WHAT WOULD I NEED TO DO TO GET 275 - 300HP OUT OF A 305 WHILE KEEPING IT EMMISIONS LEGAL? DON'T WANT TO USE SUPERCHARGING OR NOS.



I HAVE A 14X3 OPEN ELEMENT
FLOWMASTER CATBACK
HIGH FLOW CAT
THE REST IS STOCK

 

in continuance of that u should get lots of little **** like an underdrive pulley which yeild about 10-15 hp..... then try ram air with a k&n intake.......then a better rear.... something like 3.42 or 3.73.... nothing higher than that really since its only a 305..... then maybe new pushrods as welll..... new heads or port and polish your current ones.... hypertech power programmer to program how much fuel u wanna drop......make sure u get a borla cat-back which yeilds 17 about. and use a higher viscosity oil.... i use police edition 20w-50 redline b/c i work at a shop that services all the police vehicles in the township . so lets add this up....
pulley-15hp
ram air- maybe 5-10hp
rear-give u more performance to the rear wheels (dont know how much)
pushrods-5-10
heads- possibly in excess of 20
hypertech- about 15 maybe
borla-17
........... so id say ud gain anywhere from 70-90 horseys from all that i listed

 

I have never seen it done without some sort of power adder.

 

Pulleys do not give u 15hp. they give u more like 5hp
And when did replacing ur pushrods add 10hp?
Heads add up to 40hp with a good set and ported and polished from what I have seen, but they have to be real good heads which cost a lot of money.
Hypertech chips do not add 15....more like 5hp
And a cat-back and headers would add a good 25hp

Not sure on the tq ratings but they also would be a lot when u swapped out the cam,intake,heads and exhaust system. But I doubt u would see 275-300rwhp from all of that. I have never seen it done before but maybe there is someone out there with a dyno sheet from a 305 TBI that can prove me wrong.

 

hmmm, lemme think here.

-1 3/4 in primary headers
-vortec or World heads (milled to keep compression up)
-1.6 Full Roller Rockers
-LT1 or hotter cam
-good intake manifold
-Holley TB 670
-aftermarket ignition (MSD, Crane, Jacobs)
-MSD Superconductors or Taylor racing wires
-Dyno tune with custom chip

I dunno dude, it's hard to make horses with such a small bore AND keep it emissions legal. If you are worried about going faster on the LO3 then consider gears and suspension first or talk to Tim about his setup.

 

4.6L mustangs make 260HP stock with a smaller bore and longer stroke than a 305 so if you think a 305 TBI can't do the same or better you're not doing enough research. There's a guy on the carb board with a 305 and L31 heads running high 13s, low 14s.

Emissions legality is a sticky subject because it can vary so much between places. You can do it easly in 49 states but CA would be sticky. I think with the Edelbrock perforemer heads, the perforemer TBI intake, and a bored out TBI intake wiht the 670 TBI could do it in CA.

 

Check out this guys website. He has good information on pumping up a TBI LO3:

http://www.goingfaster.com/spo/modthel03.html

 

300 horse at eth wheels is not a stretch for a 305 tbi. it can be done, but you will have to step beyond the world of basic bolt ons. you can however pick parts that will work well with another motor in the future or can be optimized by a rebuild of the 305.
the one thing you will definately need is to have some custom tuning done once you have assembled your parts, the stock chip and any of those of the shelf pieces of garbage will be of little or no help to get the maximum out of the motor.
that being said, here is an outline of parts that shoudl put you in that performance neighbor hood once you get them tuned in.

1. open element air cleaner, a 14x3 flat base will easily fit under the stock hood
2. you will need top step up to eithe ra holley 670cfm tb w/350 inujectors or a 454 tb w/350 injectors and an AFPR
3. intake selection, both holley and edelbrock make direct fitment intakes for tbi that fit below the stock hood, both are capable of routing enough air to get hte job done easily. if you have a cowl or any other aftermarket hood that allows for greater clearance you can look into any 4 barrel carb manifold with a square flange and put an adaptor on it. a high rise dual plain opr small single plain will work very well and be easy to tune for, a large single plain will work as well, but will be a bit harder to tune for off idle performance(one tuned in it shoudl be able to drive just like the others)
4. heads. there are a lot fo options here. you can get L98 vette heads for pretty cheap and get them ported, but hey do not have EGR built in so you will ahve to reroute it externally.
vortech heads are soem of the best bang for the buck heads on the market. they can support a lot of power(the crate motor makes 330hp with them and they are not even close to being optimized) once again you will have to go external with your egr and you will also have to buy a different style of intake manifold because of teh unique bolt pattern.
world products torquer 305's. very good heads. they flow very well and will support your compression with their stock sized 58cc combustion chamber. they are also equiped wiht all teh stock emissions ports, so you can plug teh egr in just like stock. they are also very low cost heads at just over $300 a piece.
edelbrock centerbolt heads. these are teh heads that i chose, because they are a good flowing solid value for an aluminum head. they have a 60cc chamber so your compression will not suffer much, and they have all teh factory emissions ports just liek the world products heads.
5. camshaft. this is prolly the thing that will have th egreatest impact on your performance, teh stocker is an absolute joke.
the popular options are stock LT1 and stock LT4 cams. both are widely available on the sites that have classified ads, LT1's go for $15-50 in good condition and used LT4's go for aroudn $75-100, new bopth are inthe 180-190 range i believe. and don't get scared off buying a used cam, they are hydraulic roller, so they only wear out if there is a lifter failure adn you can reuse your stock lifters on them for the same reason.
there are a lot fo other cams on teh market new that will give you good performance too. if you re looking to keep the car very drivable you will wanna stay in teh .460's of total lift on teh intake side to prevent valve shrouding and vacuum issues. you will prolly wanna stay with a roller profile too because it promotes more vacuum and has a longer service life.
6. exhaust. you need headers at this point. 1 5/8 or 13/4 primary headers wil both work, teh 1 3/4 will prolly provide for more top end power. you want a 3inch collector and a (2) 3in. into (1) 3in y-pipe, a 3inch high flow cat or cat eliminator pipe, and a 3inch mandrel bent cat back with a high flow muffler. if you don't worry about phat tips you can get a higher flowing single 3 in/out muffler for less than a stock style crossflow muffler.

remeber to get custom tuning done!!!!! taht is teh only way top get allthese parts to work really well. the stock chip is far far too conservative to get anyting out of this combo. it will run teh car with any combination of these parts, but it will not be peak performance. so even if you do not have access to sustom tuning right away, plan on getting it some time.

then all you need to do is figure out how to hook with all your new found ponies and you will be set to win a lot of races.

later
tim

 

Phantastic piece of postin' there NJ SPEEDER, good info. Where does the Crane CompuCam fall in your opinion (and maybe w/1.6s). I've got that and the Edel. TBI Perf. intake now. Can I still make the grade?

 

That site gives some good info, but its kinda wild in its thoughts. I think thats Black Widdow's site if I am not mistaken. I've got a site that you guys might want to check out: http://www.goingfaster.com/spo/325_h...chevrolet.html thats a good site pertaining to this subject.

 

Nope, not mine

 

Let me sum up the responses for you, it would be hard to get an honest 275hp out of an emissions legal 305!!!!!!!!!!!!!

 

THANKS FOR THE REPLY NJ SPEEDER. THAT WAS EXCELLENT INFO!!!!

 

lol your name was tossed around awhile ago linking them to these some TBI sites.

 

Dude click on my link that I put up and tell me if that combo isnt emission legal.

 

NJ SPEED.,

I think I read somewhere that as you start to approach that 300hp mark, the stock 700R4 tranny can not handle the power. Is this true? What about the auto tranny in the Z28, I think it is the 4L60E. Can that handle the power?

Bill

 

K the 4L60E is in the 4th Gen F-Bods (94-up)and its just the electronic version. The stock th700r4 tranny will hold right up to 400ft/lbs just fine.

 

it woudl really depend which one you were looking at, they have a range of cams that run from mild to way too much for a 305
they are good cams though and will be prety easy to tune in. i woudl have to look at specific cam specs to tell you about any individual one though.

later
tim

 

iroc22 is rigth on about the handling capacity.
teh thing to remeber is that it is torque and shock load that kill a tranny(you shoudl see the sunshell from when i bombed mine last season).
to shock a tranny repeatedly, like a weekly racer, will kill a tranny in a lot less tiem tha ta guy who mostly cruises, even if the cruiser has more power. even if you jump on it from a roll it is easier on a tranny than launching from a dead stop.
you can also ease the burden on th etranny with you torque convertor selection. a looser convertor that is designed to "hit"(the way the stall speed comes in wehn you hit it from idle) more gently will also allow a tranny to live a bit longer.
teh biggest thing you can do to help protect your tranny and your rear is to preload the car a bit before you launch, just bring the rpm's up a little while you are on teh brakes, when you feel the car kind of hunch up liek it is ready to jump you are set.

later
tim

 

Now thats good info!! I'll read yours next njspeeder but it looks like you have alot to say there and I'm @$$ing out.

 

What is an AFPR?

(I think I got it, an adjustable fuel pressure regulator, right?)

Why do you have to reroute the EGR? Is it a strictly emission requirement or anything else? We don’t have any emission requirements in Sweden (yet), my question is therefore if I can skip the EGR entirely if I go with the L98 heads?

Thanks in advance / Robert

 

See the following thread, and then follow the links within it.

http://www.impalassforum.com/cgi-bin...c&f=9&t=000089

It's not going to exactly answer your question (but many have done that already), but it will give you a real world example of how a mild 305 will run on a dyno, and that you can expect around 10-15 hp less if the air cleaner, alternator, and probably the water pump were driven by the engine in the car. Even with those losses (which I don't think were included in the dyno test), you;d still be at the 275-280 hp level you wanted to reach.

Note well: the cam used in the test was almost the same as an Fcar LT1 cam, in terms of lift and duration.... so using an Fcar LT1 cam is a great idea in an Fcar LO3 305 modification. And many people here have already proven it. FYI. - Ken

 

I found a article that said they are good to run flat 11s. Hold on I'll look for that.


here it is http://www.700r4.com/FAQ/bighp.htm

 

their 305 that put out 291hp and the flywheel is about the setup most guys are going with...that would be almost about 270hp to the ground wouldnt it? those are pretty good numbers exspecially since it was a "mild" buildup...i say build the 305 like that and put n2o on it...youd be kicking everyones asses then well just about everybody

 

I'm gonna get 375!!!!!!!!!:lala:

 

Hell yes! Put a 100hp shot on that and you'd be the ****! Of course this is assuming that your drive train can handle 400hp.

Re that article: I wish someone would do a 305 build up that didn't include an overbore! If I was gonna go to the trouble of pulling my 305, I would be replacing it with a 350 or large displacement engine rather than having it machined and rebuilt! Wheres the sense in that?!?!

 

You want 275 emissions legal hp.. well, by saying that, most people assume that it will have all emissions equiptment.. but in many states emissions legal means just passing the sniffer. I suspect the latter is your case being that you allready made your car emissions illegal by putting on an open element airfilter


if you want 275-300 hp out of a 305 just copy my setup. Its pretty simple, big cam, ported heads, single plane, headers and full exhaust, edelbrock carb.. you could get the tbi to do the same for you but that takes alot more work than i think you are willing to put out

as far as the "goingfaster" website, for the love of *** dont believe anything you read on that page.

 

i still havent decided wether to build the 305 up some and put n2o on it or do away with it and get a crate motor...im thinking id sink way more money into a crate motor with 330hp than i would getting that out of the 305...id say with heads, intake, cam (1kish) and a 75 shot of n2o id be at 330 easy....but suspension mods are coming first tho...new shocks, struts, springs, rims and tires, SFC then ill worry about engine mods

 

This is cheaper then building your own engine, unless you get some real good deals. Should be an easy 330-350 horses.

http://www.gmmotors.com/product/1253...psandSUVs.aspx

As for the high horse 305, it can be done. Most rice burners have smaller bores, allowing a more effiecent valve sizing. If you raise the valve sizes proportionately to the bore, the valve become a smaller percentage of the bore size. With high flow heads, you should be able to actually make it more efficient (but still a little less power) then a 350. So far the strongest 305 I've seen is just over 600 at the tires with a single holley. A similar combo on a 355 was 722 at the tires. Both were all iron, even the heads, running on alky though.

I think it's good someone actually wants to do something different from the rest of the crowd. There is a lot on the net you can read into on this. Good luck.

 

...

 

dude this thread is six years old.

 

can i put a LT1 or stock LT4 cam on a 305tbi fuel injected motor because some guy told me i couldn't i was just wondering

 

wow this thread is 6 years old!!!! but its very informative! thanks!!!