Hey everyone. I cant stand the 305 anymore and can get a good deal on a 400. But my only question is the TBI. Do they make TBI units that will do 300-400HP?? If not I am going to have to re-think everything - like maybe a carb and then fool the ECM into shifting the tranny.

Does anybody make serious HP with a TBI unit BUT STOCK COMPUTER???

I have burned PROMS and have done a little tuning already but do not want to bother if I can't find a good TBI unit.

Thanks
Mike

 

only choice is a 454TBI and have one of the geniouses bore it out to 2.2". it definately won't be the best to put on a 400... i'd recommend the carb for the raw power and easy tweaking.

i just got done putting a 454TB onto my 350 vortec... i thought TBI was supposed to be easy to tweak and configure, but i stupidly assumed that these forums would help out more than they did. so of course i was left in the dark on this project which ended up really pissing me off because i seem to have LOST more power than gained with the old 5.7TB.

nobody warned me that my truck would run like crap after i'm done. they all said to go for it! durring the conversion only LOW1500 was the only one whom helped me out the most. the rest of my questions went unanswered leaving me to search old posts.

after playing with TBI i've done decided its CRAP and not worth the time cussing and bitching. sure its wonderful for the reliable ol' truck/car but performance is just too hard to squeeze from it.

maybe i've just got something screwed up in my motor? well find my posts and help me, turn me to a believer. not ONE person replied to them, so either nobody knows or i'm not asking the right questions.

i'm sorry but after basically screwing up my vechicle you'd be a little peeved off as well... now my truck just sits there in the driveway, rusting away... i'm out $500 and have a screwed truck. do i blame TBI? yes. you guys make it sound too easy

 

Ya. That was my thought too.

**** the fuel mileage anyways. That and the "reliablilty" is the only reason I wanted to dink with it.

I have never tuned a carb though. But it is probably easier to tune a carb than this computer ****, right? Or at least faster!

Thanks.

Anybody have any other experience w/ high perf TB's???

 

i ran vy little cam, vy little head, and vy little compression and made 280-290 dynoed hp. If you can't make TBI run, you're not trying hard enough. Or you just ran out of patience...


Ty

 

What the hell is vy???

Ok if I was talking less than 300HP I'd consider it. But a 400 w/a good cam wil easily be in the 350HP range.

 

What the hell is vy???

Ok if I was talking less than 300HP I'd consider it. But a 400 w/a good cam wil easily be in the 350HP range.

Sniper, dude, I guess you should try harder!

 

i'm a huge fan of 400s, and plan on doing the swap at some point. i'm still not sure tbi can support the cubic inches/horsepower i want to make.

the issue seems pretty simple at first glance. the more cubic inches you have, the more air you need to flow. the higher you plan on revving that engine, the greater your air demands become.

there's a formula for calculating how many cfm's you'll need for any engine size/rpm, but that's for cfm calculated at 3" hg, and tbis (and all 2 bbl carbs) are calculated at 1.5" hg. i've been trying to find a formula for converting cfm at 1.5" hg to 3" hg and vice versa, but haven't found one so far.

at the very least, you'll need to set your 400 up to make max power at 5,000 rpm or so. if you hope to rev it higher, you'll need more airflow, and i don't think you can get it. that's not necessarily a bad thing, however. a torquey street motor shifting at 5,000 can make a lot of power .... ask any bbc owner.

the biggest tbi unit i've seen so far is this one:

http://www.454ss.com/gallery/JimD/JimD_TBI.htm

they're bored and sleeved out to 2.2", i believe.

i've been trying to find out if anyone's boring and/or sleeving the holley 670 out past 2", but haven't found anyone yet.

the other issue is fuel. the biggest injectors available for tbis are 90lb/hr. 2 of them means you get 180lb/hr. a tpi with 8 24lb/hr injectors flows 192lb/hr, and that's on a stock 350! when you get up into the 32lb/hr injectors, you end up with 256lb/hr fuel flow from a tpi. how much fuel you actually need is dictated by the horsepower you make. the one bright spot is that tbi reacts well to fuel pressure increases. you can get significantly more than 180lb/hr fuel flow out of your tbi by jacking up the fuel pressure.

and sniper, i'm sorry you've had such a bad experience, but this board is full of people who've had great results with their tbis. don't get discouraged. truth is, i understand a carb, too and wish my car had one. unfortunately, i have to pass those yearly smog inspections. if i didn't, there'd either be a holley carb or a stealth ram on there!

 

The guy you mentioned above has researched the Holley 670 and it cannot be bored out to 2.2 inches. Casting is too thin.

FYI, some of the GM 454 TB's cannot be bored out because of casting thickness.

If you are going to build a 400, you should be building for torque.

The 454 TB should suffice for a 400; it feeds my 454 fine!

I have one of the Jim Dickie TB's on my truck. My truck has been a best of 13.42. Keep in mind this is a 4500 lb vehicle with aerodynamics of a brick. This pass was also made with a stock torque converter, single exhaust, 8.0 CR, shorty headers, off the shelf Hypertech chip, Extrude honed Edel TB intake, 3.73 gears, and a computer friendly HR cam.

I pull consistent 1.85 60 fts.

Since that time, I have added true duals, a 2700 stall Vigilante converter, RPM Air Gap, alum driveshaft, and ram air setup. Plus, I have reduced the wt of the truck approximately 150 lbs.

After the intake swap, the engine pulls hard past the 5200 range of the cam.

I can light up 315/60 Drag Radials from a roll. The truck is almost undriveable with regular T/A's.

I believe my truck should go in the 12's in perfect conditions.

I may also need to go to a 4.10 gear to recover what I lost by going with a 4 inch taller tire.

So, based on my comments, do you think the 2.2 bore 454 TB will fit your needs?

Bill

 

This has never happened, you must burn a chip. It can be made to work, but I say carb it.

 

yes... might as well fix what i've started. so how about some advice? my IAC is letting in loads of air, and i tried setting the minimum air several times. where would i find a new IAC that doesn't cost $100(dealer)? does the holley fit? (looks like it could)

could that one unit be the root of all my problems, exactly how important is it for the engine to run? i've compensated the idle air screw, and blocked off the IAC with a gasket; just so it could idle under 1000rpm.

upon romping the throttle there will be a dead spot, pop, ping, and once killed the motor. i made it less severe by advanced the timing quite a bit, a good few inches from 0* mark.

is there a corralation with a high fuel pressure, rich running engine, and advanced timing? should i try backing off the pressure and inching up till i find a 'sweet spot'? i've never tweaked with an AFPR before... there has to be a process for tweaking out TBI... what do i adjust and in what order? the more i play around the worse this engine ends up runing.

i've got error codes too.. need some help knowing what i should look for...

32. Fault in barometric pressure sensor circuit OR
Fault in exhaust gas recirculation valve diagnostic switch OR
Fault in electronic vacuum regulator valve

35. Idle speed can not be set to desired RPM
(IAC is bad and stuck open, blocked off with a gasket)

42. Fault at electronic spark timing circuit OR
Fault at direct ignition system OR
Fault at fuel cutoff relay circuit

thanks guys for not letting me give up...
"And if you mess it up, you're on your own."

 

error codes, $100 parts to get it running, tons of tuning time - all this is why i am now thinking seriously about a CARBURETOR

Yes, I may get luckier than Sniper - it may run great. But it also may not. And then what do I have - $300 invested in a TB that runs like **** when I could have spent $300 on a carb

If anybody has any glory stories of how they got a 400 small block running with a tbi, then by all means tell me (and Sniper!)

 

vy = very

and i'll stop there before i type a flame.

TP

 

Actually you have that backwards. 4V carbs and TB's are flowed at 1.5"Hg and 2V carbs and TB's are flowed at 3"Hg, but I know what you meant.

The formula is

CFM @ 3"Hg x (SQ-Root of 1.5"Hg divided by 3"Hg)

Just to keep it simple....

Multiply the flow rated @3"Hg by 70.7%

So 670 CFM x.707 = 473.69 @ 1.5"Hg

A Holley 670 CFM flows less air than a 500 CFM 4 barrel carb.

 

oops.

thanks for straightening me out.

maybe you can help me with another question.

i'd say the consensus opinion on this board would be that there's no tbi that flows enough air to support more than 383 cid and enough fuel to support more than 330 hp. if that's true, what about 454ss trucks?

look at the numbers va454ss posted earlier in this thread. i don't get it (not doubting you, va454ss, just puzzled).

the holley website lists the following formula for calculating the airflow necessary for a carb. i'd assume it's the same for a tbi:

Engine Size (CID) X Maximum RPM / 3456 =
CFM @100% Volumetric Efficiency
EXAMPLE:
350 CID X 6000 RPM = 2,100,000 / 3456 = 608 CFM


so, a 400 with a redline of 5300 rpm would look like this:

400 cid X 5300 rpm = 2,120,000 / 3456 = 613 cfm

take that 400 up to 5500 rpm and you need 636 cfm. 6000 rpm needs 694 cfm, and that's at 1.5" hg.

that makes the 454 still more puzzling, though. using that formula, a 454 with a redline of 5000 rpm needs 656 cfm at 1.5" hg. i don't think a 454 tbi unit flows that. i don't think the 2.2" sleeved 454 tbi flows that, yet va454ss is running low 13s with that combination.

va454ss, what rpm do you shift at?

using the formula of multiplying the 3" hg rating by 70.7 to get the 1.5" hg flow rate, you'd need 900 cfm at 3" hg to get 636 cfm at 1.5" hg!

that's probably a 3.5" bore! ha ha ha.

ok, my head hurts now.

and sniper, i'd suggest you find someone with a lot of experience tuning tbis to look at your car. i'm not trying to be a smartass, but you have to know your limits. i, for example, am pretty good with the theory, but am totally lost when it comes to prom burning, etc. i found a dyno facility that does tuning and chip burning and has experience with tbi. there's no better or quicker way to dial your car in than on a dyno with a wideband 02 sensor. once it's tuned, it's tuned. barring changes or something breaking, you won't have to do it again.

just my opinion, dude, no offense intended.

 

If anyone looks at the link above about Jim Dickies modified TB, you will see that he also uses thinner blades and shaft than stock.

I also smoothed and polished the entrance to the bores, plus removed the tabs that align the air cleaner.

Also, I have elevated the injector pod and my wiring exits the rear of the TB, not the front. The wiring mod was an idea I came up with while Jim was modifying the TB. This moves the wiring completely from the airstream. I also have modified the injector pod to provide less obtruction to the bores. Wish I could post some pictures, but don't have a digital camera; spend too much on go fast parts! I am the first to use one of Jim's TB's with the injectors in the stock location. I also use the vac ref FPR.

This is the procedure I used to set my IAC when I installed the TB.

Start the engine and warm to about 100 C.

Turn off the engine and grond the Diagnostic Link Teminal at the ALDL terminal. On my truck it is the A & B terminals.

Turn the ignition to run, but don't start the engine. Wait at least 10 seconds for the pintle to drive itself fully into the seat in the TB, effectively closing the IAC passageway.

With the ignition still in run, and with the terminals still grounded as above, disconnect the connector from the IAC valve itself. Try to pull the connector "straight" off, and quickly. It is important to break all of the IAC valve circuits at once, other wise the pintle may move. Alternately, you can also use a Service IAC controller tool, to manually close the IAC valve.

Remove the ground from the terminals above.

These events will have eliminated the IAC from the system.

Start the engine, and allow it to idle until the idle stabilizes.

If the minimum idle is not with spec (around 625) or a little more, remove the cover over the linkage stop screw and adjust until the desired idle is achieved. I set mine at around 750.

When done, shut the engine off, and reconnect the IAC connector.

Disconnect the battery to clear any learned IAC modifiers.

Restart the vehicle and check your IAC counts. They should fall between 5 and 40 counts. You may need to go through several start ups at different temps for the computer to learn the new parameters.

If you are using too radical of a cam, the low vac signal to the MAP sensor will cause the ECM to believe you are above an idle condition. The vac ref FPR helps with this as it lowers your fuel pressure at idle. Custom tuning at this point will be the next step.

Also, use the vac port on the rear of the TB for the MAP. The MAP sensor is very sensitive and needs the most stable signal it can get. Don't share the vac line to the MAP sensor with anything else!

You will need to make several startups for the computer to learn the new proper IAC settings based on start up coolant temp.

Hope this helps!

As to the shift point question, I previously shifted at 4800; this was with the Edel Performer TB intake. Now that I have installed the Air Gap, the engine pulls beyond the 5200 range of my cam. I need to return to the track to optimize the shift points with the new combo.

Bill

 

ok, so using the holley formula, you'd need 630 cfm.

i also noticed that formula is for cfm at 100% volumetric efficiency. since a street engine is doing well to operate at 90% ve, would that mean you'd only need 90% of the calculated cfm? if so, 630 X .9 = 567. that's a number that would appear to be in the range of what a tbi can make. using the "X 70.7" formula, 800 cfm at 1.5"hg X 70.7 = 566 cfm.

anybody know whether i'm on the right track with the volumetric efficiency?

 

Yes you are. I was going to mention that very point.

 

It has been my experience that using a larger carb then what the formula recommends is alright. Just my experience and others around me....

I use a 750 CFM 4V carb, according to Holley I don't need to.
Runs great.

 

Hey 454ss,

Tell me about that extrude honed intake. Who did it, how much did it cost, and was it worth the $???

Later, Mike

 

Extrude Hone Corp. The are located in Irwin, PA. 1-800-613-1065

They have several levels of processing.

The reason I had this done was the fact that the Edel TBI intake has ports that match the original heads, which are the "peanut" ports. The heads I installed are the normal oval port size. There was a severe mismatch.

Was it worth it? After installing the Extrude Honed manifold and the Jim Dickie TB and no other changes, my ET dropped almost 4 tenths. If I had known at the time how easy it would be to use a carb manifold, I would never have invested the money on the Edel TBI manifold. As I recall, it cost ~$360.

Bill

 

i agree... i had no idea about TBI - carb adapters. ended up getting the GM vortec TBI for $300... then had to bore it out to 2". the damn thing is i know it isn't made to flow worth a crap... (its GM.. come on) switching to a high-flowing carb manafold give much of a noticeable difference?

 

Yes, switching to a carb manifold made a world of difference.

Ran out of breath before 5K rpm.

With the RPM Air Gap, it wants to keep on windin'.

Bill

 

how much can the holley 670 be machined??