honda head milling highly modified gx460 question

I'm building gx460 back up motor. Highly modified or wild engine. IV got question about milling the head. I took 70 thousands off the head last time with 310 lift cam and have 1.3 roller rockers. I was wondering how much more can I go with same cam and roller rockers?
 
Way too many variables to tell. Piston design and cam "timing" will have more to do with it than total lift. If its still together, check how much piston to valve clearance you have now with feeler gauges between the lifter and valve. You can then decide what minimum you want I would want at least .060 but that's just me. If you now have .120 and want say .080 you can go .040 more milling. Whats your static compression ratio now? What you shooting for? some small "eyebrows" milled into the piston may help get some more milling.
 
I'm ruuning a flattop piston. With flattop piston its 10 to 1. With no milling on the head. I just want know what's best or how much should I take off. Is more better or worse. Its still together my primary is.
 
I would think you could mill .080 safely. Again, that's just a guess. You still need to check it. .100 may even be possible. 8000 rpm may not be needed with this size engine. Its more of a torque monster. If running gasoline I would not try and get a compression ratio much higher than 12.5 to 1. I know many have done higher but many have blown them up too. Alky can go higher. Higher than this and the block will split, or is likely to. This size engine needs a ton of flow too. Big carb with big ports and valves. Most of the 460 "clone" type engines come through Vegas Carts and/or Parsons Racing. Give Parsons a call. He will have better insight as to what this thing needs/wants.
 

jm88j

New member
I would think you could mill .080 safely. Again, that's just a guess. You still need to check it. .100 may even be possible. 8000 rpm may not be needed with this size engine. Its more of a torque monster. If running gasoline I would not try and get a compression ratio much higher than 12.5 to 1. I know many have done higher but many have blown them up too. Alky can go higher. Higher than this and the block will split, or is likely to. This size engine needs a ton of flow too. Big carb with big ports and valves. Most of the 460 "clone" type engines come through Vegas Carts and/or Parsons Racing. Give Parsons a call. He will have better insight as to what this thing needs/wants.
Have fun calling Parsons haha
 

DAVID PLANAKIS

New member
ok boys and girls,I have built several 440 and 460 motors,with 1.3 rockers,.310 cam,flat top piston,and 0.080 shaved off the head the intake valve will hit the piston on the down stroke of the engine,this will give you a C.R of 12.5 to 1,now this all depends on what valve you are useing,the valves we use in our motors are custom made titaniam with very small margins this helps with valve to piston clearance,we also use a custom domed and valve relevied piston that I had desighed,we run big valves,small stems,and our last set of heads flowed 170cfm on the intake and 150 cfm on the exhaust,we can spin our engines to 9500 rpm all day we are making 60 HP at the crank our bigest problem to date has been chains,I can snap the best #35 chain at will at 80mph,we have just had bulley clutches,make us some #428 sprockets for the 1 inch turbo clutch this should fix the problem,feel free to ask me any thing about these engines
 

VPGoldenboy

Member
DAVID PLANAKIS where can you find the 1:3 billet rockers for the 460? parson's only carry the roller rockers and Vegas Karts can't seem to get any of them. Our rules strictly says NO rollers!
 

Armilite

New member
Gx460 cr

I'm building gx460 back up motor. Highly modified or wild engine. IV got question about milling the head. I took 70 thousands off the head last time with 310 lift cam and have 1.3 roller rockers. I was wondering how much more can I go with same cam and roller rockers?
This Honda 460 Clone CR Chart I found says if Stock Head was 42cc = 9.25cr and if you Milled off .070" = 11.063cr. Another site said Stock Head was 46cc for 8.2cr.
 

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