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Tom Goldman · 03-20-2016, 12:56 PM

My 468" Mule has 074 GM/AFR heads which grow more than modern high density castings.
I get by with .040" on the intake with no kissing , but I have titanium intake valves and very high spring pressure.
I've never chanced anything less than .050 on the exhaust , but they have never touched , and it runs at 8500 rpm.
Also have a belt not a chain which I think helps .

03-20-2016, 12:56 PM	#5
Tom Goldman VIP Member Join Date: Jan 2003 Location: Allentown,PA Posts: 2,476 Likes: 887 Liked 875 Times in 236 Posts	Re: Iron BBC w/ aluminum head growth My 468" Mule has 074 GM/AFR heads which grow more than modern high density castings. I get by with .040" on the intake with no kissing , but I have titanium intake valves and very high spring pressure. I've never chanced anything less than .050 on the exhaust , but they have never touched , and it runs at 8500 rpm. Also have a belt not a chain which I think helps . __________________ Tom Goldman 1500 SG , 1506 STK