Small Block Chevy Engine question
#1
04-12-2006, 01:55 PM
Small Block Chevy Engine question
Are there any guides or references to building a small block 305 for fuel economy? I am building a 1980 Camaro for my son to drive. Presently it has a 4bbl carburetor and I was thinking of replacing it with a stock 2 bbl. Do you know what model 2bbl was stock?
Thanks.
-Randy
Thanks.
-Randy
#2
04-12-2006, 03:45 PM
RE: Small Block Chevy Engine question
To get most fuel economy:
1) Modern fast burn heads, such as GM Vortec.
Good haeds allow more compression with no detonation, more efficient combustion, and give more power as a bonus
1) High compresion ratio. (about 9.5:1)
The higher the compression the better the mileage. Go too high & will need premium fuel
2) Short duration & high lift cam.
This makes the combustion process more efficient, also allows more power at lower RPM, maximize low end torque.
Get max torque @ arond 2000 RPM & max power @ 5000 RPM
3) Maximum tolerable spark advance at part throttle operation.
Spark advance will have to be customized by trial & error on the road or by dyno testing
4) Free flowing exhaust.
Reduces pumping losses, allows better exhaust scavenging, thus giving better economy & power
5) Free flowing intake.
Reduces pumping losses, allows more air to enter with less effort, gives better economy & power.
6) Reduce internal engine friction
Low tension piston rings, roller valve lifters, roller rocker arms (trunnions & tips), 5W30 syntethic oil
7) Keep revs down by using tall final drive gears or an overdrive transmission. Torque converter clutch to stop slippage.
Engines are most efficient at wide open throttle while the revs are in the fat part of the torque curve.
Choose gears that will allow cruising at 60MPH at around 1500 RPM
About carburators:
The mith is that 2 barrel carbs are more economical than 4 barrel. The truth is that they are about the same as long as the same amount of engine power is called for. In many cases the 4 barrel is more economical and has better driveability. I order to get adequate power a 2 barrel has to use 2 large air passages, while a 4 barrel can use 2 small passages for cruising ( giving better economy) and has 2 more passages available on demand when more power is needed.
1) Modern fast burn heads, such as GM Vortec.
Good haeds allow more compression with no detonation, more efficient combustion, and give more power as a bonus
1) High compresion ratio. (about 9.5:1)
The higher the compression the better the mileage. Go too high & will need premium fuel
2) Short duration & high lift cam.
This makes the combustion process more efficient, also allows more power at lower RPM, maximize low end torque.
Get max torque @ arond 2000 RPM & max power @ 5000 RPM
3) Maximum tolerable spark advance at part throttle operation.
Spark advance will have to be customized by trial & error on the road or by dyno testing
4) Free flowing exhaust.
Reduces pumping losses, allows better exhaust scavenging, thus giving better economy & power
5) Free flowing intake.
Reduces pumping losses, allows more air to enter with less effort, gives better economy & power.
6) Reduce internal engine friction
Low tension piston rings, roller valve lifters, roller rocker arms (trunnions & tips), 5W30 syntethic oil
7) Keep revs down by using tall final drive gears or an overdrive transmission. Torque converter clutch to stop slippage.
Engines are most efficient at wide open throttle while the revs are in the fat part of the torque curve.
Choose gears that will allow cruising at 60MPH at around 1500 RPM
About carburators:
The mith is that 2 barrel carbs are more economical than 4 barrel. The truth is that they are about the same as long as the same amount of engine power is called for. In many cases the 4 barrel is more economical and has better driveability. I order to get adequate power a 2 barrel has to use 2 large air passages, while a 4 barrel can use 2 small passages for cruising ( giving better economy) and has 2 more passages available on demand when more power is needed.
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