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Safe fuel pressure for small cam

Posted By RobertMoen Thursday, April 21, 2022 9:35 AM
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RobertMoen
 Posted Thursday, April 21, 2022 9:35 AM
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What would a safe fuel pressure be for my 350 small cam? I recently installed a new pump and injectors that are supposed to be flowed +10% but I'm not seeing any gains in power, although it does run much smoother pulling hard. The shop who built the pump says for my pump code the pressure spec is 153-169psi, I am seeing 160 max, and only 20-22psi boost. I did not have a pressure gauge on the old setup but was seeing 25-26psi with the old setup. Egts did drop about 100-150 degrees on a hard pull and no smoke at all which isn't a bad thing.
Newto
 Posted Saturday, April 23, 2022 4:31 PM
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If you had the injectors flowed + 10% then that will drag some of your fuel pressure out because of the higher flow.....you can safely go max fuel pressure plus 10 psi....so around 180psi should get it cracking......either change the button in the pump or depending what fuel pump you have....early or AFC type you can get more flow and psi out of the throttle shaft.....give us all the numbers off the pump tag and jimfols will be able to advise the settings and what pump it is.
Saturday, April 23, 2022 4:32 PM by Newto
RobertMoen
 Posted Saturday, April 23, 2022 5:41 PM
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Engine is a cpl160. Pump numbers are 160 7160522, second line is 4182 3043327, its an AFC pump. I'm assuming the previous pump had been tweaked since it basically has the same power now as it did before. Can I adjust the AFC so that the fuel comes in a little sooner, the turbo feels a little lazy to spool up?
Newto
 Posted Saturday, April 23, 2022 7:07 PM
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AFC Screw is behind the tin plate on the pump body next to the throttle lever. Winding the screw out will improve the turbo response....try in small increments...(like 1/4 turn at a time) and test throttle response after each turn until you get quick response......too much will give you instant black smoke....(not desirable).....contact your fuel shop and ask them if they can button up the pump to at least get std max pressure....169 psi....because you won't get it on the throttle shaft if they plugged it.
RobertMoen
 Posted Sunday, April 24, 2022 6:22 AM
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Unfortunately my busy season is starting now and I can't afford to have the truck down long enough to send it back to them until November.
Newto
 Posted Monday, April 25, 2022 9:59 AM
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Any good Cummins mechanic would be able to do a "button" change on the truck in under 30 minutes........you've just got to find one in your area.
Monday, April 25, 2022 9:59 AM by Newto
RobertMoen
 Posted Monday, April 25, 2022 12:17 PM
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I'm comfortable changing the button myself if I knew where to source them and part numbers for the different sizes.
Newto
 Posted Monday, April 25, 2022 4:05 PM
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Well first stop then is contact the fuel shop that o/hauled your pump and ask them what size button they fitted.

Part number won't matter much....it's the size that most go by.....eg 25,22,20,17,12,10.......etc...the smaller the number the more difference it will make to the pressure.....I would think you would have around a 20 or 17 but best ask your fuel shop first.
RobertMoen
 Posted Tuesday, May 10, 2022 6:21 PM
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Pulled the ball out of the throttle shaft (it was plastic) and turned it out a turn and a quarter. Pressure went up to about 175, seems to have helped quite a bit. Haven't had a chance to mess with the AFC screw yet but I'm liking the improvement so far.
Geoff Weeks
 Posted Wednesday, May 11, 2022 12:49 AM
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RobertMoen (4/25/2022)
I'm comfortable changing the button myself if I knew where to source them and part numbers for the different sizes.
I order them from a Interstate-McBee dealer.

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