my brother just bought an 85 z (305 carbed) in EXCELLENT shape for 1800 absolutely no rust, bla bla nice *** car. i was wondering if it is worth it to put like an edelbrock performer and a 600 holley on it with long tubes will we see any noticeable power gains or should we just say to hell with it and put a stock 350 in it? he has enough money to do one or the other, my thought is put the stuff on the 305 for now and drive it and get a 350 like next winter seeing as how all the stuff will swap right over. any thoughts? any other ways to wake a 4bbl 305 up? 170 hp isnt quite cutting it!! he was pissed when i took him for a ride in my grand prix, he was telling me his car was pretty quick and then we rode in that and he wants more power... thx in advance.

 

Yeah, I think you should go for the intake for now, and then later on you can get the 350 and it will all swap right over. 170hp? Sounds like he's got a peanut cam in there as well. I'm just reading up on cams for my 350, and I am not sure if they are interchangeable with the 305's, maybe someone else can answer that for me. But if it does, then it might be worth it go get a nice cam for your application along with the intake. That would put you at around 220hp or maybe more! But definately look towards getting the 350, it has so much more potential.

_Clark

 

cams are interchangable, and to be honest 170hp for 1985 actually sounds like too much, i think that lg4 motor made about 155-160 in 1985
if u can do bolt ons now and 350 next winter, go ahead, the bolt ons will swap over, but if u really want some power, do the 350 now and bolt on as you go

many will tell you the 305 simply does not have the potential a 350 has, if u do a search u will find many debates, if you're going to do a 350 anyway the real question is do u want it now or later

 

Wow, 160hp from a 305? I really didn't think the numbers dipped that low.

 

The low output carbed 305 (LG4) ranged from 140hp in 82 up to about 170 in 87 (last year), the L69 high output 305 was rated at 190hp across the board. To tell the difference the best method is to check the VIN. The 8th digit is the engine code, H is a low output 305 (most common), a G would be the L69.

Your post didn't say, but I'm going to go out on a limb and guess its an LG4automatic. That means its probably got really bad exhaust manifolds, a restrictive Y-pipe, a dinky catalytic converter, and 1.75" intermediate pipe that is identical to the ones GM used on the 2.8's and 3.1's. Also you're probably dealing with 3.08 or 2.73 gears. Check the RPO codes to determine what you're dealing with, 3.23's - 3.73's are where you probably want to be.
Also the engine itself has a tiny cam, low compression, and heads that don't lend themselves to performance.

Swapping to a different carb and intake is going to cost you about $300-500 and get you absolutely no where. The stock Qjet will flow enough air for more power then the 305 will ever make, and with modifications will support a much larger engine without problems.

To get the car to perform better, start with the exhaust and gears then work your way into the engine. If you want cheap and easy get a set of exhaust manifolds from a 305HO or a TPI car, use the matching 3" catalytic converter, and get a catback of your choice. Dynomax/Walker sells a nice 3" mandrel bent catback that looks stock but sounds a little louder for under $200. The next step up would be a set of aftermarket headers, but the cheap ones are garbage and will require some ingenuity under the hood. Personally with a 305 I'd stick with the upgraded manifolds.

Also again assuming its a LG4, upgrade the aircleaner. The stock single snorkle aircleaner is not designed for power. Either a dual snorkle aircleaner of a HO or an open element aircleaner will open it up.

Once you get into the engine, I'd suggest starting with a camshaft, then heads, then a complete rebuild with flattop pistons. Or just get a 350 and rebuild that instead. BTW a 350 from the 77 Chevy pickup off the farm is probably going to produce less power then a stock 85 305 unless you rebuild it with flat top pistons and better heads.

If its a L69 then the weakest link in the stock setup is the engine itself, do a 350 swap or nitrous because the rest of the typical modifications won't be of much benefit.

 

yeah it is the h vin code, i already checked that, thats how i know it was supposed to be about 170 hp. the reason im leaning towards the carb is that the car has been in a barn for the last 10 years and its running a lil like the carb is all goo'ed up. bad karma do you know the rpo gear codes off the top or your head? i cant remember, i knew them at one time. gears are easy to find out in my 4th gen, if the shifter stops at 2 then its 2.73, if not, its 3.23 if its a stick, they are 3.42. never really worked with a 3rd gen before, just changed trannys a few times in them. never really worked with a 305 either, always just 350's so i am not sure how they respond. i noticed the other day when i was changing the plugs that the (forgive me i cant remember the name) flappy plate thing in the exhaust, i know it stays closed when its cold or somthing, cant remember the name. is stuck about 1/2 way open, i got a line on some long tubes for $50 so i think i am going towards that. but, i got to get back to work. thanks for your input. any more would be appreciated. oh yah, i dont plan on doing a cam swap on the 305, just looking for things i can do in an afternoon easily that will easily bolt onto the 350 when we do that. 350 is waiting for next winter because the car needs to be on the road in 2 days so my brother can get to work and back.

 

They're going to be GU? or GT? codes usually... Check the Camaro White book or the rpo decoder at thirdgen.org for specifics. You might also check the differential cover for a tag, it might be stamped right out in the open.

 

web site for gm rpo codes
http://www.angelfire.com/ny2/96transam/rpocodes.html

 

Eh theres nothing wrong with building up a 305 at all. You can be very rewarded by it if done right. If you have a 350 for free or REALLY cheap, then by all means use that. It doesn't take much to get a 305 rockin' though.
Oh, and to the person who was surprised by how lowly the LG4's hp is, remember this; it's an economy motor putting out more torque than even most modern-day cars, and still achieves 30mpg. All from a 21 year old v8
That's another reason why nobody believe me and my 305 build up But once I get a few hundred more, I'll show them what 380+hp looks like from a naturally aspirated 305

 

Come on, Matt! You are stretching reality *just* a little bit there. 30 mpg.

 

On a computer controlled quadrajet?? Of course. *Please* dont make me find the 20 something people on this forum that have gotten 30mpg from their 305

 

The mileage is reality, on the interstate in proper tune the LG4 will pull 30mpg. Around town I never got better then about 17mpg.

Now 300+ horsepower out of a 305 might be a stretch... havent even seen a magazine build one anywhere near that high, with their unlimited funding and 305's being freebie type deals if it was possible it would have happened by now.

 

Hot Rod built a 350hp 305 a few years ago, but it was a ticking timebomb.

- Justin

 

The 305 LG-4 5-speed cars can pull down mileage that would embarass the fuel injected guys (at least on the highway). Regularly got 26-27 MPG AVERAGE on long road trips in sharp tune.

Bad Karma hit all the highlights of what you should do to wake up an LG-4. I agree 100% that a FULL exhaust is job one (OK, maybe a better flowing open element air cleaner in place of the stock single-snorkel). You want headers, y-pipe, cat (if applicable) and cat-back. EVERYTHING in the stock LG-4 exhaust is junk.

HINT: Buy parts for a same-year L-69 HO 305 (or TPI motor). That will get you the larger diameter y-pipe, cat (if applicable), and cat-back. It'll still bolt right on to your car, but the piping will be 3" from the y-pipe back. If you get stuff built for the LG4 it will be the same headers but the y-pipe will neck down to 2-1/2 at the y-pipe and be that diameter all the way back.

On the cheap.... bump the timing up from the stock 0* TDC to 4-6* BTDC. Makes a nice seat of the pants improvement even with no other changes.

 

any of you guys know if the stock midsection (from the cat back) off my lt1 car will fit? i am going to an x pipe and bullits and i will just give my brother the exhaust with the flomaster that is on it. if it will fit.