Re: loose manifold bolts

Posted by Ross On 2013/3/3 6:08:58

Just took a look so am coming in late.

Studebaker and Chrysler products of this immediate postwar era used brass nuts--and they are quite good for the reasons noted.

Packard, however did not. They used 3/8-24 extra heavy series steel nuts. The "extra heavy" means that they had an 11/16 hex instead of the 9/16 that is standard for 3/8 threads. This in concert with the extra heavy series flatwashers under them gave much better support as the washers need to span between adjacent ears on the intake and exhaust manifolds. Will have to look and see if McMaster has these. I've never had any trouble with them coming loose, and there is no need for any locking washers.

A sure sign that an engine has been worked on when you go to look at a car is that the washers under the head nuts will be missing, and there will be small nuts holding down the manifolds.

Peter is quite right about the finish on the manifold: Best if it is smooth as a baby's backside, and with a small chamfer around the edge. A right angle die grinder with a roloc disk does that fast and easy.