Cylinder Head Issues

Greg Reimer 7376 · 02-15-2015, 08:26 PM

Anybody out there had exhaust valve seat issues in SBC heads, circa 1968 whereas a cylinder or two,or 6, show very bad leak down numbers-35-65% just like a motor with a bent set of exhaust valves, only when the motor gets pulled and the heads taken off, no bent valves are found,only to see a very rough,almost deeply rusted corroded seat in the head? My Chevelle sat since August, took it out to run it before Winternationals, it ran OK but down about a mile and a half per hour in the 1/8th mile.When I loaded the car up the Saturday before Pomona, I heard a couple of low cylinders, so out came the leak down gauge with bad results. I thought I might have tagged a valve in the water,but no bent valves or any marks on any of the pistons showed up,just the seat damage.Could it be a chemical corrosive reaction between the iron head,the stainless valve, and the residue in the fuel? Just thought I'd ask.

02-15-2015, 08:26 PM	#1
Greg Reimer 7376 VIP Member Join Date: Nov 2008 Location: Glendora,Calif. Posts: 1,136 Likes: 172 Liked 705 Times in 219 Posts	Cylinder Head Issues Anybody out there had exhaust valve seat issues in SBC heads, circa 1968 whereas a cylinder or two,or 6, show very bad leak down numbers-35-65% just like a motor with a bent set of exhaust valves, only when the motor gets pulled and the heads taken off, no bent valves are found,only to see a very rough,almost deeply rusted corroded seat in the head? My Chevelle sat since August, took it out to run it before Winternationals, it ran OK but down about a mile and a half per hour in the 1/8th mile.When I loaded the car up the Saturday before Pomona, I heard a couple of low cylinders, so out came the leak down gauge with bad results. I thought I might have tagged a valve in the water,but no bent valves or any marks on any of the pistons showed up,just the seat damage.Could it be a chemical corrosive reaction between the iron head,the stainless valve, and the residue in the fuel? Just thought I'd ask.