I am doing a TBI to TPI conversion on my new 350. I have a '92 RS with the stock TBI fuel pump and lines. I just read an article in GMHTP about changing the intank pump and what a pain in the A-S-S it is.

What about an inline fuel pump instead? Any issues with having 2 fuel pumps, one at low pressure, the other at a higher pressure? If inline is ok, what brand?

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'92 RS, ZZ4 10:1 350, Edelbrock 6085 heads, Crane 208/214 467/482 cam, GM/LT4 1.6 true roller rockers, Holley Projection TBI intake, Holley 670 TBI, SLP/Jet-Hot 1-5/8" headers, Catco 3" cat, Flowmaster 3" catback, Hughes 2500 stall converter, stock 700R4, Auburn Pro posi w/3.42, 17x9" SS rims w/BFG tires, Medium Quasar Blue w/white SS stripes, 48,000 miles....soon to be an Accel-DFI Speed Density TPI!!

 

I've researched this and you CAN put an inline fuel pump in and leave the in-tank pump in place and hooked up!! The fuel pump you need to get is made by Accel and you can pick it up from Next Gen Parts! Their web site is www.nextgenparts.com! The pump is $139.00 and that's cheap if you've ever had the in-tank one go out! Mine has gone out TWICE and the first time it cost me $250 to replace and the 2nd time it cost $350!! The pump is a high-pressure 45psi rating pump and is suitable for use up to 500HP! I called next gen and they said that the pump works fine when installed with the in-tank pump still there! He said it'll work even better because with two pumps the fuel will flow better! Maybe increased fuel mileage?? you tell me!! I think this'll help you!!

 

It's kind of a PITA to swap the intank pump, but it's also a hassle running an inline one considering you have to wire it, splice it into the lines, rig up a kill for it, etc. Plus, it won't last as long as an intank pump will due to exposure, vibration, etc.

You can get a high output intank pump that can handle just about all you will ever need for around $125.



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87 IROC-Z, 5.7, auto, 3.27, leather, !cat, Holley fpr, K&N'S, SLP 1-3/4" Jet-Hot coated headers, SLP .218/.224 .495/.502 cam, Comp 1.5 roller tip rockers, $uperPITAram, Edelbrock lower intake, Holley 52mm tb, Dynomax\Flowmaster catback. Coming Soon(?)- Fasttrack/Accell DFI

1989 Pontiac 20th Anniversary Turbo Trans Am - 161,000 miles, !cat, 9" K&N

 

It's up to you whether you wish to run an inline or intank! I believe an Accel Inline will last just as long as an intank even with exposure and vibration! Yeah you have to cut the fuel line and run wires to the pump but that's nothing! You can do that OR you can cut your exhaust (if not bolted on) and drop down your muffler, then disconnect your shocks and drop the rear end, unhook the gas tank, mess with trying to get the filler neck out, then dropping the tank without killing yourself and then after you change the pump you have to put it all back together! It's a pain, my friend did his by himself and it took him 3 days! 3 days or 3 hours?? You decide! B'sides, my stock intank pump went out 2 years ago and I replaced it...then a year later that one went out....now I've had this one in for almost a year and I'm hoping it won't go out again! So you see, an intank is going to be just as reliable/unreliable as an inline and an inline is going to be a LOT easier to change if it goes out!!

 

I can understand this to be true, but only with a high pressure TPI in-tank pump (>40 psig operating pressure). Would this also be true with a low-pressure TBI pump (10-12 psig operating pressure)? It sounds like the TBI in-tank pump would impose a huge in-line restriction. I'm assuming the TBI in-tank pump is different (lower pressure/flow) than the TPI pump. Please correct me if I'm wrong, as I do not know anything about TBI.

Are you sure he was talking about a TBI in-tank pump, not a TPI? I cannot see this to be the case with a TBI pump.


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Willie

Supercharged 1987 305 IROC-Z, Daily-Driver, Emissions-Legal.
12.57 @ 111 mph.
12.04 @ 114 mph (50-hp nitrous).
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1987 "20th Anniversary Commemorative Edition" Z28 Convertible -- Super Chevy Show Class Winner, 1998.

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[This message has been edited by Willie (edited December 21, 2000).]

 

Willie brings up a good point. The TBI pump would have to flow the same as the TPI pump to achieve the same overall pressure, right? The fuel pump issue seems to be the biggest hurdle I'll face with my TBI-TPI swap.

I have an advantage if I go with the intank TPI pump. My car is in the "put back together" stage, so the exhaust is already off and I'll be getting the rearend installed at the same time, so while everything is apart.....

 

Ok...it doesn't matter whether you have a TPI or TBI pump! I called Next Gen today because my intake pump just went out in my car 2 days ago (This is the 3rd "intank" pump in 2 yrs)! They said that even tho' the pump isn't working it can still be left in when the inline pump is hooked up! He said the intank pump wouldn't cause a lot of restriction unless you were running over 400HP!! So therefore, if the intank pump isn't working and the inline will work fine then this would also hold true of a TBI intank pump! I trust these guys, they always have the right answers for me!!

 

One other thing to remember is that an external pump will be noisier than an internal pump (the tank and fuel baffle the sound). This might not be important to you, but in a daily driven car the noise may become annoying.

 

True, the noise may be more noticeable on an external pump but it can't be much worse than the annoying mechanical buzzing I'm getting from my after market intank pump right now! Anyone who has changed their pump should know what I'm talking about! To me, the negative aspects of having an inline don't even add up to ALL the negative aspects of keeping an intank one! I think someone at GM was on drugs when they came up with the intank pump idea! Be Real!

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1986 Trans AM
305 TPI
Completely Stock
Soon to upgrade to a 327 TPI with pocket ported 64CC heads, comp cam, TPI air foil, Adjustable Fuel Pressure Regulator, possibly bigger injectors!
Current project: Installing an Accel Inline Fuel Pump since I've been through 3 Fuel Pumps in 2 Years! :-(

 

Scott,

As long as you've got most of the work done in dropping the tank anyways, why not just do it right and replace the in-tank with a TPI pump?

Also, my external Vortech T-Rex in-line in conjunction with my GM Grand National in-tank pump does not make any more noise than when I was running only an in-tank pump.

Willie

 

I just read an interesting statement in Carroll Supercharging Company's literature. It states,

"Two fuel pumps in series will deliver more pressure, but no more flow than the smaller of the two pumps."

I think this confirms my original concern. Now I'm certain that you should get rid of the in-tank TBI pump.

Willie

[This message has been edited by Willie (edited December 21, 2000).]

 

I've disassembled a TBI pump for a C2500 and can tell you that there is a restrictor in the outlet of the pump. It looks like a barrel type throttle.

The point is, the 3/8 outlet on the pump is restricted.

I personally would NOT want to pump through the TBI pump I mentioned. The restriction would probably limit the GPH possible, thus HP.

 

Willie is right, the flow of the smallest pump or a restriction in the system will control it. I have the same pump accel sells, and believe me its nowhere near as quiet as an intank pump. I've decided that I am going to swap over to an intank to get rid of the noise.

 

Having worked on many a Turbo Buick and knowing how **** Buick people are (myself being one of them). Stock appearing is everything. The only pump we install at the shop I work at is the "Walbro 340". It's an intank that is claimed to go low 10's, i've personally seen it on a mid 11 car (5800ft) that should go low 11's on it's new motor. I know Modern Muslecar sells it, i'm not sure who else might. I would look into it though. When I replace the pump in my car thats what i'm going to put in.

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Torque is KING!
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I just did the TBI to TPI swap too. I bought my car new and had never thought about taking the tank down before. I read the GMHTP article after I had already done my swap. It wasn't as bad as it sounds in that article. I did have access to a 2-post lift, but with a buddy's help, mine was done in about 3-4 hrs. I tried to read everything I could about doing the job so that most of the steps were in my head before I started and it helped. Just take your time and do it right, you'll be glad you did when it's done. Rob.

 

90FFBird...I thought the same thing it wasnt as bad a job as everyone made it out to be. And what happens in the long run if you leave the old pump sock in there? Buy a good quality pump, or you will find yourself replacing it!

Same thing with the SuperRam,its not as bad as i had thought to install either.

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Black 90 IROC, L98, A4, 323 gear. SuperRamed 406 in the works!

[This message has been edited by MikeH (edited December 22, 2000).]

 

You guys are the best!! Thanks for the replies. I think we all know what direction I'll be going. Time to look for a Walbro intank pump!!

Thanks.