i had just installed my new mallory 3 port (4309) regulator the other day and its acting kinda strange. when i turn on my fuel pump, a stock tpi fuel pump, and set the fuel pressure to anything above 3 psi, the regulator begins to pulsate slowly and the pressure wont stay constant. the pressure gauge on the line at the carbs starts to bounce from 3psi to 5psi and wont stop. i called mallory and they said its because my return line is not big enough. im using the stock tpi lines at the moment and really dont want to change them any time soon.
one of the times i was working on this issue, i had an idea that maybe it was due to a pressure inbalance after the regulator return port. so i extended my fuel hose on the return port and kinda kinked it like a garden hose. if i bend the rubber hose a bit the pressure evens out and the stock pump sounds like it is straining less. at this point i was a little confused how more restriction would cause it to flow better. i took the rubber hose off the return line and put it directly into a gas can so there was no restriction at all. the regulator now pulsates extremely fast when i adjust the presure.
Would putting a flow restrictor on the return line fix this, or maybe another regulator (dead head) on the return line?
thank you

 

did you try setting the pressure to a carb friendly 5 to 7 psi and see what it does. what if you rev the motor does it smooth out? sounds like the pump is pulsating and causing this problem, fuel filter fairly clean/new? Typically means you need a larger return line, but try it with the motor running first, mine would jump a little until the engine starts sucking fuel while running, but i'm using 1/2" fuel lines and a huge pump nothing factory.

 

i have not tried to start the engine yet. im still setting it up while all the parts come in. the higher i set the pressure the faster it bounces around...i just didnt want the first time starting the car to be a bad memory. the pump had not given me any issues when i was running tpi, but i am not going to rule it out. it just doesnt make sense that when i make a bit of back pressure to the regulator the pump and regulator work better. when i turn the pump on and it starts bouncing pressure, if you hold the regulator you can feel the whole assembly kicking around. plus my set up isnt exactly normal as far as carbs go...here a pic if your able to help me

p.s. the rubber lines are just to get the whole system set...not a perm solution

 

i've got the same problem you're talking about. but only if i set the key to ignition on... and only sometimes. when the motor is running, i got no problems with the regulator/psi bouncing around etc. stock return lines, too.

nebu.

 

i also wouldn't trust that cheap little guage on that line to tell you accurate fuel pressure, i bought one and it was off by 5 psi with the motor running compared to an autometer guage off the regulator. Mine bounced around a ton on the motor, but the autometer stayed fairly constant. although with the regulator bouncing around, mine doesn't do that which leads me to think the fuel pump is being deadheaded and surging possibly.

 

thank you for the info...i really do think that it is an issue with the regulator needing equilized pressure after the bypass valve to slow its movement down. when i squeeze the supply hose to the regulator it isnt pulsing, but when i squeeze the return hose, it is pulsating quite a bit. if it was my FP wouldnt the supply be bouncing too?

im also starting the wonder about using a larger than 5/16 hose (i dont remember the exact size) to hook up the return line to the regulator, it could be building up pressure in that hose. could you guys take a picture of your regulator set up for me?

thanks again

 

mine is all -8an braided line which is 1/2" approximately send and return. my buddy ran 3/8" return and hasn't had any problems either but both of these are aftermarket fuel line setups. if the return is buzzing then wait until the motor fires up to see what is going on since the flow will lessen while its running and the motor is using fuel. Sounds like pressure creep almost, but if the pressure isn't slowly building up i'm out of ideas.

 

no it doesnt build up it just jumps around....if i set the regulator to like 5 psi it will jump from 4 to 6 psi and do it on like one second invtervals. when i removed the return line and ran it straight into a gas can under the car it did the same thing but bounced back and forth real real quick. when i get the distributor in ill start up the car and see what happens. thanks again xpndbl3

oh and the crazy thing is... when i kinked the return line and caused back pressure the fuel started flowing faster and more consistant. pressure at the gauge also went down a little bit ...to wierd

do you think taking the fuel lines off the carbs and letting them flow into a container would simulate the engine running?

 

no that would simulate an open line with no resistance. honestly it might be that cheap guage on the carbs, i've had no luck with them and would use an autometer first. start it up and drive it around to see if there's fuel flow problems, if not i really wouldn't worry about it. I did notice in your picture that the adjusting screw/nut whatever it is at the top of the regulator is out quite a bit more than mine is, but my pump only puts out 14 psi per the manufacturers owner manual. As long as it doesn't leak give it a try. If it doesn't clear up, I do have an extra regulator laying around that worked well 2 years ago, but i'd replace the o-ring with their rebuild kit that i'll let you have for $35 shipped to your door, if you can't fix it by then. I won't be back from florida until at least january 3rd from vacation, but i will answer any PMs you send me when i get home. It'll be nice not to see snow everyday like the last 4 weeks straight now. I wish you luck.



ALSO i just noticed your from chicago, which is close to me if you want me to check it out sometime when i get back. i typically work for pizza and drinks.

 

thanks man

 

Im having the same issue's with the 3 port and stcok tpi pump. i heard of a few other people having the same problem

i was told it was because the stock pump is pushing like 40lbs for the tpi and it's trying to regulate it down to 5-7 lbs dunno how tru that is.

 

some of the people on this site have gotten them to work with stock lines and pumps. im going to try to figure it out next weekend and see what i come up with.

 

from my understanding the tpi in stock form the return line is not being stuffed back with fuel. with the carb most of the high pressure from the pump is being fed back to the tank via the return line. I dont think that this is the best way of feeding the carbs for fuel. I am looking for a way to do the carb thing myself as i just pulled my 305 and tpi.

 

does anyone know of a in tank fuel pump that just puts out less psi? My father-in-law said he had justed replaced one for somebody the other day and it put out less than 10 psi. this could be another "fix".

 

im not sure about the in tank pump, but i ordered what i think will fix my situation. ill keep you guys posted G/L

 

if you're going through the trouble of dropping the tank anyways, just buy a sump and have a radiator repair shop weld it on and run an external fuel pump like a holley blue if you're looking for a bigger pump, remember this pump is LOUD and not recommended for a daily driver at all. Furthermore if it is a daily driver carter makes a great quieter fuel pump that puts out 7 psi and doesn't need an external pressure regulator.

 

Going of what xpndl has already said and adding to. DONT trust that cheesy guage on your carb line, they are (putting it nicely) JUNK!!! When we all started racing years ago we had 5 cars lined up in our pit spots, just returning from a pass...when set static we had them all reading 7psi idleing, after they got back the numbers on teh guage varied from 0psi to 13 psi...that is no joke. Those lil junker's get affected by ambient temps, seems the hotter they get the more they fluctuate. I even bought a high dollar liquid filled holley brand and had the same results. the non liquid filled are more prone to needle dancing than the liquid filled, but either way they are not a guage to put any trust in, you need a separate quality guage that you can mount away from the engine and heat. I switched to a Autometer guage mounted under my cowl and have idle pressure set at 8.5psi and Holley guage on inlet to carb reads anywhere from 10psi to burying the guage. You also want a guage in eyeball veiw so you can monitor what's happening under WOT-I think many would be suprised what they actually see...I know I was

DO NOT put much time into this problem unti you get the motor fired, once that thing is alive and sucking fuel, it will CHANGE EVERYTHING!!! All your going to do now is chase your tail with a tedious problem that will have no bearing on anything....you dont set your fuel system psi's and such with nothing able to use the fuel....what's the point??? once the motor is fired and using the gas is when you need to address those issues. Get it ballparked for now which it sounds like it is and tune when it runs....otherwise your wasting valuable time and money for a mute point.

With my A2000 I lost no psi anywhere on the track, that gave out on me and I was forced to run a holley red (only one in stock in town) to keep me racing that day. After I set psi to 8.5 it would quickly dip down to 3-4 psi at WOT and car slowed down .3, chugged and struttered also since it could not keep up with the demand the engine required. Even my holley blue with the high pressure spring drops down to 5-6psi but I have not noticed a ET or mph change so I have to assume it's keeping enough fuel in the bowls to get me through the 1/4mi, anything longer and I bet it would start to drop off too.

Now that I've said that, and just imagning what in that motor and the rpm required with that tunnel ram to make it worth your time/money installing fuel delivery will be at a premium-your now feeding 2 carbs (though smaller it's still 2) and amount of fuel motor will need to run I would not recommend anything smaller than 140gph, that would be my bare minimum for pump capacity, 150gph would be better though. Anything that is factory preset at 7psi and does not require a regulator will not be sufficent, even if it's just a dialy driver (in this application on this thread)-which with that sticking outta the hood is highly unlikely

 

thank you very very much IHI. i'm taking the advice of waiting untill the car starts to t/s the fuel "issue". i cant do anything ATM because i dont have the distributor installed, gotta get the mechanical advance set, so i was trying to make the best of the down time till it gets here. as far as what im running in my car, its no where near as beastly as your car. besides the obvious tunnel ram and duel 450's, i have a stock block w/ flat top pistons (10-1 comp with heads),edelbrock roller cam(234 int./238 exh,0.539 int./0.548 exh. lift), edelbrock alum RPM heads, edelbrock headers no cat and full exhaust, hv oil pump, tri power distributor and coil, PJ gear drive, and then other little things here and there.
now as far as the tunnel ram, i keep catching flack from everyone how this was such a horrible idea. for some reason everyone thinks i wanna race people everywhere i go. would you guys be able to give me a good idea what i jumped into? a summit sales guy said i wont even be able to start my engine, summit tech said ill be fine if i get it tuned right, and this article, http://www.hotrod.com/techarticles/60638/index6.html ,says something different. thanks for your opinion.

oh and ill buy a new gauge

 

oops here is the site. sorry

http://hotrod.com/techarticles/60638/

 

Honestly, I've only been around 3 guys/freinds that have tried a tunnel ram. All were told by numerious people before they bolted it on they would make more power and tuning would be alot easier if they stuck with a single plenum....in all 3 cases after alot of "tuning to show everybody wrong" they came off and a sinlge plenum was bolted on and cars ran alot better.

On the other hand, I've heard/read first hand accounts from racers that claim these guys obviously missed something and they are not "that much" harder to tune than a single set-up...but I've heard/read alot more horror stories about them than good. They do have a cool factor, but you will be tested by many since it screams-"I'm fast", then when you get walked or barely keep up, "that car is slow or that car is junk" will be the new badge your car will have. The older I get I could care less what everybody else thinks as it's my car and my money, but am also of the opinion if your going to flaunt items such as big blocks, super chargers, tunnel rams, nitrous..you better be laying down some really good power/impressive number or else what's the point.

I'm not flaming you, but you set-up is not going to work together, you've got a short block and cam deisgned for low to mid rpm power and a intake that wont come in until the after the stuff it's sitting on is all done. By design the tunnel ram is not a low rpm deal and thus streetablity will suffer, now if your running strickly at the track, have a high compression, big duration, high rpm spinning combination that 377's are designed for, the tunnel ram would work great...but in this case, your is strictly eye candy that will not serve any purpose other than giving you fits and leaving alot of power on the table. You'd be further ahead money and time spend tuning by switching back to either a dual plane rpm air gap or a vic jr with a 1" 4 hole spacer. you still get the added plenum and speeded port velocity, but your bringing it in at a much lower rpm and will be able to use it.

Nothing wrong with trying new/different things, that's the route I took initally building my car years ago-trying new things to shut up the nah sayers...but you'll find as I did, with a sbc we're not re inventing the wheel and most everyting has been tried already so there is alot of merit to what the masses have to say...cost me alot of money that was literally wasted to get to a goal/point that everybody else was pointing the easy road to

Quick Edit: Just did a quick read through on your link. I will say on a bone stock motor one could "feel" 20hp and possbily see it if track testing-since mph might increase by .5mph or so. (I'll just use 20hp as an example for this since the tunnel ram made a little more power than the rest but not quite the 20hp mark)

BUT, here's your real deliema, your have a nice long block with good parts everywhere but on top. That motor should make some really nice smooth numbers through the powerband as it sits, and the simple sad fact, even if the tunnel ram can make 20hp more than a conventional set-up, you wont see it on the engine dyno 20hp will come across as a big increase (which it is if the price is right) but once bolted in the car and run in the real world, you'll never see that 20hp...but lets assume you now have that additional 20hp over conventional...how much extr money did that 20 hp cost? was the added headache of tuning and adjusting linakge worth that power you'll really never see? Then when your crusing around town and if tune is not dead nuts, is the fouling plugs, black smoke puffing, dog outta the hole really worth it?? According to the masses as can be seen by real cars on the street or track, you'll be hard pressed to find many tunnel ram set-ups.

Again, I'm not flaming ya but am really trying to help show you a better cheaper way to extract power from your combination. From the looks of the pretty engine bay I assume it's a really nice "show type" or "super clean" car, so in your case maybe the headaches are offset with the ooo and aaaa factor so it'll work in your situation. I cant emphasis enough about trying soemthing different and giving it a good run, especially with an intake. Those are a dime a dozen and easily changed...ya got it already so give'er a shot and see how you come out and let us know.

 

its nice to finally read a post that isnt just an opinion. i was a little scared to use the tunnel ram because they were supposed to be for like 6000-10000 rpm. when i looked at the cam i had and the weiand tunnel ram they only had like a difference of like 1000-1500 rpm according to the people who make them. i ran the cam w/ my tpi before i tried this, and it worked pretty good, but the cam was just too big. i loved how it sounded and how it drove. ever since a child ive been a fan of the "blower" look, and i would like to think of this as my pre 6-71 set up. i really appreciate all of this, it really helps.
hey i will give it one hell of a try, and when i get sick of it ill go to the next option thats why i bought a little 2005 41mpg toyota
thanks again

 

Fuel pump output is a combination of flow volume and pressure. The TPI pump puts out 40+ psi at a flow capable of supporting around 300 HP. If you lower the pressure, the flow goes up and vice versa. So, the pump can support more HP if used at a lower pressure, but less if used at higher pressure.

The part about stuffing the return line is a bit suspecious. Yes, the supply line is 3/8" and the return 5/16", but there is no restriction at the end of the return line. The amount needing to be returned under no-load conditions on the engine should not overwhelm the return line.

The factory had a lower pressure in-tank electric that was used in the ZZ4 conversion kit. I don't have the parts list with me or I'd give you the GM part number.

 

You could try a TBI pump, I suppose. They bolt physically in the tank pickup the same way but poop out around 18 PSI. Maybe a high performance TBI pump of some kind. No issues whatsoever with fuel pressure pulsation when I converted my 92 RS (305 TBI) over to carb, using the Mallory regulator and factory in-tank TBI pump.

 

I have a TBI pump in my tank, that is what it started life as, I have Mallory 3 port with return line that is stock. The only issue that I had was carb. Cheap carb from a discount parts house. Two carbs later pressure is 7 psi no trouble. This was the second vehicle that I did this too and this is the only issue that I had. The fisrt one was a camaro that started life with a 2.8 MPI. Left all the fuel lines stock on that one as well!!! Good guages are a must!! Don't cut cornors there.