Hi, I have a 1985 Iroc i am rebuilding and i would like to make the 305 i have in it have about 350 HP. I am pulling it out next weekend and i have no idea where to start performance wise. I am going to completely rebuild the motor and I just want to know what i can get in it that would be better, What cams with what lift? what cfm carb? headers? the more specifics you can give me the better! I am 17 but i would LOVE to learn to rebuild my first big motor. (i have rebuilt a Johnson 115 two stroke.)

Thanks,
Fernando

 

350 hp from a 305 is going to be tough. It is doable but it will be expensive. Also im assuming your talking 350hp at the crank and not the rear wheels because that would be even tougher.

At any rate ill probably get flamed for this but your money would be better spent on a 350. You could put the 305 aside (as it is a valuable motor to that car since the TPI arrived in 85 and outshadowed it a bit) and built the 350 instead. Your money will go further with a 350 build. To put it into perspective i have a 350 in mine with just forged flat top pistons, a high lift cam from comp cams and a set of dart pro 1 aluminum heads. On a dyno with a victor jr intake and a holley carb it put down 406 hp at the flywheel. With TPI i have no idea what its making but probably less than that.

My former 305 had all the basic bolt ons (headers, cam, intake full exhaust and a tune) and it only managed 216hp at the rear wheels.

Im not saying not to do it. Im just saying if your going to do something do your homework before jumping into it and getting disappointed with the results.

 

Thanks for the reply! yea, many people have told me to throw away the 305 and get a 350 but i love my 305 to death it never let me down. Not one time did it leave me there pushing it (unless i ran out of gas). I will be doing my homework and ill try getting the best results possible. i will post my reults in a month or so when i actually finish the motor.

 

If you're set on keeping the 305 get a good set of 1.94 heads, bump to the compression up to around 10:1, get a cam to suit what you plan on doing with it, and get a intake to match the RPM range of the cam.

It's expensive and not very practical but there is a 335 stroker kit available

 

Any g00b can jam 1.94" (stock 350 size) intake valves into ANY castings and take your money all the way to their retirement fund, while you SUFFER with the same, OR WORSE, slug that you have now.

First thing you need to figure out is that, as far as stock 305 motors, what you have now, is about all there is. Your motor is THE BEST 305 there ever was, or ever will be, as far as what you're working with.

Best thing you can do for yourself is to get off the "305" crap and realize that the more fuel you can burn per cylinder, the more power you can make. Doesn't matter how fervently or strongly you "believe" in your 305; the laws of physics will trump your "belief", EVERY TIME.

You're already at a disadvantage in 2013 by thinking you're going to be somehow at least somewhat competitive with your 1955 design. On top of that, you have a DELIBERATELY CRIPPLED version of it, for the twin gods the factory was forced to worship in the late 70s/early 80s, of emissions, and gas mileage. Don't throw your money away on your misguided "belief" that YOU, however smart and capable and optimistic and idealistic and young you may be, are going to re-write the laws of physics. Ain't happenin.

The "stroker kit" for a 305 is just a way for people who are even more cynical than me, but without the conscience I have, of taking your money and giving you EXCREMENT in return. Don't fall for it.

If you want to compete, throw the 305 away and get AT LEAST a 350. You don't stand a chance with what you've got.

 

If it's not broke don't fix it, more importantly don' throw money at it thinking you will make it so much better. with the small bore you can only do so much and you will hit a performance wall.


The time & money is better spent and will yield better results using a 350 as a starting point.

it will be much easier to make 1 HP per Cu in. using a 350.

than 1.15 HP per cu. in. using a 305.

 

You guys make sense, regardless i'm pulling the motor out i need to replace a few parts in the heads that are making my motor smoke I guess I can find a 350 block on craigslist to start building

 

Yup, go ahead and maintain what you've got, keep it working good, all that sort of thing; just don't touch the short block. That's kinda the dividing line between what makes good sense and what doesn't.

 

Take your time with the 350 buildup by reading and asking questions. Do this before buying parts and I am sure when you finally install the 350 you will be well pleased.