Chevy 350 or 305

[elynn123]

Hello all. I'm new here. I just purchased a 1986 Monte Carlo SS.

Its in decent shape and it has the stock HO 305. I'm not sure whether I want to rework the stock 305. Or buy a used 350 rework that and put it in the Monte. Any suggestions?

Its just sitting outside the house right now and I'm itching to get working on it.

 

[billyjack]

Can't think of a single good reason to keep the 305. Thanks to all the pickups sold in the 80's and 90's, rebuildable 350 cores are plentiful and cheap. All the parts costs are the same(if not less), and you'll really appreciate the extra 45 cubes. Any performance mods you elect to do will show bigger gains on a 350 than a 305. All your accessories will bolt to a 350, and nobody will know unless you tell them. I did a swap years ago with a dead-stock 400 in place of the 305 in my 78 Century sport coupe-total cost $200-what an improvement! As we speak, there's a 350 short block on the stand in my garage. As funds allow, I'll just keep collecting parts until it's complete, then in my El Camino it will go.

Bill

 

[83cut350chev]

350!

 

[elynn123]

I'm leaning toward the 350, the only reason I wanted to keep the 305 is to keep it as stock as possible. But I checked craigslist and there are plenty of 4-bolt 350's close by as well as a 4-bolt 400.

Thanks all

 

[Blake442]

305's are a waste of time, but if you think the original motor will help it's value at some point, just stash it in the corner of your garage.
I chose to drive the snot out of my original motor till it grenaded before replacing it with an adequit power plant... :lol:

 

[1985Diablo]

305

The most misunderstood engine in the Chevy small block family. Just check any forum, when the subject of building a 305 is presented, the reply is almost ALWAYS "build a 350" Heres my take on that, DONE, I GET IT, by using the "bigger is better" logic, we all must build a Hemi. Now lets move on to the 305. I've done a LOT of research and the result is as follows.

First to produce 400HP in a V8 you need to move 500+ CFM @ 100VE. Thats all. In stock form a 305 moves 431 CFM @ 6000 (assumed VE = 80) If we modify the intake/heads/exhaust to get as close as we can to 100 VE and bore it .020 over (now cid = 311) we will move around 539. @ 6000

With 1 hp for every 1.3 cfm, we have a potential of 414hp

The following combination, properly prepared, will do just that

1989 LB9 roller block .020 over 9.3cr

081 Heads, stock 1.84" valve flow 201.8 @ .40 lift with minor port work

Performer manifold

long tube headers, wraped

Stock LB9 cam Lift .415/.430 Duration 207/213 Sep 117 (non auto LB9 f body cam)

Dual roller chain

600 cfm carb

Performer manifold

Roller 1.5 rockers

HE ignition

Timing adjusted for 36 total advance (sb about 8-12 @ idle depending on the distributor set up)

I estimate the build will cost about $2,000 give or take, including machine costs.

I'll be building this engine next month and will post the step by step build, parts list with cost, and dyno results in late August.

 

[maliburacinfreak]

are you claiming that combo will make 400+hp?? im not seeing it.

 

[megaladon6]

350's aren't better just because of displacement. hell, the 60's chevy 302 in the camaro was a great engine with as much potential as the 350, maybe more. but that was a different design than the 305. the 305 has some major inherent flaws. the bores are too small and the valves are shrouded are the 2 biggest and the ones you really can't fix.
sorry, but i really don't see your combo doing 400. IIRC the 081's are the swirl ports, and they are better than the stocks but not by a huge amount. and then there's air velocity which comes from RPM's, cam, runner size, head design... higher air velocity rams more air into the cylinders, but if you put on huge heads or over port yours, the airflow will drop along with power.
then there's the cam. air flow is about more than just what the head can do, the engine has to pull that air in. if the valves are only open a short time, the cylinder won't fill. the stock cam is pretty small for that task, it was made for emissions, not power.
oh, and .020 over is a 308 not a 311.
here's a link to a car craft build up on a 305. http://www.goingfaster.com/spo/carcraft325hp305.html as you can see it took quite a bit to get to 325hp. and they had a larger cam, intake etc.
for $2k you could build a comfortable, reliable, long lasting 350 with 400hp and have plenty of room left over.

 

[SScamino]

I dont even see 350 horsepower with that 305 set up.. but if you would like some mild performance and room left over later on for some serious power do the 350. Cause one day you might get bored and want a 383. With the 305 your stuck on performance options. What you get with a 305 is what your stuck with.

 

[custom442]

350 sir, sounds like the advice is all mutual