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.

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.

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.

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 ?

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....:D

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!!!!

Re: Cylinder Head Issues
 

I fog the engine down at the end of the race.

Re: Cylinder Head Issues
 

Google Marvel Mystery oil for info. This has been used for many years - on the dragster we pulled the plugs and used a squirt bottle to oil the cyls, then turned over by hand. I remember Dave L. on his ramp truck fogging the Camaro after loading to head home.

Re: Cylinder Head Issues
 

Terry,

Canadian Tire did sell Marvel Mystery Oil out here in the west not sure if they still do. There is also a CRC aerosol product the motorcycle guys use but then you would have to pull plugs and spray the cylinders. Might need to go south and buy a couple of cases of Marvel. I bought 3 cases 6 years ago and only have one can left.

Re: Cylinder Head Issues
 

Cast iron rusts very quickly and always has. Your headers allow moisture/condensation to get in their especially when the exhaust valve is off it's seat.

Hold the carb wide open after a race and use MMO or ATF or WD-40 and crank the engine over to draw the stuff in past the carb.

I used to use a rag to absorb the gas from the carb accelerator pump.

Stuff rags in your open headers or find a plastic cap that fits..

Plastic Caps from various pipes might work....they protect the threads on new pipe and once you have the right size.....they work perfect....

Exhaust seat/valve rust was always a problem.....

Re: Cylinder Head Issues
 

Somebody on Class Racer used to sell header plugs that had the moisture absorbing crystals inside, maybe someone on here remembers who was selling them.

Re: Cylinder Head Issues
 

Dan Dvorak was the racer who made them.

Re: Cylinder Head Issues
 

Mike, Canadian Tire do sell a fogging oil.I used it last fall.I my have to bone up on my
procedure though.
Terry K

Re: Cylinder Head Issues
 

Thank you one and all for sharing your knowledge. This bunch of racers has more experiential knowledge of what works and what doesn't than any body else could imagine. I got the heads down to bare castings,the intakes all look great, all but two of the exhaust seats need help. I plan to reface them , lightly touch the valves, new seals, and new springs. Now, with a 327,250 horse, 1.72 intakes,1.500 exhausts, Elgin rockers, not rollers yet, new Comp springs,what spring tension should I go for?I was thinking 350 over the nose, 180 on the seat. This engine is done by 7000,so i wasn't going for broke on the spring pressures.If it was a 275 horse with roller rockers, that would be different. This engine does have a steel Bullet cam and Smith lifters. Wouldn't it be great if we could run a rev kit on a stocker motor? Just thinking.

Re: Cylinder Head Issues
 

I run 160 on the seat with comp springs, done a back to back test at the track and boosted them up to .050 before coil bind, which I believe was around 200 on the seat. It ran about the same. I put them back to 160. This was on a 295 hp 350.

Re: Cylinder Head Issues
 

Orielly's sell Marvel Mystery Oil

Re: Cylinder Head Issues
 

Nerf balls make great header plugs. They make lot of different sizes of little footballs and other balls. Cheap and easy to find at WalMart, etc. Also wont hurt much if you crank it over and forget to pull them out... they just shoot out of the headers. Might have to chase them down.
Let the pipes cool before sticking the balls into the pipes.

Good luck.
Ken

Stock 412

Re: Cylinder Head Issues
 

Fogging the motor when not in use as well as plugging the collectors works great--- we also replace the spark plugs with dessicant plugs at the end of each day to control moisture in the cylinders-- FED 387