Wheel pants on the Cherokee are about the best speed mod I know of for it.
Very true, this. Wheel pants on/off my old Cherokee 140 was good for about 8 MPH difference. BTW, my wheelpants were made by Van's Aircraft in 1973 and STC'ed for the PA28. They were very much like the stock Pipers, but shaped just a little differently on the aft ends. When I met Van in person at Oshkosh 2012, I mentioned these wheelpants to him, and the fact that the original sales receipt for them was still with the old Cherokee's logbooks, he smiled and laughed and said that he made those wheelpants personally himself, and that maybe someday someone would consider them a collector's item!
Metco tips are nice, gap seals, VGs etc.. I'd take em. I found that a seller has a hard time forgetting the checks he wrote for all the mods when it comes time to sell. The best mod on the cherokee is the HP boost to 160 if you're in a 150HP model. Might not gain you any speed but it time not climbing is time in cruise. I certianly wouldn't buy any of them to save fuel.
Metco tips really do work well. I don't know about other brands of Hoerner-style wingtips, but Metco's are solidly constructed and cost less than K2U's and LoPresti's renditions. I had Metco's on my old Cherokee 140 and they made a very noticeable difference in handling over the stock round Piper tips.
All that gap seals do is give you a bit crisper control authority, they don't do much of nothing really for speed.
One other speed mod that does work (2 MPH, maybe 3 if you're lucky) and is fairly cheap, is the nosegear scissors fairing from LFS. I had one installed on my old Cherokee 140 and it did work... but it made my nice collapseable tow bar with spring clamps unusable and I go back to the original plain "2-fingered" tow bar. It also made doing any preventive maintenance on the nose gear a royal pain since you had to remove it first. It looked cool on the plane though, but if faced with the choice again, I'd skip it.
Also, if you have a 150/160 hp Cherokee with the single big cannister muffler behind the engine up against the firewall with single narrow tailpipe pointing downwards out of the right lower side of the muffler, the Powerflow exhaust system really will give you back a lot of power that is being robbed by the restrictive factory exhaust, but man those PFS exhaust systems are breathtakingly expensive. If you have the later style exhaust, like a Warrior, or the Cherokee 180, then the stock exhaust already works about as good as you can get.
Lastly, a good slick paintjob and making sure your flaps and ailerons are rigged correctly will help. When my old Cherokee 140 was stripped of its stucco-finish-like orange and white 33-yr old checkerboard paint and repainted with AcryGlo polyurethane, that was good for 5 MPH and re-rigging the ailerons and flaps to book specs using a tool described on Art Mattson's website was good for another 3 MPH.
I would say speed mods are the biggest waste of money in aviation, except for one and that is buying a faster plane.
Absolutely. Look what I'm flying now.
