Terry Parker got hold of some Blue Thunder heads, and sent me the following pictures and information.
First, notice how much higher the intake ports on the BT heads are compared to a 4V head intake gasket. Note the bolt holes in relation to the ports.
Top view:
Width of the head:
Chamber with & without valves:
Some dims of intake port:
Exhaust port dims:
70cc chambers. Ferrea 2.1/1.65 valves.
Dimensions:................BT.......4V......Difference
Intake
Deck to bottom of port____1.715____.50_______+1.215
Deck to top of port_______3.715____3.00______+.715
Width/Height___________1.55X2.00___2.5X1.75
Exhaust
Deck to bottom of port____2.35_____.90_______+1.450
Deck to top of port_______3.875____2.90______+.975
Width/Height___________1.55X2.00___1.75X2.00
Width C/L of head bolt to outer edge
Intake side: Same as 4V
Exhaust: +.330
Port flow
"Heads were nicely tidied up as can be seen in photos. However I wouldn't classify them as being ported, but definitely more than a 10 minute tidy-up."
Lift....Int....Ex w/o pipe....ex w/pipe
.2______141_______124____________129
.3______191_______165____________172
.4______236_______194____________200
.5______273_______213____________219
.55_____288_______219____________227
.6______302_______221____________231
.65_____313_______224____________233
.7______323_______227____________236
.75_____329_______229____________239