1971 487 X Heads

Jim Cimarolli · 06-07-2024, 10:08 PM

Does anyone know when GM started heat treating the exhaust valve seats on their cylinder heads?

Dwight Southerland · 06-08-2024, 04:44 PM

1971 with the introduction of unleaded gas at the pumps.

06-07-2024, 10:08 PM	#1
Jim Cimarolli Senior Member Join Date: Mar 2002 Location: Sulphur Springs Texas Posts: 742 Likes: 144 Liked 166 Times in 46 Posts	1971 487 X Heads Does anyone know when GM started heat treating the exhaust valve seats on their cylinder heads?

06-08-2024, 04:44 PM	#2
Dwight Southerland VIP Member Join Date: Dec 2001 Location: Arkansas - In the middle of everything. Posts: 1,999 Likes: 63 Liked 772 Times in 192 Posts	Re: 1971 487 X Heads 1971 with the introduction of unleaded gas at the pumps. __________________