SIXGUNS

Im yanking my intake for a carb. i'll replace my dist. when i can get my hands on one. I just need to know who makes a good afpr to use a high volume tpi pump w/ a carb.

Jester

You'd be better off changing pumps. TPI pumps aren't high volume...just high pressure. You could get a regulator that would do it, but it would be as or more expensive than a pump.

FastBroker

TPI pumps are high-pressure AND high volume to feed high HP high RPM engines. You should be able to get a regulator from Summit/Jeg's for about $19 - $50... To make yourself feel better about this, get the flow ratings for your pump, they should be fine. Just make sure the reg can take the flow and supply the flow you need. ie, a small reg will restrict your system flow.

Phil87IROC

iTrader: (1)

I went from TPI to carb on my 383 motor. I still have the stock FP in my tank, it works just fine too. I installed a Mallory 3-port AFPR to cut the pressure down to 5-7 psi. Make sure you get an AFPR with a return line to the tank, that's how it can lower the pressure; by returning fuel to your tank. I think the AFPR was about $70 from Jegs or Summit. I have raced my car and this setup is fully functional.

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Phil87IROC
Blue '87 IROC, 383 Crate Motor, KB hyper pistons, AFR 190 heads, TPIS ZZ-9 Cam, Edelbrock RPM intake and Edelbrock 750 cfm Carb, T-5 and 3.42 rear GM gears w/new Auburn posi.
Red '89 IROC L98, 700R4, T-Tops, K&Ns, 160 T-stat, Hyper Chip.

Jester

There are only 2 AFPRs that will do it..at least that I'm aware of. The Mallory he mentioned...and the Barry Grant one I have (I do speak from experience ). But if I had to do it over again, I'd have gotten a Holley inline carb pump for the same money as an AFPR, and ended up with far more fuel flow at the proper pressure.

And what are you talking about TPI pumps are made for high RPM engines? You mean the same TPI's that came in our cars that are dead by 4500-5000rpm? IIRC (and I'm not at all positive bout this) stock TPI pumps flow in the mid-high 30 gph range.

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"American made baby. 100% American iron. The muscle among the masses. My hero. Yep, you can take your ergonomically designed, space age, computer controlled, 4 door, cup holding map lighted split double wishbone split fold down retractable cargo covered moon roof piece of transportation and keep it. For I have felt the thunder. And I know the difference!"
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Ray87Z

I'm using said Mallory unit as well. Think it was $75 or so in Jegs. Works good. My air/fuel ratio according to my guage never drops off during WOT (5700-5800ish rpms is max I've taken it to, 5500 rpm is normal max). I assume that means the TPI pump is doing alright as far as flow.

Somehow I would feel better w/ a carb specific pump but I don't want to drop the tank, remove the intank pump setup, and jury-rig a pickup, etc.

BTW, does the BG unit drop the pressure enough to work w/ a TPI pump? I know a couple people used that w/ the TBI pump (didn't you Jester?), but I wasn't aware of anyone running it w/ the TPI pump. (I assume the TPI pump is different. More flow/psi right?)

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Ray87Z
-Vortec headed 350.
86 IROC w/ a cammed 305 TPI.
Formerly Ray86IROC.
www.inter-scape.com/Ray

[This message has been edited by Ray87Z (edited September 12, 2000).]

FastBroker

If you use the same fuel pump for a carb on the same motor that was EFI, it should be fine. The same pump is feeding the same motor, just a different means of delivering the fuel... Also, ALL pumps will flow more fuel at a lower pressure. ie, TPI fump that flows 45gph at 45psi would probably flow 50gph if reg'd at only 5 psi... Check the pumps regulated flow and free-flow rates and you'll be somewhere inthe middle. I always remove my in-tank pumps on my cars and put in external Airtex pumps... This gets rid of the OEM pump and makes fixing/diagnosis on the road MUCH easier, if you need it...

I coulda swore that there were two cheaper regs in latest Summit Cat (or maybe Jeg's) that were $19.95 and $34.95 or so. You don't need a 5-50 psi reg if you are to only run a carb. You'll only need a 2-9psi reg. That Mallory unit is sweet looking, though, and the two I'm remembering may not flow enough. Need to call Summit/Jeg's tech

[This message has been edited by FastBroker (edited September 13, 2000).]

Jester

Yeah they have them, but they won't cut down the pressure from an EFI pump to low enough to use. They're only 2 ports, you need a 3 port, the 3rd being a return line to the tank.

FastBroker

I did not know that they were 2 ports.

BTW, regs don't need to cut down the TPI pump pressure because pumps dont make pressure, restrictions/regulators do. The TPI pump pressure will only go as high as the regulator says. ie, no reg, no pressure, low press reg = low pressure, TPI reg=40-50 psi... All the reg has to do is FLOW enough fuel through it and have a tank return port in it. (3 port)

Jester

True, but the problem is with pressures that high, even with NO reg, just free flow, you still end up with pressure in the lines. For example I'm running an in tank 350 Vortec truck pump, rated at 42gph@17psi. Even with the lines totally open, the carb still sees 6psi. I tried it. Imagine if it was a 50psi pump. Plus, thats just at idle...under load there is nothing to divert fuel from the return line to the carb, and the pressure to the carb will drop very quickly. You NEED a 3 port reg if you're gonna run a high pressue pump.

FastBroker

I'm with ya'. 3-port reg a must most of the time. I am not condoning not using a reg here. Regs are a must for al EFI an dmost HP carb systems, just proving a point...

If your system in free-flow state has 6psi at carb, you have a restriction in the system somewhere.

What line size you have??? for 300hp and under cars, you must have at least 3/8" on the way to carb/TBI and 5/16" to tank. Some cars need 3/8" return line, if too long and/or lots of bends. I don't mean OD, either, but TRUE interior diameter. Lots of people use "tees" and "regulator mounts" that act like tees. These can be quite restrictive and turbulent. Also, some fuel tanks have small return line fittings on them or inside the tank area that you cannot see = BAD. Check the return line pressure with the system "open" as you described it. It should be less than 1psi and I bet it is not. I'll guess at 5psi...


One thing you gotta remember, if an engine is idling, no matter carb/TBI/TPI (same engine!), the induction systems will all be using approx the same fuel, EFI a little less, actually. That engine will have the same fuel req's no matter what the induction system.

[This message has been edited by FastBroker (edited September 13, 2000).]

Jester

Yeah but TBI and TPI both have built in regulators, carbs do not.

And of course I meant with the return line connected....you can't drive it for long with the return line going to a jug in your engine compartment That means stock 3/8" to..and 5/16" to the tank. I'm not gonna put in larger return fuel lines just for that

FastBroker

When I said "free-flow", I meant w/return line to tank but no reg, silly. Free as-in no reg. Sorry. Should be less than 1 or 2 psi in ANY return line system, for that matter. carb/TBI/TPI... Gonna check your return line pressure???

That would be funny, though, running the return line out the bottom of the car or something... Pobably hurt mileage quite a bit, too. DOUGH

Jester

lol I'd say..have to stop and fill up every 10-15min. That would definatly hurt the wallet REAL quick

FastBroker

Did we help SIXGUNS??? Mallory reg sounds like it'll do the job...

five7kid

iTrader: (14)

There are two more options:

#1: In their ZZ4 conversion kit, GM supplies a p/n 10185094 pressure regulator (to go along with a 25168719 in-tank fuel pump). I don't know the price for it, but you know it will work. It uses the return line as well. I've heard it's an aftermarket piece they buy to put in the kit, but I don't have 1st-hand knowledge.

#2: If you hook your current in-tank pump to a mechanical pump with a return line, you'll get 6 psi because the mechanical pump has an internal by-pass valve that sends anything over 6 psi back to the tank through the return line.

FastBroker

Never seen an OEM mechanical pump w/return line... Using electric pump like that is VERY bad because down the road, if the mech. pump bladder breaks, (they all do, eventually) there will be the biggest fire under your hood and/or you will fill your crankcase will gas in about one minute. Death could be the result. DON't do it.

SIXGUNS

Thanks fellas.