i am still learning about cars so can anyone tell me. I have 305 tbi but if tpi is better i wil put that on.

The TPI system on the LB9 305 is the better system for performance. However: The TBI on your LO3 305 is a fuel mileage car. And with that engine & cost of changing to a TPI is a waste of money for little performance gains. I will go with the old addage of get a 350.

ive always heard that with TBI you can be torque with the TPI you can build horsepower which is why for the longest time you could find the TBI on the pickup trucks(pulling trailers, campers, cargo, dead bodies, ETC) TBI=TORQUE TPI=HORSEPOWER

which even with a nascar race car there is no real big rearends i mean in the gearing of the rear the cars have no torque, the burn the tires off of 700+ horsepower so who cares if you have torque just as long as your making some serious horsepower.

[QUOTE=Daves03;3945163]ive always heard that with TBI you can be torque with the TPI you can build horsepower which is why for the longest time you could find the TBI on the pickup trucks(pulling trailers, campers, cargo, dead bodies, ETC) TBI=TORQUE TPI=HORSEPOWER

Your above statement is incorrect to a certain extent. The TBI or Thottle Body Injection was the updating of the old Carb systems to meet mileage & emission problems on late model cars & trucks. TBI does not = Torque, the same as TPI dose not = horsepower. They both have there limitations. Now Cubic Inches = both Torque & Horsepower.

[quote=DJP87Z28;3945173]i meant to a certain extent, your not going to build alot of horsepower out of two small injectors on 8 cylinders when you could have 8 good sized injectors on a 8 cylinder car i believe this was the correct way to build a car in the first place 8 cylinders-8 fuel injectors, im not downing a tbi engine b/c my camaro is a tbi and i love it, it has plenty of power to get you into trouble with the law, my 2003 s10 v6 multi-port fuel injection 6 cylinders-6 injectors and it is plenty powerful so im not trying to lean either way here but pickup trucks have just now started switch to multi-port from the tbi's i think a 1993 chevy full size 350 tbi is a pretty stout pickup. its whatever the owner believes in(both systems have there strong and weak points)

TPI = more tq, more hp and better MPG, and it looks cooler. And more fun to mash the throttle.. That sums it up. And there's a kid on here with a stocck lo3(tbi 305) thats went form a 16.xx to a 15.10 with just the tpi switch.

110%

I have two TPI cars, and my dad has a Carb car. The Tuned Port has smooth acceleration, good cold up startups and nice fuel mileage. It definitely gives you a nice torque curve and its fun in the seat of your pants department.

My friend has a TBI camaro and the performance was ok, but it could not keep up with my 2.73 geared camaro even with 4.10 gears.

If you ever get into tuning, the tuned port is a good way to go as long as its an 86 and up based system.

There are tons of TPI cars on this board running 12 second ET's or faster in the quarter-mile.

There are only a handful of TBI cars running 13 second ET's or faster in the quarter-mile.

Does that answer your question?

Ive noticed most built 305s have carbs. Is this just a general rule of thumb or what?? I havent seen a 305 over 320 hp using TPI and if it is then its probably 2 grans worth of stealthram or something.

it's not limited to 305's.. there really arn't that many 305's making 320 hp with any system on them.. but lets face it TPI is a torque based system at the expense of horse power. They make gobs of low end torque but fall flat on their face at 4500rpms or so. Due to their long runners they excell at making a boat load of low end torque. It simply isn't a system that in stock form is capable of making a lot of horsepower. A carbed based system isn't limited in that aspect. A stealth ram is a good upgrade to make horsepower on a tpi based platform, they just don't make as much torque. It doesn't cost thousands of $$ to convert to a stealthram if you already have a working tpi setup, don't know where you got that idea from.
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see my above post, tpi is a torque based system that doesn't make for high horsepower but does make a ton of low end torque. Your post doesn't make much sense..

lol they were like 2 and a half last time i looked. but maybe that was for EVERYTHING. Ive seen plenty of 300 hp 305 builds but it never exceeds that. I certainly dont have the money to buy a 350 and all the goodies unfortunatly. I was jsut getting in here too wondering if its worth it to convert from tpi to carb based if i wanna get in the 350+hp range.

Yeah you're looking at the complete setup with the ecu and everything. What you just said is kind of contradictory, you don't have the money for a 350 but you have the money to get a 305 into the 350+hp range.. you would save a ton of money by getting a 350 block to build up to meet that goal instead of trying to build a 305 you already have to meet that goal.. 350 blocks are plentiful and cheap.. but that's been said a million times.. everyone pretty much already knows that.. to answer your question it's much cheaper to build a 350 carb based car than it is a tpi based car.. it all depends on your goals..

yeah i hear the 350 deal all the time. And i know what you mean about building to costing more. In the long run it would cost more but thats my idea at the moment because I dont have a very big income (being a student) and I can buy parts one at a time whereas I'd have to wait and save up to buy a new motor. I know that makes more sense but damn im impatient. Plus i live in the Keys and it would have to get shipped here. To add to all that Im willing to spend in small amounts but the cost of a new engine is seemingly another car to tinker with.
What is the compatibility with a 350?? Does it require a lot of new stuff to drop in a lt1 or earlier?? the very first and only time i looked LS1 harnesses were 1k.

TBI's are certainly easier and cheaper to work on, but like someone above mentioned, TPI looks better when you pop the hood.

I made over 420 flywheel hp from a 312 cid 305!

Considering 350's came stock in these cars they are quite compatable. The only difference between a 305 and a 350 is the size of the bore, a 305 is in a sense a debored 350 (no you can't bore a 305 block and make a 350, the cylinder walls are too thin). They use the same cranks, connecting rods, etc. Externally they are identical. Most parts are interchangeable. The swap consists of removing your 305 and bolting an 350 in its place (more or less, there are little things like different knock sensors, larger fuel injectors, etc.) What some guys do is buy parts to upgrade the 305 that will swap right over to a 350 when their 305's kick the bucket. Things like headers, heads, intake, etc. LT1 and LS1 swaps are more difficult but defently doable, been covered a billion times though, do a search for more info.

fast,your a little smarter than your average bear round here I believe.

It can obviously be done and has been done quite a bit.Ford makes great power out of a 5 liter engine.Chevy can too.Thing is if your going to spend the money it`s the 350 that has more potential,for the same amount of money IMO.

I do get tired of everyone downig or discouraging evryone who thinks about building a 305.I say do what you want.Be a little differant and if you can out run a larger displacement engine you got a little bit bragging rights.I`m building the 305 that came out of my camaro and putting it in my 4.3 powered k1400 when that motor dies.Just cuz.

[QUOTE=Shadygrady;3948125]It can obviously be done and has been done quite a bit.Ford makes great power out of a 5 liter engine.Chevy can too.
QUOTE]

But you're forgetting Ford's lil 302 has a much better bore to stroke ratio than a 305 with its tiny lil bore that shrouds the valves. It has an advantage in that sense. Now a chevy 302 and ford 302.. that's more of an apples to apples comparison.

Understood.Point is the 305 can and has been made to make some good power.More than a few guys on TGO have done it.I know several people in my area as well.

My 91 454SS is TBI. The injectors are bigger than those for a SBC but the power is limited to the amount of fuel that can be pumped through them.

Switching to TPI will generally make more power mainly because when each cylinder has it's own injector, more fuel can be put to each single cylinder which will make more power.

Injectors are measured by the amount of pounds of fuel per hour that they flow.

Stock 305 TPI injectors flow 19lb/hr x 8 injectors is 152 pounds/hr of fuel.
Stock 350 TPI injectors flow 24lb/hr x 8 injectors is 192 pounds/hr of fuel.

Stock 305 TBI injectors flow 55lb/hr x 2 injectors is 110 pounds/hr of fuel.
Stock 350 TBI injectors flow 61, 65 or 68lb/hr x 2 = 122, 130, 136.

Just from those numbers, you can see a 305 TPI system can provide more fuel than the best factory 350 TBI system could.

The SBC TBI systems were also very restrictive for air only flowing 490 CFM while the 454 TBI flowed about 645 CFM and had bigger injectors rated at 75 and 81lb/hr.

How much fuel do you need?
Brake Specific Fuel Consumption (BSFC) is how much fuel is required to make a specific amount of HP in 1 hour. A typical street car needs .5. High performance engines are around .45. Blower and supercharger engines are around .30

Lets say you want a 400 HP engine. How much fuel does it need?
400 x .5 = 200 pounds of fuel. Now factor in an 85% duty cycle, 200/.85 = 235.3 lb/hr. TBI injectors would need to flow 117.65lb each which isn't going to happen and 8 factory 350 TPI injectors almost make it.

The other factor to take into consideration is fuel pressure. Increasing the fuel pressure increases the amount of fuel through the injector but there is a cap on how much pressure the injector can handle. If bumping up the pressure doesn't achieve enough flow, you switch to bigger injectors that will flow more fuel at a lower pressure.

There are other alternatives for that "cool" factor. You could get a low profile dual quad or a six pack intake and mount multiple TBI units. They could provide enough fuel and have that old school look of multiple carbs under a custom air cleaner.

Don't look to me for many more answers. My car has a mechanical injection system on it but the theory is all the same. Fuel under pressure going through a metered opening

TBI injectors can live happily at 50 psi! At 50 psi as opposed to the normal 11 psi, they are roughly 2x as big as stock. Those 61# 350 injectors become roughly worth 130 lbs/hr each. I put 379 RWHP @ 5,900 down with only 61# injectors.

I Definetly say TPI. and swapping to a 350 TPI is not that expensive. I will have less then $2500 in my swap. Now that doesnt count the previous upgrades I made like exhaust. I have $400 in the setup, $35 for the sending unit and pump from a v6 car, $600 for a used L98, $35 for a set of 081 heads, $200 in new bearings, gaskets and such am I missing anything Oh new injectors althow I can get away with my 19lbs will be about $170. Now I am having work done to the heads(porting myself $45 for a porting kit and maybe $150 to have 1.94/1.50 valve put in maybe another $100 or so for valve springs.
Now I didn't do it all at once. I imprved the 305 a little(full exhaust, lt1 cam, double roller timing set, pulleys, ignition system) then I swapped on the TPI the entire swap cost less then $600. Now i'm putting in the 350. I got a slightly used but in great shape L98 for $600 it doesn't need any machineing. Just a clean up hone and I'll replace all the bearings and gaskets, it doesn't need this done but I'm doing it anyways. Being a single dad BUDGET is a big thing for me so yes this can be done on a tight budget bc I am doing it and with all my mods I should be touching 300 horse or there about which is fine for me for now.

[QUOTE=Daves03;3945181]This is not true. The 4.3 uses CPI( Central Point Injection) 1 common injector mounted inside the intake manifold with 6 tubes leading to nozzles that point at each intake port. It is a completely different system. kind of a hybrid of TBI and MPFI

Small correction needed here.

The rods are not the same, they are smaller across the beam.

And the crank is lighter, although the same casting. (because the pistons and rods are lighter)

How did you do that?

IMO, if you are going to do a TPI swap, go ahead and get a good cam to stick into the engine.

Try to pick a cam with 112 LSA or higher so you can tune it. (Yes you might have to get into tuning to make good power).

Has anyone run an LT4 hot cam in a stock 305 TPI motor? I think we need some experts to chime in on how the camshaft influences the powerband on a TPI.