Rusty V8

Stretch Cab

Stretch Cab

Well-known member
While working in Mexico I bought and had rebuilt a late 40's flathead. Moved and put the motor in storage and am ready now to get back on my project after about 4 years. In that time the top of the deck and some of the cylinder walls have rusted. Kind of a weird rust that makes me think the motor wasn't washed well after tank cleaning. How much surface rust can i clean off with cylinder hone and still be ok or do I need to take the motor back apart?
 
Does what you call a weird surface rust have sort of a golden tinge? Does it seem to be thin enough that some is removed by buffing with a cotton cloth or a terrycloth choreboy? If so, I'd be tempted to liberally coat/spray the affected areas with MMO and let it set a few days and repeat before trying to run it. I doubt a 4-year hiatus would do that much rust damage unless stored in a very humid or corrosive environment.

Jack E/NJ
 
I had it stored in a small covered trailer and it just seemed to corrode rapidly but stopped after a certain point. The rust won't wipe off. The trailer was parked in a very humid area here in Fl.
 
Hmmm? I'd spray MMO into the cylinders etc anwyway. Let it set a day or so. Repeat. Then try to turn the crank pulley ratchet with a socket wrench by hand to make sure it's not frozen. It should turn fairly easily with a breaker bar. I'm however assuming the cylinder rust isn't that thick.

Jack E/NJ
 
take a scotchbrite pad and some MMO and carefully clean off the Heavy part of the rust "before" you try to move the pistons, if you can get it down to slight rust in the pores of the metal you got it-then roll the engine over while applying liberal amount of MMO
 
Corrosion pitting on the deck can be sealed at head installation and can be honed easily with a large oil stone. If you have concentrated pitting in the cylinder bores you will have to re-hone for sure. To get a good crosshatch you'll have to have the pistons at BDC or remove them to keep the cylinder walls straight. If pitting is too deep to remove easilly, you'll have to judge whether your piston clearance has been exceeded. A badly pitted area close to the top of the cylinder can cause a loss of compression right out of the gate.

You'll have to be the judge whether to go back to the machine shop or not. I just pulled one appart that I had in storage for better than 20 years and the cylinders were OK. I used SAE 140 gear oil on them when I originally put it together and it had no signs of rust at all. I was really surprised. Even though it was stored in Kansas where rainfall is pretty scarce, I expected to see more corrosion just due to the amount of time that had lapsed.

Kerby
 
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