TECHINSPECTOR1, WHERE ARE YOU?

Well, Psycho, In the absence the authority, I dug around in the big mess I call "my files" and found some information that may be helpful.

Your 413 came with a bore of 4.190, so you would have to go .060 over to bring the displacement up to 426. The 426 is fairly similar to the standard 413 but it was cast "beefier" to allow for the larger cylinders.

If all you want is an additional thirteen cubic inches that would get it, but to make the engine feel a little more like a 426 you'll need to think seriously about the heads, because they are probably the biggest difference between the 413 and the high performance 426. The intake and exhaust ports are 25% bigger and the opening for the exhaust valve is 1/4" larger than in the 413 head. The intake valve is the same as in the 413 (2.08) but the exhaust valve is a quarter inch bigger, and the heat crossover passage was eliminated.

From what I can find out, the best heads ever made for these engines (next to the "hemi" heads) was the '62 "Max Wedge" head; 2.08 intakes and 1.88 exhausts. I wouldn't bother to look for any. If you found some you'd have to mortgage the farm to pay for them.

HOWEVER .... the next time you're scratching around in Honest Andy's wrecking yard, look for a '68 through '70 383 or 440 with a four-barrel carburetor on it. Their heads have the usual 2.08" intake and a 1.74" exhaust. They flowed air well enough that they were used on the Roadrunners and 440 Magnums of the era. These are called "906" heads. To make sure you have found a set, take off a valve cover and look for a casting number on top of an intake runner. It should be a seven digit number the last three of which are "906". They are reputed to be some of the best high performance heads Chrysler ever produced.

Jim