+1 to Ace's idea of a proper C.I. motor in fireball trim, tuning is easier with a far better range of performance parts easily available...
HOWEVER, being a 500 AVL fan I don't see why you can't have a hybrid engine, and as this topic shows, a well-sorted AVL engine is a fine bit of kit.
My original 500 AVL hybrid engine was built by Henry Price in the UK and later modded by Bullet Whisperer. It uses a set of older C.I. 350 crankcases which needed quite a bit of modification. A set of late 500 C.I. cases would be much easier to adapt.
The cylinder stud centers will be the same, ideally late cases will be threaded for metric cylinder studs which is what the AVL engines use. If your cases have CEI 5/16" studs you will need custom cylinder studs or some 8mm helicoil inserts for the AVL version.
The AVL crank will fit straight in, though a new set of quality main bearings would be a very good idea.
The oil feed on the scavenge side is different from the C.I. models, one oil way is in a different position in the crankcase, but very late C.I. models have the "blob" of alloy in the right place which can be drilled out to match the AVL timing cover. The hole in the old position can be plugged, ideally drilled and tapped for a 5mm grub screw so it can be re-used in C.I. configuration at a later date. I also found mine needed the slightly undersize oil pump worm to prevent premature oil-pump spindle wear. These are the version with the bonded-in rubber seal, which needs to be removed to allow it to fit over the AVL crank's oil feed.
The AVL timing cover does need some work to make it fit. The cam spindle housings need reaming out from 15mm to 5/8" (15.88mm) for the fixed C.I. cam spindles. The bosses for the 1/2" idler cam spindles aren't fully machined, one isn't bored out at all, and both need milling to set the end float for the idler gears, assuming you're keeping the C.I. contact breaker drive (or fitting a magneto...).
The 500 AVL crankshaft has a different style of alternator which will need a set of Electra-X or 500 AVL Classic primary transmission cases. These will bolt straight onto the E/S crankcases. If you don't want to use the C.I. ignition and all the timing gears you can use the crankshaft-triggered TCI version from the Electra-X or AVL Classic. If your crankcases are for a right-foot shift model you can only use a 5 speed box with the right-foot shift conversion, and there will be two holes for the left-foot gear shift to plug.
Using the C.I. cam followers/tappets is actually a good idea, they're tougher than the AVL (re)design, but you will have to play with the push-rod configuration to match the AVL rockers to C.I. cam followers.
Hmm, are you still there, Matt? Are you still interested?
I think that's all the main items, but I might still have forgotten a few odds and ends.
A.
(Photo courtesy of Bullet Whisperer)
Topic: DanB's Ace AVL head (Read 38870 times)