I'm debating whether to go carb or not. Seems like with carb you have the advantage of not having to buy any hardware to work on it, and your cam selection isnt nearly as limited.

So how far can you relaly take TBI? It seems like in the stickies I've read (It's just a LOT of info and I've read through them dozens of itmes but sometimes it's just a bit of an information overload and you start blanking... ) you're lucky to get past 300hp or so with all the fancy bells and whistles.

It seems like you cant really go too far with the TBI and everoyne looks down on it, but would using the EBL and a 454 injector/TB setup get around a lot of the bottlenecks that everyone talks about? How much power/torque could a setup like that make assuming hte induction is the limiting factor?

 

It certainly will open up the possiblities with being able to tune and fuel bigger cams. Something that alot of people skimp on during their builds is the heads. If you build your combo so that the cam (not necessarily the biggest one on the page), your heads, your rocker arms and your intake system all work together then you'll put up the numbers to a point.

After about 350hp (not counting nitrous), I would think that it becomes a displacement limited problem. The EBL has given us the ability to break through a lot of the previous barriers that existed.

 

I jsut dont understand how it's a displacement limited problem when it seems like carbuerators can go faster. It's a TBI problem then is it not?

It's just a huge investment to stick with the TBI, and if it doesnt have any room to grow...

For the record, my setup is gonna be 083 heads. And with EFI, I figure my cam options are pretty limited. Or at least a lot more limited than they are with carb'ed setups. Time to do some research I guess.

 

Well, maybe a better question is then how fast do you want to go with the 305 NA? What is your goal?

 

The 454 TBI is comprable to a 650 CFM carb, so whatever you can stick a 650 on, TBI can run it as well.

 

All you have to do is supply an engine with enough air and fuel in the proper quantities and spark it off at the right time.....thats it. Everything else about modding an engine has to do with physically getting air into and out of the engine and has nothing to do with TBI.

You might want to rethink how expensive TBI is compared to a carb.

Most new carbs are well over 250$, you can pick up a used one for $125-$150. You can get a BB TB and injectors for about the same price on ebay so we'll call that a draw.

You'll need a fuel pump for either type of injection, your stocker won't feed more than 200hp, so you'll need a walbro 190 or equivalent, with a carb you'll need to pull the stock pump and install a mechanical pump, or get a 100$ regulator to regulate down you stock electric pump and even then it may not feed your carbed engine. We'll call this one a draw as well.

This leaves us with tuning hardware. You can get going doing your own proms for less than $150. With a holley you'll need a jet assortment, pump shot cams and possibly squirters. This will all add up to some where between 50$-100$. So you are correct in thinking that TBI is a bit more expensive to tune.

As for what a 2" TBI setup is capable of, 300hp has been made with a stock small bore TB with small injectors at a very high FP. Guys have made it into the mid 12's with 2" bore TB and bigger injectors. The true limit of TBI is between 425 and 450HP. Once you are past this point you simply run out of time to inject the necessary fuel. Once you become proficent in tuning your own chips you can run any cam you can run in a carbureted engine. If anything you won't loose as much bottom end as you would with a carb because TBI doesn't require vacume to atomize fuel the way that a carb does.

With that said learning to tune your ECM is not easy, it takes dedication and plenty of time. If all you want to do is make power, slap a carb on there and have fun. If you want the added fuel mileage and drivability that FI can give you get learning. Don't be fooled into thinking any other form of FI is immune to the same tuning issues as TBI. You'll quickly see that it will take an enormous amount of money to make a MPI system make the same power as TBI. A properly setup MPI system does have some advantages over TBI, but the price difference is enormous. Everything you learn while tuning your TBI setup will translate right over to any other from of FI.

 

Excellent posts guys, very informative.

a few more details, the 305 is on the way out. It runs fine and all, but it's just high mileage and I wanna get something fresh and fast in it. Now my idea of really fast would be 300 rwhp, but I think a more realistic goal is 300 fwhp. I want a practical street car. Not a track car. I want a street car that's quick at the track, not a track car that I can drive on the street. I understand I will have to make sacrifices to that end, that's fine.

I've got a 350 block waiting to be assembled. The question is... should I carb it, or TBI it? Everyone gives me this funny look when I say I want to keep the TBI, but Im just trying to figure out how big of a performance difference using the EBL and a 454 TBI can make...

It's looking to me like I"m spending $750 on computer stuff and the throttle body alone.

This is how i'm planning to do it:

EBL $300
Chip burner - $100
Chips - pocket change
454 throttle body/injectors - $150?
crappy laptop to datalog - $150

That comes out to $700, and I know there's gonna be other things that come up. The fuel pump is the one thing I'm dreading dealing with...

But it does come out to be a lot cheaper than a $2500 HSR kit...

Im learning as much as I can in the meantime about tuning for a TBI system, but I dont understand how you can tune for big cams... ? What is it that you have to do? There was a thread linked in one of the stickys about it but the link didnt work. Just remap all your VE tables and spark tables to compensate for the fact that the computer thinks theres a higher load on the engine than there is? Because it's my understanding that these huge lopey cams make less vacuum and confuses the MAP sensor... Is that right?

 

"Just remap all your VE tables and spark tables to compensate for the fact that the computer thinks theres a higher load on the engine than there is? Because it's my understanding that these huge lopey cams make less vacuum and confuses the MAP sensor... Is that right?"

In a nut shell.....you're absolutely correct.

A speed density (MAP based) FI system uses a fuel table that is based on RPM and Vaccum to look up how much fuel to inject. So if your new cam idles with half the vacume, that particular part of the fuel table may not have the proper amount of fuel that the engine needs. Start with the "Free tune" thread at the top of the forum and then move over to the DIY prom board and keep reading. This should give you a good idea of what it takes to tune an ECM.

Also keep in mind that your stock ECM is more than capable of running a 300hp motor, the EBL is an awsome upgrade but not completly necesary.

 

The EBL seems like it would be a lot more user friendly and downright useful than the stock ecm. It's expensive and that hurts me a lot, but I figure things like its ability to "learn" over time and how intuitive it seems to be will give me a big leg up on getting the car driveable after the engine swap.

Besides, I'm gonna spend some time with it all hooked up to the current 305 and it hopefully will help me there too at least.

 

If you're dropping in a 350, then you don't need a big cam for 300 RWHP. I was putting down 262 RWHP and 365 RWTQ with 55# injectors running at 18psi I think and without the EBL.

I now have the EBL and 65# injectors, but haven't been back to the dyno. If I've said it once, I've said it a million times . . . build a combo that works well together and you'll put up the numbers. Slapping a huge cam in and expecting a monster result is stupid, especially with EFI.

FWIW, my cam is a tiny 204/214 .429/.452 116LSA with some 1.6RRs.

 

Am I the only one who finds it strange that so many people are able to go out and spend the money on a new engine but then wince at spending 300-600 more to buy EBL and other tuning tools like a wideband to keep your INVESTMENT running its best. If you have a thousand in your motor swap, congrats, slap on a carb... if you've spent 3k on a motor and other swap, spend the extra and go efi.

 

I think it's more of the idea that spending that money on aftermarket tuning tools will result in nothing more than pounding one's head on the desk.