I checked on the roller cams when collecting parts for my next project , came across a few things on the cams and roller arms , the site ranger station and a few others on the net , a few roller cams were diffrent and the roller arms were also , first sliders were 1.50 to one but do not care about those , first gen rollers were 1,64 , got those , last gen was 1.84 or 1.86 , but you have to widen the rails for the valve stem .061 for them to work on the older engines , got those also along with the cam, also got a bridge port to mill to fit , the cam i have is out of a ranger 2.3 along with the duel plug head , the other is out of a LRG425 industral (2.5 engine) which i got for the crank , NOT looking for high RPM horsepower , rather this engine will never see over 2700 RPM ever , unless I am in a dive , its going into a home built aircraft that was designed around 1929 using a for model A engine , A Pietenpol , I am looking for low speed torque , anything i get as long as it is over 50 HP a 2700 RPM will work fine , duel plugs like an aircraft , same weight a the old model A , plus side is this engine engine is very reliable , cheep and easy to take care of , I race them back in the late 70,s and you could not destroy it unless you drained the oil and water from it or hit a tree at sub light speed , figure in six months I will have it on a test stand to find out what combo works , advanced cam timing I will also try , got a adjustable cam sprocket , also the holes in the roller cam that lube the rollers are smaller which will help oil pressure , will post photos when up and running ,