stock AFPR - multiple unanswered questions..

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Oct 18, 2007 | 07:10 AM

Tbi-MAX

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stock AFPR - multiple unanswered questions..

okay so we all know the write up on TGO... but does it need updates?

Quote:

OK lets get down to it!
Tools/Materials needed:

T20 Torx bit (you can get away with an allen key but be carefull)

Dremel with a cutoff disk (optional) You also MAY need an injector pod gasket though most may not.

Directions:

Disconnect negative battery cable
Remove aircleaner assembly
Remove gas cap to relieve system fuel pressure
Disconnect injectors and get the injector plugs out of the way aswell as the aircleaner stud (just turn it to face away from the injector pod)
Remove the Eight (8) Torx screws on the top of the injector pod. Take note of the positioning of the 3 longer screws.
With the screws removed from the top of the injector pod lift away the "roof" of the injector pod. Some fuel will leak out and be very carefull with the gasket so it does not tear or any debris fall into the path of fuel. The fuel pressure regulator is attached to it. It is the gold iridite "cup" looking object. Take note of the tab sticking out of the fuel pressure regulator cup. This represents the range of adjustment. The higher the tab is the more compressed the spring is equalling more fuel pressure. You'll see what I mean later. GM seems to have no set fuel pressure as those who have performed this mod have all had varying fuel pressure settings from the factory.
Now you will have to dissasemble the fuel pressure regulator. There are four torx screws holding the cup to the injector pod "roof". Slowly and evenly loosen the screws while maintaining firm pressure on the cup because it holds a spring under some tension. remove screws evenly while maintaining pressure. Once all 4 screws are removed carefully lift away cup. the spring will release tension and you may set it aside along with the injector pod roof.
Take note of the fuel pressure regulators function. A small platform with a tab that sticks out the side of the cup rides on a threaded shaft. The higher the platform in the cup the more compressed the spring and the more fuel pressure is acheived.
Now to make that threaded shaft movable and furthermore, adjustable easily. You will have noticed the shaft does not move. Flip the cup over and take note of the pressed in cap in the hole on the bottom of the cup. This must be drilled out. Its pressed in there quite well, and is not easy just to pull out. I and others have had to completely drill out the cap. Be carefull so as to not exert too much pressure as it is possible to knock out the metal peice that is pressed into the cup on the bottom in which the cap sits
Now that you have drilled out the cap you will find that the screw and platform inside the cup are not only movable but removable from the cup. By turning the screw counter clockwise you raise the platform thus raising fuel pressure. You can raise the platform to a higher pressure and put it back together at this point but that takes away some of the adjustability to it.
Now if you have a dremel with a cutoff disk this is much easier though you might be able to accomplish this with a hacksaw. Cut a slot in the head of the screw so that a small flathead screwdriver can turn the screw.
Reassemble with a slightly higher fuel pressure setting. This time turn the cup around so that the tab does not face inwards and is not visible but faced out and is visible so that you can view the amount that the platform is raised. If you dont understand what I mean, just skip that.
Put injector pod "roof" back on top of injector pod. Be sure to snug down all screws to prevent leaks of fuel. REconnect Injectors, Put gas cap back on and reconnect negative battery cable.
Start car with aircleaner assembly removed from car and watch for leaks from the top of the injector pod. No leaks? great! If you have a leak be sure you tightened the screws. You might need a new gasket. Most autoparts stores sell gasket material to make one or you can buy one from GM. You might also be able to find a gasoline compatible silicon sealer. BE CAREFULL THOUGH you CAN clog your injectors.
Put aircleaner back on and refer to TUNING WITH YOUR O2 SENSOR & DIGITAL VOLT METER in the tech section to be sure you have the right pressure! To re-adjust pressure its going to take you to remove the 8 screws on the injector pod roof again and just use a small screwdriver counter clockwise in the little slot you made to raise fuel pressure and clockwise to decrease it.

This article is for educational purposes only. Do not think about attempting unless you feel confident with your mechanical abilities and know the basics of your TBI unit.

ok, fair enuff...

i did it on my SBC tb and it worked fine..

and side view

okay, so now I got my BBC tb, and it is more described as the TGO write up, with the cap on top, and the actual tab on the side sticking out the slot...

but here is the thing... the write up doesnt say which way is up or which way is down... can some one explain better? i think its a typeo.. wouldn't backing the screw outwards increase pressure???

I would think backing the screw outward more would raise it.. its slightly different than my SBC i modded.. and the SBC was welded all the way tight, the BBC is welded about 3/4 way out... it also has the heavier stiffer spring..

i have read about spacers, and putting quarters in the regulator etc... so what tips or what else can i do to make the stock regulator a higher psi? or what is the stock psi rating on the BBC regulator?

my idea is just to swap the moded regulator casing from the SBC, use the BBC spring, and have it adjustable. and mount it up into the 454 TB... as FAST355 said it would swap over.. looks to be the same size too.

454 regulator

tab

inside

should i put a spacer, and what location does the spacer goes in the regulator?? I also heard and believe I can seal up the bleed off valve??...

I would like a psi set of around 16 psi or so... is that too much for my mods on my 383? what would be a good psi setting b4 i return to the dyno?

i need a answer to these questions b4 i rebuild the tb... put the pod and regulator on... I took everything apart, and cleaned it up well, all the breather holes, etc.. and lubricated it well..

454TB

Last edited by Tbi-MAX; Oct 18, 2007 at 07:17 AM.

Oct 18, 2007 | 07:50 PM

Tbi-MAX

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Re: stock AFPR - multiple unanswered questions..

anyone know about the spacer in the regulator, or block the bleed off valve?

Oct 19, 2007 | 12:21 PM

dimented24x7

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Re: stock AFPR - multiple unanswered questions..

Id avoid spacers as theres nothing to locate the spring with a washer/quarter/whatever covering up the pocket. Just drill out the plug and use the screw to adjust it. Also, get a better spring. The stock one wont go over 12 PSI.

Oct 19, 2007 | 05:45 PM

Tbi-MAX

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Re: stock AFPR - multiple unanswered questions..

Quote:

Originally Posted by dimented24x7

okay, im not doing the spacer, cause i see your point there. but I know Fast305 has jb-welded the bleed off valve, im thinking about doing this.. its the tiny hole, on the inside of the inner walls of the regulator... if i remember correctly..

are you sure that the 454 regulator is 12 psi as well? cause this spring is HUGE compared to the 350 regulator spring... its alot stiffer as well, as thicker..

after I make my road trip out of town this weekend, then im finishing the rebuild

Oct 21, 2007 | 01:25 PM

Tbi-MAX

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Re: stock AFPR - multiple unanswered questions..

just found out from the 454ss forum, that the stock regulator is good to 19 psi, not a problem...

so ill prob just set it to 14 psi with the bigger 90# injectors... just wanted to notify others about the 454 huge spring that is alot thicker & stiffer! and good for more psi..