I set my valve lash yesterday after changing over to the super six, and noticed the two intake valves side by side have now bottomed out and can be tightened no further. They're set at about .012 which seems fine for now but what does this mean for the future?

Also - any insight to what the heat riser in the exhaust manifold actually does?

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Take the pushrods out and make sure they aren't bent. Or perhaps they aren't closing all the way, guide and/or seat issues?

Wouldn't hurt to do a compression test on those 2 holes.

How many miles are on this engine?
DD

The manifold heat control valve directs exhaust to the underside of the intake manifold floor so that liquid fuel that tends to pool on the manifold floor with a cold engine, at low engine speeds, and under hard acceleration, will be vapourised before it is drawn into the engine.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Thanks Dan,

Doc - The motor was rebuilt about 10,000 miles ago.

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Uhmmm... I wonder where you lost that travel, reground cam & lifters?

Seeing that the engine is in good overall condition, you may want to remove the adjuster screws and grind those rocker arm surfaces a little thinner / flatter.
The other option is to order some longer ball screws or push rods.
DD