RedLineS2k10

I have a BC stage 3 exhaust cam on the f24c...I checked the tolerances are VERY tight, (more then .21). The head has stock valves/springs, Intake cam is stock..

What tolerance should it be set at? Factory OEM settings (assuming not), or call BC for further info?
Any help guys?

Gernby

I don't see any reason why your choice in cams would change the valve lash requirements. If you are using the stock valves, seats, and rockers, then I'd stick with OEM spec minus 0.001" for intake (.007") and exhaust (.009").

roadents2k

When I got my BC stage2 N/A cams it came with a paper that had the new valve lash specs

KC2001AP1

ya when i bought my bc stage 2 cams they cam with a paper telling all the specs .And bc dose have there own specs ,if you call them they will tell you everything you need to know.

wadzii

the cam profile determines the proper valve lash, not whatever valves and rockers you have

Gernby

Why would a cam profile have anything to do with valve lash? Valve lash is the slack between the cam and valve when the valve is cold and fully closed (not touching the cam). As the valve heats up, the metal expands, and the gap closes. The cam profile has to do with the valve being open, not closed.

wadzii

thats not what valve lash is for at all

if it closes completely the valve will never shut, if its too loose the valve train will be shocked when the cam lobe finally catches up to the rocker flopping around.

Gernby

I think you misread what I typed. If the valve is closed, then it's shut, but there needs to be at least some slack between the valve and cam when the valve is shut, or it will leak. Valve lash is the gap that allows the valve to shut tightly. If valve lash is insufficient, then the valve will leak, and possibly burn. I don't see any reason why the cam would have anything to do with the amount of slack necessary, since the cam makes up such a small amount of the expansion area. I guess if you made a cam out of a material that expanded a LOT more than the stock cam, then you would need to increase the valve lash, but I believe MOST of the expansion due to heat is going to NOT be from the cam.

chris_barry

The end of the cam profile lowers the valve onto the seat gently. If you have too much valve lash the valve is dropped onto the seat abruptly and over time can cause the head to break off the valve, or the seat to get pounded.

Similarly, the initial movement of the valve opening is gentle to avoid shock loads as the lash is taken up, if your valve clearance is too large the cam takes up the lash on a more aggressive ramp and can damage the rockers and other parts of the valve train.

RedLineS2k10

BC gave me this:

Intake-.010'
Exhaust-.008'

Not an expert by anymeans, but in my opinion from what i see, the cam has everything to do with the valve lash.. Factory specs calls for
Intake (.021-.025)
Exhaust (.025-.028)

Im not a genius, but when BC tells me the valve lash is to be set at .008, i find it hard to believe the cams dont have anything to do with the valve lash. Just look at the numbers. Now imagine if i set my valve lash to .025 on the exhaust side..Probably would get 3 seconds of the car running.

When i pulled my motor apart, certain valves were dirtier then other, cylinder one was completely nasty. When i started the valve lash i took note to check the the lash on those certain valves, and the leaky valves were the ones with the valve lash off the most. Theres a reason BC sent them a spec sheet....