Ok, i'm going to sum it up. I swaped my points dist for a hei from a 350 buick engine. Since that swap my car when floored would pop thru the carb like a cam lobe was out and the car also had a loss in performance. The trick to fixing or at least gaining better gas milage is to be sure the hei has 12 volts running to it. Everything else on the car was rite except that. On my 71 buick that came with a point's type dist and coil also came with a resister in the coils hot wire the pink one. So DO NOT HOOK IT TO THE NEW HEI. Instead what I did is ran a BOSCH 30amp relay under the dash to turn on when they key is on ran 12 volts from the battery and ran that thru the relay strait to the coil. On a buick pre 75 I think the coil wire for the regular coil when the car is starting reads out 12 but when it's running it drops to 5 or 6 volts. The way this works is a white wire from the starter joins the pink wire so the starter relay apply's 12 volts only during the key-on/start once it's running the relay disengages and it drops to 6. Hope this helps some of you.
poping through the carb. Sounds to me that the mixture is too lean and/or you need to regap the spark plugs wider
Xarva, This is indeed a common problem with HEI swaps. You're not alone, many people report that the HEI runs worse than points for this reason. You may want to check a couple of other things as well: One other reason for poor HEI performance is the coil in cap setup of the HEI is usually burned up. MSD sells a $20 coil relocation cap that will allow you to retain your existing coil. You can get a pickup rebuild kit for around $25 + a new GM module (don't bother with cheap aftermarkets that lack a dwell circuit) that will fix any age problems with the "guts" of the distributor. It's 4 1/4" bolts, takes about 1/2 hour for a rebuild. There are also reputable rebuilders available if you're not into the DIY thing. A good article on re-curving your HEI: http://www.73-87.com/garage/hei.htm
