Posted by R Davis on Wednesday, November 29, 2000 at 03:09:53:
In Reply to: What is the torque/hp specs of a stock 251? posted by Roy Sanders on Tuesday, November 28, 2000 at 07:42:58:
To get the real scoop on "projected" hp/torque specs from a rebuilt 251 with modifications done to increase hp/torque output,you would need to find a shop that does hi-po work and has experience with L-heads and does DYNO testing.Using the available info on engine upgrades to max. engine output such as milling the heads to raise compression,performance cam,points to electronic ignition upgrade,intake and carb or fuel injection upgrade,and headers just to name some none radical performance upgrades should yield surprising results.The 61'-68' 251 is rated at 115-125 net hp meaning the power loss from water pump & fan,alt.,etc. has already been deducted from the gross hp rating.What do you think the above named modifications would add to the overall hp/torque output?10-15-20 or more hp? Then get an elect. water pump w/elect. radiator fan(s), could that add an extra 5hp? I saw a small used blower mounted to a in-line 6 intake at a jeep parts house for the 4.0 in-line 6 for $300,Boy!,when you switch that sucker on I bet the HP/torque curve really peaks!
Honestly,I personally have only looked into the matter,doing enough research to assume my theory of greater power gains through not too radical eng. modifications.
I personally believe that folks are too afraid to try and increase the power output of the 251 for fear of engine failure and that is understandable when that fear is reinforced by negative fearful comments that abound.But seriously, we're not talking about racing our PWs just increaseing the engines efficency and performance while operating it in a normal,responsible manner.
The 251 is a reliable and dependable engine that can be upgraded in ways as to effectively increase performance without the fear of eng. failure because of its percieved short comings,mainly its older flathead design.I believe the mods I mentioned above (minus the blower) could easily yield as much as 25+ hp which would give a total of around 150+ net hp out of the 251.Mid-70s thru 80s 318s and other make engines,hp ratings were not much more than that.
Remember, all thoughs legendary PW tales of strenght and mighty deeds were accomplished with those old stock L-6 engines.