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Has anyone blocked off the coolant holes going to Intake Manifold?

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HI Everyone,

Been working on getting my 1971 Datsun 510 back and running. It has aftermarket headers, and a Cannon Intake Manifold. I am having trouble getting a solid seal between the intake/exhuast manifold and the head. Considering I do not need coolant running through my intake manifold, would it be an alright idea to somehow plug those? What has everyone else done to ensure proper seal? 

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I rely on the stock gasket.


I bet the thickness of the header flange is different than the intake flange. The bottom row of studs use a cone washer and nut to bridge across and hold both tightly to the head. Only natural for the the thicker flange to tighten first. See which is thicker and grind it down where the nut clamps it so it's level with the other.


Home made intakes. Flange same thickness as stock exhaust manifold. In this case 1/2"


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I put Pipe plugs in the head.  Pipe plugs are wedge shap slightly and you put in flush and should be tight when you do it right.

I forgot the threaded tap to use but you might not even need to drill it as the Datsun water passage hole might already be the right size.


But as  Mike showed key is the wshers are matched up and flush. Persoanlly cheap headers might be the issue also

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Yes, with aftermarket intake without the coolant passage, plug the holes!  Just as Hainz says, tap threads & install pipe plugs with some sealant.


And as datzenmike says, make sure both the intake & exhaust manifold flanges are the same thickness, thus use normal washers.  If different thickness, no worries, just find a washer that makes up that difference & cut to fit.  You might want to weld & grind to suit, cuz hard to hold half a washer in place by hand!  If you have the factory THICK washers, you can grind thinner in that area to create a "step" so it seats on both flanges evenly.

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