Got bored and did injector spacer

[jjwalker]

I spaced my injecotrs some more with a spare gasket I had. I must say there are NO noticeable gains whatsoever. Now It doesnt hurt to do it because it lets the bores take a little more air, but dont go off and buy a spacer of the net (CFM tech makes one, dont waste your money). Use an old dust gasket and stack it, or use the gasket on there to make a template.

Your best bet is to go to the salvage yard and "lift" a couple, and dont worry about breaking them, just glue them back together.

[Matt 4.3 TBI]

I did an injector spacer a few years ago. I noticed only a SLIGHT difference in mileage. I believe at the time it went from 18.5 city/hwy mix to 18.6-7 city/hwy. No noticeable difference in power. A dyno might show about a 0.25 hp increase, who knows.
They show up on ebay from time to time (I think I paid $2.50 for mine) so I think over the past couple years it's at least paid for itself :)

[imdawrlus]

can you make your own injector spacer?? i have an extra gasket, can i just pull off the injector pod and put the other one underneith, tighten everything and have the injectors spaced? how much do u usualy space it? i think i finaly have my rough idle figured out so now i'm ready to try some performance stuff

[T Man]

An injector spacer came with my TB spacer, and I completly agree. It doesnt hurt, but it sure as heck doesnt help as much. Yes, you can stack the gaskets. Since they are just there to prevent metal to metal contact, they do no sealing, so it doesnt hurt to stack them up.


And guys, I wont be in the 60 degree club much longer. Sorry to say.

[jjwalker]

traitor!!!! my forum will die!!!

[imdawrlus]

how many gaskets can you fit under there without having to use longer studs? would it be possible to put a few washers inbetween the two gaskets because i only have one extra one....i think i'm gonna try this...i'll let u know how it turns out...

[jjwalker]

well, if you use washers, it will let unfiltered air in!

Also, if you space it more than 2 gaskets, you will lose some fuel to the outside of the throttle bores!

[imdawrlus]

how does it let unfiltered air in?? were talking about spacing the injectors not the throttle body right?? how does the unfiltered air get in by raising the injectors with washers?

[Matt 4.3 TBI]

Washers (as in round metal washers) will let unfiltered air in underneath the injector pod. The gaskets seal the injector pod to the throttle body.

[imdawrlus]

what are the gaskets supposet to be sealing?? is there air that needs to flow through the injector pod into the throttle body?

[imdawrlus]

we're talking about the gasket underneith this bolt and the two on the other side, right? how would washers let unfiltered air into the throttle body?? i'm just going to add in my spare gasket, but for the sake of learning, i'm curious as to what you guys mean...http://www.sicgmtrucks.com/forum/attachment.php?attachmentid=1432&stc=1
tbi.JPG

[Matt 4.3 TBI]

Turn the TBI upside down, look at the fuel inlet/outlet area. That is the bottom of the injector pod. You'll notice the injector pod sticks through the TBI base by means of a triangular hole. This area is sealed from the inside of the air cleaner by the injector pod gasket. Spacing the pod without using full gaskets will allow air to enter in this area.

Really hard to explain without pics, but I don't really want to take my TBI apart at this time of night :D

[imdawrlus]

blessing in disguise.

well thats what sums up my experience with the throttle body spacer...

i went out and started riping the throttle body apart to get the extra gasket in, all is good, as i put it back together the huge fitting that screws into the actual throttle body (not the smaller fitting, the one that screws into the meat of the tb) cracked!! the peice of meat around the threads completly cracked ruining the throttle body....so i went down the street to a kids house who has a ton of truck in his yard, he didnt have anything, but he called his friend who is selling a holly throttle body from his parts truck for 50 bucks!! seems like a good deal to me, i just hope the throttle body will work on my truck, its from an 88 or 89 pickup, like mine, with a 350, like mine....so lets hear what you guys think of this...

[imdawrlus]

did i score a good deal or what??

[Sparky2263]

Yassir, yassiree!!!

[imdawrlus]

is this tb gonna work?? thats the only thing i'm worried about...what should i gain (performance wise) with this tb?? will it hurt the gas mileage?

[Sparky2263]

I'm pretty sure you're gonna need to swap injectors or it'll be bad rich. I'm sure one of the tb guys will chime in.

[imdawrlus]

swap injectors? the throttle body is on a 350 right now and its going into a 350...haha i like this forum so much i never bothered to find a new one when i got a new truck....i figure all gm vehicles are pretty interchangable so its all relavent...

[Sparky2263]

I was reading your sig. Says 4.3

[Matt 4.3 TBI]

4.3 Holley TBI injectors flow more fuel (about 5pph more- around 50pph) than the stock Rochester unit. The 5.7 Holley will be more like 60pph, so you'll be running pretty rich. Might be able to get it pretty close by lowering the fuel pressure on the Holley tho. Only takes a hex bit to adjust the Holley!

[Matt 4.3 TBI]

Also, the Holley's butterflies are larger, and they'll bind on the intake bores unless you have on of their spacer gaskets, or enlarge your intake to match. The linkage should match up fine, unless you truck has the RPO code CTF.

[imdawrlus]

The 5.7 Holley will be more like 60pph, so you'll be running pretty rich.

what makes you say this? its designed for a 350, and its going onto a 350.....also, can you really adjust the fuel pressure on the holly??? this things gonna be SICK!!!

[Matt 4.3 TBI]

what makes you say this?

Because your sig only notes your 4.3, not a 350. Yes, you can adjust the fuel pressure, but you can on any TBI unit. The Rochesters just require a new regulator cover, or modify the stock one by removing the factory adjusting bolt, tapping a hole in the bottom and inserting a long bolt so you can adjust it with the TBI in place.

To get to the adjuster on the Holley you need to drill out a small metal plug on the top of the regulator cover. I could never get mine quite right, so I put the Rochester back on.

Don't throw more fuel pressure into it than it needs. You'll just run too rich, especially at WOT. You'll bog, lose power, and fuel economy. Set it just a bit lower than what you have right now and it should be good since the injectors are larger than the ones you've been running.

[imdawrlus]

ok so i get to the guys house and there isnt a holly on it, ITS A STOCK TBI...so i was pissed, i went to the junkyard to see what they wanted for a tb, 75 BUCKS, so i said to hell with it and went back and got the stock tbi....a very very dirty stock tbi....so anyways i clean it and put it on and it runs the same as before, maby a little rougher, i get a code 44 yet again, running lean, so...if anyone wants to tell me how i can make an adjustable fuel pressure regulator it would be appreciated...pictures are a plus...THANKS...

[Maximus]

Just look up at Matt's post described it to a T.No pics though.

[imdawrlus]

ok i read the article and i understand it pretty good...i have a couple questions tho...first, once you get the nut welded to the regularor housing, and you get a bolt that will be the correct size, it seems like it would be hard to adjust...does the bolt stick down far enough to be able to adjust it below the two fuel lines? also do you need a gauge for this? i'm thinking i would just adjust it as lean as i could and still have a smooth idle...thanks guys...

[Matt 4.3 TBI]

Ideally you would use a bolt long enough to adjust with the injector pod on the vehicle. You'd use a socket on a small ratchet to adjust the pressure.

I would highly recommend a gauge, as fuel requirements at idle are vastly different than higher rpms and especially WOT. I run rich at idle, but fine through the rest of the band.

[jjwalker]

yeah, same here (the rich at idle and perfect all other times)

[Matt 4.3 TBI]

http://www.thirdgen.org/newdesign/tech/tbi-afpr.shtml

This method doesn't require drilling and brazing, might be a bit easier on you. It'll be harder to adjust, though.

I'm still looking for the writeup of the method I described, I know there's one out there with photos of the process.

[Maximus]

Here is a good article on the TBI system and fuel pressure. How can I adjust the fuel pressure on my TBI system?



Bolt on an aftermarket adjustable TBI regulator from Turbo City, Hypertech, JET, etc. All of these will adjust up to about almost 15psig, depending upon your setup and pump voltage. This would be a logical replacement for a factory 9-13psig unit, for an engine that has been warmed over with a few mods.
A step beyond......GM TBI regulator P/N 17113186 is a direct bolt-on jobbie, and will give you about 18-20psig fuel pressure. Additionally, this regulator has vacuum compensation capability. If you hook the included vac port to manifold vacuum, then you'll get a part throttle fuel pressure decay of roughly 1psig per every 2"Hg manifold vacuum. This comes from certain marine and HT502 applications.
A little bigger step beyond.......GM TBI regulator P/N 17113079 is a direct bolt-on jobbie, and will give you about 26-32psig. It does not have vac compensation. This comes from some of the late 90's BBC applications.
You can add vac compensation to any TBI regulator, if you have the time and patience to get creative. Basically, you just need to make the can assembly that surrounds the backside of the diaphragm "sealed", and then plumb it to manifold vacuum. You can either do this thru sealing/welding shut the existing can, or machining a new can. The shop manual tells you not to disassemble these regulators, but in truth they are quite easy to dis/re assemble if you are careful.
You can change the setpoint of your stock regulator by roughly +/- 2psig, quite easily. Sometimes without even having to disassemble it. Remove the whole fuel meter cover and regulator assembly from your TBI and flip it upside down in your left hand. You should note a rectangular window cut in the side of the regulator can, with the end of a tang visibly located somewhere between the extreme ends of that window. The tang is attached to the spring perch within, and it's relative up/down position is roughly proportional to the setpoint of the regulator. Move tang up, more pressure, move tang down, less pressure. Now, look at the bottom of the can and you will probably see a beefy collar with what appears to be a screw tack welded in the middle. You can either dremel away the tack weld and manipulate the screw, or, you can try this next approach. Firmly grasp the collar with a good set of vice grips or channel-lock pliers, and gently attempt to force the collar counter clockwise. Chances are pretty good that the tack welds between the can and the collar will snap, and you can then proceed to turn the whole collar assembly counter clockwise to raise the pressure slightly. If this does not work for you, or if your regulator does not have a collar (as some don't), then you'll have to disassemble the regulator to modify it. Again, spin the perch counter clockwise on the screw shaft to compress the spring and raise the pressure.
The external regulator approach.........You can also leave your stock TBI regulator in place (no need to gut it unless planning to get really wild with pressures, and fear a burst diaphragm), and then graft in any flavour of external regulator, into the TBI return fuel line, remote from the TBI assembly. The external regulator can either be a "fixed" pressure jobbie without vac compensation (intended to continually override the setpoint of the stock TBI regulator), or, it can be a "variable" vac compensated jobbie (intended to provide more fuel when needed and then cut back and allow the stock TBI regulator to take control during cruise).
Whether to run a fixed pressure, or a variable pressure, at the TBI injectors all comes down to your personal level of comfort with the TBI software at hand. The most elegant approach is to select a fixed pressure operating point, then modify the software injector BPC's to suit, and then cal the VE's to suit your engine mods (this carries with it the assumption that you will either measure or calculate your new injector flow rates at your new pressure setpoint). But, if software modifications are troublesome, then variable pressures can be used to at least get things pretty durn close, and then rely upon the INT/BLM features to reign things into control.
As a general rule of thumb, I've found that most GM Rochester TBI injectors will comfortably tolerate up to 30'ish psig without issue, assuming that they are connected to individual 4/1 amp drivers. There are some TBI injectors that can be driven has high as 70psig, but they are an exception rather than the norm. Posted by Walt Sherwin.

[Maximus]

Here is some illustrations and directions to rebuild a TBI.Sorry if it's too small to see some parts.
http://www.sicgmtrucks.com/forum/attachment.php?attachmentid=1441&stc=1http://www.sicgmtrucks.com/forum/attachment.php?attachmentid=1442&stc=1http://www.sicgmtrucks.com/forum/attachment.php?attachmentid=1443&stc=1http://www.sicgmtrucks.com/forum/attachment.php?attachmentid=1444&stc=1

[Maximus]

I found this web page that looks like he copied it from some were else.The order he has directions and the pics to go with them are a little confusing.But it will give you the visual on how to make yours adjustable.TBI adjustable regulator (http://www.fl-thirdgen.org/TBIAFPR.html) On another note though I would just buy the GM brand regulator P/N 17113186.It's adjustable and has the vacuum compensation for a more accurate fuel delivery.GM parts direct has it for around 40 bucks but I'm sure you could find it some were else cheaper if you look around.Like that one article says it's the best option when you can't get a custom burnt chip.

[Matt 4.3 TBI]

I tried the vacuum-compensated regulator, with mixed results. The stock regulator spring on a stock engine WILL stall at idle. It will pull off 1psi for every 2in/Hg vacuum. At 14in/Hg (a stock engine in good condition) that'll leave you at 6 psi. There is a website that makes springs for this purpose (but for 305/350 TBIs). Supposed to give you about 10psi at idle and 13-14 at WOT. Tried that one as well, and adjusted it to give me 9 at idle. When I would open the throttle blades, vacuum would drop, and it would jump up over 15psi and the engine would bog terribly.
Did some more research, and decided the vacuum was acting faster than the computer was switching into open loop. I bought a vacuum-delay valve intended for a Ford distributor. It delayed the vacuum transfer just a hair under a second. Plenty of time to be in synch with the computer. Took it on a test drive, stomped it, it went 'put put, and then blew black smoke from the excess fuel once the regulator caught up.
I might have luck with it now, since I pull more like 12-13 in/Hg with my cam, but it runs fine with the stock regulator.

[imdawrlus]

what kind of nut do you use so that the bolt dosent back off??

[jjwalker]

http://members.cox.net/dogmatix/Thread%20Hijacked.JPG


Please refrain from speaking about the original topic!

[Maximus]

Yeah but has some very beneficial information.Matt's experience with the vacuum regulator is information I really needed.I have used them on V8 applications with great results but not tried a 4.3.I need to go ahead and install the adjustable regulator I bought but I want to make the stock adjustable to do a right up for the tech section.What kind of pressure does your stock regulator hold.Mine only holds 8psi at idle and is starving for fuel under load.I also have a 454 TBI to be used if the damn project engine ever gets built.I'm gonna need a lot more fuel and air with it.I actually had to return it to the junkyard I got it from.I got one off a newer 454 with the high pressure injectors.Matt we need to do up a tech article for all the mods for TBI's and make it a sticky.

[jjwalker]

Umm, this might help on your quest for injectors maximus!----->

http://home.earthlink.net/~jcgebhart/msindex.html

All of the injectors have color codes on the very top between the terminal posts. Match them to this. Be sure to read about the mismatched injectors too! And as matt said, vacuum regulators on 4.3 are trash! I think those are originally ford TBI regulators, because the ford meter with fuel pressure, not injector pulse width.

[jjwalker]

And to add because I am tired of editing my post, At a certain point you cant add more fuel with a regulator, or bigger injectors plain and simple and requires computer modification. That is the point where you cant get the fuel metering correct because the computer either compensates too much or too little. The TBI comp really is stupid, and it might as well be blind and deaf because it runs off only one O2 and MAP. Personally I think GM should have made TBI MAP and MAF simultaneously.

[Matt 4.3 TBI]

Don't forget the TPS, JJ. I have to agree, it would benefit from a MAF system. MAP is too prone to incorrect readings...ever get a vacuum leak? Throws the whole fuel map off.
Trying to fix fuel issues with fuel pressure and bigger injectors is a tough game. The computer will try its best to compensate to get it back within its programmed specs. Really, the best way is to burn a new PROM, but not usually the easiest method.

Heh, that info looks pretty familiar, think I posted it a while back :lol
http://www.sicgmtrucks.com/forum/showpost.php?p=2915&postcount=2

[Maximus]

Umm, this might help on your quest for injectors maximus!----->

http://home.earthlink.net/~jcgebhart/msindex.html (http://home.earthlink.net/%7Ejcgebhart/msindex.html)

All of the injectors have color codes on the very top between the terminal posts. Match them to this. Be sure to read about the mismatched injectors too! And as matt said, vacuum regulators on 4.3 are trash! I think those are originally ford TBI regulators, because the ford meter with fuel pressure, not injector pulse width.No I don't need any injectors I took the 454 TBI back and got another one.I just need to get the engine together.

[Matt 4.3 TBI]

Hey Max, my stock regulator and spring hold right around 11.5psi.
LMK if you decide to mess with that vacuum regulator, since I have one that'll probably never be used, and the spring from these folks: http://www.top-downsolutions.com/product_info.php?cPath=23&products_id=39
and one of the vacuum-delay valves they advertise.
Like I said, it doesn't work that well with stock levels of vacuum, but if you go with a cam that pulls less vacuum, it might work like intended. It MIGHT work good on mine now, but since the chip's been tuned for the fuel requirements, it's not necessary. As it was, I could tighten down the regulator to get enough fuel at idle, but then it would go far too rich when the vacuum dropped. It's probably a matter of finding the right spring for the damn thing.

I'm gonna be pretty busy until next weekend, but I'll start trying to gather the TBI mod info and we'll put something together.

[Maximus]

Sounds great to me bro.

[imdawrlus]

alright guys well i made the adjustable fuel pressure regulator and all it cost me was 5 bucks including the weld...no big problems that i couldent get around with my creativity haha...at first when i put it on, i didnt adjust it and i took it for a ride...ran pretty good...then i got a code 44...so i come home and fatten it up a bit and it runs and idles even smoother, so i drive it and i dont get another lean code for another 3 or 4 days...so i fatten it up some more and now it runs even smoother and i havent had a lean code yet...thanks guys!!