John Dunn

Tappet clearance HOT vs COLD

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I've just redone the valve job on my 38 RC humpback and now setting tappets. I've got some original manuals from 1935-41 and a 50s vintage MoPar shop manual on the industrial engine versions. The 35 book shows .006" intake and .008" exhaust, 41 Dodge truck manual shows .008" intake and .010" exhaust, and the industrial engine book shows .010" intake and .014" exhaust with up to .018" for the sodium cooled exhaust valves. THEY ALL say to check and set with engine at normal operating temperature and one place even said to do adjustment with engine running at idle. I've adjusted  overhead valve engines while running but can't imagine doing these flatheads like that. Has anyone ever adjusted valves on Mopar flathead 6 while RUNNING with the HOT exhaust manifold in the way? 

What clearance should I set while cold with engine apart???? I'm guessing clearances close up a bit when engine is hot? I was thinking maybe .010" intake and .014" exhaust cold. 

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Yes. Not really hard to do but takes some practice.  The only accurate way to set them is hot and running.  Hot and not running is okay if you start and run the engine after setting every four valves.

On my Pontiac you needed one extra wrench because the adjusters had a lock nut.  That is why I put WPC adjusters in my engine at the last overhaul.

Edited by Tinindian (see edit history)

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An absolute must has to be running and hot....otherwise you will get a nasty slapping sounds on the valve train...I always put a tray under the engine and keep a magnet stick around....if your not experienced things tend to fly around and out of your hands....

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Once you get them adjusted to specs let the engine cool completely and mark the clearance cold. Let us know what they read.

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