V6 Chevy 90 degree engines
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All the engines share the same firing order of 1-6-5-4-3-2. The two smaller engines, the 200 and 229, have what is called a "semi-even fire" sequence which alternates between 132º and 108º. This comes about due to the "slipped disc" crank pins; each pair of rods are offset by 18º. This required the connecting rods to have 0.050" narrower ends to fit onto the available rod journal space. | All the engines share the same firing order of 1-6-5-4-3-2. The two smaller engines, the 200 and 229, have what is called a "semi-even fire" sequence which alternates between 132º and 108º. This comes about due to the "slipped disc" crank pins; each pair of rods are offset by 18º. This required the connecting rods to have 0.050" narrower ends to fit onto the available rod journal space. | ||
| − | The cam and distributors are specific to these two engines and they cannot be interchanged with the 4.3L V6 engine. | + | The cam and distributors are specific to these two engines and they cannot be interchanged with the 4.3L V6 engine. Distributor bodies used on the V6-90 are identical to the one used for the Chevrolet small-block V8 except for the pickup coil and pole piece assembly. The main difference between the semi-even fire series (200/229) and 4.3L distributors - the 4.3L distributor pickup coil and reluctor wheel has six equal points every 30 degrees. Also, a majority of the distributors used on the 4.3L has a small distributor cap (commonly used with the TBI and CPI motors) with an external coil - the 1985 model year 4.3L used in Chevrolet trucks, vans (including the Astro/Safari) was the only time that the traditional large-cap HEI was used on the RPO LB1 motor. Marine applications used a unique small-capped distributor not interchangable with those used in automobiles. |
| − | The 4.3L V6 engine has an even-fire sequence, occurring 120 degrees apart. This is accomplished by having a larger 30º offset on the rod journal pairs. To gain back the strength that the wider offset takes away from the crank, the rod journal diameter is larger than the other V6 engines and also larger than the SBC, at 2.25", which makes them unique among the Chevy V6 and V8 engines. | + | The 4.3L V6 engine has an even-fire sequence, occurring 120 degrees apart. This is accomplished by having a larger 30º offset on the rod journal pairs. To gain back the strength that the wider offset takes away from the crank, the rod journal diameter is larger than the other V6 engines and also larger than the SBC, at 2.25", which makes them unique among the Chevy V6 and V8 engines - these rods are not interchangable with the traditional small block. |
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| + | There are two production connecting rods - one for engines built in Tonawanda, NY and Romulus, MI - these sets are not interchangable. | ||
==Intake manifolds== | ==Intake manifolds== | ||
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