Hello Jason, when I first bought my six/300 it was an ugly duckling to say the least,the paint was like 220 sand paper and it had no wheel pants on it at all and the doors didnt close tight at all. even had the original front baggage door on it which didnt close tight, so to make a long story short...........it true out at 132-135 knots at 6000 feet here in Florida. well I had it painted put knots 2 U speed mods on which consisted of wing root fairings,wheel pants, gap seals,and dorsalfin (which just looks cool)new windows and adjusted the doors and now we cruise along at 21 mp and 2350 rpm at 6000 ft at a blazing 141 knots and 15 gph
Jason - at least! I used to drive two Archers, one with pants and one without. The one with was about 8 knots faster. Of course, there may have been some other factors that I'm not aware of...but it was not a close race. Both Archers, BTW, were the ones that Mohammad Atta of Twin Tower infamy trained in in West Palm Beach. Hard to believe that I sat in the same seat that that asshole sat in.
I measured a 5-knot difference in TAS on my fixed-gear Saratoga between pants/no pants on the mains. I leave the pant on the nosegear, so there's probably another couple of knots there compared to a PA32 with no pants at all. My POH says to subtract 8 knots from book speed if no wheel pants are installed.
My "book speeds" are very sensitive to density altitude. The 75% cruise power performance curve starts at 134 knots at sea level and rises to 148 knots at a DA of about 7,500. My observed speeds are pretty close to this. Altitude is your friend. The book speeds for the 78/79 6-300's are the same as the Toga. Earlier 6-300's were about 4 knots slower.
Another thought for the OP: have you checked your tach? As tachs age the internal spring weakens which tends to make the tach read high. So while you're setting your engine to 75% per the gauges, you may not actually be getting 75% power. Your A&P will probably have a digital or stroboscopic tach which can be compared to your "steam" gauge - it's an easy test.
