340 exhaust manifold vs stock 318
i picked up a 1973 340 driver side manifold along with a 360 passenger side for $40 bucks so i didnt break the bank. i have a 318 with a mild cam and right now its got the stock 1967 273 exhaust manifolds. wanted to swap them out and was thinking would there be at least a 10 horsepower increase ? i have a 318 with a 600 cfm eddy with a lb4d intake 2.25 exhaust dual. any info will be great! thanks
The 340
driver's manifold is the best (cast iron) driver's manifold you can use. Stock
318 manifolds had a
1 5/8" exit hole (L & R). The 360 manifolds came in many different sizes, exit holes. The 92/93 360 Magnum manifolds were 2 1/8" exit hole as well as the 96/97/98 Jeep Grand Cherokee (JGC) but you can only use the passenger (JGC) in an A body. Well... you might could use the driver's side magnum manifold if you did some extensive modifications??
You didn't show a pic of the 360 manifold that you have so I don't know what size the exit hole is?? They made magnum engines for many, many years but they only used Large Hole manifolds in certain years.
92/93 360 manifold- 2 1/8" exit hole
96/97/98 Jeep Grand Cherokee 360 manifold - 2 1/8" exit hole
Stock 318 manifold - 1 5/8" exit hole
70s 340 passenger manifold - 1 7/8" exit hole
All 340 driver's manifolds - 2 1/4"
60s 340 passenger - 2 1/4" exit hole
PS - There are also other 360 manifolds that were used on vans and other vehicles that had a large exit hole but the shape of the manifold causes it to pass very close to the passenger's fire wall which will make the floorboard hot, it will work but why bother if you can get a JGC manifold!!
treblig