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Re: 56 Desoto Hemi Rebuild in San Diego?

From: Hank Dozier
Date: February 20, 2002
Time: 20:48:58


Gary.... Your 330 Firedome can be overbored by 0.060" with no problems. In fact, the 56 Adventurer engine used a 0.060 overbore to get to 341 CID. Cheapest way (relatively speaking, given cost of DeSoto parts) is to use STD bore 1957 341 pistons. Gives you 9.25:1 CR, since the head volumes are the same on all high-deck DeSotos. To improve performance further, you can get or have your cam reground to 1957 S25/26 specs, and use a 1956/57 Fireflite manifold and carb. Should give you close to the 295 HP of the 57 Fireflite. Getting more exotic, you can use a AFB or Edelbrock carb and either use a spacer or or bore the manifold for the larger throttle plates. For flat-out esoteric and wild, find a 56 or 57 Adventurer 2x4bbl setup, and get an Adventurer grind on your cam if it will stand it. I would call Chris Nielson at Chris Nielson cams in Utah (contact him at and find out what he suggests. But be warned that you will most likely need to improve your valves and springs plus lifters with this stage of build. I speak from experience, as I have a 56 Adventurer, and it will wind to redline. Stock HP was advertised in 56 at 320, and in 57 with no changes but a 0.020 overbore at 345, so we suspect DeSoto lied about the power in 56 so as not to embaress the 300B. Double roller timing set from a 340 will bolt up, and only potential mod here is to narrow the thickness of the cam gear (depending on vendor) if you want to use your mechanical fuel pump. Electronic 318/340/360 distributors fit this engine if you cut the shaft and use a Hot Heads sleeve. Or you can load the electronic breaker plate/reluctor setup into the iron distributor for stealth setup and hide the box. I would definitely have exhaust valve seats installed for unleaded fuel. Have your heads pressure tested first, as DeSotos have a tendency to crack between the seats (I got a couple of those type heads I'm figuring out how to repair at the moment). You can use a 340 internal balance harmonic balancer, but need to get a new keyway broached to put the timing mark in the right spot and to make it the correct width. All in all, you can make a good reliable approximate 300HP with one of these motors on regular pump grade gas, and that 3.8" stroke will give you the best time you can have with your clothes on! Good luck.


Last changed: July 19, 2018