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Old 06-23-2017, 04:32 PM   #1
Nomadicflyer
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72 C20 intake gasket

What say you all, push on or stop to burnish these old scuff marks? I'm changing the intake gaskets on the 350, due to high oil consumption. High, as in a quart per 100 miles, with no visible effect as to where. At highway power. Around town, she's an angel.

Anyway, prior repair revealed under the old intake gaskets, where someone really went after a stuck gasket with a sledge hammer and chisel! Fairly deep gouges and scrapes. Do I press on, put the new gaskets on? I had planned on using gray RTV on the intake manifold side, to tack the gasket in. Maybe I should tack it to the block, to fill in these scratches, instead? What say you all, oracle's of the old?

Thanks!
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Old 06-23-2017, 05:41 PM   #2
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Re: 72 C20 intake gasket

Update:. Looks like the PO installed the restrictor plates at the back coolant ports. Because those rear ports are just blank pads on the intake manifold side, coolant was trapped between the restrictor plates and the aluminum manifold, and......
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Old 06-23-2017, 06:50 PM   #3
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Re: 72 C20 intake gasket

your good the intake is made like that you could put a little g/b weld in that deep scratches
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Old 06-23-2017, 07:13 PM   #4
AussieinNC
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Re: 72 C20 intake gasket

Just fill in those corrosion pits with some JB Weld metal putty, wait to dry fully, file then flat sand...plug up those intake ports first then put some more JB on those deep scratches and gouges...

I suspect your oil consumption is more aligned with a bad PCV valve and or bypass oil loss then burnt...

Looking at the under valve cover surfaces, I can see a bit of sludge and some old valve stems seals...dried out old seals, plus bad PCV, all add up, especially if losses are more significant at highway speeds...

Question....what oil are you running?

Have fun everyday...
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Old 06-23-2017, 09:02 PM   #5
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Re: 72 C20 intake gasket

Leave the gouges, Black RTV is the way to go. Anyone will say the same, also use it on the lifter valley top of block.

You also can buy a copper gasket spray that will tack on the intake gaskets. Do not forget to run some of the RTV up the intake at the front and back of valley. Makes for a leak free install.

Now the Heads, that would be a whole nuther ball of wax!
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Old 06-23-2017, 10:12 PM   #6
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Re: 72 C20 intake gasket

Outstanding, thanks for the help, toolbox, Aussie and Camtoys!

If a new PCV valve and intake gasket doesn't work, I'm figuring on fabbing an oil separator for the PCV line. While it's all apart, I figure I should do a compression check, too.

This year was getting rid of the rust, putting on some color and such. I was hoping to get the engine and trans after building up the parts fund! Maybe I can patch er up for a while, yet...
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Old 06-23-2017, 10:25 PM   #7
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Re: 72 C20 intake gasket

If you suspect the pcv is pulling oil thru just replace the pcv hose with a clear hose for a test. You can get clear hose in the plumbing section of the local hardware emporium.
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Old 06-24-2017, 05:36 PM   #8
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Re: 72 C20 intake gasket

Thanks, Geezer! I've got to do something to track this down. If I'm really pulling that much oil through the PCV valve, I think I wanna catch it, see how much is going through. Maybe I'd make an air/oil separator out of an old jar, or something. I've looked to see what is 'acceptable' case pressures, not much out there. That way I can judge the affect of a fix, over time.

Putting the intake back in today. Tomorrow I'll finish, and do a comp check. In airplane motors, we do the compression check really slowly, bringing the piston up to TDC, then adding 80 psi of air through a regulated flow restrictor. The result is cylinder compression /80. 70/80 is good, more is better. 65/80 shows leakage that should be further investigated. The important thing is the ratio between all the cylinders, making sure one isn't a large percentage lower than the rest.

Doing compression checks on the 350 is different, I see. I have the gear, I just need to read the procedure a time or two. Make sure I do it right.
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