newbie to rocker geometry.. 1.25 rockers on 110cam

[starbugs1977]

Hi everyone, ok ive searched and searched on here for how to setup rocker geometry, but im struggling to find a step by step instructions on how to do this.

I have a twin port 1641 with and engle 110cam and twin 40 Kadrons, msd 6AL ignition,electric fuel pump with regulator, stock heads, direct port nitrous oxide and controller. I have bought a set of 1.25 rocker arms that i niaevly thought i could just fit up onto my stock shafts bolt em on set clearance and of i go.. apparently not. So im looking for a step by step guide on how to do this that i can follow/learn from....

From what ive read i may need rocker arm shims and shims for under the rocker shaft itself along with shorter/longer (i cant figure out) pushrods. I dont have a dial in guage.

ive watched a few youtube videos but most are as clear as mud

My motor has only coverd 4500miles and is in perfect running order.

Thanks in advance

tony

[hemicat]

All you need to set the geometry itself is your good ol eyeball. If you got solid shafts (Bolt on ends instead of the spring washer and clip) for the rocker arm set up then yes you will need a set of rocker shims for between the rockers themselves. But we will get into that later. When setting geometry all you are looking to do is make sure when the valve is at half lift the adjuster screw is in line with the valve stem. That way you have even amount of travel on both sides of the adjuster screw and an even amount of side load on the valve stem. If you have more travel on one side than the other then you can either shim the stand or will need to get shorter or longer pushrods. They make an adjustable pushrod tool that makes this job much quicker and easier. If you need info on how to shim the rocker shaft let me know and I will help you out with that too.

[FJCamper]

Hi Tony,

Being new to rocker geometry, the first thing to know is why we need to set it. Originally, the VW valve adjuster screw tip, where it touches the end of the valve, needed to hit the valve stem tip slightly off center, so it forced the valve to rotate as the engine ran. The idea was this kept carbon buildup off the valve head contact surface with the valve seat, and promoted more even wear overall.

But, over at Porsche, as the 911 engine was being developed, one day after a few (one or two or eight or ten) beers, they took exactly the opposite approach, designed what we now call the "elephants foot" adjuster, and worked it into the 911 six-cylinder valve train. All the "geometry setting" required was the flat face of the swivel foot hit the valve stem dead center. And it worked. The valve even continued to rotate, turned by slight spiral forces from the collapsing and expanding valve spring.

It didn't take long for "911 adjusters" to make it to VW (same thread and everything) and engine builders work became a little easier.

The good news is a set of 911 adjusters will work for you. The bad news is it's hard to get good quality ones, even under brand names. At one race, we had a brand new set fail where about half of the adjusters just came apart.

You will have to shim out your rockers for 1.25. Shim to the absolute minimum to get a proper valve lash adjustement without compromising, meaning too little threads left on the adjuster for the locknut to hold.

If you really want to get lazy, buy a set of stock-length steel pushrods. Your engine specs don't require chromoly. Now, you have no valve lash to get right. Just adjust to a "loose zero" which means (cold) that you tighten down on the adjuster until the pushrod cannot be turned with your fingers. Then loosen it so the pushrod will turn, but no more.

No more rocker geometry or valve lash problems. The only thing you're giving up is some upper RPM's due to heavier push rods.

What's your Kad's specs, venturi, main jets?

FJC

[Marc]

...All the "geometry setting" required was the flat face of the swivel foot hit the valve stem dead center...FJC

That's NOT what the term "rockerarm geometry" is in reference to. Hemicat said it right. Lateral location of the contact point, valve rotation and rocker sideplay settings are but tangentially related subjects.

It doesn't matter what style of valve adjusting screw is used, if the rockerarm geometry is incorrect you'll have accelerated guide wear and elevated oil temperatures (where there's wear, there's heat!). There's even a little "free" horsepower unlocked when it's right.
With either 911 or Mazda adjusters, the rockerarms typically need to be ground away on the underside to make room for the bulkier adjuster in order to get the geometry right. Because the valves are not parallel to the rocker studs, shimming out the shafts to compensate for too-long pushrods will make the contact point with the valve stem climb upwards - it's the easy-sleazy way to make valve adjustment possible, but it's not the right way to address the problem.
The #1 cause of failure of either type is neglecting to check that they don't run out of travel at full-open and full-close - which is almost certain to happen if you merely toss them on with valve lifts nearing .400". Happily, to avoid that the best place to start is to get the geometry right - that'll also allow the maximum range of travel before the adjuster bottoms out. Even the highest-quality, most expensive adjusters there are can't survive sloppy assembly practice; the cheap ones are much less likely to fail when they aren't overstressed, either.

[hemicat]

Also some companies sell aluminum "cut to length" pushrods. I used chromoly for a little while and will NEVER do that again. The steel expands much less than the aluminum head and will easily allow upwards of .030" lash when hot. Been there, measured that. The cut to length have one tip already installed and you cut them to the exact length needed and you just hammer the other tip on. Do not try to get all fancy and use any sort of press, it will pre-bend them for you. Just FYI, and dont ask how I know. LOL Just thought I would pass along the info if you need to go that route.

[Piledriver]

How hot do your heads get?
I burned my fingers doing the same sort of testing and never read much over .008" at the hottest I could manage.
(long period of idling with the air seal boot off, recirculating hot cooling air. CHT was ~400F)

Most folks recommend CrMo pushrods for safety reasons: the clearance at least goes the right way, rather than burning the valves. Of course the std adjuster tips tend to be the big wear point IME.

[hemicat]

Really dont know the temp when I was running wih them. Didnt have any temp gauge at that point but now I run mostly around 280 and idle around 230 under the #3 plug. Still havent finished tuning but think it is getting close finally.

[FJCamper]

Hi Tony, Marc;

Actually I agree with Marc, but I didn't go into the detail.

When I wrote about Porsche developing and adopting the swivel feet, my comment "...All the "geometry setting" required was the flat face of the swivel foot hit the valve stem dead center" was about the Porsche, but on rereading it, it sounds like I was referring to both the Porsche and VW.

Checking half-lift and grinding out some swivel cup clearance is still necessary but to be specific, on the swivel feet you need to have the face of the adjuster hit the valve stem flat and dead center. That actually reduces or eliminates sideload on the valve stem, and saves wear. It does not rotate the valve.

Oblong center shaft valve guide wear comes from sideloading.

And again, to be specific, just using swivel feet does not exempt you from error. I use a jig with an old head and valves with hardware store springs behind them to set up my adjuster-to-valve stem contact, where I can manually depress the valve all the way down with the rocker arm, to make sure the rocker arm spacing on the shaft is right. Then, with the rocker spacing right, I put the rockers on the actual head(s) and look for binding of the valve spring coils or contact of the adjuster cups with anything as I rotate the engine.

This is where I'm looking for "full lift" but I have my own way of doing it. I have painfully measured various lifts with my dial indicator and judge the depression distance of the valve stem end from a straight edge along the row of valves. I set a caliper to gauge the depression.

With the head on the engine, torqued down, adjustable pushrods in place (I have four) I rotate the engine until I have the desired depression on whichever intake or exhaust valve I'm measuring, and set the pushrods to that length.

In doing this, I find if I need rocker shims to get the full lift. I'll either have pushrods cut or rockers shimmed, depending on the need.

Now, here's the caveat. I only build race engines and valve guide wear is not so important to me as it would be for a street engine. So I'd stick to the book method if you need daily driver reliability.

FJC

[Piledriver]

Google for "mid-lift".

Jake used to have an excellent procedure posted, not sure if that still exists...
(it was probably for T4s, but the procedure is identical)

[FJCamper]

Hi Piledriver,

Since we're among friends here, here's an admissin. Back in the day I used to read so much about rocker arm geometry and found so many different opinions and techniques, I developed my own way of observing and implementing not just geometry, but other mechanical things.

I took an engine case, put a cam and lifters in it, and a crank with a cam drive gear. No rods, pistons, oil pump, nothing. On one side I had empty cylinders and a head with valves and springs. That way I could rotate the crank and with pushrods in place, measure exactly how far a pushrod moved, and with a set of rockers in place, measure how far the rocker opened the valve with my straight-edge reference along the tops of the valve stems.

I found advertised lift and what I was measuring usually didn't agree, so I just said screw it, and went for one observable measurement. How far did any one specific cam actually open an intake valve? I'm not talking about duration, overlap, etc. Just lift.

I became very familiar with a few Engle and Scat cams, and while there were always some minor variables in lift, a 110 was very close to another 110, etc.

Then I learned how to make a head jig with very weak springs so I could move the valves easily to set up rocker arm to valve stem contact, and of course I never assumed all valve stems were the same length.

What made me do this was my first experience in putting a set of 1.25 ratio rockers on my daily driver back in the very, very early 1970's. I barely knew how to adjust valves. I had no idea then about shimming, cutting pushrods, whatever. So as I learned I made my own mockups.

I have long since learned the shop manual valve geometry, but being old and set in my ways, I still do it with my mockup heads.

I have never used more than a set of 1.25 rockers, preferring to let the cam do the lifting, but I know there are some good cam/rocker combos out there. My engines run well, and I believe I'm getting all out of any cam I use within my favored and familiar few.

FJC

[Piledriver]

"Works is always Job 1", or should be.

Generally, if you do the work to achieve max lift, you have probably found as ideal a geometry as possible given whatever you have to work with.

Not all rocker setups are "good", geometry wise. The stock VW stuff isn't a bad place to start

The Porsche 911 style elephant foot (or any ball setup) changes geometry far more than it might appear, but setup properly worn guides should be a thing of the past. (the stock pivot is at the face of the valve, with a ball/swivel foot its much higher, at the center of the ball)

The only reason I posted the "mid-lift" note was I always find it easier to get from A>B if I understand what I am trying to accomplish. OTOH some of the Mid-Lift website is as clear as mud.

This one is about as clear as it gets:
If you have ball end or 911 adjusters, pretend they are roller rockers.
Pivot is in center of the pivoting ball.
Start here:
http://www.mid-lift.com/TECH/TECH-Installed-G2.htm

Note the ideal geometry/setup is 100% cam lift dependent.
Once you are reasonably close, the 911 style adjusters make things very forgiving.

A hardened .060" thick washer under T4 rockers with 911 swivel feet (rockers modified per usual for adjuster clearance) is usually a pretty good starting place, and T1 8mm rockers with 911 feet I'd probably modify rockers and start in the same way.

[FJCamper]

Hi Piledriver,

Thanks for the link.

The reason I ended up with so many adjustable pushrods over the years was the first one was my Engle 110 cam and stock rockers rod, on a un-flycut stock dual port head. I kept it adjusted and locked just for that parts combo.

The variables are always the head and the valve stem length.

My purpose was always to make sure I was getting full valve lift and that I had no valve spring binding.

I know my mock-up "monkey-see monkey do" routine is simplistic, but with a set of known-measurement parts on hand and all you have to do is see if the pre-adjusted and locked adjustable pushrod drops in and works, it made my life a lot easier.

I've never thought my way was any more simplistic than stuffing some Plastigage or modeling clay between two moving parts and see what was really happening rather than what I calculated was happening!

FJC