Strange situation with power block/720 on MK2

[Glem.Chally]

Just got a power block and 720 plenum installed on my MK2. Went smooth no leaks after but my power is way down.

Seems to be making more power at 110 bar than it did at 160. This is the first impact I've played with that doesn't have the return spring in the plenum. I've even tried it with no return spring at all only pressure keeping the valve shut. Seems very timid.

New spring, 6 gram hammer weight, new hammer. Even tried an 8 gram hammer weight I have it's no better.

C1 is bottomed out around 5mm of reveal, I'm stumped. Seems to be an insanely short dwell.

 

[Vetmx]

When you have the valve knob assembly off, does the valve rod move smoothly when you push and pull on the C1?

 

[Glem.Chally]

When you have the valve knob assembly off, does the valve rod move smoothly when you push and pull on the C1?

Yeah I was just thinking of adding that, valvepin moves very smoothly.

 

[Vetmx]

When you shoot do you hear the plenum refilling?

 

[cfs916]

Isn’t the valve seal larger? If so that will have more surface to close the valve faster. Only thing I could think would be a heavier weight to over come that. You might also want the softer return spring at the front valve adjuster

 

[Glem.Chally]

When you shoot do you hear the plenum refilling?

No, but I've been checking the reg gauge and its stable.

Isn’t the valve seal larger? If so that will have more surface to close the valve faster. Only thing I could think would be a heavier weight to over come that. You might also want the softer return spring at the front valve adjuster

I've tried both a heavier hammer weight and the weight it came with (that is heavier than my previous) And currently running no return spring.

 

[cfs916]

Interesting. How heavy is the hammer? I think you’d want something around 14gram

 

[Vetmx]

Did the valve housing come already installed in the block. If it’s somehow not indexed properly, you might be getting restricted flow which would equal the short dwell you believe you detected. And also would cause the gun to not take a big enough gulp of air in order to hear the plenum refill.

 

[Glem.Chally]

Interesting. How heavy is the hammer? I think you’d want something around 14gram

Haha the tungsten one is 11 I think. It came with a 6 gram and I tried with a 8 gram also.

Did the valve housing come already installed in the block. If it’s somehow not indexed properly, you might be getting restricted flow which would equal the short dwell you believe you detected. And also would cause the gun to take a big enough gulp of air in order to hear the plenum refill.

No it was all in pieces, I'll pull it apart tomorrow and check it out. I'm familiar with how it goes together with the flat and set screw that goes from the rear block to the valve house. Valve house is flush with the rear block, the pin tip isn't flush with the valve house but maybe that's normal with this setup? Thanks for your input b

 

[cfs916]

The pin tip isn’t flushed with the rear because I think you set it c1 at 5mm.

 

[Vetmx]

My pin tips aren’t flush on either of my power block guns. No issues. Disassemble the gun again just for peace of mind. Most Impact owners are members of the multiple tear downs in one day club. Consider it quality time spent with a loved one.

 

[Glem.Chally]

Ok I guess I got it, maybe this spring is weaker than my previous one. I compared it with my shorty and both on max with similar preload on the HST this one the angle is further back on the cocking handle before I'm hitting spring tension.

Turned up the preload and it's pounding even at the 110 bar on the reg. Might swap out the hammer springs tomorrow.

 

[Vetmx]

Or just use the more friendly spring that came with the kit. I’m shooting at 160b with that spring. Just as long as you don’t run out of adjustment with your hammer screw you should be fine.

 

[bigHUN]

The Valve poppet size (when sitting on the cone) that drives the distance how far the 2mm Valve Rod pin will stick out on the hole. Only if the poppet wears out the pin can get flush with the outside wall.
I don't have the new Power Block but I can imagine the airpath holes are larger=unresticted. I did machining on my Rear Blocks and that unleashed soo much power that a rubber ball in the Valve Adjuster is a must. Guess how I know?