What rocker arm ratios do people see? Options

[stugray]

I am adjusting the valve geometry while putting in a Raby 9700 cam and I am seeing .38 on the exhaust cam lift and .496 at the valve (an exh rocker ratio of 1.3) and I have a .39 on the intake with a .546 at the valve ( an int rocker ratio of 1.4) is this what everyone else gets for rocker ratios:

Intake rocker ratio = 1.4
Exhaust rocker ratio = 1.3

These are the 1.7 (1.8?) rockers that accept the 911 swivel feet.
I am using the swivel feet, have modified the rocker faces, adjustable push rod, and zero lash to do the meaurements.

Do those rocker ratios look like stock?

I want to take 50 thousandths off the Combustion chambers to increase the CR, but my measurements say I wont have enough clearance on the Intake valve once I shave off 50 thousandths.

I only have ~0.075 clearance now from the piston to the Int valve as it is with a deck of 0.030 and everything else (crank & rods) stock - flat top 96mm pistons.

That Intake valve travel of ~0.55 looks huge to me. Anyone else care to comment?

Stu

[Dave_Darling]

The stock ratios range from 1.3 to 1.4, so you're in the range.

--DD

[edwin]

Call European machine works?
They've helped in the past haven't they?

[stugray]

Dave - So is it possible to find an intake rocker with a ratio of 1.3?
Or are all intake rockers going to be 1.4?

The .550 intake valve lift seems like a LOT.
I didnt want to have to relieve my pistons for clearance if I could avoid it.

Edwin - I will probably give them a call. Someone here stated that Jake's cams are just rebranded from someone else - anyone remember who that was? ( I seem to recall webcam). I would prefer to give them a call.

Stu

[monkeyboy]

I believe WebCam actually makes them, but they are his grinds, not a simple rebranding.

[brant]

I too believe they are built to order...
custom order by a respected builder
proprietary design

[Mark Henry]

I too believe they are built to order...
custom order by a respected builder
proprietary design

Yep, even if you can figure out the exact specs WEB won't make it for you.
Why don't you ask Jake about it....

[Dave_Darling]

Dave - So is it possible to find an intake rocker with a ratio of 1.3?
Or are all intake rockers going to be 1.4?

I am not certain, but I believe that the intakes tend to be around 1.4:1, while the exhausts tend to be around 1.3:1, but the numbers are not completely consistent.

--DD

[bobhasissues]

When you say "at the valve" are you actually measuring at the retainer?
You should have received a cam card from Jake that tells you what the lift should be. If you are following his geometry instructions, then everything you need to know can be obtained with the info on the cam card.

If you didn't get one, it's likely they did not trust you with it after your rant sessions regarding Jake.

Why have you determined you need a CR of 10.5 to 1?
Altitude?

[stugray]

bob -

When you say "at the valve" are you actually measuring at the retainer?

Yes - and simultaneously at the pushrod to verify the rocker ratio.

You should have received a cam card from Jake that tells you what the lift should be.

I did - it shows a lift of .368 on both the intake and exhaust.
Nowhere in his valve geometry instructions does he mention that you must multiply that number by the rocker ratios to determine the valve lift. I only found him mentioning it after searching through his forums. Then you need to know YOUR rocker ratio.

If you are following his geometry instructions, then everything you need to know can be obtained with the info on the cam card.

NO - you cannot. you need to know YOUR rocker ratio.

If you didn't get one, it's likely they did not trust you with it after your rant sessions regarding Jake.

I spent over a thousand at Jakes store before EVER having a "rant" and the "rant" was because he told me to FUCH off for asking perfectly valid questions about his products (that were NOT HIS products after all...). My only questions were about the conflicting instructions included with his product. He said one thing on the included documentation, and another when I asked on his forum. When I questioned his answer he deleted my entire thread and pretty much said "no one questions MY answers on MY forum" ( I thought that was what it was for...).

Why have you determined you need a CR of 10.5 to 1?
Altitude?

Yes - this is a 2.0L vintage race motor with 40 IDFs and to be run at greater than 5000 feet altitude.

Stu

[bobhasissues]

Stu,

Nobody will try to help you if you continue with your argumentative attitude.

MY Raby cam card shows the peak cam lift and peak valve lift based on 1.3 rocker ratios. I would think your card shows the same.

All factory Type IV lifters regardless of 1.7, 1.8 or 2.0 have a 1.3 ratio. Go with 1.3, stop trying to re-evaluate a known value.

Jake's article explains that shims and pushrod lengths will affect total lift.
Look at the value for peak lift valve on your cam card and shoot for that.

[stugray]

bob-

Nobody will try to help you if you continue with your argumentative attitude.

I see nowhere in the previous post that could be considered "argumentative". Sorry if it seemed as such it was "just the facts".

MY Raby cam card shows the peak cam lift and peak valve lift based on 1.3 rocker ratios.

Mine does not mention rocker ratios, but here is what is does say:
Intake Exhaust
Valve Lift: .368 .368

I dont need to post any further info to show that those numbers clearly represent Cam Lobe lift.
Since my measured Valve lift is:
Intake Exhaust
Valve Lift: .548 .480

So it is clear that THIS cam card from Jake shows "cam lift" not "valve lift".

All factory Type IV lifters regardless of 1.7, 1.8 or 2.0 have a 1.3 ratio. Go with 1.3, stop trying to re-evaluate a known value.

Sorry, but I just measured my exhasut & intake rocker ratio and "they" are not 1.3.
They are 1.3 - Exhaust and 1.4 - Intake, just as was verified by others above.

So still trying to understand but:

Look at the value for peak lift valve on your cam card and shoot for that.

wont work unless I want to change to 1:1 rockers

Perhaps what I got as a "cam card" and what you got are very different.
I would just scan the damn thing & post it, but I'm sure somebody would say that's not right...
It only has 8 numbers on it and 4 of them have "*" astericks but no footnote...

Stu

[ChrisFoley]

I'll gladly trade you a set of 1.3 ratio, 1.7L intake rockers. (IMG:style_emoticons/default/smile.gif)

[Mark Henry]

Dude the reason I don't help you is simple....most of the time it sounds like your off your freaking meds. (IMG:style_emoticons/default/blink.gif)

WEB cam supplied the cam card, it's no different from how all cam grinders supply their cam cards. Are you going to start telling us that WEB cam doesn't know what it's doing? While were at it WEB cam doesn't make it's own new cam blanks, it uses the same cam blanks as many other cam grinders use.
And are you going to tell us that VW doesn't know what it's doing when it built it's rockers? BTW VW didn't make it's own rockers as well.
Why don't you swap those rockers around and see what happens, I bet your frick'en head explodes.
(IMG:style_emoticons/default/blowup.gif)

Buddy! pros and amateurs, thousands of these engines have been built and I've/we've never had the "issues" you seem to have. We would have all just abandoned this car.
To me you you should have just paid someone to build you an engine....but I'd pity the fool who took the job.

I'm done...peace out. (IMG:style_emoticons/default/rolleyes.gif)

[stugray]

WEB cam supplied the cam card

That's funny because it says Type IV store right across the top of it.
And it says ON THE CARD - VALVE LIFT: .368, .368.

Are you trying to tell me that I am supposed to shoot for .368 lift AT THE VALVES?

I am trying to follow Jakes instructions to the letter, and when he says you have to meet the cam card specs to within 5% after multiplying by a rocker ratio of 1.3:
.368 * 1.3 = .478 however on my Intake valve I get .548.
Last time I checked .548 is not within 5% of .478.

So I guess you are right - I am off my Meds.

And I never said ANTYTHING about webcam not knowing what they are doing.

I am also reading on Jakes cam instructions that I need .050 clearance from the Intake valve to the piston, but I WILL have only 0.023, so I guess i should just go with it?!?!

And What "Issues" have i had? I measued my deck height and discvoered that I had sunken registers. I had them fixed just like most of the pros on this forum said is normal for these engines. I bought a race cam and i am having the exact "issues" that most people said i would have. I dont get the "issues" you are talking about. As far as i can tell everythign is working just like it is supposed to after i bought the correct measuring tools.

The "issue" I am having now is that if I follow Jakes instructions to the letter, the numbers do not add up. Therefore I as the question: Are 1.4 ratio Intake rockers normal?

Stu

[r_towle]

post a picture of the cam card.
It will possibly get you some help.

You may see lift at valve, lift at lobe
You may see degree of rotation at the crank (not camhsaft)

You may also need to shim your rockers to get the right ratio.
That is also part of the process.

For a race motor that will see higher RPm,s .040 is as close as you should get if you have no valve reliefs in the piston, which you never mention in all you posts...that would be a key piece of information to share when building a motor.
Valve reliefs will also change your compression ration numbers and should be measured accurately.


Post the card.

rich

[stugray]

rich,

Thanks. I will scan the card & post it when I get home.

Above I said "flat top 96mm pistons." & "I didnt want to have to relieve my pistons for clearance if I could avoid it.".
I have someone that can relief cut the pistons, but then I know I have to compensate for that in the CR calcs and cut even more from the heads. I am having trouble grasping how shimming affects ratio. I thought the main point of shimming was to give more clearance for the swivel feet. Of course all of these measurements are not to cut the pushrods (yet) until I cut the heads. It is mainly to find out if I have a problem before cutting (which I DO have a problem).

Racer Chris - My next step was going to be to measure all sets of rockers to verify the ratios. If all of my Intakes are 1.4 you would trade me for a set of 1.3s?

The engine that I got these rockers from was a race engine used by the PO with FI and I can tell he made a few mods to it, so it is possible he purposely found a set of 1.4 ratio matched rockers for his 1.8L.

Stu

[ChrisFoley]

I am also reading on Jakes cam instructions that I need .050 clearance from the Intake valve to the piston, but I WILL have only 0.023, so I guess i should just go with it?!?!

.050 is too close for an intake valve IMO. I don't like less than .120 in a race engine, .080 on the exhaust valves.

The valve lift numbers you're getting are suspicious.
There is no way you should have .548 intake lift.

It's pretty hard to believe that you have intake rockers with a ratio of 1.4.
I've never seen anything close to that, and if they are, that's desireable in an engine built for a race class requiring a stock cam and rockers.
I would trade you for them.

Either the cam is bad or there is something wrong with your geometry or measuring setup.

And the cam card is fubar - reminiscent of military-like precision. (IMG:style_emoticons/default/lol-2.gif)

[stugray]

There is no way you should have .548 intake lift.

I will take pictures tonight.
I measure .388 Cam lobe lift & .548 valve travel.
The measurements were made separately and simultaneously - both gave the same results: .548/.388 = 1.41.

The exhaust valve measurements are dead on at 1.3 ratio.

I measured it repeatedly. I'll scan the cam card and post pics of the setup.

Stu

[nathansnathan]

"Valve lift" is taking the ratio of the stock rocker into account. "Cam lift" is the term for the lift without the ratio and may not be a figure that is on the card. Since you will be measuring at the valve retainer, you just use the valve lift figure and no mat required.

The whole point of doing your valve geometry is determining how far out the rockers need to be to get advertised lift. The pushrod will lengthen accordingly, but how far to shim the rockers is the main factor. You will have to stop shimming when the adjusters start hitting the head covers. (IMG:style_emoticons/default/biggrin.gif)