Hey guys, I've got a 1984 Trans Am with a carbed 305 non-H.O. It's pretty much all stock, with the exception of an engine rebuild 30k miles ago at a shop, the previous owner had it done. I've finished the cosmetic work and got it looking good, but I need some more power! I've driven worse, but I've been driving around in my buddy's mildy modded 5.7 IROC and it's making me realize how slow my 305 really is.

What I'm asking is, whats the best way to make the most out of the engine with simple mods? My plan is to go with a new carb (looking at an Edelbrock Performer 500/550 cfm, they say that anything above 600 for a 305 is overkill), a good pair of headers, a good flowmaster 80 series muffler, maybe gut the cat, and a better intake to top it off - maybe an Edelbrock Performer, just for the sake of matching with the carb. My car has some decent gears, 3.23's from the factory so I'm not too worried in that area.

Am I wasting my time to try and do up a 305? I've gotten mixed opinions about this. I'm not looking to have a 500hp drag car, but I am definitly looking for some power to hold it's own against the Mustang's and TPI's out there.

What would you guys reccomend for turning a stock 305 into a considerably fast engine, using not very complicated mods?

 

People do this all the time. You use what you've got until it's not enough, then you get more. A 305 is fine to cut your teeth on, and it sounds like you've got some pretty good ideas.

A 305 will take an RPM or Air-Gap dual-plane intake just fine, but there are off-brand copies that are much cheaper than Edelbrock.
This place is about as cheap as I've seen: http://www.motorville.com/

A Carter style or Edelbrock AFB with 600 CFM won't be too big for your 305.
A 600 has small primaries and an air-valve over the secondaries that prevents "overcarburation" as it is understood. Your factory carb was likely larger than 600 CFM. You'll be fine with a 600, and you can usually find those at swap meets or ebay in the $50 to $100 range.

For some extra power, do a good job blocking off the exhaust heat crossover passages that feed hot exhaust up into the intake manifold. Some intakes like the Air-gap, Air-street, or Crosswind designs won't have the crossover passage which is a plus for power. The Renegade brand goes for $133.99 new.

Your exhaust will be a big power producer for you, so don't cheap out in that area. Spend the extra money to get good quality stainless headers.
You can install the larger 1.75" primary headers on your 305 with no problem. You will hear that this is too big and can hurt power, which is true in some instances, but will not hurt power if you stick with a stock type camshaft. Shorty type headers with a 3" Y-pipe is more than enough for a 305.

You will likely need a distributor upgrade, and there again quality is important. I really like the MSD-8361 model distributor. It is top quality and has everything. It also makes it very easy to add an amplifier box in the future if you wanted.

I don't agree about it being a waste on a 305. The parts will make more power like you want, and every part I've mentioned can transfer to a larger cube Chevy smallblock. They are not 305 specific.
I would consider the purchase of the smaller 1.5" headers in mild steel to probably be a waste as they are not enough for larger engines, and will corrode away in a relatively short time.

 

Listen to this guy, he knows his stuff!

Although in AZ Mild steel lives forever and I still say 1.5 is big enough for a 350


If you want to earn a few extra horses and don't tearing into it a little, you might consider a set of vortec heads as well. Very good castings.

 

Thanks for the reply's, more than helpful guys. I'm definitly going to look into all the stuff that 305sbc reccomended, it seems like it doesnt get too complicated. I'm not very experienced with working on cars, to be hoesnt part of the reason I bought the Trans Am was because I wanted to get some experience and have fun doing so. All I've really got to do since then was brakes though, so I just want to be careful not to jump into anything over my head.

I was alsdo thinking about new heads, how hard or intricate would you say they are to put in? You wouldnt really need a motor stand to take the motor out would you?



Thanks

 

Saying we're rating motor work on a scale of 1 to 5 where 1 is replacing valve covers and 5 is pulling the motor, pulling and replacing heads is about a 3.

It is MUCH easier to do with a non CC carburetor.

To pull heads and replace them correctly you will need to know how to:

Find TDC

Lash Valves (This is how i ruined my motor, VERY IMPORTANT!)

find the correct tooth on your dizzy


You will also need a rough knowledge of vacuum lines and what they power, and an awareness of where ALL your grounds are and what you intend to keep/what is leaving. You will need to know your state's emissions regulations (Replacing heads can render your A.I.R./EGR system inoperable. Some states dont care, some do).

You will need to know what you need to replace as well. Check for collapsed lifters, be aware that Vortec heads are a different bolt pattern and will require a different intake manifold. You will want to replace the head bolts (you can get away with not doing it, but this isn't recommended).

Aside from all this, you will need time. The very first time you do this will take you DAYS. You will be worn out, grubby, and unenthused. If you do decide to do it though, fear not, because re-assembly is much, much faster and simpler. While you're at it you can even swap to a bigger cam if you don't mind it riding around on old bearings (add another day's work at least).

If all this seems pretty intimidating to you and you're not sure about it...don't worry about it. Do lots of reading and talk to other forum members who've done it before and take a whack at it later when you've built up enough confidence you think you can do it right. Look to spend a high estimate of 600 bucks knocking it out if you junkyard a set of heads. This price should include a 50 dollar top end gasket set, a 200(ish) dollar manifold, the heads, and the other odd bits and pieces you will need (bolts, broken stuff, lube, other goodies).


if you're interested in undertaking this, feel free to ask around as to how to do it, there's lots of members who have done it before that can walk you through at least the basic instructions. If not, just adding the bolt-ons you were already looking at should net you a handful of HP and torque

 

Thanks for the reply, I appreciate it. I'm thinking I'll tackle the new heads a little but later on. I think I'll need a little more experience to do that, I dont want to risk messing anything up too much. I only used the Trans Am in nice weather last year, but I'm thinking this year it is most likely going to have to be my summer Daily Driver so I've gotta be careful and not jump into anything I cant finish. Thanks for the help though, it sounds like something I'll probably try to start over the winter when it's off the road.


How does a Holley 600 sound for the carb? Found a re-manned one locally for $225, including new gaskets for the carb to manifold and carb to air cleaner. Electric choke is what I'm looking for right?

Previous opinions have told me that a 600 would be too big, but from the info in the thread it shouldnt be. I dont want to cheap out when it comes to the parts, and I've never used a Holley but I hear they're one of the best. A buddy of mine put a Holley Throttle Body on his 89 IROC and it made a good difference.

 

Headers and exhaust are an excellent idea. The carburetor isn't holding you back at this point, and replacing it would be a waste of time and money.

 

The stock carb might be old and crudded up however.

Replacing it isn't necessary, and to be honest I'd keep it just because buying a new carb and tuning it for street manners is a pain, however rebuilding it or having it rebuilt isn't a bad idea at all.

Choosing a carb, if you decide to go that route, is pretty simple. It goes like so: Holley = tunability, Edelbrock/carter = ease of operation, stock app Qjet = factory street manners and better MPG.

EDIT: 600 is about as big as you want to go, but it's not too big. I am running a 600 edelbrock 1406 on my 305 at the moment, and all I did was turn the primary jets down a couple sizes and change the metering rod springs. RUns clean enough to pass emissions and pulls very nicely.

 

Thanks for the carb breakdown. I'm planning on doign the headers/muffler first, and maybe I'll get the stock carb tuned and see if I notice a difference. If not, I'll pick up a new one.


I'm planning on doing the headers and muffler over spring break in a couple weeks. Its my first time doing anything like that, any tips you guys could give me? I dont have a motor hoist so I'm doing it with the motor in place, which I head is a pain.

Also, any specific headers you guys could reccomend? Going into a carbed non HO 305, from looking around I think I'm going to go with an edelbrock set http://www.summitracing.com/parts/EDL-68723/ , just for the sake of they seem like a good choice, any advice or experience with them you guys could give would help. I think I've chosen an 80 series Flowmaster for the muffler, again just from hearing it was good on our cars. I'm open to advice with that choice too.


Thanks alot, really appreciate the help

 

getting the factory manifolds off is a pain because they have these cheap-o nut locks made from stamped tin that are a bitch to get around and a bitch to bend out of the way. Other than that, it should be fairly simple. my shorties dropped right in.

EDIT: If you get your headers, you might as well plan to redo the whole exhaust system. I got mine done headers-back for 250. Headers ran me about 100 shipped

As for a muffler, do you know what you want? Flowmaster is by far the loudest and meatiest sounding. Flowtech offers an "afterburner" muffler that is pretty quiet until about 4 grand. Magnaflow sits right in the middle as far as volume goes.

 

Really? Thats a great price, $100. Thats another question I was going to ask, I see alot of brands of headers that I havent heard of or arent as popular, they sell for alot less and I was wondering if I was better off getting these? The 305 isnt the most powerful motor GM did to begin with so I dont want to cheap out, I want to get the most out of it. It just seems like the name brand thing might be in play, I figured maybe the no-names could offer almost the same performance at half the price.

As for Flowmaster, I definitly want it loud sounding. Not obnoxious, but I want that muscle car sound. I've heard FM's before and I liked the sound, as far as Ive heard they also flow good so I think I'll give them a shot.

What else would I be looking at as far as re-doing the entire exhaust? I think I'm going to put my focus solely on exhuast right now, I'll worry about the carb if I have to later one.



Thanks,
Ryan

 

Hi:

I have the 305 with 4 Barrel Quadrajet. A couple of good performance upgrades that really help performance and will not burn your wallet:

**Rebuilt my Quadrajet for performance- My Mechanic worked for Pontiac for many years and has has a friend that did it for me. Big difference !!

**Catback Exhaust- My Exhaust is larger than stock, but appears stock looking. Also changed the Catalytic converter.

**K&N Performance Air Filter

**Performance Spark Plugs- Many Choices here from Accell to Denso. I like the AC Delco Platnum series plugs.

**Convert to Synthetic Oil- Amsoil or Royal Purple work well. Amsoil Preferred. Change the rear end gear oil to Amsoil.

Performance will be better, but a TPI car will always be a faster car !!

Hope this helps

Rob