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Hi,I'm looking for info and help on my 73 dodge winnebago,it has a 413 with a 4 barrel holley,and k&n air filter,on a motor with 43,000 original miles, i wanna put a little more HP in her any suggestions,thanks



I've wondered and thought about what you could do with one of these to make a better HD engine. It depends on how far you want to go. Here are some suggestions:

Step 1: Well matched carb, low restriction exhaust, low restriction intake. It sounds like this is done already.

Step 2: Heads and cam. Clean up and pocket port heads, good valve job, hardened seats if not already there, mill for a little more compression, add some duration and lift to the cam. Muscle Motors seems to understand iron heads, I'd ask them what they can do.

Step 3: Quench and compression. Use a step piston if necessary to get compression up with .040" quench. May require fitting each piston. I believe the cr was quite low with these engines (8:1 or less?). If you are willing to buy premium fuel, I bet 9:1 would work and still keep good detonation margin for sustained hard running in hot weather. A bit more cam would be needed with this approach also. There was a poster who did this with a 440 and had a good running and surprisingly efficient truck engine - I don't remember who.

Step 4: All of the above plus stroke it. Don't go crazy - perhaps a 3.9 stroke. A bit more cam would be needed also.

Done carefully, you would gain mid range power without loosing bottom end torque; torque loss caused by the bigger cam would be balanced by benefits of better compression and breathing.