Originally Posted By Cab_Burge
Originally Posted By crabman173
Hi--will a 65 273 exhaust manifold seal and work on a std 340 / 360 head like a J head?? I know bolt pattern is same just wondered if it will cover the port and seal--Thanks!!
No, I had one customer do that exact same thing using OEM 1965 273 exhaust manifolds on a 340 motor with J heads in his 1965 cuda fastback, it was a real turd through those manifolds tskMeasure the height and width and go from there scope Maybe the Hi Po 4 barrel 273 mnifolds might, might scope have enough meat in them to allow opening(porting) them up big enough to work on the later heads shruggy
Let us know what you find out and do thumbs


The low po 273 2bbl and hi po 273 4bbl used the same exact exhaust manifolds.

The only direct dyno test I seen showed all the small block manifolds within about 10 hp on a 300 HP magnum crate engine. Everything from the 273 tiny ports to the early 340 "pot o gold" manifolds. I know my old 66 dart when I started off had the factory 273 manifolds and switching to 340 manifolds did not show up in the time slip but it was a stock 360 at the time(talk about a huge let down after hearing all the hype and coughing up $500), maybe a big built stroker or something would show more difference. Even the FAST guys all seem to be in agreement that extrude honing is pointless also. I think if you are running manifolds run what you brung and don't worry about it.

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