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Old 03-02-2007, 11:40 AM   #1
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TBI V6

I know I shouldn't really post over here, but you guys seem to know a little more about the TBI stuff than anyone else.

Here's my dilemma, the stock V6 MPFI setup SUCKS, so I have acquired a 4.3 TBI and an Edelbrock Performer Carborated intake manifold. I'm going to purchase the 4bbl upper manifold and a 4bbl to TBI adapter plate. All this will go on my 3.1L +.060". The head work I have done includes unshrowded the valves, gasket matched, and leveled/smoothed the walls down to the valves to eliminate any bulges. I wish i had a pic, but if I do the swap I'll take the heads off to take them. I also have a .430" cam, 206* duration, 105 separation, flat tappet hydrolic.

Do you guys think that this will be a better setup than the MPFI? It will far out flow it, but noone seems to encourage me to do it. Everyone is stuck on MPFI and trying to improve that intake setup.

I think it would be a step in the right direction to make the little V6 produce more power. IMO, the MPFI is seriously flawed by design. 52mm TB, 17" intake runners, and a non-functional plenum volume.

Thanks a million!

-t
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Old 03-02-2007, 12:51 PM   #2
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hey man ive got one better for ya,i posted up a link to the carbed manifold on ebay,u could use that with a tbi tb,and have injector bungs welded into each port, this way u could have the better manifold and still have the mpfi.


on the other hand im in the middle of building a custom manifold foe firstfirebird,its my custom upper,with a 75mm caddy tb and should flow even better then the tbi/or carbed manifold
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Old 03-02-2007, 01:19 PM   #3
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I've looked into doing the TBI with MPFI bungs. The 60v6 doesn't have enough room to make it work. I have the carbed, MPFI, and Edelbrock intakes at home and I've looked to see if it was possible before. If you have a pic of a successful design tho, post it!

I just have this grand goal of making the V6 produce more HP than torque at 6000RPM+. With the cam I have and valve size, it is totally capable. I'm tired of having 20 less HP than Tq and I blame the long runner/small plenum design.

Look at the difference between the LT1 and TPI setup. Plus with all the research I've done on manifold design, the long runner MPFI is just a waste. And when I can get a stock dual 1-11/6" SBC TBI that flows 500cfm+, I'd rather do that than rely on aftermarket parts. Plus I could go dual 2" if I find a restriction problem (I doubt it though, it is a V6 after all).

I realize that what daves12secV6 is doing is great, I'm just going to approach it from a different angle and try to use the unsung hero manifold to do it.
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Old 03-02-2007, 01:42 PM   #4
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hey got pics of a tbi manifold?
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Old 03-02-2007, 01:45 PM   #5
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Not on me. But I have it at home. I can post pics of everything I have. That would be a fun pic huh? Put all three of them together?

I'd like to see a BBC dual 2" TBI on a V6 and a turbo. That would be crazy.
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Old 03-02-2007, 03:48 PM   #6
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I said do it, just do the wiring different then you plan too.
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Old 03-02-2007, 04:58 PM   #7
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I will. The harness in my car right now isn't quite right, so I'll swap it out regardless. One good thing, I just remembered that my LT1 car came with a 5.0TBI computer! I also have a TBI computer from you Dale. So all i need is the harness and it should be good to go. I also have the High Volume Low Pressure fuel pump too.
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Old 03-02-2007, 08:12 PM   #8
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Why wouldnt you do a GENIII top end swap? You could even change over to DIS ignition, and use a FWD prom. Perhaps you should do some reading on 60degreev6.com. Going to TBI is like taking 10 steps backwards, IMO.
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Old 03-03-2007, 11:07 PM   #9
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The easy way would probably be to switch over to a later SD ECM form the 90+ cars and use that rather then the earlier stuff that used the Botch garbage MAF. Use a carb manifold w/ injector bungs and a stripped down 4.3L/5.0L/5.7L TBI. The BBC TBI will be WAAAAYYY too much for the V6. Youll be at full manifold pressure before you even open the throttle 1/4 of the way. Itll work, but the car will be hard to drive.

The stock TBI system will have its own problems. If you do decide to use it, steer clear of any early TBI computer as they suck in stock form. Bad setup for a high revving V6. Better one is the UTBI or the truck TBI/CPI/MPFI PCM. I have the PCM with some mods and I love it.
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Old 03-05-2007, 12:51 PM   #10
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I don't want to do the GENIII swap. I just built this motor not that long ago and i don't care to do another V6 motor just for the head swap. Plus the whole point of this project is to do the best intake for an iron head V6. To go GenIII would require me to put different pistons in if you didn't know. And DIS really isn't much better than the typical Dizzy setup, just WAY more expensive.

TBI would not be going backwards. TBI is basically a 2 injector fuel injection system. I've already done a SD ECM swap. I had planned on using the same MPFI ECM to control the TBI unit. Both ECM's are bank fired anyway so it should work. I have a couple of TBI ECM's to use if the MPFI EMC doesnt work right.

Thanks for the heads up on the BBC TBI problem. I hadn't considered the problem of having too much flow! I'll keep the SBC TBI and go from there. It should be more than adequete.
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Old 03-05-2007, 10:21 PM   #11
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IIRC, the MPFI ECMs may only be able to drive one TBI injector so youd be forced to use a monobody if that was the case, which probably wouldnt fly on a V6. Maybe the drivers in the V6 ecm can handle two injectors in bank fire mode, who knows. With TBI, there is also the issue of the dynamic fueling range with large injectors. TBI injectors can provide lots of fuel, or a little fuel, but its hard to get a lot of fuel out top and still be able to properly meter a little fuel at idle.

Edit: Saw that part about the intake not having enough room, and your definatly right. The runners are obstructed with the carb intakes plenum.

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Old 03-05-2007, 10:41 PM   #12
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Correct me if Im wrong, but didnt the mid 90's buick centry's come with 60 deg V6's? I seem to remember this being the case. My dad has one, and although its been several years since Ive worked on it, I remember it having an LT1 style intake and aluminum heads. Now Im curious. If it really is the earlier style block, maybe it could be used in an LT1 style intake swap while somehow retaining the earlier dist.

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Old 03-05-2007, 11:05 PM   #13
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I checked out 60degreeV6 and it is indeed the case. I remember now. MAF, wasted spark coil packs, 68HC11 OBD-1 based PCM SFI, etc. Has the block itself from the mid 90's cars changed alot? Great setup, and the PCM is actually hackable, but it looks like it would be alot of work to swap it in. Im sure this has been hashed to death somewhere else, but has anyone looked into adapting the intake and heads to the earlier setups with standard dist.?

There has to be an easier way to accomplish this using MPFI. My feeling is that TBI isnt the right choice for ultra high RPM setups. The dynamic fueling demands will eb too great.
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Old 03-06-2007, 10:52 AM   #14
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Intake Comparison

So here's the intakes that have been put on iron head 60v6's, all together for the first time that I've ever seen.

On the left is the MPFI, center is TBI, right is the Edelbrock Performer. All are shown without throttle bodies, and the edelbrock is shown without its plenum cause I don't have one yet.

Runner lengths are:

MPFI 17"
TBI 3"
Edelbrock 6"

I do like the Buick 60v6 intake over the other Cavi/Burli intakes. Doing the swap would still require swapping heads and pistons and I'm trying to avoid that. I'd like to find a performance option that fbody people can do in a weekend without pulling the motor.

Why would the MPFI computer only be able to control one TBI injector? The MPFI computer has two outputs, Inj #1 and Inj #2. I'm sure with careful tuning that mid open throttle performance can be made acceptable. It may be hard to get it perfect, but close enough to run is good. GM has been able to do it for how many years?
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Old 03-06-2007, 11:23 AM   #15
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Quote:
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Why would the MPFI computer only be able to control one TBI injector? The MPFI computer has two outputs, Inj #1 and Inj #2. I'm sure with careful tuning that mid open throttle performance can be made acceptable. It may be hard to get it perfect, but close enough to run is good. GM has been able to do it for how many years?
The MPFI computer won't control the injectors properly. TBI injectors are PEAK and HOLD. MPFI drivers are Saturated. Then you get into the fact that TBI injectors fire twice as often.

If you were going to switch to TBI, repin to run the P4 "427" PCM from a 1995 TBI truck. They are much better than the C3 ECMs used in the earlier trucks

The TBI setup on a V6 is good well past 6,500 rpm, which is where my 3.1 TBI peaked. I have since gone to a 3.4L intake from a 4th gen with MPFI.
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Old 03-06-2007, 11:41 AM   #16
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Now thats some information I wasn't expecting. Good looking out.

So it sounds like I should get that TBI ECM from the wrecker and redo my electrical. No prob. Does anyone have one for sale???

Fast 355, when you swapped intakes what did you notice? I'm expecting you to say the 3.4MPFI intake had more torque but less HP than the TBI.
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Old 03-06-2007, 12:52 PM   #17
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IIRC, some of the early FWD cars with the monobodies came with teh smaller injectors and 7730 ECMs. Issue is there will be extra heat and current draw with the larger injectors if you try to use the MPFI ECM. Could burn out the driver or overheat the injector due to the low impedence of the injector. I think the low Z CPI injectors where also driven in the standard manner, but dont quote me on that. As fast said and I implied, not worth the effort with all the other options available.

From the sound of it, it doesnt seem like there is an easy way to do MFPI.

The only thing is that with a high revving TBI V6, you may have to raise the idle in order to keep the pulsewidth from disappearing. I have this issue on mine that on decel and low load cruising, the PWs get really, really short due to how much flow I have. It sometimes can cause the engine to act erratically. The one saving grace on a V6, though is that the injectors only fire 3/4 as often as a V8. If you dont mind having to tweak things, go with the TBI. When your in the yard, look for the blue and red 32 pin connectors. If it has those, snag it, because youve found a PCM. If it has the 24/32 pin black connectors, its a junk ECM. Not all 93+ trucks had the PCMs. This PCM will also do MPFI (both batch and bank fire), so if you have a change of heart, you can switch over with little or no impact on the rest of the system. The 7749 is also another system if you ever plan to run boost. This does bank fire, which works fine with TBI. Any more then 2 DRPs per firing, and you have lean issues between firings.

So you do have to use the heads as well... Any idea on what the CR would be? With aluminum, its not uncommon to have 10:1 CR as the aluminum sucks heat out of the chamber. With proper squish and properly working the heads over, it could make for a potent setup.

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Old 03-06-2007, 01:07 PM   #18
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The computer you are talking about is the 95 PCM? The OBDI system? Will it work correctly running the 700R4 behind my V6? I have a 94PCM system in my LT1 3rd gen. I don't know how the Truck systems were different.

I don't mind having a high idle, under 2k is acceptable. Just means the torque converter will stay loaded. Hehe.

Aluminum heads.... I am going to avoid using them at all costs. Why would I have to use them? I have plenty of intake manifold options with the Iron heads, I still don't see a reason to go Aluminum. Other than the obvious benefits of splayed valves, runner design, blah blah.
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Old 03-06-2007, 01:31 PM   #19
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Im not famililar with the V6 aluminum heads, but if the chamber is different and better, then it might be worth it. Vortecs make a huge difference over cast iron V8 heads due to the crappy chambers and lower runners. Switching over, I needed less timing, had less detonation, and more power over the standard iron heads. Just food for thought.

The idle wont have to be quite that high. Maybe 800 RPM. Im thinking of going back to a fast idle when I get around to swapping out my cam. Doesnt sound as nice, but it gets the job done.

With the 93-95 PCM, its somewhat similar to the LT1 PCM, but still isnt flash as some where and uses the standard memcal. Fast and I are using the truck PCM with a non-CC trans and an LS1 MAF. No issues. The PCM was a cross-over, so it has everything to run everything. Its the swiss army knife of computers. Itll run the V6/700-R4 without issue and supports lockup in the usual manner.

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Old 03-06-2007, 07:08 PM   #20
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Quote:
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Im not famililar with the V6 aluminum heads, but if the chamber is different and better, then it might be worth it. Vortecs make a huge difference over cast iron V8 heads due to the crappy chambers and lower runners. Switching over, I needed less timing, had less detonation, and more power over the standard iron heads. Just food for thought.

The idle wont have to be quite that high. Maybe 800 RPM. Im thinking of going back to a fast idle when I get around to swapping out my cam. Doesnt sound as nice, but it gets the job done.

With the 93-95 PCM, its somewhat similar to the LT1 PCM, but still isnt flash as some where and uses the standard memcal. Fast and I are using the truck PCM with a non-CC trans and an LS1 MAF. No issues. The PCM was a cross-over, so it has everything to run everything. Its the swiss army knife of computers. Itll run the V6/700-R4 without issue and supports lockup in the usual manner.
i can shed some light on the aluminum heads for u
the example im going to use is a stock 93 f-body with a 3.4 v6
i forget what the stock rating is on the iron headed 3.4 160 hp i belive id have to dbl check
but anyways a guy on ftv6 swaped to a unported gen 2 topened
and made 200 hp with no other changes(besides the pistion change heads/intake)
after that he swaped the gen 2 topend for a stock gen 3 topend (heads/intake) and hp jumped up over 224 hp.
if u dont swap the pistons u will end up with a cr ranging from 11.2-1 to 11.5-1 depending on which thickenss head gaskets u use.



while the stock mpfi manifold is a shitty design (see my cutaway pics in the v6 section) it dosent take much to make it outflow the heads.
so going to the tbi manifold is better for high rpm the heads are still going to be a pretty big restriction.
the cost of doing a gen 3 swap is pretty cheap,though i dont know what kind of parts u have lined up for doing the tbi swap already.

im one for doing things differently but i think if u weighed the cost vs the amount of power u will see tbi swap vs aluminum topend swap,im thinking the topend swap would be the better deal.

granted on the 93+ 3.4s they already have dis,so u would have to deal with that,but a gen 2 topend can be clearanced enough with a grinder to fit a dizzy.

have u thought about making a custom plenum for the edelbrock manifold maybe there is some way u could get the injectors in there if u did that

Not sure how set on doing a tbi setup u are .But if u want more info for the topend swap if u decide not to do the tbi swap
i can give u a few links to all the parts u need to get,should cost about 250$'s for the heads/intake/new pistion set
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Old 03-07-2007, 10:08 AM   #21
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Seems like you're correct with your figures. I think the 3.4 is at 180hp though. The 2.8 was 140hp 160ftlbs, 3.1 160-180, and the 3.4 180-200. If you are pretty confident that the MPFI manifold can be ported to outflow the heads, then maybe I'm just beating a dead horse(iron heads). Plus with the added complexity of redoing the engine wiring and ECM, it may be far worth it for simplicity and performance to do the head/intake swap and leave it with that. Sounds like the 3400 head swap for the 11:1 would be pretty fun too though. Hehe. I don't know why anyone would swap out the pistons if 11+ CR could be achieved! And to think that I traded all my GenII stuff away not that long ago.


All I was after was to do an intake setup that a person could do without pulling the motor and yield better results than the MPFI. I guess I'll rethink my thinkin' and start over again.
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Old 03-07-2007, 12:03 PM   #22
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If the existing wiring and ignition can be reused, youd probably be happier with the newer heads and intake. TBI can make plenty of power, but if the heads are holding it back, then it probably wont help much over the stock intake. Are the current ones still bone stock heads?

I clicked the link, and it looks like the engine has dished pistons already. How big is teh dish in the 3.4L pistons?

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Old 03-07-2007, 02:42 PM   #23
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Good question.

Hey Dave, what is the piston difference between a 3.1 FWD and 3.1RWD? I know that the 2.8 iron head FWD/RWD have flat top pistons, but do all 3.1 cranked 60v6's have the same pistons?
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Old 03-07-2007, 03:48 PM   #24
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a rwd 3.1 piston has a .105 deep dish and a fwd(aluminum head piston has a .200 deep dish) i forget how wide across the dish is, i have pics of the pistons,ill post them up when i get out of work in a few hours

the chambers on iron heads are 48cc on aluminum heads they are 25cc
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Old 03-07-2007, 04:58 PM   #25
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I know that 2.8 valve clearance is .007", would that magically go up when you swap to a 3.1 crank/piston?

I'm liking this buick GenII swap idea. Short LT1 style intake.
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Old 03-08-2007, 08:52 AM   #26
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no the pin location is moved on the 3.1 piston to account for the added stroke.

anyways heres 2 pics showing the dish in a rwd piston,the fwd piston has the same diam dish its just .100's deeped then the rwd piston
Click the image to open in full size.
Click the image to open in full size.
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Old 03-08-2007, 10:07 AM   #27
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What I meant to ask was, is there more valve clearance with the 3.1 dished pistons FWD and RWD than the 2.8? And would there be more clearance on the FWD than the RWD with their appropriate heads since the dish is deeper? I'm just thinking that if an aluminum head is put on the .100" dish RWD pistons that the valves may collide with the pistons.

Having the FWD piston with a deeper dish accomodates the smaller cc's of the head. The crank and rods and wrist pin positions should still all be the same FWD to RWD. ?
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1994, 1995, 31, chevy, diam, diffference, fwd, gm, injectors, prom, rwd, system, tbi, tpi, truck, v6, v8, vs, wiring
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