Building an inline 6 Chevy 250 engine

The Chevy inline 6 is a design that has been around in one version or another since 1929 until 1990 in North American-market vehicles. During the fall of 1961, a modernized version of the six was introduced (with the Chevy II) which has 7 main bearings and a short deck displacing 194 c.i.d. - the rear block face was redesigned with a bell-housing pattern which matched the Chevrolet V8's in production (both the small block and W-series) - transmission bell-housings for the V8 (both manual and automatic) were shared. The Chevy straight 6 250 c.i.d. engine was brought out in 1966. It has a 0.280" longer stroke (3.53") and the same bore (3.875") as the 230 c.i.d. straight 6. It boasts a 7 main bearing bottom end- quite an improvement over the previous generation inline's 4 main bearings. Although production ceased in 1990 for automotive use, the inline six (including its four cylinder variant still in production as the Vortec 3000 marine/industrial motor) was produced overseas in Latin America for Brazilian-market GM products until the 2001 model year. 250 production ended in 1984 (North America only) but the 292 tall deck engine remained in production in Mexico until 2001. Besides Latin America (e.g. Brasil, Argentina) where the six was locally manufactured, it was also manufactured by GM's Port Elizabeth, South Africa assembly plant until the company divested from South Africa in the mid-1980's during the Apartheid regime.

Throughout its production life cycle, the inline 6 Chevrolet came with a one barrel carburetor. Carter YF carburetors were used with the early engines until some point in the mid-1960's when the Rochester Monojet (1MV) was phased into production. The 1MV was used until the end of the 1979 model year (with passenger cars) but continued production with the 292 until its 1990 phaseout in North America and marine applications. Rochester 2SE (Varajet) was introduced in 1978 - only known vehicles using the Varajet were the C/K light duty truck (half ton) and G-series vans including the P series box vans. One drawback is the uneven fuel mixture with the stock one barrel carburetor where the front and rear cylinders have an uneven fuel distribution.  

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. The cam gear on aftermarket performance timing sets is often aluminum. The undesirable gear set with the micarta (plastic) cam gear is best avoided - these were used during the mid-1970s - mid 1980s with the 250 and 292 (including the Pontiac Iron Duke which shared its design with the 153 with the exception of a crossflow cylinder head and repositioned distributor while using some components from the concurrent Pontiac 301) in both passenger cars and light trucks.