Powerhouse 305 build

[Shadow-phoenix]

Ok, before i get started, let me ensure everyone who reads this, I fully understand that i could do more with a Gen 1 SBC, an LTX or an LSX. I also know that i will probably receive several negative comments about the 305, and how it is best suited to be a boat anchor, coffee table, etc... I am, however, determined to prove that the 305 is not the junk motor that most people think it is. I have done some research, and stumbled across an article from the January 2007 issue of Popular Hotrodding on a 305 build they did (here is the link for anyone who wants to read it, http://www.popularhotrodding.com/eng...s/viewall.html ). I have based my build plans on the same basic setup they were using, with some adjustments. In the article, their final result was a 372 horsepower 305, and that was using off-the-shelf aftermarket parts.

The motor, after it is finished and dyno tested, will be going into my 1984 Recaro Edition Trans Am, backed by a Tremec T56 manual transmission.


-What I'm proposing: A 500-525 horsepower fully built Carb'ed 305. (insert snickering, laughing, and 305 bashing comments here)

-My Plan: It consists of the following parts (subject to change assuming i can find parts better suited to the end goal)

-Block: completely stock 305 iron block from my 92 Camaro.


-Rotating Assembly: New 3.48" stroke crankshaft, new 5.700" connecting rods, new flat-top pistons, all standard size, no overbore, and no upstroke.


-Heads: 185cc intake runner Vortec Heads. Heads will be milled down by approximately .030" to reduce combustion chamber size to 58cc and in conjunction to the pistons, i should be running 10.2:1 compression (roughly). They will be running 1.95" intake valves and 1.5" exhaust valves, Comp Cams Elite Race dual springs.
A word on the heads, the Vortec heads from GM have an intake flow of roughly 233 cfm, this is, proportionately speaking, the equivalent of running a set of 290+ cfm intake flow heads on a 383 small block. running the 1.95/1.5 inch valves will keep shrouding to a minimum, but still allow enough flow into the cylinders for decent power.


-Camshaft: I am going to be running a custom grind cam. 276/282 total duration, 232/238 duration at .050" lift, .492"/.492" valve lift (with 1.6:1 rocker arms the valve lift would jump to .525"/.525") I will be running Hydraulic roller lifters, and 1.5:1 full roller rocker arms.


-Intake Manifold: I will probably run either a Victor Jr. or Super Victor single plane Intake Manifold for the top end power, I have looked into both dual and single plane, and the single plane seems a better fit for the build. I am still torn on this, as I have been looking at both the Victor's and the RPM Air Gap units...


-Carburetor: Holley 770CFM Ultra Street Avenger Carb (with black anodized metering blocks of course... since its going in a black car)... Electric choke, vacuum secondaries.


If anyone has any questions, comments, or any input at all, please feel free to comment!

[demonspeed]

What is your time frame for completion?

[Shadow-phoenix]

it's going to be a while. I will be finishing the 327 for my 92 Camaro before i tackle the 305 build.

[garcmol]

Subscribed. I have a '91 with the 305. I've thought about going the carb route as well. Not many tuners around that I'm aware of. Mine was rebuilt in 2006 (before I had it) and is solid. Just think it needs a good tune.

[stk1697]

Ok so who's bashing the 305? Mine has run a best of 10.8 @ 118 mph in G/SA.

[Shadow-phoenix]

stk1697, what does your 305 setup consist of, (heads, cam, intake, etc)

[SSBUSDRVR]

Good luck. Left half the engine on a highway in Pittsburgh at 4AM on way to work with app 22k on an '82 Z28. Replaced entire drivetrain and topped it off with a 406. Glad to see some have success with it. Subscribed

[stk1697]

Originally Posted by Shadow-phoenix

stk1697, what does your 305 setup consist of, (heads, cam, intake, etc)

In Stock we are heavily restricted on what we can do to the engine. Mine has a stock cast iron intake, 600 cfm q-jet, unported stock heads with 3 angle valve job, stock lift cam, etc. There's a few things we can work with such as cam duration.
Where we pick up most of the et is with getting the suspension, trans, rear gear and converter to work as efficiently as possible. You have a freer range with the cam, intake & carb but a 750 carb with the Victor Jr should work well together. The one draw back besides cubes is the smaller intake valve size but with a good cam design you can make some pretty good power.
Keep updating here once you get it together.

[SSBUSDRVR]

In Stock we are heavily restricted on what we can do to the engine. Mine has a stock cast iron intake, 600 cfm q-jet, unported stock heads with 3 angle valve job, stock lift cam, etc. There's a few things we can work with such as cam duration.

Are you allowed to replace the Cam/Cam Gear in Stock Know that was what caused my failure way back then.Gear shattered. Guess Chevy had an issue with the Nylon Gear on many 305s
Thanks and good luck in racing season.

[stk1697]

Originally Posted by SSBUSDRVR

Are you allowed to replace the Cam/Cam Gear in Stock Know that was what caused my failure way back then.Gear shattered. Guess Chevy had an issue with the Nylon Gear on many 305s
Thanks and good luck in racing season.

Yes you can put a good chain and gear set in. It wasn't just the 305's that got the quieter nylon gears, all their sbc's got them from back in the 70's.

[SSBUSDRVR]

Thanks. Like the Avatar. You need wheelie bars it. Don't want to steal the thread but a couple of weeks ago was at a show Guy built a 3rd Gen ProStreet Took it out for a test drive. Got a little too much traction and and got a little airbourne.He had a little bit of pucker factor going on I guess.

[willhe64]

You are going to make about 400 horsepower max with the combo you are proposing.

[Shadow-phoenix]

OK, well, my timeline for getting the Trans Am up and running just got moved ahead. i'll be bringing her out to Texas at the end of the month, and i'm going to try to pick up the 305 from Arkansas on my way back here...

also, the build specs have changed a bit, going to be building the 305 as a carbureted supercharged motor, mechanical secondaries (trying to keep the electric choke because the TA doesn't have a manual choke in the car), still aiming for that 500 horsepower goal, but if i dont hit it. thats ok with me... lol

[COPO_Chevy]

Any updates as of now? I am also going the way of the little 305 and modding my LG4 that is in my 1987 Pontiac Grand Prix L.E. Should be fun, looking at around 300-350hp hopefully, which should be enough for what I'm using the car for. Besides, how many people can say they have the original 305 in there car? With just freeing up the exhaust and a better cam makes for a big improvement..

My plans call for 059 L30 vortec or 906 L31 vortec heads, vortec matched intake, exhaust, cam (to be determined), and 3.42 gears. Should be a good boost from my 165hp 245 ft/lb torque, 2.41 gear car now. Keep us updated with your build, interested to see this 500hp figure your hoping for.

[2010 SSRS]

I have seen lots of fast 305 IROCS

[gpskinzhut]

I remember reading about a guy who went by "Fast355" on several boards who did a lot of work with TPI 305's and various heads (vortecs, 193's and even the TBI heads) and making good power with them. I seem to recall him claiming he was running mid 14's in a full-size Van with it or something like that.

[SSBUSDRVR]

gpskinsnut nice car. Use to be based out of Bradley Airport. Rented a place right down the street from you first in Enfield CT then Lake Congamond when your car was born 87-88 Had some fun times back then. Sorry to stray OT. Back OT It sure looks like it would respond well to a little boost.

[gpskinzhut]

Originally Posted by SSBUSDRVR

gpskinsnut nice car. Use to be based out of Bradley Airport. Rented a place right down the street from you first in Enfield CT then Lake Congamond when your car was born 87-88 Had some fun times back then. Sorry to stray OT. Back OT It sure looks like it would respond well to a little boost.

Thanks man

I'm curious to see how this all turns out. I've been weighing on either doing a mild 350 (L31) crate engine or swapping some 059's and a vortec TPI base and mild cam on my 305.

[motorhead]

770 cfm carb is pretty big for that combo you are doing.

[detltu]

I'm planning on doing a very mild build of my 305 for the 91 1LE. I would like to get to somewhere around 290-305 crank hp. I've owned 2 third gens with 305s and my 1LE was originally a 305 car (hence why I am swapping back to that). Some people think I am crazy for swapping a 350 for a 305, but I would like to get the car back a little closer to original form.

[COPO_Chevy]

Originally Posted by gpskinzhut

I remember reading about a guy who went by "Fast355" on several boards who did a lot of work with TPI 305's and various heads (vortecs, 193's and even the TBI heads) and making good power with them. I seem to recall him claiming he was running mid 14's in a full-size Van with it or something like that.

I remember reading a few posts by him too in the past. Pretty good for a 5,500 some odd pound van, IMO. Just takes a little "massaging" with this engine, but they can be decent and peppy little motors. I should see if I can track down some posts by "Fast355" once.. If I remember right, he also went by the name of "Fast305" before going to a 355. Would be interesting if he found this board and could give us all some more insight. One can hope anyway..

Hopefully the OP gives us some updates soon.

[one92rs]

i also think 400 will be max. shaving the heads for the 305 is going to be needed just to keep up the compression to stock unless you are going to be using non dished pistons. that is a smallish cam for that much power in which you are wanting.

[Iroc-z86]

you can do a lot with a 305. I have a 305 with dome pistons, alum vette (l98) heads, lunati voodoo series cam, heddman headers, magnaflow catback, stock tpi with stock tune. Took it to the track with crappy street tires and horrible reaction times I ran a 14.8. I figure if i get it tuned properly should pick up a few tenths also along with some practice at the track wouldnt hurt. lol

Keep us updated!!! Good luck!