Lift vs Valve size

fastback · Post by **fastback** » Thu Jul 24, 2008 4:16 am

Just did some calculations on my valves and lift.
I have put a FK-8 in my 2200 turbo WBX
with 40mm intake valves
This cam has 9.70mm (0.382") lift @ cam.
with 1.1:1 rockers this gives a lift 10.67mm (0.420") @ valve
When calcualting valve area of the 40mm it gives a area of 1256mm²
When calcualting the area between the seat & Valve @ full lift (with 1.1:1 rockers) the area is 1323mm²
Which is more than the area of the valve itself. (not calcutaled with the stem)
Would it be any benefits using 1.25:1 rockers on this combo or is the valves to small to benefit from this?

Stripped66 · Post by **Stripped66** » Thu Jul 24, 2008 12:33 pm

The calculations you've have done are pointless and will not produce any meaningful comparison of how much lift you should run for your valve size.

You have a K8 cam; it is designed for 1.4:1 rockers...so run 1.4:1 rockers.

Now, I'm certain there is some voice in the back of your head (or somebody's head) saying, [Prof. Frink] "Well, if the heads don't flow any more air beyond 0.475" lift, then why would you want to run more lift" [/Prof. Frink]. Here's why...if the heads are limited in flow at some valve lift, such a 0.475" (this is an arbitrary value, don't get hung up on it), a hi-lift cam is going to lift the valve to that point sooner and hold it open past that point for longer than a cam that only has 0.475" lift. You get more airflow.

Run the rocker ratio that the cam is designed for (and please tell us you're using Type 1 lifters with that cam). The additional lift means that, even though your heads don't gain any additional flow past .xxx" lift, the valve will be open at least that much for a longer duration than if you ran 1.1 or 1.25 ratio rockers.

fastback · Post by **fastback** » Thu Jul 24, 2008 1:59 pm

Thx.!
A LOT of thought's in the back of my head, Alway's

Ratio rockers it is!
So i have to throw away my caclulator and buy a flowbench

I'm not running type 1 lifers but , solid type 4 with big foot and oil hole like the lube-a-lobes.they also have the large "groove" on the side like the hydro's. 110Grams
these are 30mm diameter.
I have checked lifter to cam geometry and it's ok.
A VZ-25 was not.
Have seen a couple of combo's that did not check this.

Type 4:

Stripped66 · Post by **Stripped66** » Thu Jul 24, 2008 8:11 pm

fastback wrote: So i have to throw away my caclulator and buy a flowbench

Certainly knowing the limits of your port/chamber WRT valve-lift will help when choosing a cam, but because you've already got the K8 in there, run as much lift as the profile is designed for.

I'm not running type 1 lifers but , solid type 4 with big foot and oil hole like the lube-a-lobes.they also have the large "groove" on the side like the hydro's. 110Grams
these are 30mm diameter.

Cool. Aside from the possibility of incompatibility between the radius of the Type 4 lifter and a Type 1 cam, the next biggest issue is that the smaller Type 4 diameter is going to net less duration than the larger diameter lifters. At 30mm, you should be spot-on!

fastback · Post by **fastback** » Sat Jul 26, 2008 4:15 pm

Here's the lifters i use.

tencentlife · Post by **tencentlife** » Sun Jul 27, 2008 8:42 pm

OK, so who makes those lifters?

Post by **Piledriver** » Sun Jul 27, 2008 11:12 pm

Yes, who???

Price
Contact info... PLEASE.

fastback · Post by **fastback** » Mon Jul 28, 2008 12:29 am

i bought them localy here in Norway.
I've heard that one of the type 4 guy's in the states has similar lifters.
not shure who it is maybe EMW??