408 Engine Question

[Bob318]

Originally Posted by Bryn Tirion

This is old, but I think worth a bit more input. I have always understood that since the Bristol factory was always willing to upgrade your V8 Bristol at a price, there is no penalty in value (or in exhibition) so long as you do something that they would have done. So putting in a later Torqueflite is fine, and putting in a 383 (for instance) would be fine. A 340 would not have been an option, as it was never fitted to Bristols, and is indeed a lumpy street engine and not a smooth cruising Bristol engine. I happen to think the 313 is a fine engine, developing 250 bhp at 4400 rpm stock from Plymouth Canada. They can be sourced easily in Canada, having been put in Plymouth Belvederes and Dodge Senecas among others, and even in combine harvesters (my neighbour has one in a Massey Harris combine). They could easily be booted up slightly to a 318, but keep in mind that this is an A engine and not an LA, as pointed out by others, so one has to be careful about the 318 parts and what hey are intended to fit. The 318 version of the A engine was put in a number of US market models also, between about 1958 and 1962.

Actually, the 313 and 318 A-series poly engines are essentially the same, save for a slightly larger bore on the 318. There was even a 326 version in 1959 only, and only in Dodges (this had hydraulic lifters vs. the mechanical lifters in ALL other A-series polysphere engines.

The 318 is most common and was in fact offered from 1957 through 1966 in the US and 1967 in Canada. They're easy and cheap to find and buy. And except for the pistons and pushrods, the bottom end is the same as later LA wedge-head 318s (1967 and up for US). Upgrades? The 318 A poly engine is strong to start with, including forged cranks and connecting rods. 1957-58 versions came with two four-barrel carbs and 290 hp; those dual-quad manifolds are plentiful on ebay. So are aftermarket aluminum four-barrel manifolds. HOWEVER, you're better off using an original cast-iron 4-barrel manifold, which is dual-plane for better low-end torque. There were even old Edebrock and Weiand triple two-barrel manifolds--a great option--though they're much rarer.