aerosmithr0cker

First off I don't want any posts about toss out the 305 and put in a 350. I'm deadset on a 305.

I'm building a 305 TPI and want to know what stuff I can do to get it up to 300HP.

Like good headers that fit good, what type of cam, etc...

Thanks in advance.

91z28ss

iTrader: (4)

Hi,

You will be able to achieve to 300HP but at a Torque expense with your 305... I am actually myself preparing to rebuilt my 305 from my 91 camaro. I removed it back in 1998 at 47000KM and it was stored since.

Do some research and you will find some proven combos! As from me, I probably go with aftermarket intake and runners, mid cam, 1 5/8 headers, CAI, L98 heads or Vortec (not sure yet) roller rockers, custom Eprom etc. and hoping for a realistic 275 HP

I will take my time since I am not completely done with my current 355 tuning. But sincerely, can we ever be done with our project

aerosmithr0cker

Never done with a project, like my fiero i got plans to put a v8 in it but i gotta get my maro rebuilt before i tackle that.

Just a little details on my car it is a 1989 Iroc-Z its gonna be a 91 z28 clone when im done though i always liked that body style more anyways and i dont plan on selling this car. I basically have everything for the car i need to put it back together and just about to reassemble the engine, just want to push close to 300. So before i bought my cam, lifters, and rocker arms i wanted some input from this forum.

LB9GTA

iTrader: (1)

I have roughly 325 engine hp, check in sig.

SLP IROC-Z

iTrader: (1)

i see a bunch of "it should" "it will" has anyone dynoed their worked 305?

AZ406TPI

iTrader: (2)

if $ is no object.. get some AFR heads, huge cam, better intake, stroke it and forge the bottom end. (so u can spray on top of this.

but as everyone else will agree.. just get a 350 dude. ur not going 2 have the TQ of a 350, and imo, "waste" this $ on a 305 when u will c MUCH better results with a 350.

LB9GTA

iTrader: (1)

Or you can do what I am doing and build your 305 till it blows.
Just make sure all the parts you are putting on your 305, can transfer over to a 383.(that is my intention)

aerosmithr0cker

i dont want to spend the money on a 350 when i already got the 305. Work with what i got with. For that matter throw away the 350 and get a 400 right? 350 cant compare to a 400 tq and power. Or hell lets go big block!

I dont want to hear the 350 argument.

I got a cam picked out and my 305 will have more than enough power to blow away stock LT1s and possibly stock LS1s.

speed88

Good luck with that!

ThirdGenFire

I can beat LT1's? Why is it ???
It took more work but it is being done. Now LS1's are another story but the Auto's are there. i am about a .3 behind his 00 T/A with a Flowmaster and a K&N filter with SLP lid. The 01-02 LS1 with the LS6 style manifold is another story as well. LoL. too many stories going on.

onebluemcm

I wondered how long it would be until the "get a 350" comments would show up cause they always do.....

Right now, I'm on the "give the 305 a chance" side too mainly because I own one. I just want to say I'm still not clear as to why it's so hard to improve on the GM 5.0 comapred to the Ford 5.0. I am an admitted ford-convert - wholly in the Chevy camp now - but I've had some experience with the Ford 302 and have seen some amazing things done with them with out the consideration of forced induction or juice. Is it something about the design of the 305 or just a really poor aftermarket parts availability as compared to what's out there for the Ford 302? I just feel like I've never gotten a good answer on this.

I only bring it up because it seems so easy to get 300 naturally aspirated horsepower out of the 302 and so friggin hard to do the same with the 305 and I just can't wrap my mind around the reasons why.

K

speed88

LT1's and LS1's can and do run 13's and 12's repectively stock. No 305 TPI is gonna do that with only a camshaft. He said he has a cam picked out that will get him there. Not gonna happen. 305 TPI's run 16's and 15's stock, it'll take more than a cam to get down to 4th gen territory.

LB9GTA

iTrader: (1)

He's right.
I put in a cam, and actually lost power until I did my exhaust!!

Even with the nitrous, I am only in the 13's.

Pretty hard with just the motor and 305 to get in the 13's, let alone keep up to a stock LT1 or worse, a LS1

LB9GTA

anesthes

iTrader: (12)

Then why are you asking us how to build a 300hp 5.0 ?

-- Joe

GTA matt

iTrader: (1)

The GM 305 has a smaller bore then the Ford 302. This means smaller valves=less airflow=less hp.

Orr89RocZ

iTrader: (20)

trick flow makes new heads for the smaller small blocks. be perfect with a 305. if ported out, even better to match up with a Super ram or Stealth ram.

a stealth ram and a lingenfelter 219 cam on a set of ported trick flow small block heads, i can see an easy 350hp+

80smetalfan

Auto LT1's run high high 13s stock, and many run in the 14s, with the incredible unreliability of the early Optispark system not helping. Granted, even a slightly built LT1 will blow away most well built streeted 305s. However, to have a goal getting a TPI 305 to BEAT (just forget about "blowing them away", not happening) bone stock auto LT1s (especially the 2.73 axled ones) really isn't that unrealistic. It's not happening without tuning, but it's not just totally impossible.

The only 305 TPIs running 16s are horribly out of tune or have some similar problem. My RS ran 15.8's on street radials with a totally stock 305 TBI, 2.73's, one wheel peelin, and 180,000 miles. The only mods to get it into the 15s were straightpipes, Open element Edelbrock air cleaner, chip, timing advance, and low tire pressure.

As for the thread starter:

With that in mind, I don't think it's hard to simply get a 305 TPI into the 14s if it's in good shape and not out of tune. However, getting into low 14 territory probably isn't worth the investment required unless you're either using parts to swap onto another motor, or forced induction to swap on another motor.

I'm gonna side with the 350 guys here. While your argument of "there's always a bigger better motor" is true, the 350 is by far the cheapest and most plentiful, and is usually cheaper to build than a 305 because of the heads. To take out V8 4th gens on a N/A 305, you're going to have to either do a head swap or get your LB9ers ported. Porting isn't cheap (unless you can do it yourself), and aftermarket heads for the SBC are more plentiful for the 350. You can maybe spend a lot on aluminum 113 heads and keep your compression, or buy less expensive 64 CC iron 350 heads and have the crap milled out of them. Either way, spending maybe $200 for a decent 2-bolt 350 is probably cheaper.

I like the 305, it will always blow the 350 away in terms of MPG, but it's not really a performance motor in any aspect. Like swirlport heads, it's obsolete smog-era equipment. Good truck motor, bad Camaro motor. Not a good choice for a 4th gen killer.

Lucid

iTrader: (4)

I'm on the same quest as you are my friend, have an LB9 thats been bored .030 over and since mine is an '86 I made sure i put the L69 cam in there to get the HP back to 215 stock. If i knew more about engines back when we rebuilt the LB9, I would have put a more aggressive cam in there because the heads are restrictive and so is the intake so it is better to get more lift to suck more air into the small cylinders. The Ford 302 have a 4" bore and the Chevy 305s have a 3.75 bore but a longer stroke than the Fords.
The biggest things are making the engine more efficient, it will give you more power and also make the horsepower and torque you need. I know you don't want to hear about a 350, but you need some better heads to suck more air into that small motor, and the 350's have heads that you can mill and bolt onto the block, the vortecs are nice since they are cheap and great out of the box. If anyone has any information on how to do this can you please let me know? I'm not really sure about this so if anyone can help me out..... I believe you are going to want to put a roller cam and roller rockers with at least a 1.6 to 1.7 ratio, roller cams don't have the maximum lift constraint that the hydraulic non lifters do, and are more efficient? Someone will have to help you with that one, but it would behoove you to take advantage of technology and put the old tech to rest.
I just had the 3" exhaust from the 3" catalytic converter hooked up to a 3" borla muffler, which is freaking huge by the way, he had to bend the muffler shield to get it in there. This made a considerable difference, the flow is so much better that it really doesn't make much noise (whooooosh), all you really hear is the engine. To get the car to launch I put boxed lower control arms which push down on the rear so the car can move forward and reduce wasted energy flexing and rotating the axle. Ok enough ranting, I hope this helps a little, remember get the most air and fuel into the engine as possible...

Buddy

Do a search on here. Type in a couple different things, and talk to Dave at Thunder Racing. There are 5.0 on this board beating stock LT-1 and LS-1's. Alot of people knock the 305, yes you could go bigger, but if that's not what you want, just like a 350, you can just keep building, the skys the limit. I have an early High-Tech magazine, there was a guy (Tom Poston I think???) with a street driven 9 second 305 Iroc, looked mild from the unsuspecting eye. Anyone who says a 305 can't run no matter what you do to it, does not know what they are talking about. You have to take alot on here with a grain of salt. There are alot of guys that know there stuff, but even more that don't. Hopefully some of the guys that are running respectible times with 305's can chim in here and you can see.

-Tom Poston?-
(Actually I think it might have been Preston Smith or something like that)

niceroc

iTrader: (2)

http://www.goingfaster.com/spo/modthel03.html
they have it all

IROCZ4BD3

iTrader: (4)

haven't had the time to dyno it but prolly close to 300 HP on Desk Top dyno.And legally passes emissions.

305TA85

supercharge it

bnoon

If I remember right, that's a destroked larger bore engine built to slide in under a 5 liter engine class rule. Does really count when comparing to a small bore factory 305 engine.

A single turbo 3.75" bore 305 still wouldn't be a bad idea though. It would put some respectable power down and if you kept a rather mild cam in it you could get some amazing MPG on the interstate too! Hummmmm, might have to rethink this stroker idea of mine...

tpi86z

Check out www.speedomotive.com they have a stroker kit.
340ci.

Larry

http://www.goingfaster.com/spo/325_h...chevrolet.html

1MeanZ

iTrader: (9)

with a 22% driveline loss of my 700R4 i am making 294 horse at the flywheel and 364ftlbs. I had the car dyno'd 3 weeks ago. i have since chewed up my automatic and am in process of installing a Tremec TKO600. anyhow, someone asked if anyone had actually dyno'd their car and i have. my mods are in my sig. i ran the 13.9 with stock exhaust, and horrible traction. with my new tires and suspension work i think the car could go a 13.7, but i am swapping in a 5speed now so we will see about that.

PS. the guy with the 9sec 305, his name is Preston Smith, and yes it is destroked to 5.0 liters. also do a search for Tim Burgess. he has an NA 305 TPI in the 12s. kinda makes the rest of us look like weenies.

IROCZ4BD3

iTrader: (4)

Guess I know about where my HP & torque #'s are

Fast355

iTrader: (2)

I had a 305 in a 5,000# G20 that was running 14.8s in the 1/4. That was with the stock 1,200 rpm stall in the 700r4, 3.08:1 gears, and P235/75/R15 tires.

Stock 1983 G20 305 shortblock W /flattop pistons.
Comp XE-274H camshaft, ported 601 HO heads, dual exhaust, stock cast iorn intake and exhaust manifolds, an all Stock Q-jet (Stock specs=70 Primary Jet, 50M primary rod, DR secondary rods, F-Hanger), and a recurved HEI distributer 32* advance at 2,700 rpm total advance.

Add TPI, tuning, better stall, better gears, and insert it into a car that is over 1,000 lbs lighter and you would be suprised how the times would drop.

Don 79 TA

i'm no chevy expert, but the 305 is prone to detonation, especially when modified.

can you get 300 hp from a 305, i'd say yeah sure
what's it gonna take???
guess there's alot of avenues you can go down, like using a supercharger

the reason why people always say 350, is same parts, you'll get more output
and MORE torque

torque is where it's at.

i'm sure doing a roller cam, with some full porting, good flow (intake and exhaust) you can make it.

Fast355

iTrader: (2)

I was easily making 325 hp out of my 305.

The 305 is less prone to detonation due to the smaller bore. Why do you think GM went to it in the first place. They could run leaner mixtures and more advance for emissions and fuel economy. The only problem is GM went overkill with leaning it out and advancing the timing. Most people leave stock carbs and distributers on the engines when they modify them which causes it to detonate.