Quote: Originally Posted by RBob Do you have the Holley TBI unit? The FPR on those should already be adjustable, and from the top side. Not sure if a AFPR set up for a GM TBI unit would bolt on either. RBob. Yes I have a HOlley, I was told to get the aeromotive Uni bypass regulator? So what are you saying here? I dont need one I can adjust it already? Whats up???

Depends upon what you are looking for. The Holley TBI unit FPR is supposed to be adjustable on it's own. By how much can be a question. Although springs are easy to come by.

I've also seen the Holley TBI unit FPR vacuum referenced. Not sure how much additional work was required for this.

However, both of these you can check out with what you have.

For the best setup, even more so when using a GM TBI unit, is the Aeromotive 13301 FPR.

The thing is, depending upon what is required, you may be able to use what you have with the Holley TBI unit.

I just don't like seeing folks spend money when they don't have to. Plumbing in the 13301 isn't going to be cheap. On top of the regulator still need fittings and hose. And with EFI, I don't trust a lot of rubber lines.

RBob.

Hey rob, well I dnt have all the money in the world. but if it benefits my baby and I am going to need it I will put the money in sumtimes. But right now I jsut want to get my baby running correct and everything. She is still a 305... sooo I did most mods I want to do to the engine wise. Next I will be getting a 350 to drop in. So just point me in the direction

yes I know hoses, I was going to replace my fuel lines with some braided steel hose with 6a/n fittings anyway, I dont like the stock lines, and they are getting in the way. Sound like a good idea??

Also If I want to replace the fuel line that goes all the way back to the fuel pump, what should I use? Or where can I get it? even the return Ill change too since I wil be underthere.

Now if I am going to change the fuel sending unit becuz my gas gauge doesnt work now. Should i go and replace the fuel pump, with a 190 gph? or should i just leave the stock I have ???

upgrade the pump. epically if you are going to put at 350 in there eventually. it will allow you to bump up the fuel pressure down the road if needed.

I had a very similar build up in a 5 speed silverado I had that had the stock TB. I found a throttle body off of a 454 and sent it to a guy in Texas. He takes the cores and sends you a different 454 throttle body thats been overbored with new butterflies and your choice of throttle linkage. The one he sent flowed about 850cfm. I had to port my edelbrock intake on a mill at my shop. I also bought some Venom 65lb injectors and rebuilt the injector pod with an adjustable fuel pressure regulator. Lemme tell you, it made a WORLD of difference with all that had been done to the rest of engine. The guy sells them on Ebay, I'm sure I could find a link if your interested. Has excellent feedback, and had it to me in about a week. The throttle position sensor plug is different on the 454 TBI, but you can get an adapter plug for about 12 bucks that plugs right in.

Performance costs mucho dollar... and a lot of reading when it comes time to tune the thing. So get used to it.

While were on the topic of larger TBI units, how much horsepower can a bored out stock TBI unit support assuming it is 46mm and flows 490cfm?

Quote: And with EFI, I don't trust a lot of rubber lines.

Not to be confused with Aeroquip synthetic push fit lines with corresponding fittings. State of the art I might add and sooo simple to work with. Costly? You be the judge!

I cant see how a GM 7.4L or a Holley 670 CFM can be much of a restriction for most of the modified TBI engines we have seen. Seems injector capacity is the restriction unless you use a large injector and then it supports > 400 HP. My last WOT run showed 80% duty cycle with 80 lbs injs at 23.5 fuel pressure. Not sure what that equates to in HP but I suspect around 350. MAP with key on is 95 and that WOT log showed 95 so certainly not restrictive for my 7.4L GM unit.

thread resurrection

ive got an opportunity to pick up one of these holley throttle bodies for a good price. has anyone found out the adjustability of the regulator on these? does anybody know what the flow rate on the injectors are?

also a separate, somewhat random question about the aeromotive regulator. on summits website it says that it comes with two springs, one for presssure from 3-20 psi and another for pressure from 20-65. lets say i require 30psi at WOT so i use the second spring. in theory, wouldnt that mean that at idle the fuel pressure will be as low as possible with that spring(20psi) but still be way higher than needed causing flooding and other issues? or is my understanding of how the regulator works not right?

I have that reg and I used both springs. the weaker spring I run at 19 lbs (80 lbs injs) and it it pulled down to around 13-14 at idle. the heavy spring at 22 drops to around 17. So idle quality was better for me with lighter spring. Without "special tuning" what happens with overfueling at idle is it moves to asynch firing of injs and idle gets funky.

so if i were running that regulator using the bigger spring would i be able to smooth out the idle if i were using something like EBL? Or would idle quality still not be as good as it would be if i were just using the smaller spring.

Well I sent an email to Holley asking what the flow rates are for the injectors and I just got a response. They are only rated at 58lb/hr at 12psi. So other than having 2" bores, it appears as though they arent much better than the stock unit.

Holley rates the injs at higher pressure that GM. I believe the ratings they publish are 20 lbs. That info is at their site in install manual. Idle quality is better IMO with smaller injs at higher pressure. So I would use the smallest size that adequately fuels engine at WOT at say 30 lbs. Not sure if Holley injs can be run at thirty lbs FP. Holley would know.
If you have to run say GM 80's at 22 lbs then yes the VAFPR is helpfull. A WB will help you determine what is going on in your tune at idle.

hmm, thats slightly conflicting info there.

my plan is to replace the injectors in the 670 with the 85lb holley injectors and use the aeromotive fpr using the smaller spring. that should provide plenty of fuel at WOT with lots of room to grow while still providing a smooth idle.

Holley 85 lb are smaller than GM at 80. IMO. I recd that info from Holley over phone back when I was needing to meet demands of my mods. That was 2003 and it may have changed. also it is in the install manual for Commander TBI System. Not Holley unit if I recall.

see this:http://holley.com/data/Products/Technical/199R10502.pdf

see this for flow: part 522-54 60lbs at 12 and 85 lbs at 21. That is there largest injector. http://holley.com/types/Commander%20...ce%20Parts.asp

i just found the injectors on holleys website. the 85lb injectors are rated at 21psi. according to holley, thats 60lb at 12psi but the fuel pressure calculator im using says thats 64lb. and if you go by the 60lb rating at 12psi, that converts to only 79lb at 21psi using my calculator. so now i dont know which one i can believe.

522-43 is the 60lb@12psi/85lb@21psi injector. and that is the page i was using but the conversion between the two flow rates and pressures are wrong.

either way, it would appear as though that is the injector i would need to run. ill just have to do some playing with the pressure to get it right.

I an not positive but I think I read the holley inj pod can be replaced with a GM and then you could run GM injectors if you care to in that Holley TBI. Older Holley were not the best but I think recent ones are A-OK.

I run the Holley TB with a GM injector pod on top of it

thats something to consider. where did you get your injectors at? i cant seem to find any place that sells GM tbi injectors anymore. either the links from the tbi build threads dont work or those companies no longer sell the injectors mentioned.

FIC Injectors (rebuilt) GMpartsdirect or RockAuto (new)

Can try Ebay also.Thats where I got my 80lb injectors