Impact power block porting size?

[Airgunmann]

I upgraded to the 720 on my mk2 it came with everything but the power block I was wondering what size the porting in it was and what size the grub screw is thought about just porting my original block to that size and installing larger grub screw thanks for any info

 

[bigHUN]

This what I did (w/o 720 plenum, I still have the original PP). I didn't wanted to alter the original parts so I ordered new parts everything to have a spare.
The grub screw at the bottom of the RearBlock is M8, so the drill hole before tapping is 6.8-70 mm.
I toke a cylindrical carbide bit I guess it was close to 8mm OD.
On my MiniMill I converted a 6.8 mm hole into a 8x9 mm slot.
But ones I had the parts in my hand, I re-drilled the ValveHouse hole from 6.5mm to 7.3mm ID, also mirror polished the cone (you can see the shine in the picture). Also recut the transfer hole into the same slut as in the RearBlock.
A friend of my cut a peek poppet on a lathe for me.
Also, I replaced the delrin puck with a peek on the Hammer nose that hits the C1.

With these changes I have unrestricted the air path, the power increase is enormous:
.25x700 Superior Heavy, original PP, Heavy HammerSpring140 bars on the Reg propells the 44gr ZAN with 1020 fps, and still there is about 2mm travel on the HammerSpring slider. I never went into investigating how much really max power I can get.

 

[Airgunmann]

From what I've found the grub screw is a m8 x 8 mm long I was thinking opening my block to that size doesn't look like I can buy just the power block any where so I may get a bit and a tap along with a grub screw

 

[Airgunmann]

The only peek upgrade I did was a peek ring in the 720 pp with a viton o-ring to help with fps to stay close to the same after sitting added a 13 gr hammer weight and can push 34 gr pellets to 950 if I drill the block out I might as well do a peek poppet for the valve to at 110 bar I was getting 920fps with spring backed off and power wheel on one which has the hammer in free flight before hitting c1 had to slow it down some with the valve adjuster

 

[Airgunmann]

Looks like a m8-1.0 calls for 7 mm bit which would open it a 1/2 mm

 

[heavy-impact]

When I do this type mod I don't drill out any plug threads. Instead I reach past the threads with a carbide burr to enlarge the passage. No need to drill when precision is not required.

 

[bigHUN]

The M8x1 hole is drilled to 6.8-70.
The dremmel style carbide bit shank is 3mm.
With a 7.0 mm (a hair smaller so you can reach inside the threaded hole) cylindrical carbide bit you can make a +2 and -2 mm = 4mm slot from a hole (+ 3mm the shank).
And WATCH it, you dont make a slot in block longer direction but sideways is narrow direction

 

[Airgunmann]

Thought about that but drilling would be better as not to get into the sealing surfaces of where the o-rings are probably would have to be way off to do that but with my drill press or mini mill I could easily drill it straight

 

[Airgunmann]

Either way I would want to go to a peek poppet if I'm going to mod the block might as well do a peek seal to

 

[heavy-impact]

Thought about that but drilling would be better as not to get into the sealing surfaces of where the o-rings are probably would have to be way off to do that but with my drill press or mini mill I could easily drill it straight

If you have a mill you can use a boring bar and leave the threads intact.

 

[rappert]

When I do this type mod I don't drill out any plug threads. Instead I reach past the threads with a carbide burr to enlarge the passage. No need to drill when precision is not required.

Good idea H-I. four-jaw chuck - lathe hmmm...