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.

Mike Semeniuk · 02-16-2015, 12:02 AM

Greg, I was told the metal in the seat area of some older heads was porous and susceptible to seat rusting. C11 also attracts moisture and causes rusting in combustion chamber unless you use Marvel Mystery Oil or something to fog the engine when sitting betseen races.

Greg Reimer 7376 · 02-16-2015, 10:53 AM

Thanks for your reply. I'm going to finish tearing the heads down and see just how bad the seats are.I'm prepared to replace all the seats with hard seats if necessary.The car had been run on mostly C-12 with a dash of 76 Union premium as well. (not at a NHRA race with that mix).If you ever saw an engine that had been run on propane, valve seat erosion is a problem on such a dry fuel.I've seen the Marvel Mystery Oil treatment, it may become the new norm around here.

Greg Reimer 7376 · 02-22-2015, 07:37 PM

Well, seems like we're not alone. I talked to a racer with a 305 '85 Camaro, he had the same problem affect one set of his heads. They are touching the valve seats, repairing the pitting, and going back together with whatever they need. Seems that the practice of lubing the engine with Marvel oil or ATF is going to be a new practice. Ever see a light rust haze on cylinder walls when opening up an engine ?

Kevin Panzino · 02-22-2015, 09:52 PM

I too always wondered about C11... The residuals from combustion seem to be terribly hygroscopic.... I've seen rust on almost every part post-combustion, but nothing on the intake side... Its not the fuel itself, it appears to be after its burned....

If I know I'm not going to run the car for a while, when I pull it in the garage, I open the hood, then kill the fuel pump and work the throttle on the carb while I spray in the oil, and keep the Revs up until the float bowl is dry and the engine dies. This has alleviated all of the issues. The white smoke and odor of this operation wafting up through the house is not at all appreciated by the wife however....

terry1 · 02-23-2015, 08:16 AM

Not to hi-jack the thread,but, is it common practice to turn off the fuel pump when fogging the engine?
Also the "mystery" oil is a MYSTERY to me up here in the white north.
I can get a "fogging" oil from a lot of suppliers but not mystery oil!!!!

02-15-2015, 08:26 PM	#1
Greg Reimer 7376 VIP Member Join Date: Nov 2008 Location: Glendora,Calif. Posts: 1,112 Likes: 165 Liked 654 Times in 209 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.

02-16-2015, 12:02 AM	#2
Mike Semeniuk Junior Member Join Date: Aug 2004 Location: Sherwood Park, Alberta Posts: 99 Likes: 19 Liked 6 Times in 2 Posts	Re: Cylinder Head Issues Greg, I was told the metal in the seat area of some older heads was porous and susceptible to seat rusting. C11 also attracts moisture and causes rusting in combustion chamber unless you use Marvel Mystery Oil or something to fog the engine when sitting betseen races. __________________ Mike Semeniuk 632 GTMA

02-16-2015, 10:53 AM	#3
Greg Reimer 7376 VIP Member Join Date: Nov 2008 Location: Glendora,Calif. Posts: 1,112 Likes: 165 Liked 654 Times in 209 Posts	Re: Cylinder Head Issues Thanks for your reply. I'm going to finish tearing the heads down and see just how bad the seats are.I'm prepared to replace all the seats with hard seats if necessary.The car had been run on mostly C-12 with a dash of 76 Union premium as well. (not at a NHRA race with that mix).If you ever saw an engine that had been run on propane, valve seat erosion is a problem on such a dry fuel.I've seen the Marvel Mystery Oil treatment, it may become the new norm around here.

02-22-2015, 07:37 PM	#4
Greg Reimer 7376 VIP Member Join Date: Nov 2008 Location: Glendora,Calif. Posts: 1,112 Likes: 165 Liked 654 Times in 209 Posts	Re: Cylinder Head Issues Well, seems like we're not alone. I talked to a racer with a 305 '85 Camaro, he had the same problem affect one set of his heads. They are touching the valve seats, repairing the pitting, and going back together with whatever they need. Seems that the practice of lubing the engine with Marvel oil or ATF is going to be a new practice. Ever see a light rust haze on cylinder walls when opening up an engine ?

02-22-2015, 09:52 PM	#5
Kevin Panzino Senior Member Join Date: Oct 2002 Location: Pittsburgh Posts: 521 Likes: 246 Liked 550 Times in 106 Posts	Re: Cylinder Head Issues I too always wondered about C11... The residuals from combustion seem to be terribly hygroscopic.... I've seen rust on almost every part post-combustion, but nothing on the intake side... Its not the fuel itself, it appears to be after its burned.... If I know I'm not going to run the car for a while, when I pull it in the garage, I open the hood, then kill the fuel pump and work the throttle on the carb while I spray in the oil, and keep the Revs up until the float bowl is dry and the engine dies. This has alleviated all of the issues. The white smoke and odor of this operation wafting up through the house is not at all appreciated by the wife however.... Last edited by Kevin Panzino; 02-22-2015 at 09:55 PM.

02-23-2015, 08:16 AM	#6
terry1 Member Join Date: Sep 2006 Location: Moncton, N.B. Posts: 276 Likes: 24 Liked 24 Times in 13 Posts	Re: Cylinder Head Issues Not to hi-jack the thread,but, is it common practice to turn off the fuel pump when fogging the engine? Also the "mystery" oil is a MYSTERY to me up here in the white north. I can get a "fogging" oil from a lot of suppliers but not mystery oil!!!!