Editing Building an inline 6 Chevy 250 engine

==Introduction== The Chevy inline 6 has been around in one version or another since 1929 until 1988 in domestic vehicles. The Chevy straight 6 250 cid engine was brought out in 1966. It has a 0.280" longer stroke (3.53") and the same bore (3.875") as the 230 cid straight 6. It boasts a 7 main bearing bottom end- quite an improvement over the previous generation inline's 4 main bearings. ==Some things to consider== Building a straight 6 250 is not any harder to do than any other inline 6, be it a Ford or Chevy, GMC, etc. Parts aren't as common for the inline 250 as they are for a SBC, but there is info and quite a few suppliers for parts, as well as places that cater to almost nothing but the Chevy inline 6 engines. The inline 6 Chevy 250 should not be compared to a SBC engine. Besides the obvious differences, they share practically no parts w/the V8 engines. Because of this fact expect it to cost more per horsepower than a Chevy V8. The reward is this is not a "belly button" engine; instead it is considered "old school" and has cred because of what it ''isn't'' as much as for what it '''is'''. To the right person, building a 250 Chevy 6 can be just as rewarding as any other engine, and if parts are selected in a coordinated manner and the engine used in a way that accentuates its strong suits- like dependability and good lower RPM torque production for its size- a very satisfying result can be had. It's a fool's mission to build a NA inline 6 like the Chevy 250 expecting to run amok on all the SBC and SBFs out there. Not only will the results be very humbling, but the amount of money that would need to be spent in order to go toe-to-toe with a SBC 350 will break most people's budget all to hell. So instead of trying to beat the world, it may be much more satisfying to build a Chevy 250 to make around 0.8-1 HP/cid (~200-250 HP), and revel in the uniqueness of it and enjoy as torquey, strong running engine that has a sound and look all of its own. That said, given enough time, effort and cash, an inline Chevy 6 can make >/= 2 HP/ci naturally aspirated and far more than that using a turbocharger. Superchargers can also be used, but the turbo is the preference of many who are going for boost. ==Engine ID== Obviously casting numbers and VIN stampings can be a big help. Chevy inline 6 casting numbers can usually be found just above the starter on the passenger side of the block. See '''[[Building a Chevy 250 engine#Resources|below]]''' under '''Resources''' for a few sites that have casting number info. [[File:Vin stamp.jpg|thumb|300px|Location of VIN/application code stamping for 1962 and newer engines]] The deck height of the Chevy 230 and 250 inline 6 engines is shorter than the 292 inline 6 engine. That means the pushrod cover is shorter on those engines than the 292 Chevy 6. ==Cylinder heads== Beginning in the mid-'70s, the inline 6 Chevy got an integrated intake cylinder head. This was a step in the wrong direction for doing performance mods- the intake being cast as part of the head means it would take too much work to remove it to be able to use any kind of 4-barrel carb. Because of a lack of aftermarket support for the inline Chevy 6, that leaves the hotrodder with the removeable intake head as the best choice for performance use. ===Intake ports=== The Chevy 250 head has a "3-port" intake. That means two ports are siamesed into a single port. This design, while fine for a daily driver or truck, leaves a lot to be desired for high performance work. So it comes as no surprise that improving the intake port flow will help power. A big improvement to the Chevy inline 250 cylinder head is to install an intake port "lump". For years, these were one-off, hand-made pieces that were quite a chore to fabricate and mount. Some were better than others, and some were worse than nothing. Nowadays, [http://t6racing.org/index.html T6 Racing] and [http://www.12bolt.com/home Autowerks] have designed a lump kit and can supply all the necessary tools and info to install it. It is cast and machined pieces of metal that fit onto the intake port floors to vastly improve flow. {| |[[File:Milling boss for lump port mod.jpg|thumb|300px|left|Milling of boss just started]] |[[File:Boss nearly gone lump port.jpg|thumb|360px|left|Boss nearly gone]] |} {| |[[File:Top lump port w arrows.jpg|thumb|370px|left|Arrowed area has to be blended away]] |[[File:Cutaway lump in port.jpg|thumb|290px|left|Cutaway showing lump in port]] |} ==Intake manifolds== The integrated intake head isn't well suited for performance duty. About all that can be done for the intake is the 1 barrel can be swapped for a 2 barrel by using an adaptor. Not the hot ticket. Using the earlier head with the detachable intake from a 230 or 250 inline Chevy 6 offers a much better platform. {| |[[File:Offy intake.jpg|thumb|350px|center|Offenhauser 3 x 1 barrel aluminum intake for the Chevy inline 6]] |[[File:4bbl inline int.jpg|thumb|350px|center|4-barrel inline 6 intake]] |} ==Timing gears== The Chevy inline 6 uses a pair of gears and no chain to turn the camshaft. There are high performance gear sets available from Comp and others. ==Exhaust== ===Manifolds=== In the past, the stock exhaust manifold was "split" to run two exhaust pipes from the manifold. This helped performance, marginally. Eventually the aftermarket came out with manifolds made for the inline Chevy. [[File:Exhaust ciron.jpg|thumb|350px|left|]] <br style="clear:both"/> ===Headers=== Headers are going to give an improvement over what can be expected from a cast iron manifold- especially a stock one. Heddman and others can supply them. [[File:Heddman-69310 6 header.jpg|thumb|350px|left|Heddman header for the 250 inline Chevy]] <br style="clear:both"/> ==Resources== [[File:Power manual.jpg|thumb|150px|left|[http://www.amazon.com/Chevrolet-Inline-Six-Cylinder-Manual-Edition/dp/1931128278/ref=pd_sim_b_1 Chevrolet Inline Six-Cylinder Power Manual 2nd Edition]By Leo Santucci]] <br style="clear:both"/> ;ID'ing the Chevy inline 6 :[http://www.1954advance-design.com/Stovebolt-engine/casting-numbers.html 1929-'62 numbers], from 1954advancedesign.com :[http://www.novaresource.org/codes.htm Engine codes], from NovaResource.com :[http://www.adchevy.com/tools/castinglookup/ Casting number look up tool] and link to c/n lists from adchevy.com. '''[[Building a Chevy 250 engine#Engine ID|Return to top]].''' ;Wiki articles :[[Chevrolet and GMC inline / straight 6 engines: Guides and resources]] :[[Six cylinder inline engine parts and info sites]] ==Parts suppliers== *[http://www.stoveboltengineco.com/ Langdon’s Stovebolt Engine Co.] *[http://www.cliffordperformance.net/index.html Clifford Performance] {{youcanedit}} [[Category:Engine]]

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