Ok, so I finally got my 250 ready to fire and break the cam in. I borrowed an engine run stand to do this on. Now, about the engine, it's a 0.040 over flat top (307 pistons) 255 with a lumped and ported head with 1.84-1.60 valves, and a Comp 268H cam and kit. It has a full Pertronix ignition with an Ignitor II, their wires, and Flame Thrower coil. I have a set of long tube headers and a Holley 600 carb, and am going to get an Offy 4 bbl intake. I plan to intall these after the break in.
For the break-in though, I wanted to use the stock intake/carb and exhaust manifold as to not run an untested Holley 600/Offy on a fresh motor. Well, once I got through the initial snafus, like little leaks and capping off all of the vacuum ports, it fired up and sounded great...problem is, which I was afraid of, it runs lean, and it won't hold at a steady 2000-2500 rpms without a little variation in the throttle. It sputters and wants to die out if I try to hold it at a steady rpm. After about 6-8 minutes of break-in, I had to shut it off because of temperature. It had a radiator with electric fan running the whole time, plus it has a 180 thermostat. But once the temp got into the 215-220 range, I let off of the throttle, which immediately made it die. I checked the temps on the engine with a laser temp gun, and it showed the most heat in cylinders 2-5. Numbers 1 and 6 were cooler. I figured it was better to let it cool down and finish another day.
I originally thought it could have been the filter or a clog, but it was clean, and the lean condition makes more sense, as this combo probably doubles the factory horsepower.
I haven't bought the Offy intake yet ($280) since we have other priorities going on right now, like getting ready to move to Northern Michigan. Is there any way to fatten up the stock 1972 Rochester Monojet so I can finish the break-in period? Or would it be better to go ahead and get the Offy intake? I can't take the engine run stand with me, but I have about 2 months before I'm moving. I would just like to know the engine is broken in and in running condition so I can install it in the truck and make it easier to move 500+ miles away.
Thanks in advance.
Last edited by 47Thriftmaster250; 01/22/15 08:57 PM.
