chevy 305 upgrade

[nico 84 gp]

hello everybody...
new to this forum...
i own for about two years now a 84 grand prix in amazing cond, 57000 k miles
stock305 v8 engine 3 speed transmission
this question was probably was posted here before but if anybody can help
i want to get some more power and more hp from the engine and dont want to swap to a 350
im not a mechanic so i cant change parts by myself ...
will i be too deep with money to get some more power from a 305?
is the different will be even noticeable ... my first car choice when was looking for a g body was a monte ss with the h/o 305
which is about 50hp more as far as i know. can i get close or over that without to much modes ...?
ive been told by some mechanic to go with cams ,headers , bigger carbs but wasent sure if they just want to get money out of me and to be disappointed from the result...
i will apriciate any help/replies about what i should do first and if its even worth it?
the only thing i changed is a dual exhaust flowmaster 40 but dident remove the cat convertor
thanks
nico

 

[G_Body_Enthusiast]

for the money you would put into the 305 you can put into a 350 and have more power. i call it the smile ratio, more smiles per dollar spent. we've all seen or read some article somewhere of some guy making gobs of power with a 305 and i really dont want that being rehashed over and over here but dollar for dollar you will get more smiles per dollar with a 350.

getting a 350 put in might cost less than having someone put a bunch of stuff in your 305, the cost of labor is an integral part of the equation and the current engine is over 25 years old with who knows how much wear on it. you'd be better off getting it rebuilt which might cost more than getting a 350 and dropping it in.

i say get a crate engine and have it installed. i think it's the better choice.

 

[lilbowtie]

I assume you have a bone stock computor controled 305. My question to you is what do you use the car for and why do you need more power. Sounds like you have a nice car and enjoy it. There are a lot of little upgrades that can be done but seeing your not a mechanical person I would just leave well enough alone.

 

[techg8]

chip the ECM for some more pep and modify the secondaries on the carb to open fully with a richer set of rods

 

[DRIVEN]

My suggested upgrades in order:
1. A good thorough tuneup including compression test. This will let you know if this engine is mechanically sound enough to be worthy of any upgrades.
2. A rear gear ratio change. This will make your engine feel more powerful and probably actually improve your in-town MPG at the same time. Something in the 3.25 range would be a good match for your 3-speed. Maybe a limited slip upgrade at the same time.
3. Cam swap: If the engine passes the health evaluation, a modern cam grind focusing on low-midrange power would be my choice. Obviously replace the timing set too (it probably needs it anyway). If your car still has CCC intact, you'll definitely want to consult the cam manufacturer's tech support to make the right choice.

I wouldn't spend any mime or money beyond that. The thing to remember about a 305 is that it has a tiny bore and small valves. It was never intended to make high RPM horsepower. It's purpose was to get the car moving and keep it moving -- nothing more. I would say to just put a 350 in it but you said that wasn't an option. It would give the best $/HP return though.

...and welcome to GBF.

 

[Clone TIE Pilot]

Bump the base timing to 8 degrees, there used to be direct fit emission legal headers by Edelbrock and Hooker but both no longer makes them. You can hunt for a used set if you want. Also not all 350s are better, there were many factory 350s that were built much weaker than 305s. Your biggest problem is that you have the early LG4 low output 305 with only 8.5 CR which is really going to hold you back. The later LG4s had a 9.0 CR and the high output L69s had 9.5 CR which makes them respond to upgrades alot better. As for the small bore 305s have, it doesn't become a problem until 6500 RPM.

 

[jae]

I agree with driven, get the foundation in tune and in shape first since you are not able to swap to a 350, used or crate. I also would not bother with a bigger / different carb as that is a waste; between the tiny bore / ports / valves you would be wasting time with increased CFM and enriching the mixture. With G_B_E, tons of articles exist of high-hp 305 but they are just dyno-queens and are on the ragged edge of self-destruction; they are mostly to show you "CAN" get a 305 to make a ton power for a ton of cash, time.

For the cam you could look into the grind used for the H/O or something a little better (I think the code was L69); not to crazy but something that may help in the torque department. You could maybe do an aluminum intake for a little weight savings but again, the power / cash ratio may not be worth it.

With the shorter rear-end gear (numerically higher), maybe going to a 3.08, 3.23 will give you some pep. I wouldn't go higher than 3.31 or 3.42 with the 3-spd. The 3.23 will give good balance with fuel economy and power level; plus you can keep this ratio if you upgrade the power train, whether larger motor, 4-spd trans...

For the exhaust if you must keep the cat I would try to go to a less restrictive one than OEM. I can still use the 02 sensor if needed by welding a bung before it. These 02s were REALLY basic back then so you don't have too much to worry about. For headers, perhaps a pair of shorties and a mandrel-bent y-pipe to the converter (sometimes called a J-pipe). As with the rear-gear, these are things that can be kept if you ever upgrade to a larger engine or later sold to help cut expenses.

Hope this helps