Hey guys I got a 80 Camaro T-Top an its a auto. I am changing it over to a manual probably a 5 speed an the engine in the car now is a 350 4 bolt main. I have a guy who wants to swap me a 305 high output with 350 heads an all that for the 350. The 350 is a real 4 bolt main numbers confirm it an its got 350hp. I am going to use the car for a daily driver vs my truck an I am wanting something fair to good on gas in a V8. I was told the best setup would be 305 with 350 heads an I was also told the 305 high output an 350 would get about the same MPG. An a 305 is that not a 350 block with like 283 crank rod & pistons in it an if so could it be made into a 4 bolt main? An which carb should I go with 2 or 4? Can someone explain which would be best to go with?

 

A 305 is not a 350 with a 283 crank. Both the 305 and the 350 have the same 3.5" stroke; however, the 350 has a 4.0" bore vs. the 305's 3.75" bore. All things, except for the displacement, being equal, the 350 will always outperform the 305, for two basic reasons. One being the larger displacement of the 350, and the other due to the lager bore in the 350 which allows the heads to breathe better due to less shrouding of the valves by the cylinder wall.

 

305s tend to have weak bottom ends. I think it was the first SBC that they tried to remove weight from in order to compensate for low power and they were trying for a little more MPG.

 

Ehhhh, wild guess here....the guy who wants to trade you his 305 for your 350 told you all that? I have a 3.1 laying around, and I'll be a real pal and swap you straight up. How's that sound? Keep the 350, it's a better engine.

 

What are you guys talking about? My dad's '83 Z28 is equipped with the 'legendary' LG4 305. That thing is a torque monster!

 

Good point. Not many engines can hold a candle to that LG4, with it's whopping 150 h.p.!

 

A guy I work with told me the best set up for MPG would be the 305 with 350 heads which would make it a high out put. I heard the 305 have problems with the cam going bad. What is so bad about a 305 & how can you improve it without killing the MPG on it? Both engines are Chevy truck engines the 350 is out of a 73-77 Chevy truck an the 305 is out of a 76 Chevy truck. The 350 4 bolt is legit numbers back it is a real 4 bolt main. I don't know much bout these old engines always had new like vehicles only engines I ever worked with old Chevy 350 & Ford 360 an still on a learning curve on both of them.

 

The difference in gas mileage between the two would be minimal, definitely not worth the swap effort if that's your goal. 350 heads on a 305 does not make it an HO. Technically, 305 HO heads makes it closer to an HO.
What's wrong with the 305? Simple, it's 45 c.i. less than the 350. And a 305 with 350 heads is still going to have noticeably less power than the 350. Also, it depends on which 350 heads you put on the 305. If they are larger chamber heads than you have now, your compression ratio will be lower, and so will your h.p. Like I said, keep the 350. This guy is either purposely trying to blow smoke up yer ars, or he just doesn't know what he's talking about.

 

Typical 350 heads will have 76cc combustion chambers whereas most 305 heads use 58cc combustion chambers to achieve an already low compression ratio. Installing 76cc heads on your average 305 will drop the compression ratio way below anything usable.

 

Ok so if I go with this 305 what could or should I do for a little more power an how could I do it without killing the MPG on it? The 305 & 350 are both truck engines.