Join Date: Sep 2017
Location: South Eastern PA
Re: 2 1/2in exhaust manifold for small block Chevelle
I know this topic has been dormant for a while now, but everyone please let me know your thoughts on this. If any of you are familiar with Troy Thornton, owner of Thornton Restorations in Quakertown PA, you know he is THE top Oldsmobile restoration shop in the country. His restorations and restoration parts are second to none. Several years ago he saw a need for the Olds 350 owners to have a freer flowing exhaust manifold, so he developed the '350 Junior' manifold. It's a like-for-like manifold only with a 2-1/4 outlet (vs.2") and larger ports. Basically a W-30 manifold designed to fit a 350. He then designed a header that fits the factory manifold dimensions, so to can hook your factory downpipes straight to the header. Admittedly not a tuned header, but better than a shorty since you don't have to have a custom downpipe made to hook to the rest of your system.
Which leads me to my point..he has developed a similar header for the A,F,B & X body SBC. They have been sent out for production (haven't been delivered yet though) and look very, very nice. They have a true 2-1/2" outlet and like the Olds, exits in the same location as a stock 2" manifold. What you would do is use a Big Block downpipe such as Pypes DGU20S, hook it up to Pypes/Flowmaster/MagnsFlow system and you have a true 2-1/2" exhaust without the hassle of long tube headers.
Which leads me to my NEXT point..I asked him if he would be willing to make a 2-1/2" cast iron log manifold for the SBC, like the Olds 350 Junior. He looked at me and said "That's a very interesting question, do you think there's a market for it?". So I'm asking everyone out there- "Is there a market for something like that?". His concerns, and rightfully so, are that these things need to be produced in larger quantities to be competitively priced, and larger quantities mean larger quantities of cash to put up front to start production. It would be a lot of expensive cast iron sitting on his shelf if they don't sell.
So, if you were in the market, would you rather have a 2.5" Cast Iron Log Manifold or a Header that is dimensionally the same as a manifold? Is there a market for both? BTW, the header was worth 11 HP over the 350 JR manifold on a hot 350 Olds.