Poly 318

[Thor]

I wish I could be more help with this thread, but I cannot find the original manifolds of my 409, I think I have sold them already (my car has some fabricated parts).

I am absolutely sure that the manifolds were not made specially for Bristol, I have books about tuning Mopar engines which show identical manifolds on 318 'A' engines (not 'LA') from series models, but the tuning books don't talk about the models the engines were fitted to.

I can confirm that the correct manifolds for a 409 could be described as : Right hand manifold has a central outlet and includes a butterfly valve controlled by a bi-metallic spring (intended to restrict flow and direct the flow across the heating passage in the cylinder heads and inlet manifold to the other side of the engine, when cold). Left hand manifold has a rear outlet. Both manifolds are simple 'logs', i.e. there is no separation of the exhaust flows from the different cylinders.

I believe the engines were bought from Chrysler in only two batches, the first being 313 engines probably in 1961 or 1962, mostly used in 407 and 408 cars, and then a batch of 318 engines probably bought in about 1966, mostly used in 409 and 410 cars.

As the new 'LA' engine became available from about 1965 on, it is very difficult to pin down the models for the second batch of engines. I would advise contacting the very small number of companies offering specialist tuning of the 'A' Poly engine, and asking them to obtain the correct manifolds on your behalf.