I was just wondering if y'all think there's some validity to the output of the setups they have on these 305 engines or if you think its a crock. Just want some opinions.

http://www.goingfaster.com/spo/carcraft325hp305.html

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

http://www.goingfaster.com/spo/290hp305.html

http://www.goingfaster.com/spo/343hp305.html

http://www.angelfire.com/nb/thirdgen/400hp305.htm

 

Of course it's possible. Nobody gives the 305 a chance when it comes to modding because the internal engine parts are slightly cheaper.

If you have the cash, I'd ditch the stock heads unless you are on a budget and get the s/r torquers and have them ported, or get the AFR heads for the 305's, I think they are the 180's?

 

Thanks for the reply. Just trying to get a feel for opinions from fellow members on the board. Most of the time when I'm just scanning through various posts the typical response to a post for modding 305's is "get a 350." As if everyone wanted to or could spend the dough necessary to get 350. When my 305 actually goes out then I'll think about getting a 350, not before. Keep the replies coming!

 

The last one... the 400HP 305... blew up shortly after the test. See what they spun it up to, 7200RPM? What were they thinking. A 305 can be built to make decent power, just like any other motor. It's got its restrictions (small bore), but people generally give it a bad rap because most 305s only made 150-170 in stock trim.

305man - IF you ever get rid of that 305, you'll find that the 350 is almost always going to be cheaper than a 305. My 350 (4 bolt 010, steel crank) with World Products S/R heads and a slightly hotter cam (Class 1 engine) was $120 cheaper than a stock replacement 305 from Jasper.

 

This is for Marc 85Z28. When the engine goes out I'll get a 350, dont get me wrong. I just don't think it would be to my advantage to buy a whole new engine when the one I have works. Might as well mod it to where most ricers won't be able to beat it, just to represent Chevy power better until a new engine becomes neccesary. Everyone whose looking to mod a 305 is not out to try and beat Z06's and modded LS1's, just trying to be more respectable you know?

 

In that case I'd start with things that will swap onto the 350 when you do have to replace the engine. Stuff like the exhaust (which is really the best starting point anyway) and intake system, the ignition, and you'd be surprised how much a little suspension work will help your acceleration.

 

The bolt ons Car Craft did to the LG4 to get 230ish hp with the stock cam, and 260 something with a cam are very real. All any 305 needs to be decent (240-250hp) is a good full exhaust with headers, along with a good intake and cam setup. Not that hard, and not that expensive. I think if you get into rebuilding the block and swapping heads and stuff then it's just a little ridiculous, unless you got some heads for dirt cheap or whatever. Otherwise the money is better spent getting ready for the 350...

BTW, I have that article scanned up on my site if you want to read it: www.inter-scape.com/ray/305buildup.htm

 

I agree with both of you (TheGreatJ and Ray86TROC). I myself never intended to do a complete buildup of my 305. Just like what y'all were saying with mods that will be there when I do put a 350 in and maybe a couple others. I just wanted to see if the more experienced and open-minded members of the forum thought these numbers were feasible by a 305 with those mods.

 

The 305 can be made to make power just the way the 283 made power. One thing to keep in mind is it said that they did the dyno runs on a engine dyno not at the rear wheels. Those HP ratings will be less at the rear wheels. But still around 250 rear wheel HP will get you into the mid 13.5 or so with a little traction.

 

That's true about those being engine dyno's. But I think mid 13's are respectable numbers. Especially from engines that were far from that stock. I'm assuming all the engines they used were carbed right?

 

Yes you are correct that all the tests were with carbs. I am pleased to see the results the had with the little motor. I went a best of 13.6 @99.89 with my 305 befor I went to the 350. That was with a set of SLP runners, 58mm throttle body, L98 aluminum heads untouched, zz4 cam and full mac exhaust. I did not think it was to bad for what it was.

 

Yes, goingfaster.com is a crock.

 

Just remember, the "rule of thumb" is that 1-HP/cubic inch is reliably achievable but when that is exceeded durability becomes a big issue.
So before you go and try to squeeze out 400hp from a 305, you better put some money in the bottom end...
The biggest problem with a 305 is that the bore diameter shrouds the valves. Things like the placement and size of the valves make this unavoidable.
I've seen some racing classes, forced to stay with the small bores, grind the top of the cylinder away to unshroud the valves.(HIghly NOT! Recommended)
I think a perfectly attainable goal for a 305 is about 325HP, and still have a long life. Which you should be able to get with some good heads(like the S/R Torquer 305's) a moderate cam like the Comp 262*, 1 5/8"headers, high flow cat(s), good 2 1/2" exhaust, matching chip etc, etc.
Sorry to say, some things like; heads, cams etc won't be able to be transfered to a 350 later, as a 350 needs deeper breathing than the 305 pieces will allow.(like more cc's, more duration/lift etc.)

 

Good info.
I have a 305 that runs good for now but plan on upgrading to a 350 in about a year or so, I'm doing bolt ons that will add HP to the 305 AND will transfer to a 350 like Cowl induction, high flow air cleaner, and filter, Flowmaster Cat back exhaust. EFI stage 2 chip.

Plan on headers next, and high flow CAT, and looking into the TBI bypass trick.

From what Ive read here is a break down of HP increase from these bolt ons


K/N high flow Air Cleaner filter(closed Air Cleaner) or High Flow open air cleaner
10-15 HP

High Flow Muffler(Like Flowmaster
25 HP

High Flow CAT
10-15 HP

Cowl Induction Hood(Functional with High flow open Air Cleaner)15 HP

TBI Bypass trick
8 HP


Headers
10-20 HP

Stage 2 EFI/ECMChip
15-25 HP (depends on what intake and exhaust you have, the more intake/exhaust upgrades the more these chips add in HP)

High Octane pump gas 92 Octane non ethanol
5-10 HP

Octane fuel additive
5-10 HP

TOTAL with all upgrades on
143 HP!

Stock 305 TBI
175 HP

After ALL the above bolt ons and highly tuned with nice plugs/wires clean filters ect.
318! HP

Somehow I don't think thats accurate but according the the HP increase claims in these bolt ons it should be

Anyone that has done all this and has before and after Dyno tests please reply.

that will give most ricers a bad day hehe. Without the headers, and Cat upgrade I'm already stomping alot of ricers who have done a couple bolts ons. The ones that have added all the above are giving me trouble or ones that have added High performance turbo's and or NOS have beet me at the top end.

I may go with a bigger Throttle Body, and intake manifold If I think it will transfer ok but I don't know jack about throttle bodies, so Ive been trolling these boards for info on it.

 

K&N: 2-3HP
Muffler, cat, and headers: 15-20HP
FULL catback with cat headers: 20-25HP
Chip: 5-10HP
Fuel: 0HP

Those manufacturers claims are WAAAAYYYY overrated!
Realistically you'll be barely pushing 210HP