Okay, well Ihave a 305 TBI engine, and I feel it isn't as fast as I want it to be, and i was thinking about looking into some aftermarket performace parts for my engine. my dad seems to think that my engine is too old and tired and will just blow up if i mess with it, but I'm really not sure. The engine has 182,000 miles on it. Is that too much to be modifying? or is it ok? the engine has been well maintained all its life. and nothing is aftermarket besides a muffler, and I just replaced the oil, cap and rotor,plugs and wires, injectors, fuel pump, water pump, air filter, rad. hoses, flushed system, and checked all vaccumm lines, and it is running great. And if I should modify it, what's the first thing i should do?

in the same boat as u. mine has 130k and its definitely not as fast as i want it to be either. mines also had been very well taken care of...

im subscribin to ur thread cuz i wanna see what other ppl have to say

Take the engine apart .. your heads have TONS of carbon built up inside, seriously hurting flow and also creating hot spots

thanks (even tho im not the original poster lol)! awesome advice. its alot of work, but its free so it'll be worth it. just clean that **** out? or do u have to get new internals

i'm replying also cause no one on the site has really given me help with this LO3 engine. My car has 95000 miles on it and i need to replace the motor.

forget a 350 cause i want to keep it mostly stock. And I don't need a high horsepower racing machine. My 305 TBI has served me well over the years, I am the original owner and bought it new in 1992. I also want to know what I can do for the new motor without tweaking the computer.

I'm considering a 3704 performer manifold and headers on it.
I have an slp exhaust from the cat back and a random technologies cat.
I removed the stock air cleaner, and raised the air filter and changed to a 14" k&n element with that funky k&n lid. With the 2" cowl hood it really helped the car breath better. Thats why i'm considering headers for the new motor to make breath easier.
I reworked the suspension already and the car handles great.

I also have the accel cap and rotor and MSD wires and coil.

Any help woulld be greatly appreciated.

honestly you have to spend money to go fast. it all depends on what your looking for. on a high milage engine even if it's tight and well maitained messing with it could open up a can of worms or even bring out a problem that otherwise might not even be an issue if you leave it alone. if i were you i would do cheap external bolt ons. msd ignition, k&n air filter. if you start messing with a cam or heads or even worse put nitrous in it or a blower on it and don't do the lower end of the motor i can guarantee you will have problems. 305's were never known to be fast stock. but you can certanily build one up to run with the best it's just a question of how much you want to spend

Thanks, i'm not lookin for high horsepower, the add ons i had done before losing the motor were a good step, just wondering abought the performer intake and a set of headers for the new motor, i know i can do a 350 but i have reasons for sticking with the lo3. Mainly time and the labor costs involved, although I am competent with my wrench turning abilities, I just dont have the time to do this myself and will be paying for the labor.The main one is resale value many years down the road. ( not that i'm going to be selling it). And its my daily driver.

Thanks again for all those who have taken the time to answer my questions.

My understanding of the 305 is that it has a good strong bottom end and as long as you have good oil pressure and an otherwise sound motor it will take quite alot more power than was originally intended,even blowers,turbos or a squirt.Of course if you go for too much boost or too high a shot you are gonna eat pistons and head gaskets etc,300 horse should be ok.

First thing I'd do with that bad boy is get the headers. As vorgath said take your top end apart to see whats up, for sure theres going to be carbon on the valves which is robbing you of horse power(below stock Hp rating because of it) while its apart check to see if the vavle guides are still within GM spec's (if not there also a cause of lost horse power)now would also be a good time to get new springs(there are some great deals on the classified's part of this forum).

If your a DIYer or even up to the task you could do some port work with a dremal to get a little extra power and take down the valve boss some what.

Good luck with the 305

thanks guys i was thinking if I'm going to be taking off my heads...should i just replace them? I read somewhere that the stock 305 heads have low flow, does anyone have any suggestions on what type of heads would be good for raising performace with a stock engine without spending a huge load of cash?

BTW: i think my intake mani has been off before because there is black liquid gasket seeping out all the way around, so someone might have done a valve job previously...

The 305 i plan on building consists of these parts
world torquer 305 heads $760 a pair
Comp cams extreme energy OE roller $254
Holley Pro-Jection TBI manifold $165
Holley 670Cfm TBI $390
Figure in about 100 for gaskets and your total is about $1,700
I figure that should equal good performance gains and you might notice improvment in gas mileage as well. Just my input on the subject

Just a few suggestions

Vortec heads plus an intake manifold will cost the same as the torquer heads and make more power to boot.

Which cam you go with will make all the difference in the world.

TBI specific intakes tend to be a low rpm torque design, you can get more performance for less money by using a carb intake with an adapter plate.

The holley TB is overpriced for what you get, they come with 55 or 65 lb injectors. A better use of your money is to get a stock 454 TB, it'll be the same 2" TB with 70/80/90 lb injectors and cost 70% less than the holley.

You also didn't list any tuning equipment, this combo won't even idle without tuning. Need to make tuning an intigral part of your modding process.

everyone says it has so much torque, but it seems to pull the least in the lower-midrange. it pulls the most around 5-7k..

It's all in your head, there is no possible way you are making any kind of usable power above 5500 rpm. I say you just have some tune-up issues that keep your motor from running like it should.

wanna see a vid?

Okay I am thinking of doing the same things to improve performance of my GREAT running 305, currently at 126,000 miles.

Thinking of doing this over the next 3-6 months:

MAC headers and Y pipe
upgrade timing chain
new cam (not sure which one yet-still researching)
upgrade valve guides and lifters
Edelbrock intake
Edelbrock chrome valve covers (centerbolt)

suspension:
Edlebrock 3 point strut tower brace
Sub frame connectors

Hopefully this will all improve my 305 and not depress me or my wallet. If not at least I tried. I like the 305, it seems like a decent blend of performance (if upgraded), economy (gas wise) and durability.

My 190k mile 305 TBI wants to give up the ghost at around 4k RPMs... just not much up there... How in the hell are you spinning it 5-7k and getting any power out ofi t?!


And to the OP, any change you make is going to require computer tuning. It's just the nature of Speed Density systems... So figure in another gaggle of money to do that.


I'd be hesitant about putting that much money into an old 305. It's why I'm in the process of putting a 350 together.

The Only Way to Make Power with the some what stock L03 at 5500+ if you can get it passed that (in gear), Is if the rear gears were Changed.

well im almost positive i still have the stock 272s

if someone wants to give me their email address ill send a vid or two of the tach going up to 6500 and pullin hard

No offense, but with the stock 305, its unlikely its making any real power out there. The engine lays over at around 4000 RPM. The most likely explation is a faulty tach. Its probably overreporting the RPMs. They tend to do that after awhile.

A good quick and dirty test for the power out top is to get out on the highway during off-peak hours and stab the gas at 60 MPH. Every 10 MPH increase in speed (up to around 100 if you dont mind a ticket) should take less than 2-3 seconds if the car is making decent power. Taking 2 seconds to go from 70 - 80 MPH is ~180 RWHP, 90 - 100 MPH in 2 seconds is ~220RWHP, etc...

193K is alot. I rebuilt my motor at 154k cause it was going through a quart of oil every fill up of the tank. I went to PAW and got a super stock rebuild kit for the bottom end, crank, pistons, rings, bearings, rods. You could reuse your internal and have a machine shop hone, boar, and polish to get everything back in spec. Just keep careful track of everything as it comes out of the motor. Throw in a better cam made for computer controlled F bodys so you dont have to get any special tuning right away. People say the LT1 cam works great. Check out my sig at the bottom for other things that work great for these cars.

Oh I also run her to 6K when I'm racing. Gave me the best times at the track.

I am interested in getting more power out of my 92. I don't want a lot of power, and I do think that it needs to be gone through. With it having 163k and not using oil, would it hurt to tear down and replace all gaskets and clean? What gaskets should I look into replace if so and what should I clean? I don't want cams and things yet, I want to see how many miles she will run!!!! Plus scared of doing to much without knowledge of what would be good for my baby.

Tearing down the motor for new gaskets will do more harm than good unless it's leaking oil like crazy. There is most likely a LOT of gunk and carbon buildup in the motor and taking it apart will just break it up and put it through your bearings most likely resulting in a spun bearing.

Keep trucking and save your pennies for a full rebuild with all the machine work.

I have a 89 RS 305 TBI And mine is having the same issue as the other guy.. According to my dad from factory the rs would burn oil and overheat....IDK why he didnt force them to give him a new motor...but im looking into maybe rebuilding it with in the near future....

save 600 bucks and get nitrous. my 164,000 miles 150 shot breathing BEAST of a 305 is a lot of fun to drive for an semi-old car.

is it stock other than the nitrous????????

yes.
click on my past , present, and future therad below.