Multifuel exhaust valve question

[cranetruck]

For the purpose of maximizing the braking power of an exhaust brake, it's important to know the maximum back pressure permitted on the exhaust valve springs before they open.
I have been using 35 psi as a "safe" value. Called Hercules engine co and they don't have a clue, so here are the spec from the TM.
Can someone elaborate on this and perhaps come up with a max back pressure for an exhaust brake as applied to the multifuel engine?
Thanks.

 

[WillWagner]

Bjorn,
When we used to install potato brakes on the mechanical B and C engines, the brake mfgr stated 30 PSI max back pressure at rated RPM with stock springs. The stockers have coils that are about as big as the multi's springs. The HD springs could go to 65 PSI. The HD springs had very large coils and were barreled. JB hunt had Williams brakes early on on their N14's. The back pressure was also 30 PSI. No hd springs available for those. I'd say you are at the max with 35 PSI. Is that reading at rated RPM?

 

[bottleworks]

I believe your going to need to measure the surface area of the valve exposed to the back pressure.

 

[m16ty]

I believe your going to need to measure the surface area of the valve exposed to the back pressure.

Without the accual specs this would be the best way. Find out the surface of the top of the valve. Then figure how many pounds of pressure it takes to open the valve ( this could be as simple as taking the valve cover off and applying weight to the valve stem untill it opens). Then divide the weight by the surface area of the valve to get the PSI.

 

[cranetruck]

Will, I have not used the brake at an rpm over about 2,400 and the reading on by back pressure gauge has been kept to 30 psi or below, so I guess I'm maxed out with the standard set-up. Hercules does not have heavy duty springs for this engine.
Still, the exhaust brake is a nice comfort factor on long downhill drives.

Thanks for the suggestions, bottleworks and m16ty.