Rust on the intake valves

bblars · 05-28-2004, 08:17 PM

I am not trying to rebuild this engine. I am just trying to get it running. This is the worst of the six. A couple have very little rust and the others are so-so.

How bad is this?

I put some Marvel mystery oil in the plug holes and its seeping its way through as we speak but i'm worried about this rust.

Oh yeah, it's a 1983 3.0l w/ CIS

afterburn 549 · 05-28-2004, 09:14 PM

well evryone wants to say how to do it exactly right.......but all you can do is just try it and see........if the valve is not sezed up in any way it will probly work-if it do not your no worse off it had to come aprt know or later.......probly the biggest danger is kissin a piston

Wayne 962 · Wayne 962's Garage

Hmm, that's not lookin' too good. However, engines have a habit of cleaning themselves up after running for a while. I would slap it back together and see what happens. Turn it over by hand of course and make sure nothing sticks...

-Wayne

911pcars · 05-28-2004, 11:52 PM

I'd verify the valves are free to move before trying to crank/rotate the engine. If one or more valve stems are seized, something's gotta give. No telling what part that could be (broken rocker arm, cam?).

Using a dead blow hammer or fiber mallet, tap the end of the valve stem; lightly at first to see if it moves. You can tell by the sound. If stuck, try running some Kroil or other thread solvent down the valve stem followed by the aforementioned MMO, then repeat the blows with the hammer. You could even try this in conjunction with some torch heat on the valve guide. Repeat on each valve until they're able to slide open/closed in their valve guide.

Sherwood

Doug Zielke · 05-29-2004, 06:55 AM

If there was enough water inside the engine to do this, what are the chances the piston rings are also rusted to the bore?

Jim Sims · 05-29-2004, 07:22 AM

"If there was enough water inside the engine to do this, what are the chances the piston rings are also rusted to the bore?"

Or a mouse has built a nest complete with lots of soil (as in decomposed rock) on top of a piston in a combustion chamber (I've seen such a thing in a 911 engine). If the engine doesn't turn over freely it's time to take it apart. Jim

power · 05-29-2004, 08:35 AM

I had an engine with similiar rust. I spent a long time cleaning it out. I fabricated vacuum hoses to fit in the intake while I cleaned it. I also fabricated one for the spark plug hole to suck up all the oil and pentrants I used on the cylinders. ****Warning dust and gas/oil do not mix well, I also spent a long time cleaning my shop dedicated vacuum to rid it of fumes and contaminants after***** . It started and ran fine (after filling the neighborhood with smoke) I started with fresh oil then changed oil immediately (3-4 min.) after start up and again after a couple of hours run time. Compression was good, I got lucky.

jgparker · jgparker's Garage

I have a similar story, but it ended up needing a complete rebuild. Rusty valves, squirl's nest inside the fan housing. A real mess. The rings were frozen to the bores, so it could not be salvaged without opening it up. I bought the car for the price of the Webers, so I didn't have much to loose.

Wayne 962 · Wayne 962's Garage

Yes, I advocate doing things right, but I also advocate trying the easy things first. The easy thing would be to get this thing running for 500 miles (if possible), and then doing an eval after that to see what it takes. The rust on the valves may have permanently damaged the valve-to-seat seal, but then again, you never know. I would spend the few hours cleaning the thing out and seeing if it runs. Then do the normal checks on the engine (http://www.pelicanparts.com/techarticles/mult_Engine_Rebuild/mult_engine_rebuild-1.htm) to see what it needs...

-Wayne

markwemple · 06-03-2004, 06:24 AM

Wayne, Glad to see that you are one who doesn't go to the immediate overkill route. These 911 engines are quite hearty and I wouldn't be at all shocked if that engine just needs a good run in along with several oil changes to bring it back, as you said. One thought on the oil. I have seen amazing things happen on tired engines when run with rotella 15/40. Don't know why old german engines like diesel oil but I have seen several saved just doing a few frequent oil changes with this stuff.