Packard Forum Index » Pre-War (1899-1942)

I'm trying to get my exhaust to release my intake on my '37. Are there any Whitworth size bolts on Packards? The bolts I'm struggling with are 17/32 inch or 13.5 MM.

No Whitworth threads on Packard automotive engines. Treaded fasteners on Packards, especially the prewar ones, were predominately NF with NC used more sparingly.

But it's unclear to me exactly what you're trying to separate from what, how about a better explanation or even a photo of what you're facing?

If you are talking about the bolt head size on the two bolts that hold the pipe up,they probably are scaled down to a smaller size. It happens a lot on exhaust systems. If the pipe doesn't want to drop,there is a holder(hanger)that bolts the pipe to the side of the bell housing with 2 of the clutch pan bolts using the same bolt holes.

Sounds like he is talking about the bolts that join the two manifolds together.

If it is the bolts which hold the intake and exhaust manifolds together than were talking of three bolts. One is behind the exhaust flange between the block and manifold exhaust pipe flange. Its a good time to replace your heat riser at that time(usually they are worn loose or frozen fast).
1937 6 cyl. exhaust manifolds were prone to getting cracked,but later ones will work,though they don't look exactly the same.

It could be the bolt heads are reduced in size by corrosion. This is common on exhaust manifolds because of the heat.

I should have been more specific. My exhaust manifold would not release my intake manifold. Yes three bolts. The confusion came when all three bolts measured exactly the same.
All three had rusted exactly the same amount and evenly. They all looked fine but they were between a 1/2 and a 9/16.
I have since torched them off. Now I just need to extract the remnants out of the intake manifold.