and the like are getting very minimal oil. Jake not to be agrumenitive but I thought the opposite was true? That drainback to the sump was a challenge because so MUCH oil was trapped atop the heads (im lazy or id go a searchin in a earlyer post that showed how much in a windowed valve cover?) (IMG:http://www.914world.com/bbs2/html/emoticons/wacko.gif)

I, remember that also, it was a picture of a type 1 cover with a window, showing lots of oil, I don't know if the type lV, would be the same? Someone asked if the oil would help head cooling? And someone responded no, if it didn't help head cooling, at the very least it would help valve spring cooling, which would be a big benefit to help prolong valve spring life. And maybe even Ratio Rockers without oilers?

I remember, Jake saying he restricts oil to the rockers, maybe he doesn't think prolonging valve spring life, is important? (IMG:http://www.914world.com/bbs2/html/emoticons/happy11.gif)

[Type 4 Unleashed]

QUOTE (V6914 @ Jun 30 2005, 10:40 PM)

Here is an article out of the 2002 VW Trends Where it says that varying the length of the pushrods is used to achieve maximum cam lift, and shimming the rocker pads to achieve the correct geo, and it also says both of these vary depending on the cam size and the valve installed heights. This guy in the article is also named Jake (IMG:http://www.914world.com/bbs2/html/emoticons/happy11.gif)

I, referenced this article in setting up my rockers with 911 adjusters, this was my first stept in geeting a set of heads ready for the Pauter Rockers.

The springs are 1.250" small block chevy, Installed heigth of 1.820, I'll be able to run over a .600" lift cam, as soon as I figure out a couple more problems.

[Jake Raby]

Processes like cryo and REM coupled with very high quality valve springs ane even guides have decreased the need for the valve covers to be absolutely filled with oil. With these components and processes the stock rocker is VERY beneficial because it gives adequate oil delivery without all the oil ending up in the valve covers and out of the sump. With the stock rockers the oil is fed up to the rocker shafts, through the rockers and up to the adjuster and splashed directly on the valve guide and spring. This is by far the best method for engines running at lower speeds that do not operate at 5K RPM+ at all times.

The Pauter rockers pour oil out of the adjuster AT THE BOTTOM of the rocker and depend on RPM to splash the oil up to the only components that need it....... Generally they just dump the valve covers full of oil and guys wonder why they can't keep the oil light off in a hard left hander- All their oil is in the valve covers and can't return to the sump fast enough!


As for the article and valve train geometry:
There is no standard, there are numerous settings deeper inside the engine that can attribute to the ease/difficulty of attaining proper rocker geometry.

The statements I made in that article are generalizations but many times the length of the pushrod AND proper shimmming of the rocker assembly are both required to attain both optimum net lift at the valve AND proper geometry at 1/2 valve lift.

Now, If you guys want to sacrifice all the lift that your new bad ass camshaft is capable of because you are too damn hard headed to listen- Thats all on you.. Read all the books and articles you want but nothing supercedes doing something, tearing it down and seeing the results. I do this dozens of times a year and have gained my views through not just assembly but also through tear downs and failures.

BTW- Lets hope that you are running a larger diameter lifter on that .600 lift cam or a very slow ramp speed or you'll be chewing up lifters as fast as you can change them, and all that force of those heavy springs are multiplied times the rocker ratio at the cam- don't forget that... Higher rocker ratios increase the load of every component down stream of the centerline of the rocker shaft.

Rocker geometry is so important and misunderstood that I have dedicated an entire handboook volume to it- It'll be ready for sale by the end of the year so add it to your christmas list... It is much more in depth than the article in trends that was butchered by their AFU editor- I gave him a real ass chewing for chopping the important parts of that article away without a resubmission and proof read.

[Type 4 Unleashed]

QUOTE (Jake Raby @ Jul 1 2005, 12:10 AM)

Processes like cryo and REM coupled with very high quality valve springs ane even guides have decreased the need for the valve covers to be absolutely filled with oil. With these components and processes the stock rocker is VERY beneficial because it gives adequate oil delivery without all the oil ending up in the valve covers and out of the sump. With the stock rockers the oil is fed up to the rocker shafts, through the rockers and up to the adjuster and splashed directly on the valve guide and spring. This is by far the best method for engines running at lower speeds that do not operate at 5K RPM+ at all times. The Pauter rockers pour oil out of the adjuster AT THE BOTTOM of the rocker and depend on RPM to splash the oil up to the only components that need it....... Generally they just dump the valve covers full of oil and guys wonder why they can't keep the oil light off in a hard left hander- All their oil is in the valve covers and can't return to the sump fast enough! As for the article and valve train geometry: There is no standard, there are numerous settings deeper inside the engine that can attribute to the ease/difficulty of attaining proper rocker geometry. The statements I made in that article are generalizations but many times the length of the pushrod AND proper shimmming of the rocker assembly are both required to attain both optimum net lift at the valve AND proper geometry at 1/2 valve lift. Now, If you guys want to sacrifice all the lift that your new bad ass camshaft is capable of because you are too damn hard headed to listen- Thats all on you.. Read all the books and articles you want but nothing supercedes doing something, tearing it down and seeing the results. I do this dozens of times a year and have gained my views through not just assembly but also through tear downs and failures. BTW- Lets hope that you are running a larger diameter lifter on that .600 lift cam or a very slow ramp speed or you'll be chewing up lifters as fast as you can change them, and all that force of those heavy springs are multiplied times the rocker ratio at the cam- don't forget that... Higher rocker ratios increase the load of every component down stream of the centerline of the rocker shaft. Rocker geometry is so important and misunderstood that I have dedicated an entire handboook volume to it- It'll be ready for sale by the end of the year so add it to your christmas list... It is much more in depth than the article in trends that was butchered by their AFU editor- I gave him a real ass chewing for chopping the important parts of that article away without a resubmission and proof read.

I liked your edit. (IMG:http://www.914world.com/bbs2/html/emoticons/happy11.gif)