Chevy 305 engine
m (moved Hotrodding 305 engines to Hotrodding the 305 SBC engine) |
(Text; format; links; images; clean up. Interim save) |
||
| Line 1: | Line 1: | ||
| − | Basic details and suggestions on hotrodding 305 | + | ==Overview== |
| + | Basic details and suggestions on hotrodding the SBC 305 (5.0 L) engine. | ||
| − | == | + | ==Introduction== |
| + | The 305 SBC engine was introduced in 1976 to have a Chevrolet engine smaller (and supposedly more economical to use) than the SBC 350, yet having adequate torque for the same applications that used the SBC 350. | ||
| − | The 305 | + | ==Cost== |
| + | The 305 is cheap and plentiful. The cost to rebuild is about the same as the 350 but piston selection isn't as good as for the 350 and there is a definite lack of aftermarket support for cylinder heads. Regardless of the cost to rebuild the 305, the power-per-dollar is less for the 305 than the 350. In practice, there seems little real advantage in gas mileage over the 350, but you may get less costly insurance rates. | ||
| − | The 305 is | + | ==Design considerations== |
| + | The 305 engine is much-maligned and shunned as a performance build, mainly due to its small bore diameter of 3.736" which limits breathing. Limited breathing also limits naturally-aspirated power potential. The primary appeal of the 305 may be due to its "underdog" appeal, or simply because that's what is on hand at the time. Unless you already have a pre-'87 block, the '87-up block is preferred because of the one piece rear main seal, and the cast-in provisions for the factory hydraulic roller lifters and thrust plate for the cam. Also, these later blocks tend to display far less bore wear from carb-related fuel washing of the cylinders, as most were EFI. | ||
| − | + | ==Cylinder heads== | |
| − | + | ===Pre Vortec heads=== | |
| + | Generally, the 305 heads were akin to 350 heads except they had smaller intake valves (1.72" or 1.84", depending on the application), as well as a smaller combustion chamber as mentioned above. | ||
| − | + | There are a couple 305 heads that are marginally better than other 305 heads, the c/n | |
| + | |||
| + | ===Vortec heads=== | ||
| + | The L30 5.0 L Vortec head is quite a bit different than the L31 5.7 L Vortec head. While the Vortec L31 5.7 L heads had a totally new intake port with a raised short-turn radius and raised roofs, the L30 5.0 L Vortec heads were somewhat of a carry over. The L30 Vortec heads use the same intake bolt pattern as the L31 5.7 L Vortec heads, but share few other similarities with them. | ||
| + | |||
| + | The 305 Vortec heads have a spark plug location similar to the swirl port head, and a similar combustion chamber shape as well. The chamber volume is less than the 5.7 L heads, just like any other 305 vs. 350 head. This is to keep the compression where it need to be. | ||
| + | |||
| + | While the 305 Vortec head has a swirl vane in the intake port, it is much smaller than what's seen in the 5.7 L swirl port heads like the c/n 191 and 193. | ||
| + | |||
| + | ===Swirl-inducing vane=== | ||
| + | [[File:Tbi swirl port vane.jpg|thumb|left|350px|TBI swirl port vane.]] | ||
| + | <br style="clear:both"/> | ||
| + | |||
| + | {| | ||
| + | |[[file:305_VORTEC_SWIRL_RAMP_CN_059.jpg|thumb|center|305 Vortec L30 casting number 12558059.]] | ||
| + | |[[File:305 VORTEC CHAMBER CN 059.jpg|thumb|center|305 Vortec L30 casting number 12558059 chamber]] | ||
| + | |[[File:L31 305 VORTEC HEAD CASTING ID.jpg|thumb|center|305 Vortec L30 casting ID.]] | ||
| + | |} | ||
Swirl-port, pre-Vortec heads were used for all of the TBI 305s, and do not respond to porting and big valves. Don't even think it, it's been tried. | Swirl-port, pre-Vortec heads were used for all of the TBI 305s, and do not respond to porting and big valves. Don't even think it, it's been tried. | ||
| Line 27: | Line 49: | ||
Polishing the intake ports is not advised. Doing the chambers is good if you protect the seats. Doing the exhaust ports is great. Gasket-matching the ports isn't necessary, and for the exhausts it's not helpful, either. | Polishing the intake ports is not advised. Doing the chambers is good if you protect the seats. Doing the exhaust ports is great. Gasket-matching the ports isn't necessary, and for the exhausts it's not helpful, either. | ||
| − | If you are going to have a 305 block bored oversize, | + | If you are going to have a 305 block bored oversize, always bore to the next smallest oversize. If you can get away with a 0.020" overbore, all the better. |
| − | + | Use the same guidelines as you would for a SBC 350 for selecting the type of piston. Cast are fine for engines that won't see nitrous or boost, forged if it will. There are those who say using cast pistons and nitrous/boost is acceptable. And it is- providing the tune is spot on and the engine never sees detonation. If it does, the cast pistons will be the first thing to fail, and when they go they usually damage the bore and possibly the cylinder head as well. | |
| + | |||
| + | ==305 intakes== | ||
| + | 1986-back heads use a "regular" intake | ||
| + | 1987-'95 heads use straight center bolts | ||
| + | 1996-'02 heads use the Vortec bolt pattern | ||
==Parts suppliers== | ==Parts suppliers== | ||
| + | |||
| + | ==Resources== | ||
| + | *[http://outintheshop.com/faq/casting/castings2.html SBC head casting number go-to site] | ||
| + | *[http://web.archive.org/web/20080518030656/http://www.mortec.com/ MorTec archived] | ||
==References== | ==References== | ||
Your Privacy Choices