If you will be taking your valve out again, a good way to test fit is to put the valve back in without the innards, so it can't hold any air, then you can put the pump arm in all the way without any back pressure. Look at how the pump arm hole lines up with the pump tube hole and adjust the length accordingly.Usually there is very little adjustment, no more than 1/16 inch, but it makes a big difference.
I didn't replace it on my 397, but I installed an adjustable valve on a Blue Streak that I rebuilt a couple years ago. That's how I determined the length. I don't know what the gun shot before I rebuilt it but after the rebuild I got around 687 fps with 14.3 grain .20 Benjamin pellets and 8 pumps. Lots of power.
When I first learned how little the pump rod had to be lengthened to get an appreciable increase in power I was amazed, and a little doubtful. Then I realized that that last 1/16” or so of air that isn’t getting pushed into the valve is highly compressed air. Multiply that by 8 pumps and you’re getting an extra half inch of highly compressed air into a fairly small valve. More than a few people have reported getting an extra 40 to 50 fps out of their Sheridans when they eliminated that little bit of space between the valve face and the pump cup.One thing I noticed when I was working on my two Sheridan’s is that the replacement pump cups that are being produced these days are slightly less thick than the original pump cups in the old Sheridans, so if you stick with your original (non-adjustable) pump rod and put a new pump cup on it you’re going to lose a little bit of power because you will be increasing the space between the pump head and the valve face.When testing the pump length, don’t use the roll pins to hold the pump assembly in place. Way too hard to put in and remove repeatedly. Take an old 3/16” drill bit and sand the shank just enough so that you can easily push it in place to test pump the gun and pull it out again if you have to adjust the pump rod length. Also, you don’t have to put anything in the forward hole on the pump tube cap while you’re doing these fittings.I already mentioned the solid steel 3/16” by 1” pins instead of roll pins when you’re ready for final assembly. They fit tight, you have to hammer them in, but they are not as tight as the roll pins because a 3/16” roll pin is slightly bigger than 3/16” in it’s uncompressed state. I put a little moly on the pin and inside the pump arm hole before installing.
Did you get your adjustable pump arm from TimmyMac? If they are like the originals in the early Sheridans the pump head itself is threaded, and the nut you see on the rod is the lock nut, so you won’t need to get another lock nut.
I only did the solid pins on my recent 397 gun. By the way, it was Rob 112o that I got the idea from.Now, with your talk of this pin remover I'm thinking I might tear into my two Sheridans again. I've been wanting to swap stocks on them, but couldn't stand the thought of pounding those roll pins out again. With a pin remover, and the easier to install solid pins I might just do it. Looking forward to hearing how that pin remover works for you.
Hate to hear that. Hope you get well soon.On the roll pins, I used a rubber mallet and laid the bbl. on my leather rear rifle rest bag.I had a very small screw driver set that had a shoulder that fit the roll pins perfect lol.Worked like a charm. Takes a couple or three fairly hard licks to get them started coming out, but once they move, they come out fairly easy.
Quote from: 35 shooter on March 12, 2019, 05:57:46 PMHate to hear that. Hope you get well soon.On the roll pins, I used a rubber mallet and laid the bbl. on my leather rear rifle rest bag.I had a very small screw driver set that had a shoulder that fit the roll pins perfect lol.Worked like a charm. Takes a couple or three fairly hard licks to get them started coming out, but once they move, they come out fairly easy.I'm gearing my courage up !!wll
If driving a spring pin out with hammer and punch, I drill a hole in a block of wood that I align the pin with , that gives me a solid backing , and since I have swung enough hammers, I can get them to move with the first solid deliberate swing. Also a Good heavy 2lb + hammer helps. Just a tip
I just modified the punch a little with some leather around contacting parts and a stop to allow for the compression tube to fit in easily.This is now ready for this weekend ;- )wll