If any of you are having trouble adjusting the range of fuel pressure as I was. I found a better spring to use. I tested the spring that came in the VAFPR at about 18 lbs/in. The stock spring tested at about 8 lbs/in. The new spring I am using is rated at 15.5 lbs/in., 2" free length, zinc plated. Unfortunatly I had to buy a pack of 6 to get them. So if anyone else needs one e-mail me. I'll sell them including shipping for $4. Oh, I adjusted the screw from flush 7 turns in and now get 8.5 psi at idle and 15 psi at WOT. I couldn't adjust the stock spring beyond about 13 psi at WOT. The VAFPR (orange) spring wouldn't go below 18 psi at WOT.

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90 RS Convertible
Owner: Top-Down Solutions
(626)369-0040
http://us.f1.yahoofs.com/users/eef01...irv07AYOGczvLs
http://www.sc3gfb.org/members/lonsal.html
http://www.taskerinc.com/gs3/profiles/Lon_profile.htm

nice additional info. THANKS, and ill take one spring. https://www.thirdgen.org/messgboard/smile.gif

I'll take one!


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89 RS parts car
Daily driver 91 RS auto LO3 70k, 14x3 K&N Open element, cat-back delete.
Coming soon: 350, headers, loudmouth exhaust.

Just out of curiosity where did you get the springs? Parts store or dealer? Do you have a PN? My vapfr should be going in on Saturday.

What kind of fuel pressure gauges are you guys using?

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'87 Silverado
350 4 bolt main bore .040 over
TB Injected
Ported and Polished heads
Comp cams 268h cam and top end
Flowtech headers
3.73s on Detroit locker

Tom, have you done any orifice-restriction work within the vacuum line(s) feeding your pair of vFPRs? You don't really want an instant increase in the fuel pressure when you get on the throttle, nor do you want an instant decrease in the fuel pressure when the engine is at high rpm and you back off the throttle (which could make the engine go lean). You want delays in the rise time, and decay time, of the fuel pressure.

See my post:
https://www.thirdgen.org/messgboard/...ML/001593.html

Also, any difference in track behavior before/after the vFPR mod? I would have emailed this to you direct but couldn't find your address. TIA. - Ken


[This message has been edited by kdrolt (edited September 28, 2001).]

I purchased the springs from a local parts supply company. The spec's are: 15/16" OD, .080" wire diameter, 2" overall length, 15.5 lbs/in spring rate, Zinc plated high-carbon steel. The ends are closed, but not ground. I made a special setup to grind the ends. My fuel pressure gauge is from AutoMeter. It is a electric gauge, having a pressure transducer that is mounted in the rubber inlet pressure line. E-mail me if you want a spring.

Ken, I haven't done any expirementing w/ orfices(on my fuel system-lol). I hear what your saying about a time delay, but I don't want one. I do want my presure to react immediately. As soon as I open my throttle, my engine needs the added fuel. If my VRFPR had a delay, then my engine my engine would bog on acceleration, and flood when I came to a stop and pushed in the clutch.

[This message has been edited by Tom 400 CFI (edited September 28, 2001).]

I wanted to try an orifice also for the same reason. But we've come up with something better. The car was too lean with 8.5 psi at idle. We installed a little vacuum delay device commonly used between the vacuum source and the distributer. Once it was installed the pressure came up to 11 psi at idle, yet still climbs to the 16 psi I've set for WOT.

What does this vac delay do when you let off the gas at high rpm?

The vac delay switch slows the drop-off of pressure. It just smooths the pressure adjustment overall in both directions. It still reaches the same pressure as before that I set for WOT, just less radical of a change. The engine isn't going to like a big instantaneous spike in either direction anyway. 8^)

Just a FYI for all those that said they wanted a spring. No ones check has arrived so far. Let me know if you still want one of these springs.

I will send you a check next week.

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89 RS parts car
Daily driver 91 RS auto LO3 70k, 14x3 K&N Open element, cat-back delete.
Coming soon: 350, headers, loudmouth exhaust.

I'm putting mine on tonight! I'll let you guys know how it goes. This seems like the best mod for the money for our cars.

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91RS convertible 355 TBI 65# inj. custom compcam grind .480/.480, Edelbrock TBI manifold, open element, hedman hedders, Y-pipe, cheap cherry bomb muffler, Hypertech cop car thermomaster, Accel coil, wires. 2.02/1.6 cast iron heads. Engine specially made by Pflugerville machine shop. Forged bottom end, balanced. Coming soon: Vacuum controlled FPR, better exhaust, Torque converter, DIY PROM, bigger TB.

Three springs sold. Two still available.

got my spring. its beautiful, very shiny. and it comes with a little tip quide, and explination why you need it. nicely packaged and sealed in a little plastic bag. https://www.thirdgen.org/messgboard/smile.gif

thanks man. ill let everybody know when i get around to using it. hehe.

The "nice & shiny" is from it being zinc plated. So it should hold up great, without any fear of corrosion (other than where I had to grind the ends square). Let me know if you want to coordinate on a tech article for setting up the vAFPR. I can contribute what I've discovered. I was planning on doing it on my own, but more input is always helpful. Lon (DBA Top-Down Solutions).

More info on the vacuum delay device I used in the line to the vac port on regulator. It is called a Distributor Vacuum Control Valve (aka Spark Delay Valve) by Napa/Echlin P/N 2-1010 (cost between $10-$12) available at most auto parts stores.

I got my spring awhile back, looks great!
It'll be awhile before I put it on, but I'll let y'all know how it turns out.

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89 RS parts car
Daily driver 91 RS auto LO3 70k, 14x3 K&N Open element, cat-back delete, Richmond 3.42's, Zexel Torsion posi.
Coming soon: 350, headers, loudmouth exhaust, gutted cat.

Hey guys, I want to get one of these, but I will probably switch to a 454 tb later on.
Will the same part work on both TB's??

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89 RS parts car
Daily driver 91 RS auto LO3 70k, 14x3 K&N Open element, cat-back delete, Richmond 3.42's, Zexel Torsion posi, Accel remote mount Super Coil.
Coming soon: 470HP 383, Hooker SC/LT headers, true dual Loudmouth exhaust, gutted cats.

The only difference with the gm 454 or bb tbi is the bore size tps and iac, well, on some i guess the tps's are the same, but anyway, the injector pods are interchangable. you can even use the vafpr with your gm injector pod on a holley 670 tb unit, if you grind the little nibs off that are on the bottom of the pod to help it line up on the gm tb's for mass assembly purposes.

Thanks a lot! Looks like I'll be ordering one in a few minutes.

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89 RS parts car
Daily driver 91 RS auto LO3 70k, 14x3 K&N Open element, cat-back delete, Richmond 3.42's, Zexel Torsion posi, Accel remote mount Super Coil.
Coming soon: 470HP 383, Hooker SC/LT headers, true dual Loudmouth exhaust, gutted cats.

article would be great, Lon, judging from the mini brochure that came with the spring, im sure anything you write would be just fine, then all you gotta do is put it up and ad pictures. if you want to write it, i could organize it etc.. and then we just have to put it up somewhere for dirk to link to it. Or better yet, let dirk put it on the thirdgen server so its always up, but that really hasnt been a problem with mine being linked from tripod.

You could also get a little plug in there for selling more of em.

Would it work for Crossfire? Just curious.

yes, one of the guys above who is using it right now, is using it for xfire. there were pics of his setup, with it on, but theyare dead links now.

Someone needs help with their vAFPR. So back to the top this topic goes.

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90 RS Convertible
Owner: Top-Down Solutions
(626)369-0040
http://us.f1.yahoofs.com/users/eef01...svrK8ATT_dzvLs
http://www.taskerinc.com/gs3/profiles/Lon_profile.htm

Just for anyone's reference, here is my experience with the vAFPR so far. I have a 350 Police option Caprice with heads, cam, headers. I am trying the vAFPR to get more fuel at top end. Engine does lean out. With the spring that comes with the unit the pressure below about 3500 at WOT was too rich. Above that, it helped. Don't know timeslip wise which was better. The spring that was in the stock regulator was just too weak to get enough pressure at idle. Not enough adjustment in the screw to make up the difference. I'm going to get a medium rated spring as described above with a shorter initial length and make a spacer to make up the difference. This, I'm hoping, will give me enough initial preset to get enough pressure at idle but still provide enough force to raise the pressure at WOT. THere is a huge industrial supplier named Mcmaster-Carr in NJ who can provide that spring as well as many others. I don't have the part # but can post it if anyone is interested. The spring specs are exactly as described in the previous post. They cost about $10 +shipping for a package of 6 pcs.

P.S. You cannot simply disconnect the vacuum if you dont like it because the vacuum lowers the pressure at idle and high vacuum situations. Disconnecting will create too high a pressure.



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93 9C1, Torquer heads, Comp Cams,TBI spacer, injector spacer, cut front springs, SS rear springs,F-body sway bar, Jacobs ignition, drain pipe intake in works.

well i have been sitting around reading what everyone has to say about this. i just want to try to get a consensus between everyone.

looks like using the VAFPR with the magic spring that you guys purchased, with that vacuum delay valve is the way to go?

lonsal, do you have any springs left?

i am planning on stopping into the local Chevy place today after i get out of class to order me up one of these little treats https://www.thirdgen.org/messgboard/wink.gif.

looks worthwhile considering my lack of custom proms and lack of knowledge on burning my own.

the question was asked, but not really answered (i dont think)...is this better or worse as far as eprom burning goes?

Jon are you out there? you havent really had anything to say about this..seems like it would be right up your alley.

-Brian

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1991 Camaro RS
GMPP 350 HO crate engine - Holley TB, MSD ignition, SLP exhaust, everything is new
700R4 - 2,400 stall converter, vette servo, shift kit
My car's webpage - z28boy.cz28.com
President - Central New York F-Body Association
Email - z28boy@twcny.rr.com
AIM - "Z28 Boy"
http://z28boy.cz28.com/pictures/3go1.gif
http://z28boy.cz28.com/pictures/3go1.jpg

Still have two springs in stock. I just had an e-mail inquiry from Brian Annicharico for one (AKA z28boy) and sent back contact info.

I got the springs at a local supply co. But they come with the ends closed, not closed & ground. I set up a fixture to grind the ends flush, like the original springs are.

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90 RS Convertible
Owner: Top-Down Solutions
PO Box 5601
Hacienda Heights, CA 91745
(626)369-0040
http://us.f1.yahoofs.com/users/eef01...svrK8ATT_dzvLs
http://www.taskerinc.com/gs3/profiles/Lon_profile.htm

They also offer the spring with the ends closed and ground.

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93 9C1, Torquer heads, Comp Cams,TBI spacer, injector spacer, cut front springs, SS rear springs,F-body sway bar, Jacobs ignition, drain pipe intake in works.

Z28boy, it's not a replacement for prom mods. This is a way to increase the fuel flow capacity of the current injectors for modified engines. I have not tried the vacuum delay but that may prevent the over rich situation when flooring it from a dead start.

yeah i know its not a replacement, but what i meant to say is that its good UNTIL i get my eprom burning up to snuff. we'll see how that goes...everyone pray for me..

-brian

o *** who art in heaven. etc.... https://www.thirdgen.org/messgboard/smile.gif or something like that, sorry not very religious. https://www.thirdgen.org/messgboard/smile.gif

as for doing it then prom burning, i guess it was answered that its easier to tune, or at least not harder.

and i think it could at least offer some releif for one who is not yet ready to do their own proms.

Yes you can. If you just lower the presure with the adjusting screw to the same presure had before you did the mod, then the preformance of the VRFPR will be identical to the stock unit, if the vacuum is disconnected.

I guess that would be true. My experience is that there is not enough adjustment range in any FPR spring to make an adjustment of that size. Guess I should have clarified.

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93 9C1, Torquer heads, Comp Cams,TBI spacer, injector spacer, cut front springs, SS rear springs,F-body sway bar, Jacobs ignition, drain pipe intake in works.

I had to swap back in my original spring from the stock non-adjuatable fpr at the track temporarily because the vafpr one was causing it to run way too rich at WOT. With the stock spring, the set screw adjusted and the vacuum line disconnected it was just like the stock unit. That was of course before I bought the new spring and vacuum delay valve.

hey, lonsal. Did that vacuum delay help with the over rich situation from the pressure spike that you get when stomping on it? Did you take any rich/lean data? You got a 305 or 350? What did you end up with for pressure at idle?


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93 9C1, Torquer heads, Comp Cams,TBI spacer, injector spacer, cut front springs, SS rear springs,F-body sway bar, Jacobs ignition, drain pipe intake in works.

Yes the pressure switch helps with the pressure spike. The idle is set at 8 psi, WOT to 15 psi. Too rich at WOT was cured with custom programming a chip (only because the chip programming was already paid for). I believe it could have been cured by adjusting the spring as well. We backed off the fuel add table so I have more room to tinker with adjusting by spring at the track. Stock 305 with 105K miles on it. Running a LT1 cam with stock springs and running a LT1 fuel pump in tank. Check my profile by clicking on the link if you need more details. Lon

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90 RS Convertible
Owner: Top-Down Solutions
PO Box 5601
Hacienda Heights, CA 91745
(626)369-0040
http://us.f1.yahoofs.com/users/eef01...svrK8ATT_dzvLs
http://www.taskerinc.com/gs3/profiles/Lon_profile.htm

Thanks alot. Mine's away for the winter now but finishing this up will be the first priority for spring.

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93 9C1, Torquer heads, Comp Cams,TBI spacer, injector spacer, cut front springs, SS rear springs,F-body sway bar, Jacobs ignition, drain pipe intake in works.

FYI guys, I've just re-stocked on springs. Five in stock currently. Still holding the $4 price. E-mail me if interested. Lon https://www.thirdgen.org/messgboard/eek.gif

http://us.f1.yahoofs.com/users/eef01...OK8b8AWHsjzvLs:eek:

OK, I'm trying to figure out the best way to make this FPR work for my combo. Mods are in my sig. The spring it comes with has me running way rich. I pulled my o2 sensor and it was very black. Would the stock spring be ok with 65 pound injectors, or should I switch to 80# (I have a spare set), to keep from going lean if I go to the lower pressure? If you guys that are using this spring post your engine combos and results, I would appreciate it very much, as it would help me (and others) decide how to go about properly using this FPR. Also, what do you guys think of running 305 injectors on a 355 with the Vacuum FPR, with the spring it comes with? Ideas? Is there any way to reduce/adjust the pressure on the vacuum unit without changing springs?

The 305 is rated at 170 fwhp, and the max duty cycle is around 82%. The stock injector pressure is approx 10 to 11 psi. The vFPR is good for 18 to 20 psi at best, and the fuel delivery will increase by the square root of the new to the old pressure:

sqrt(18/11) = 1.28 or 28% increase. So that means that if you still use an 82% duty cycle on the injectors (for longevity), then you'll make only 28% more power. So that's 170*1.28 = 217 fwhp. That's waaay too little for even a modified 305, let alone a 350 (or 355).

The above gets you in the ballpark, it's not meant to be precise. In this case, it doesn't much matter because the conclusion isn't that sensitive to the exact amounts.... whether it's 28% or 25%.

Conclusion: you need larger injectors, and a lot of tuning. The stock 305 injectors are too small, and the vFPR isn't enough to do the job. A new ECM also wouldn't be enough. You need (a) larger injectors, (b) vFPR and (c) maybe (later) a new ECM.

Remember that GM went to vFPRs on ALL L98, LT1 and LS1s. They may have even used them on tpi LB9s. There is a reason -- the injector's don't have to pump at as high a duty cycle if the fuel delivery is enhanced by increased fuel pressure ON DEMAND (at WOT). FYI. - Ken

beautiful response

Which way did you guys install the Spark delay valve? with the distributor side toward the vafpr or the other way?

Distr side towards the vafpr. The purpose is to delay the vacuum to it as you would to a distributor. Lon

Yeah, that's what I was thinkin. Just making sure I had it right.

Who is using this unit still with a stock spring? I'm curious because from the info that's been posted, the stock spring is WAY too weak and any good big of vacuum will cut the fuel pressure by at least half (according to my experience with the holley). I think so far I'm the only guy running a Vac.AFPR holley 670 because I had to make it myself (not hard at all).
I'm really curious about the fuel pressures, to test FP at WOT just unhook the vac. line and plug it up.
I've noticed a HUGE difference in the idle stability even with a stock eprom, definatly a good tool to use so long as it's not dropping the FP too much.

This was a good post to bring back, Jon. I was aucutually going to look for a good thread on this stuff, but it looks like you found it for me :)

Wow this old. I started it even.

I am using the stock 9c1 spring and a quarter...On my 89 9c1 Caprice.

so what are the part number for every thing that i need to do this

I used the stock spring. 14-15 PSI @ WOT, and 10 PSI at idle. Works sweet.