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Increasing PT pressure

Floridianson

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So I made the jump today and put together the pressure gage for the PT's
NAPA had everything I needed plus hyd. fittings and they made me the hose. Used a swivel fitting on the PT end and hooks up in no time. I started playing with the M816 and here is what found. First I drilled out the ball on the throttel shaft and hooked up the gage and took her out. I started in second low and took it to the govener and show maybe 50 lb then when I hit third low and she started to get close to Gov the gage was moving fast. When I hit the Gov then she showed herself. She pushed 165lb. and defueled. I then turned the throttel shaft screw counter clockwise 2 full turns and repeted the test. This time she defueled at 195lb. I had them make me enough line so the gage reaches easy to the passenger side and sits in my lap when I test. I will be doing some more trucks later this week if I can to see what the base is on them and if the same amount of turns produces the same effect on all the 250's. It was a short test with the 816 today so I can not say she did much better as I only got to third low to check pressures. I was talking with a man that has been around the PT's and he said he felt all you need to do is increase the throttel shaft screw and felt that the Idle plunger could be left alone. So to cap I will test some more but one compleat turn counter clockwise on the throttel screw should net just about 15lb rail increase. I would never tell someone to turn up the throttel screw inless you have the gage on the PT to see where you base line is and where you end up after after adjustment.
 

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AMGeneral

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Thanks for the info Floridianson,i'll be checking the 813A1 out later this week.

I already had the proper line and fittings in my test gauge I made for the Hydramatic transmission in the GMC deuces.
 

Floridianson

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Yea AM I would like to see someone else get some readings and we compair. I will be backing down the 816 and will shoot for 185lb defuel.
Don't know what you gage increments are but my 200 is easy to read. Also it is nice to have another person to read as they climb fast and drops fast when it defuels.
AM you going to do the idle plunger as it would be nice to see how well that effects the rail and then the throttel shaft?
 
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AMGeneral

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Mine is a 0 to 300 psi gauge similar to yours.

If I keep the 813A1,I plan to do the idle plunger(fuel button) as well as the dual feed line mod,and see how it runs from there.

As of right now,it starts great with no lope at idle cold, and it make a slight haze on acceleration with no load.

I have not had time to drive it on the road yet,I just picked it up from Ferro's place Saturday.
 

Jakelc15

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I've been wanting to put the gauge on mine too. I'm going to change my filter since it's about due before starting. I have already done the dual line mod. I got my pyrometer to 1100° this winter with the plow on the front and pulling a trailer.
I would definitely stay under 200 lb on the fuel.
Thanks for sharing your findings.
 

Floridianson

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If I had some buttons to try I would but I got my hands full right now just trying to make a good plan with the trucks I have now. Please post your rail numbers if you guys get a chance and the numbers on the buttons you use. Thanks
 

jarhead1086

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I am pulling my PT today and will take it to a shop to flow test it on their bench. I have a 20 and a 22 button to try. I will never have a load on, just a few hundred pounds of camping gear and some chow. I will be watching the pyro closely though. I am happy with the dual fuel line mod, it does idle smoother and revs quicker. The engine sounds happier to me. I will mail you my extra button Floridianson. I sent my pressure gage/kit back because of the 600 psi range and the obnoxious bubble where I would have been trying to read it. I am hoping the bench test gives me the information I need and will share what I find in about a week.
 

73m819

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I dropped my button from the stock 27 to a 22, the 819 sure pulls better, I am fixing to order a 2 1/6" fuel pressure gauge for in cab mounting, I am going to replace the cold start fuel pressure gauge (got rid of the cold start a long time ago) with the after pump gauge. come to find out modern trucks do not have fuel pressure gauges like ALL the old trucks did, fuel pressure gauges tell you a LOT about what is going on with the fuel system.
 

Jakelc15

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I got 160 - 165 psi. Stock with dual lines. 1/4 turn brought it up to 175. Still running about 1100 ° egt. I'll probably play with it some more after I drive it a little. Hit some hills and make sure my numbers are good.
 

Jakelc15

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That's what I was thinking. Stock for some of the big cams where 180 - 190. I've heard of them being turned up over 200 but that's awfully hard on the cam and rods.
I have a turbo coming to help the egt. Then I guess I'll be looking for a button!
 

JasonS

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I dropped my button from the stock 27 to a 22, the 819 sure pulls better, I am fixing to order a 2 1/6" fuel pressure gauge for in cab mounting, I am going to replace the cold start fuel pressure gauge (got rid of the cold start a long time ago) with the after pump gauge. come to find out modern trucks do not have fuel pressure gauges like ALL the old trucks did, fuel pressure gauges tell you a LOT about what is going on with the fuel system.
Will you be piping fuel into the cab or using an isolator?
 

73m819

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Piping to the cab, the cold start has live fuel to the gauge, If done right, should be fine.
 

73m819

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Shop made hose to the firewall, copper to 6" from the ip, shop made hose to the ip. This will take all the vibration out of the feed and also will be 3/8" id so I can get a truer reading with no restrictions.

I may use stainless steel line because I have 8' of 3/8" instrument tubing, rated a lot higher then 200lbs.
 
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Jakelc15

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It's a good idea to replace those plastic lines even of you are keeping the hand pump. They get very brittle, the dot air brake line seems to last longer.
I also ran a 3/4" hose from the filter to the pump, trying to reduce restriction.
uploadfromtaptalk1396792588093.jpg
 

Jakelc15

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Hanover Pa
patracy posted this in another thread -pyro button installDP-141623 IDLE PLUNGER (5)
DP-141624 IDLE PLUNGER (7)
DP-141625 IDLE PLUNGER (10)
DP-141626 IDLE PLUNGER (12)
DP-139894 IDLE PLUNGER (15)
DP-140417 IDLE PLUNGER (17)
DP-141629 IDLE PLUNGER (20)
DP-141630 IDLE PLUNGER (22)
DP-141631 IDLE PLUNGER (25)
DP-141632 IDLE PLUNGER (27)
DP-141633 IDLE PLUNGER (30)
DP-141634 IDLE PLUNGER (32)
DP-140922 IDLE PLUNGER (35)
DP-140418 IDLE PLUNGER (37)
DP-140923 IDLE PLUNGER (42)
DP-140924 IDLE PLUNGER (47)
DP-140925 IDLE PLUNGER (48 )
DP-139618 IDLE PLUNGER (52)
DP-139619 IDLE PLUNGER (55)
DP-140926 IDLE PLUNGER (57)
DP-140927 IDLE PLUNGER (60)
DP-141636 IDLE PLUNGER (62)
DP-141637 IDLE PLUNGER (65)
DP-141638 IDLE PLUNGER (67)
 
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