FART_NUGGETS

Been reading a ton.

This is my 1989 Convertible Iroc. LB9 305. Runs great.

Pleasure cruiser. Not a daily. Sundays, Shows, and Family Outings, random drives, etc. Not racing.

I want to get to about 325 at the wheels (~360 flywheel) as inexpensively as possible, but at the same time I'm not looking for snake oil. I know with a 305 this is about the limit.

Changed the plan. Looking to make a quicker feeling car. Don't need a specific number of HP. But want the car to feel considerably more 'quick' around town, etc.

I do not want a 350. I do not want an LS. I do not want an LT. I do not want a Vortec from a truck. I want the LB9 to push me.

My parameters are that I need to pay for major machining time, but I can port match parts no prob, I'm a surgeon with a dremel and a drill, and I can do all labor. I grew up on SBC and I have built one from a bare block that almost scared me I have good torque wrenches and I know how to use plasti-gauge. And I know how to make responsible decisions and not cut corners.

I know the top end has to go. No prob. Lower, runners, maybe upper, I want to spin 5500-6000 without wheezing so I know I need to swap out the TPI parts to get there. Whats my best bang for my buck here? not looking for 400+ hp. Just want to scoot around town.

BUT: I want to retain the visual appearance of TPI. Siamesed/etc is OK. But I want the factory TPI style runners. I do not want a tunnel or LT1 style intake.

Heads? Cheaper to mod the ones I have (I need to pay for machine time, I do all labor). or buy something? Used is OK as long as I can clean and refurb it in the budget. I'm happy with a good performing factory head.

Cam? I had a comp cams 292H in my old 355 10.5:1 1975 Vette I built. Too much for the 305 I know. But it was fun with the 3k stall and a TH400. So Lt1 cam? The Comp 260 series? What? I am not opposed to a higher stall converter as long as I retain lockup. And I don't mind a lumpy idle. As long as it's not stalling in traffic.

2.72 rear now, would love to bump that somewhere near 3.50 or so Never done a gear swap. Cheaper to find a used good condition factory axle and just slap it in? Or swap gears? Would prefer to keep the 10-bolt factory axle. My Posi is working great so far.

My head is spinning trying to wrap it around the best course of action. I want reliable, fun, I don't need to break 12s in the quarter, as long as it feels like I might be stop light to stop light

I would love to do an in-car winter engine project and come in under $2500 total. Less is better. I am willing to sweat and be sore tomorrow to save a dollar today. Do not want to touch lower end.

She runs great now so I also don't want to ruin that. Reliable, just more power.

Help me out here!

BigWhiteGTP

Getting 300whp from an LB9, retaining TPI, and all for around $2500....good luck.

Just to get a hi flow tpi setup, you will need as much flow as possible (look Into what Dyno don and company has done with the tpi, hogged out to high heaven) will cost you over a grand. So now you have $1500 left. Stock heads....suck. Again, you want 300whp, it ain't happening with hogged out iron heads. You mentioned the lt1 cam....I'm just going to stop and say that you need to do a lot more research. I'll let someone chime in who's actually built an LB9 to 300whp.

Nitrous 150 wet shot & a walbro fuel pump, plus all the safety stuff will get you to your goals and money left over for tires. And best of all you won't have to touch the motor. Stock drivability, reliability, and mpg.

88IROCvertZ

iTrader: (1)

I was able to break 12s with my 305 5-speed without doing a lot of what you are talking about.

-modified air box and MAF sensor to increase air
-K&N filters
-Flowmaster Muffler
-Hollwed out Cat
-Hypertech Chip
-Power Pulley
-removed belt from smog pump
-Hurst Shifter
-Centerforce Dual Friction Clutch
-Heads ported and polished
-MSD Ignition
-160 thermostat

So the car apparently had a nice stock cam and 3.42 rear end. The 305 5-speeds supposedly had 225-230 hp and the autos were 215hp.. I think 88 and 89 were a little more hp to start with as well.

I usually ran low 13s but one time I squeaked a 12.9 when I borrowed some slicks from a friend.

I used to beat my friends 5.7 who used to beat me before the bolt ons and the head work. I used to be able to beat my friends 1996 Camaro SS which ran 13.6-13.4. He had 310 HP stock I believe..

I did start to blow through T-5 transmissions when the car got faster.. had the last one rebuilt and he said it just couldn’t handle the motor..

I got to the point where the car would pin you to the seat and was a contender on the street.. nowadays you can get a 2017 Camaro SS into the 10s with minimal tuning so times have changed..

The engine looked stock still.. I was happy with it like that. I’d maybe do Magnaflow instead of Flowmaster because it’s a little quieter at idle, but growls nice when you give it gas. I got my heads done because I was getting the blue smoke at morning startup and needed valve seals..

It’s not too hard to get a little more from your 305..

People didn’t believe it back then when I told them what the car had done to it but they’d get beat.

I had some Grand Nationals, blown Mustangs and cars with nitrous beat me but I was happy with it.

88IROCvertZ

iTrader: (1)

...

Drew

iTrader: (58)

I'll bet you've caught some really BIG fish too.

Everybody knows you just do the TPIS Insider Tips mods, like gutting the airbox and using your Swiss Army knife to cut the screens out of the maf, bolt in an airfoil, port the plenum, and strap on a Flowmaster and any 305 will make 305hp, no problem Bob.

Oh I almost forgot, don't forget your K&N airfilter, synthetic oil, and SUPER-COIL... Pitty you didn't have a 5" MONSTER tach, it'd have helped that T5 hold together.

88IROCvertZ

iTrader: (1)

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88IROCvertZ

iTrader: (1)

I think the head work and the cam helped dramatically but just after the bolt ons I went from getting beat by more than a car length by 5.7s to beating them by a car length. Those stupid things add up.. army knife and all..

I don’t know what the car had for a cam, but a couple guys that looked at it said there was no way it was a stock cam.

12.9 isn’t that crazy. It’s not that big a fish.

13.3-13.1 on street tires

Considering the new Camaro SS can pretty much do 10s stock..

We were all chasing 12 sec back then.. guys were taking the seats out, etc.. anything you could do quick and cheap to make the car faster. A guy I knew with a Grand National was trying to get 11s

My car frustrated several people that would lose street races and demand I pop the hood.. my friend that used to laugh at IROCS bought a brand new 1996 Camaro SS because I smoked his car.. he came for a ride in mine and was like “holy crap” and went out and got a Camaro.. he was annoyed I could still pull on his SS.. he did some mods and we were neck and neck..

It pinned you to the seat off the line and had really good top end.. it would pull hard..

I think that would be tougher with an automatic convertible with 2.73 rear end..

I’m glad I don’t give a crap about 1/4 mile times anymore.. i probably have a video somewhere on VHS from 1998.

BigWhiteGTP

He didn't say 12s. He wants 300whp. Also how much did you spend btw? OP wants it for $2500

88IROCvertZ

iTrader: (1)

I didn’t think of the budget..

This was back in 1995 and I had done all the bolt on mods already which got me running faster Than a stock 5.7.

I needed valve seals so I did all the head work at that time..

My car came with a power pulley and smog disconnected from previous owner, some suspected it couldn’t be the stock cam in there. It was a G92 car and had the 3.42 gears already..

The engine work was probably $1700
Exhaust $600
Air box K&Ns $100
Chip $170
Centerforce Clutch $700 installed
MSD Ignition kit $600

Probably $3000-4000 over a couple years..

He’d have to do the gears which I didn’t really need to do..

I thought the point was to feel like a 12 sec car from stoplight to stoplight but still look stock under the hood..

My Tahoe has over 300hp but doesn’t feel like a 12sec car..

$2500 is a tough budget when you do the math..

dmccain

iTrader: (2)

I just don't see it happening with a 305 for $2500. Unless you put nitrous on it.

Flycaster1977

iTrader: (1)

Lets say, for arguments sake, remove the budget. Now what would a person have to do to get to that 300 hp level. The op was asking legit questions and i dont see any real answers.
Assuming headers and free flowing exhaust, what else? Port and polish factory heads or look at torquer sr or possibly trick flow 305 heads? Port the base and runners or replace? Etc
Tpi was designed for a 305 and not really for a 350. If a person was to put the work in, it would be ok to assume that the tpi gains on a 305 could be better than the tpi gains on a 350.

88IROCvertZ

iTrader: (1)

Exactly.. let’s not forget the 2.73 gears are a problem for the stoplight to stoplight fun too..

I think a lot of people have a problem with putting money into a 305 because for the money you could have a stupid fast car with a bigger engine.. people think it’s a waste to put money into it.. the op wants to keep the 305 though which I understand.. it just might cost more than $2500 to get the results..

I think swapping gears and doing a shift kit and some bolt ons would be a start.. Exhaust too.. might even be happy with that for a minute

arrg

Here's a recipe for a 360 hp 305 from the magazines:
http://www.superchevy.com/how-to/pro...-engine-build/
Just realize that with tpi you'll make more torque but less hp than they did with their carb setup. You aren't going to get to your goal with stock heads (not even with massive porting). You'll also need a heavily ported lower and siamesed runners to see 6k rpm with your tpi. Don't forget lots and lots of computer tuning to get the most out of it. It would be fun to drive, but don't get hung up on numbers, because even with all that work, your 305 tpi still isn't going to make 325 rwhp. You'd be lucky to get there with all the same parts on a 350.

zs&tas

I don't have a v8, I'm not up to speed on the tpis, giving yourself a hp goal 50-60% over stock is a big task. Getting a car driving nicer , feeling healthier without big hp claims is a better way to go around thinking about things, for sure find some good cheap heads, or port what you have, port the intake your self, make sure you have headers get a nicer cam and swap out those gears. It will be cheap and transform the drive of your ride.

Flycaster1977

iTrader: (1)

I am in the same boat sorta. I have a .040 over 305 that came in the car. Only has 3k miles on it, but other than the overbore, its all stock. Also the same mileage on a rebuilt trans with a shift kit. 3.23 posi, 9 bolt rear that functions well.
My plans are to add headers and exhaust. I have a used lt1 cam already, so that will go in too.
Was planning to port and polish the tpi base, possibly add as&m runners or port and polish the stock pieces myself. My big expense will be heads. Im looking hard at the trick flow and world torquer heads. I probably wont see 300 horse, but it should give me a pretty good boost and won’t break the bank.

dmccain

iTrader: (2)

250 HP is plenty fun in these light cars with a great shifting tranny and some gear.

Orr89RocZ

iTrader: (20)

If you did a decent cam and a short runner intake on stock heads it would get to 300 crank. Thats only 250 whp give or take. Pretty easy to make

Want much more than that need aftermarket heads and fresh bottom end lol alitte more comp for the cam. With tpi you would need big ported base and runner to get flow to support the heads and rpm needed. But short runner intake would do it easier

Street Lethal

iTrader: (16)

OP's avatar is hilarious. Is that your real license plate lol? What part of New Jersey are you in?

Why is it the limit? If this is not a daily driver, switch to E85, up your static compression, work your stock heads and intake, get a good custom camshaft, larger injectors, and start your tuning. Should meet your goal no problem. You can even meet your goal running pump gas, just be sure to run 93 at the pump and take it easy on the compression bump., but overall I don't see your goal being a problem whatsoever...

- Rob

Orr89RocZ

iTrader: (20)

Bore size limits valve size which limits airflow in a 23 deg head. You'd really have to turn it some rpm to make much over 400 hp. You really need to get the ducks in a row to get up there. Definitely a purpose built na motor deal.

Tootie Pang

iTrader: (2)

Nitrous and save some money.

http://www.jegs.com/i/NOS/741/05151/10002/-1

Not sure why, but for 305 only 100HP is advised. I would have thought 150HP was safe...

cuisinartvette

wouldnt sweat rwhp #s much esp with a TPI
do the best you can with your heads, intake a 256+- type cam headers and have a blast. It will pick up nice for dirt cheap if youre good with porting.
Try not to breathe that iron dust or get it in your eyes!

Drew

iTrader: (58)

I ran a 125hp shot on my 3.1L, no problem. What kills it is the cost of refilling the bottle, and how quickly 10lbs goes. If you hate filling the gasoline tank, filling the N2O bottle to the tune of $5/lb every night will drive you crazy.

Tootie Pang

iTrader: (2)

^^ True that! Can't be too loose with the juice.

FART_NUGGETS

The license plate is a photoshop. My 5 year old son and I are big "buddy thunderstruck" fans. Buddy says "FART NUGGET" as an expletive I happened to be signing up for this message board while we were watching the show, and decided to make that my user name. Took it a step further and photoshopped a plate on the back of my car as well. Fooled a lot of people on facebook!

OK so I think there's a lot of good points here.

Like everything else with this car, one day I think I know what I want to do, the next I don't. I am really happy with a good looking, good running drop top Iroc. I would like it to feel faster, but I also want to be able to reliably cruise the back roads.

I have a lot of fun right now with the basically stock 305, only thing I have done to it so far is to go with 1.6:1 ratio rockers ( was doing the valve seals so figured what the hell, while I'm in there...). It also has a flowmaster catback on it from the previous owner which sounds awesome. As far as I know, there are no other performance mods done. Has the factory cat, newly installed, the car came with a badly leaking straight pipe where it was. No AIR pump or plumbing.

I think going to a 3.42 rear would help a lot. I do like the look of the tires sitting out flush with the wheel arches, so a 4th gen 3:42 with discs might just be the ticket there... Over the winter I want to clean up the TPI intake (appearance wise), so while it's off the car I'll probably port it as best I can. Might go with some larger runners.

So lets change the rules and see what we get.

Lets take the HP goal out of the equation.

Want a faster, quicker feeling car, with minimally invasive mods.

If I'm pulling the intake over the winter anyway, would there be a good cam that would work well with the stock heads and a mildly ported TPI? Or should I stick with my peanut and the 1.6 rockers?

The trans shifts great, I don't know if I'd want to mess with it. I limited my WOT to about 90% travel using a strategically placed zip tie on the little ear of the throttle linkage, and readjusted the TV cable to be at full deflection at this 90% throttle position, it holds gears to exactly where I would be shifting if it was a stick, very responsive. Without limiting throttle travel with the zip tie, at full throttle travel, the TV cable pulls out a few clicks past where I like it, resulting is early shifts and a slow sluggish feeling car at part throttle. I'll be doing the TV spring mod another member told me about so I can lose the zip tie, but honestly the car doesn't feel like it lost any top end only using the 90% of the throttle travel.

Some days I want to focus on the motor, other days I want to focus on appearance and squeaks and rattles

Maybe I can reduce my scope here and get a good compromise, get some performance and save some budget for other stuff, or the unexpected that is sure to pop up.

Tootie Pang

iTrader: (2)

Yep, that's a good plan. Near mine exactly.

3:42's and the Sonnex TV cable spring will make the car feel a lot more sporty and launch harder without messing with your freeway RPM's much and IMHO perfectly safe for the trans- shorter TV cable increases clamping force and raises upshift RPM points vs stock setting in all conditions.

I got a performance ECM tune for a 180 thermostat. Adds a nice little bit to the engine feel and sound. They are inexpensive.

I also replaced my OEM Multec injectors with Bosch D3s (22-lb). I bought an adjustable fuel pressure regulator but ended up only mildly needing to adjust it to get my BLMs correct. The 22-lb "rated" (commonly rated by injector sellers), are the correct ones for stock LB9. Engine runs noticeably better with these.

Also, sub frame connectors are a night and day difference on these cars.

FART_NUGGETS

Oh yeah, previous owner upgraded to 22-lb injectors. They're also new. Didn't mention if he re-tuned for them.

Street Lethal

iTrader: (16)

Then don't touch the engine. What the car lacks is a stall speed and rear gears. If I were you I would get a 3000 stall speed converter, lower your rear gears (higher number) then just tune the engine either yourself, or get a credible shop to do it for you. I guarantee it will be an entirely different vehicle with just those modifications. But if you have your heart set on pulling the intake and want a cam to go with those stock heads, there are some decent cams out there to raise your RPM with those stock runners. You just have to sacrifice a little vacuum at idle...

- Rob

1991vortech335

I totally agree!!! I’m just shy of 600 hp at 10 pounds of boost and I have room for 10 lbs more. The 305 always takes a bad rap but it’s still a sbc with all the same principles. Sure mine might be a 335 now but built right you can make a monster.

FART_NUGGETS

I like you bozos

spurgeon76

Why not look for a L31 engine from a pick n pull?