TBICamaro

Hey carb people. I thought of posting here because you guys seem to be less **** about things, than in some other boards.

My question is, im switching from my tbi to carb, and was wondering about that nice little fuel return line. I bought a cheap 3/8 puralator regulator and was thinking of simply pluging in the fuel return line and regulating the main fuel line(to 5 1/2 psi) like i would on my simple(i love it) 73 camaro, and leaving my charcoal canister intact, for presure relief.

Do you guys forsee any problems? have any of you done this. Like I said i like carb people "usually" because they are a no BS kind of people. So what do you guys think. And dont tell me that ill get a code 32 or something like that..HEHE


Anyways thanks for the help!!

TBICamaro

Oh yeah by the way, its a 600cfm edelbrock. Also do you guys know about hooking up the tv cable on this damn thing. Damn overdrives, i love it.

I was just gonna hook it up, but then all the picky people told me my tranny was gonna fly out the window and the car was gonna blow up and fuel spew into my eye. (TPI people hehe ) Kidding

Thanks again guys

five7kid

iTrader: (14)

Carb-equiped cars used the return line. It's 5/16", same as FI cars. The pressure your pump puts out is higher than the mechanical pump would produce, but the factory had retrofit kits using an in-tank pump and regulator to solve vapor lock problems, and the ZZ-4 conversion kit uses the same. If they did it that way, you shouldn't have any problem doing it, either. Only real question is if your "cheap regulator" will do the job for you.

I'll defer on the TV cable question. There's a post on the general engine board about problems like that with Edelbrock carbs. Take a gander over there.

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82 Berlinetta, orig V-6 car. Rescued w/86 LG4/TH700R with all harnesses, sensors, ECM, etc. 3.08 open, cat-back from '91 GTA, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LB9 w/ZZ3 cam, World 305 heads, exhaust, paint, etc.).
57 Bel Air, my 1st car. Currently 396 .030 over, Weiand Action+, Edelbrock 1901 Q-Jet, Jacobs Omnipack, 1-3/4" headers, TH400 w/TCI Sat Night Special conv & shift kit, 3.08 10-bolt, AMSOIL syn lubes bumper-to-bumper. Best 15.1 @ 5800' Bandimere. Daily driver while Camaro was being put together.

Jester

That reg won't really work for ya man. you'll burn out your intank pump in no time flat cause of the extra resistance...if you're just gonna regulate down the stock pump you MUST get a 3 port regulator, bout $70. If it were me I'd just get a Holly inline electric pump for the same price.

There is an article on this swap in the tech section here, might wanna check it out.

As far as the TV cable, the trick is to make the mounting point on the throttle arm the same distance from the shaft as it was on the TPI. I've never seen an Edelbrock up close, you might have to get an adapter or drill a new hole or something.

TBICamaro

DO you really think my afpr would kill my pump? Even if its only around 10 psi down to 5 1/2 psi. I dont have tpi which i believe is around 40 to 50 or so, I would see a problem with that but do you really think that 10 down to 5 1/2 psi would hurt. The box in the afpr says not to use it on systems with more than 10 psi, so i thought 10 down to 5 1/2 would be fine?????

I know my fuel pump is rated at 9 to 13 psi. I hope i got a weaker one then.

Thanks for the advice guys anymore that you might shed would be greatly apreciated.

THANKS

Ed Maher

What Jester means by burning out your pump is apparently you are using a dead-head style regulator (no return line.) Whenever it sees more than X psi on teh carb output side, it simply shuts fuel flow down. This will put extra pressure and resistance to the pump which will be fighting to push fuel. This is what will burn it out.
You need a 3 port regulator so that when there is over X psi the xtra fuel flow back to the tank, keeping the pump moving and happy.
As for the carb. I'm sure it can be done, there is probably an adapter kit made for it, seeing as how there are plenty of people running those carbs with the 700. Check Jegs or even call theirs (or edelbrocks tech line) and ask. Or maybe someone here will quick post and know the PN you need.
...ed

FastBroker

FOr the one hundredth time, pumps don't make the pressure, regulators/restrictions do. You do not have to "regulate down" any electric pump pressure but you must install a regulator to get the pressure up!!! ie, If you unhook the TBI (or TPI) fuel inlet/supply line at the TBI (TPI) unit and aim the hose into the air, you will shoot fuel into the air with only minimal line pressure, the pressure being a result of head loss and the minor resistance of the fuel line internals itself (fuel touching sides).

Any 3 port regulator will work just fine as long as it can flow enough fuel in both return and feed circuits.

Also, I believe that a two port regulator can be teed in to a carb system so that when the pressure gets above that 2-port reg's max, fuel will bypass by the regulator and back into the tank via the return line. ie, in the line from the TBI pump to the carb, splice in a tee and naother hose to the INLET of the two-port reg. Then connect the OUTLET of the two-port regulator to your existing return line.

CamaroZ_85

i use an edelbrock 600 cfm (#1405) w/ my 700R4...the only thing i needed was the little pin that the tv cable snaps on to, i forget the part number...but look in an edelbrock catalog...they have a carb accesory section and it will be in there. also, you might need the throttle/tv cable brackets from a carb motor, im not sure if it's diff. from the tbi...

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350, Comp 262, Edelbrock Performer intake 600 cfm carb and exhaust, headers

FastBroker

Hey CamaroZ, how does your setup (in signature) run??? Looks like good driveable combo... Most people are run too much cam and manifold but yours looks ok and matched.

TBICamaro

Hey fastbroker, what you just said about the 2 port hook up. I like it! Please explain it in greater detail, i am thinking along those lines but im not to clear on it. On how to hook it up.

If i get the line hooked up with a two port afpr then ill give you the tbi for practically nothing.

Thanks for everyones help

five7kid

iTrader: (14)

I must have misunderstood what you were trying to do. By all means, use the return line! I'm not sure if what Fastbroker suggests will work, though, as the regulator responds to outlet pressure, not inlet pressure. Putting it in the other way around (inlet to the return line) probably wouldn't work, either, as the reg will be open at less than 5 psi (for instance), and close down as the pressure got higher than that - exactly the opposite of what you want to do.

Using a three-port is your best bet.

TBICamaro

Ok im gonna think of some crazy shi$ right now. Ok now listen closely. WHAT IF...

I put a spliter on the incoming fuel line and split it in two take one of the NOW split hose and route it to the regulator and from there to the carb, then take the second hose from the spliter and route it directly to the return line. I would probably drop tremedousely in presure and alot of the fuel would probably end up right into the return line right before it passes the regulator. BUT WHat if i put a restriction on the line that fits right before the return line (the now split fuel line) to slowly "bleed" the fuel and relieving just enough pressure so my pump wont have a hearth attack.

I dont know if im getting this clear across. Im trying my best to explain this in writting. Crap ill make a diagram of the posibilities.

I know alot of you would just tell me to get the three port, but i dont have the money to spare (literaly not even enough for a 3 port afpt). And money is now needed for my son, so i must make this work, I got the parts for free, anyways otherwise i woulnt be doing this.

Thanks again guys, your help means alot!

five7kid

iTrader: (14)

That could be done. Sizing that restriction would be the nightmare, as you would only be able to optimize one fuel demand condition. Too large, you only have adequate pressure at low demand. Too small, you have too much pressure except at high demand.

It would work if your "restriction" was actually a relief or check valve, set to open at 5.5 psi. But, now you're talking about more $'s.

You'll either have to try your 2-port and hope you don't do your pump in, or get a 3-port.

FastBroker

The "restriction" you are talking about that will make 5.5psi is a REGULATOR, man. Just have to find a two-port that works as a bypass. SOmeone sells them, but not sure who. This is the way the reg works inside the TBI unit, actually, just on a smaller level. ie, inlet side is also running by injectors and pushed on the spring/seat. When the pressure beats the spring, fuel flows by the seat/spring assembly, "bypassing" the reg, and going into the return line and back to the tank.

TBICamaro, I'll take you up on that TBI unit, by the way.

[This message has been edited by FastBroker (edited September 22, 2000).]

Ed Maher

OK, enough torturing this guy. Here's your quick dirty solution to a 3 port regulator.
Use a mechanical fuel pump in series with your electric. You can score a stock style pump, w/ return line for prolly $20 or less.
any objections...ed

FastBroker

I do not recommend an electric pump to feed mechanical because if/when the bladder on the mechanical pump breaks, fuel will spray onto your headers and kill you and/or fill-up your crankase with raw fuel, which could also kill you...

[This message has been edited by FastBroker (edited September 22, 2000).]

Duffster

silly idea here....do what i did...
PULL THE FUSE FOR THE ELECTRIC!

------------------
Duffster (age 31)
BEAT DOWN HARD 88' Camaro SC,
1978 Caprice Classic motor havin'(WITH NO COMPUTER),84' Z-28 Nose clip wearin',
84' Z-28 Hood covered,
AND THE TIRES:
245/60-16 Firehawk SS20 (1),
245/60-16 Bridgestone CompTA's(on rear),
235/60-16 Pirelli P600 w/a curb check or 3(1),
REAR HATCH MASTER OF ALL!!!
Duffster_Camaro@HOTMAIL.COM
Owner of the Camaro 0 out of 10 Third-genners approve of, also part of the non-existent Iowa crew.

Ed Maher

You make a valid point fast, BUT the fact is, lots of people run a push pull set-up like this. Think of it this way. It's far more likely that one of the rubber lines he is no doubt plumbing this with with fail, and if/when that happens, it will certainly be quite a conflagaration. I know thats not very reassuring, but too many people run this set-up all the time for it to be worrysome IMHO. If i were in his shoes, this is what i would do.
Duff, you can't just pull the fuse. AFAIK, all stock EFI pumps are positive displacement, which translates to if left in series with the puller pump they will be a restriction and limit fuel flow significantly.
...ed

FastBroker

I'm with you, Ed, but I've seen it happen twice. Once to me, and once to a buddy. Once about 10 yrs ago, once about 5 yrs ago... Fire on mine (fire estinguisher in my car, thankfully), screwed up bottom end for him.

I agree with that fuse thing, better off dropping tank and putting regular inlet pipe w/screen on it in place of electric pump for him.

TBICamaro

Wow, thanks for all the replies people.

Ive worked on many cars before but they were straight foward(I love mechanical pumps) they are all ive worked with, the electrical pump is easy to but with my pathetic lack of money it becomes complex. That inline thing with a mechanical pump sounds good, but the death and fire issue kinda scares me just a little. JUST A LITTLE. Why would the pump break we arent talking about 150 psi of presure. Just asking!

What about my little restriction idea. I was thinking of for the return line getting something like a pvc pipe without the hole and making a pin like hole in it and putting it in my fuel return line(so it flows just as a small relief). I know this IS in theory a regulator. Shoulnt that drop it a couple of psi to mayber around 8 or so, just enough so my pump wont kill itself.

This car really wont need that much GHP (I dont think starvation is an issure) since is still fairly stock. Im still thinking about getting an xtreme energy cam later on(happy thinking). One of their milder ones.

Hey again thank you all for helping me it, it mean a great deal to me and ill remember you guys when you need help. But try to keep it to engine building etc HEHE

Damon

I run a push/pull electrical+mechaincal setup on my Malibu right now and i have worried about ALL of that. My solution was to use the RIGHT electric fuel pump. I chose the Carter street pump that only puts out 5 PSI without needing an external regulator. No chance that 6 PSI is EVER going to blow out a fuel pump gasket. All it does is give the fuel a little BOOST up to the mechanical pump which pushes it up to the carb and also serves as the final pressure regulator (6 PSI Carter Street mechanical pump). THis combo has proven DEAD NUTS RELIABLE into the 11s using nitrous. My pressure never even WIGGLES off of 6 PSI under any and all conditions. Also, it has the added benefit of redundancy- I can limp home on either pump if the other one fails. 5 years of street use, towing and racing and never a single problem.

Yes, a line COULD pop off or get sliced by road debris but you run that risk with ANY electrical pump you use. You could rig up a switch to turn it off in an emergency, you could also run the ground to the electric through the oil pressure switch so it only runs when the engine is running (or has oil pressure) and there's a million other ways to build in safety. This way just has the benefit of NEVER having any high pressure in lines that were never intended to hold that high pressure.

I know that doesn't directly address the issue at hand with the factory fuel pump setup but I thought I'd throw in my experience.


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94 Firebird Formula M6- No options but Z rated tires. No mods over $10. 13.5@105.
79 Malibu "beater" w/junkyard 400 SBC, tweaked QJet 4bbl, finally a decent set of heads, a few other tricks. A maddening 13.000001 @ 108 on the motor with little traction. No nitrous runs with the new heads yet.

"One of the last remaining QJet tuners on Planet Earth!"

[This message has been edited by Damon (edited September 23, 2000).]

merf23

I personally recommend getting the 3 port regulator or a holley "red" pump. that being said, the low flow return line you were talking about will work. I put one on a $450,000 1934 V12 Packard that was having trouble vapor locking. One thing i learned (after several designs) it that the return line must be very close to the carb inlet. I ended up using a 3/8 from the tank and a 1/4 return line.

FastBroker

The electric fuel pump won't damage the mechanical pump. It's just that mechanical pumps work because of a (deterioratable) rubber diaphragm. I've just seen it happen and am a fond believer of just doing it right and not needing/using both types of pumps.

FastBroker

TBICamaro, did you get everything straightened out??? Still waiting to here from you about that TBI unit...

TBICamaro

Im gonna go with my original idea of the slow bleeding return line, it will work fine. However I have to probably put my project off for about 1 to 2 months, since i need brackets for the carb(to put on tv cable). And i also need a points type distributor. So ill have to wait for those things to come in, in time. I cant wait. And fastB i will only get rid of the TBI itself and injectors im keeping the ecm and harness(they might start smoging florida soon. If you still want it in two months just ask me and its yours.

Why do you want it for? Just curious. I was thinking myself of doing a dual tbi system for a 350 im rebuilding in the garage(yeah right when i have more money) , its not to complicated it can be pulled off fairly simply.

Anyways thank you guys again for the help.

FastBroker

Gonna do a dual system=expensive.

What motor is your TBI off of (305 or 350?) and/or what size injectors do you have? Is it in ok shape?

TBICamaro

If you buy someone else wiring etc. (Turbo city, it VERY expensive) I can rig up my own wiring, ive been messing with the harness diagram(electronic engenering major), and it seems possible. All i would need is an extra tbi(i can get them cheap) and a couple of other things. It would be marginally more expensive than a carb setup(if you are extra cheap like me).(not including the dual quad manifold)

As far as the tbi is concerned its freaking beutiful. Super clean and perfectly intact. I even cleaned it up a while back ago(it didnt need it but im a freak). I bought this car of an old lady(not lying either). So maintenance was great and you could probably eat of the engine bay if you had to. It has 305 injectors but the 350 injectors are very easy to come by. This car ran 15.9 in the quarter with only a 3.42 rear end and nothing elso done to it(auto)and a sligthly boster fuel pressure. my friends z28 dialed in at 15.8, and i was in front due to my raction time of .560... I could have probably gotten the same time as him but i didnt wanna burn the tires at take off so i was a little conservative. Not stellar performance but im satisfied, for now. It feels better than 70 percent of the cars out there.

FastBroker

Ya know, you may be a person who can help me get what I REALLY want. You say TBI units are inexpensive and easy to come by? Hard to find for me here, plus I am too busy to spend the time to look...

Can you get me a used 454 2" OEM Rochester TBI unit w/injectors (80lb or 90lb)??? I cannot find them (2") around here and maybe you can help me with your connections. Please? thx


You'll be able to do the wiring by yourself, for sure. It'll be fun, too, and you'll know how to fix the problems...

Damon

TBI Camaro- You mentioned you are going to go with a "slow bleed" return line. I'm not sure exactly what that means but I hope that means you will have a 3-port regulator in there somewhere. If you just rig up a return line with a fixed restriction in it to get the fuel pressure lower it won't work. As the carb demands more and more fuel (more engine load) fuel pressure will gradually drop off.


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94 Firebird Formula M6- No options but Z rated tires. No mods over $10. 13.5@105.
79 Malibu "beater" w/junkyard 400 SBC, tweaked QJet 4bbl, finally a decent set of heads, a few other tricks. A maddening 13.000001 @ 108 on the motor with little traction. No nitrous runs with the new heads yet.
Grandma's old 78 Malibu (33K miles!) soon to have the powertrain from the 79 put in it.

"One of the last remaining QJet tuners on Planet Earth!"

TBICamaro

Hey fastbroker the tbi are easy to find here (305 units) those mistirious 454 units are hard to come by anywere. I will still look for you anyways.

My current pump is at aroudn 9 to 13 psi. the two port would "probably work" without a return line and the pump probably woulnt go(to soon anyways). I intent to put a good size restriction on it, to just maybe reduce pressure a couple of psi. I will have a pressure tester to fine tune it. I am pretty sure it wont starve. I was talking to a friend of mine Luis(races pro stock). and he told me he has done it before on ex tbi equiped cars with only a small restriction and they have never starved for fuel even on high load. That why im confident it will work, i was pretty sure before but now im even more sure