If you have a good running 5.9 Magnum and replace the beer keg with an Air-Gap intake manifold and Eddy 650 carb what horsepower would you get? I think that the OEM rating was 245 hp with the TBI.

I doubt that you would get more then 245.... The Cam isn't very much on the engine as it is. Intake, Headers and Cam then it will be working much better...

I'd bet you'll pick up 40HP. Add headers and you should see 300HP.

A very quick run with
1995 Magnum 5.9L specs on
Performance Trends Engine Analyser 3.2b computer program
using mods of

650 carb
dual plane intake manifold 1.72" effective diameter runner with 8 inch runner length flowing

shows 245 SAE hp at 4200 rpm
327 ft-lbs at 3200 rpm
with the stock factory streamlined Magnum manifolds and stock exhaust

286 SAE hp at 4400 rpm
364 ft-lbs at 4000 rpm
with a change to
forty-two inch long 1.625" internal dia primary
4 into 1 tube headers 6 inch long collector
and a 550 cfm rated aftermarket exhaust that gives less than 2 psi backpressure at 5200 rpm WOT

for 'standard dyno room' horsepower numbers
add 2% or more to the above numbers

Kevin at Performance Trends only claims that this engine simulation program comes within 7% of actual engine tests,
but that dyno to dyno variation is about that (or more)

Patrick is right. The crate motors rated at 300 hp have made 325(magazine hp) with TTI headers and the M1 dual plane. The truc motor has a slightly bigger cam and if you use the eddy air gap you get a better manifold so I would say you should make 325 real world HP easily. The carb may be just a hair small but not bad.

Thanks for the information. I was thinking of picking up a good running 5.9 and making it a daily driver motor. $600 for a used motor and throw on an intake/carb/headers for 300-325 horse, not too shabby.

I have pretty much the same setup you have listed. Im very happy with how it runs on the street. I planning on make a trip to the track this weekend to see what kind of a number it will run.

I have the same setup in my truck except a Holley 600. It will pin you back in your seat and off the line torque for a heavy vehicle is good with this engine.