3400 series hercules

770puller · Oct 20, 2015

Looking for info on 3400 series Hercules i.e. Stock bore and stroke and how big one can be made as far as cubes, also who would be good to have build one

Allis Fields · Oct 20, 2015

339 cubic inches 4" bore by 4.5" stroke.

MH49 · Oct 21, 2015

Here is some information I pulled off of here some time ago and I believe it to be true based on what I have seen:

"You can bore it out to 4.125 with out hitting water but at 4.250 you will get wet. Stroke the crank 1/2" use 198 or 298 rods will have to cut cam down to clear and do some minor clearance on the block."

The combination listed above will make 401 CID and that block is really tight inside to make them much bigger than that. My bone stock 3400 has clearance ground into the cam for the crank swing. I am not sure which 298 rods to use as there are there are civilian and military versions of that engine. They love RPM so if you pull where you can twist them, you will do fine.

3400 series hercules

770puller

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Allis Fields

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MH49

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