piston clearance question with afr 185's

if you use 1.94 intake valves, and keep the valve lift under .500", you should have plenty of clearance. when the valve lift goes over .500" and/or the intake valve gets in the 2.02" range is when you start having problems.

I think you'd be better off with 165's both with the 289 and later the 331. I've got Canfields on my 331 that are pretty much the equivalent of 165's and they worked great, and no issues with valve clearance, even with the Z303 roller cam and 1.7 rockers (.585 lift/228 degree duration @ .050) Just remember that the 58 cc heads will be better off on the 289, but the 331, you'd do better with 64 cc chambers, you won't get the compression you'll need with em on a 289. If you've got 9 to 1 now, with 64's it'll drop to 8 to 1, if not less. Not good with a big cam with lots of overlap. Might be OK with an RV type cam with a wide LSA. With 58 cc chambers, you can choose a piston for the 331 that's dished to lower the comp ratio if needed. Mine ended up with 10.4 to 1 with flattop SRP's and 57 cc chambers. With more compressed volume, I could probably have run it on 87 octane gas instead of 93.