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Engine Mechanical / Electrical / Re: Boost with iron heads and no intercooler
« on: February 18, 2021, 05:23:06 AM »
I'm sure staying at the level I'm at, or even going to 6 lbs will be the safest in the long run. I guess I just feel like the carbs will help keep the charge air cooler (not as cool as an intercooler, but that is one of the principles carbs aid in.) I was told but TBS, that the 6-71's don't start to become INefficient until 7500 rpm. Makes me think that spinning it at 6000-6600 rpm (2.5% O/D - 11% O/D) isn't really that bad. I hear people running 8-71's running at 13% O/D, 8:1 cr on straight av gas, no intercooler, (yes with aluminum heads, but that allows for just a little more leeway), and seem to be fine. I plan on bumping up the jetting one for the bigger exhaust, maybe a few more to richen it back up on avgas (I never jetted up from 93 before, but I saw 9-10:1 afr when on the 93 so I was probably still in the safe zone when I put av gas in then). Perhaps lower the timing to 28* (BTW, engine made 11 less hp at 28* timing compared to 31* on 8 lbs boost) Thanks for the help, fellas












