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

[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