1322-1377 valve work

[K.O.]

"  nice valve work K.O.  pretty decent gains....
are you using a lighter valve spring? "

Dagnabit getting old sucks (well it beats the alternative by a country mile) getting forgetful...

Squeezed the springs in a large set of pliers and toasted with bic lighter for a couple seconds.






copy from other thread/
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Increased valve volume of my stock 1377 by about 2 threads, slight easing of corner of air passage, thinned poppet shaft and coned head,  matched nose of valve to pump cup, still need to shim cup back out, tops out at 550fps with a seated 7.4 pointed Crosman,  a gain of 20-30fps  16 pumps. This is in prep for 1760se barrel ordered last week.

I also increased valve volume of my  1322 by almost 3 threads,  a touch of hogging out the thick walls of the front  portion, air passage eased 3/4 of way to poppet seat, poppet shaft thinned and coned head, cup/valve already matched but need shimmed much more than the five thicknesses of pop can I used, enlarged transfer and barrel port size  to just over .140/ a loose 9/64,  tops out at 550 fps @ 17 pumps a gain of 10- 15 fps.
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I think if I had another 1322 barrel I would  hog the barrel port out to closer to .160 and use a different(bigger) transfer port. I think the valve work would show its stuff a bit better and I just might reach my goal of 570-580 fps with a 14.5" barrel.

this  1322  barrel proved itself to well after the leade work to mess up, it and the stock valve gave very consistant small groups out to 30 yards...

honestly I need to get another 1322 later this year for all this 

The cost seems to be consistency  (1 in 25-40) shot of 570-575.

Most on both seem to be 540-550

I actually do not understand the odd 570s???



the 1377

I would do more leade work on the 1377 (get it to seat the pellet just past the port with a tap or very little effort) but  I think I have a very tight barrel and it leaves wide bands on the head and skirt of the 7.9 hollow points and 10.5 ultra mags, so would it help

also 18-20 pumps (1377) I get some 570s but it is very inconsistent 545-570 past 16 pumps...

I think the tight barrel makes it very head size sensitive???

the ultras and hollows each gained about 20 fps also...

I am hoping that when the 1760se barrel get here it is just a touch looser...

I decided to go with cutting it at 18" inches and will be very please if I get 600 fps.

piston/valve fit,

the pop can shims 1/100" each, will come out of both once I figure out what is just right (will be made from Guitar picks I have a ton).

the 1377 was just right contact wise (left a slight impression  of valve face in pump cup) the 1322 had some head space.


Oh the 853 got a new pump tube but started out slower than the old one and is gaining fps, after about 15 shots,  is where the old one was at 420 fps I was hoping for more like 450...

Will be experimenting with taking up valve space soon, the piston face is flat already (factory)and touches face of the valve.

I do see  some small possible smoothing of flow also...

[K.O.]

It is a blast trying to figure these things out...

[DBOdude]

FWIU ...... increasing the valve volume ( reducing the threads & hogging out) increases the volume of air that can be compressed .... but ...... increasing the volume of air means it takes more pumps to achieve the same pressure . unless your'e gonna be pumping a lot (20-25 or more times) it's gonna reduce the FPS/FPE with the typical 10-15 pumps most folks seem to stop at .

i'm new so hopefully someone with more experience will come along and correct me if i'm mistaken . 

[WyoMan]

That's pretty much the basics DBO, but if you reduce the headspace enough you more than gain those extra pumps back with improved pump stroke efficiency...more air goes into the valve with each pump 
The testing I did early on showed I could increase the valve volume by 20% and the break even pump number was 5 @ 7000' elev so that would be about 4 at sea level...

*oops...meant to say break even for energy, not pressure. Your right DBO the pressure will be less with the same number of pumps (until you max out your pump) but the increased volume makes up for it

[DBOdude]

thanks for the clarification WyoMan 

i think i have my headspace correct on my F/T P&V . i used these directions .

http://accustomparts.blogspot.com/2013/05/installing-flat-top-piston-and-valve.html

i have about a 1/2 inch gap between the back of the pump arm and the main tube without the o ring . i could feel it bottoming out , took it back out , put on the o ring with some secret sauce and put it back together . its definately louder on 10 pumps and the pump arm holds in place .

[K.O.]

the 1377 had one type of headspace and the 1322 another

the 1377s valve had to be sanded back to fit the pump cup the way I wanted it to; it did leave just the right amount of imprint in the cup to tell me it fit just right for the staying closed/cam-over/not to tight equation; but the nose hit first and since that left space between the sloped part of the cup and piston = headspace

so sanded down the nose until it fit the cup and the cup skirt makes contact first and then allows  the center portion to collapse very slightly to the point of leaving a slight imprint in the cup and cam over is about 3/4" before closing pump arm....

I should have measured before and after grinding valve nose but did not (it would have told me just how much shimming needed)

there is now .065 worth of shim and I think I got it just enough, add a bit more and probably cam over just a touch sooner without undue wear but I feel it is pressure wise as far as needed...

.065 of headspace going away at once can not wait to see what effect that has...

the 1322 well the pump cup fit very well I can not tell if the skirt hits first or the nose and the sloped portions are tight... but it did not leave an impression with .04 worth of shim it now has .05 worth and cam over feels right, once again could go just a touch tighter but do not think it necessary.

will see what fps says about it soon

My fps break even( with before valve mods) on both is at 10 pumps but for different reasons(I think)

with the 1377 I feel it has to do with the tight barrel and 10 pumps is the point of overcoming high initial drag.

the fact that I was able to gain fps without an increase  in barrel length points to valve volume not being optimal for the barrel length/snugness/pellet weight balance.

It was topping out stock with no further gains past 10  pumps at 520-530 fps, was also some what due to headspace...  how much???

just tuning headspace add 2-15 fps?

I kept the easing of the corner small, by gut just enough to reduce turbulence and small enough to keep the charge velocity high because I believe those that  feel that high initial charge velocity is most important for a light .177 pellet.

results seem to point to that with an 18 inch barrel I could increase valve volume some more I am guesstimating it is now about .12-.13 c.i.  and If I am willing to pump 20-25 pumps  then  .14+ c.i.  would give gains...

But how much is pellet fit in this equation???


the 1322 with 14.3 grain pellets  breaking even fps wise at 10  pumps is because it is no longer at the I am a leaf on the wind weight level...

I feel that the port at just over .140 cannot provide the torque of a larger wall of (.160 or so) air can to get the pebble moving...

I did all work but left the barrel un-ported to check that theory,

When I ported the barrel(very little to a loose 9/64s bit)  to match the transfer port I gained 7-10  fps so I am thinking the wall of air way of thinking is right for the 1322.

I think I got the valve volume/barrel length balance right...

It will be interesting to see what taking away  that last .01 of headspace gives...

[K.O.]

Oh my part of town is at about 1900 above sea level.

the 1322 had a pump cup pin the 1377  did not....

I weighed about 60 Premier hollow points

6= 14.5g
6= 14.4g
2= 14.2g

the rest  weighed 14.3g counting 3 14.35s

[K.O.]

Ok

I feel like I scored a KO 

but it was one step back and then another swing that did it...

.065 proved to be to much shim I ended up losing 20 fps (I will have to try and figure out why?)

went to .045 shim and  bang 17 pumps gets a five shot string of 559.7- 570 fps centered in mid 560s...  15 pumps a respectable 548-560 fps

Still breaking even around 10 pumps.

I did four shots at 20 pumps  three scattered in the 570s and one hit 600 I did  one shot at 22 pumps and also hit 600...

I think I could shim tighter to get it perfect by adding .001 at a time but I am happy now.

so I am jazzed I think I went the right way in my valve work the first time...  (hey ya sc%&# the pooch on it and they are only  $5)

40 fps out of just a headspace tune and valve work at relatively benign pump levels, and 70 fps pushing it a bit...

It felt real cool to hit 600 with a 10.5 barrel...

any guesses what happens with a 18"  barrel?  (mine is 610- 615 at 17 pumps) (If for fun you guys give a guesstament , give number of pumps and a 5 fps range  )

Unsorted 7.4 Crosman points from the tin,  fps is average over 15'.

no time for testing the 1322 today to see if I got shims right?

[K.O.]

first 1322 findings

increased shim from .05 to .053

Saw a 2-3 fps gain below 8 pumps and 6-7 fps at  15 pumps so I am starting to rethink not trying to get it perfect on the 1377.

with a lighter pellet it should make a bigger difference...

on the 1377 front a bugout pump grip got in today along with a 1760se barrel.

7.4 points

12 pumps  583-588 fps
15 pumps  614-620 fps
17 pumps  620-627 fps
20 pumps  652-656 fps

7.9 hollow

17 pumps 617-630 fps

10.5 mags

17 pumps  522-525 fps

I am betting I do not lose to much cutting it down to 18" except  for the ultra mags.

?

[K.O.]

 the 1377 barrel is now at 18" and velocity is

7.4g points

12 pumps  581-695
15 pumps  605-612
17 pumps  613-620

7.9g hollow

17 pumps  600-615

10.5g  mags

17 pumps  517-532

[Ryan]

I always let my my 13xx to rest with 2 to 3 pumps. One would hold up the pressurized air for 2 to 3 days while the other one would only last for a few hours.

I realize that the air would eventually leak from the valve. Under the best condition, what would be the normal time frame for the air to remain pressurized inside the valve, a couple of days or weeks? I guess for the one that only last a short while, replacing the check and exhaust valves would fix the problem.

[Trophyhunter49]

  Ryan , I have one of my pumpers (1322) that will hold air for 2 weeks with 5 pumps in it ! That is about as long has I can go with out shooting it 
Replacing the check and exhaust valves sould fix the problem. I have one that I have replaced all the o-rings and the check valve and the exaust valve and it still will not hold air over 2 to 3 hrs. Going to replace the whole valve assm.

[K.O.]

Could simply be dirty and I have heard of lapping the valve and poppet for a better fit...

If you got it used and do not know what lubes were used....

New and proper lube then maybe scratches or imperfect machining etc...


The longest I have gone without shooting my 13xxs is two days and they both hold three pumps very well...