Technical 331 Build Questions-

Alright- after much deliberation I'm leaning forward on building a 1955 331 (that was sold to me as a 354- just my luck lol). I have spoke with a couple reputable machine shops in the area and they don't seem to be very comfortable with boring the block the .125 it needs to be built as a 354, even after a sonic test. Now the way I see it, I have two main courses of action:

1- Find a shop that is comfortable with it and build it as a 354. I'd like to hit the magic 10:1 compression ratio that 73RR advises is optimal (I'd love to see some successful build sheets if possible from folks that have gone that route as I seem to still be drinking from a fire hose). Not necessarily looking to build a monster but would like a strong runner...

2- Build the 331... I've been advised by a few on here to go this route and see no issue with it other than this year had relatively low compression and I'd like to up it (again with a recipe for success so to speak) and end up with a strong runner. By no means am I rich but I'd like to do it right once and for all.

Appreciate the help guys- and I'm still reading all that is the hemi tech guide.
Nik

 

The piston walls of a 331 are pretty thick. I've had a 331 engine built recently its 60 over no issues with machine work but other minor issues I hope to have fixed by spring and then back to the dyno. Why not just bore what it needs though?
There is or was a 331 hemi build on the internet if you google 331 hemi build I think it will show up hot rodder magazine or something like that and shows the steps it took to get there. Good luck on the build.

 

I don't know why they have so much apprehension about it, both shops have been around for a while and build some great motors (they both have motors in cars on street outlaws). One of them was even going to be worried after a sonic test- thinking that the water jackets may have some deep rust pits that weren't picked up by the test. I'll look into that build- appreciate it greatly!

 

Minimal overbore equals the strongest block. It also means there is less chance of creating steam pockets which can lead to cooling issues.
There is very little to be gained by massive overbores, (ok, 23 inches) especially if you are planning to buy forged pistons and run the c/r up to 10.
The 331 truck block is the only exception in my book since it was usually cut from a 354 casting and has thicker walls to start with. Look for a large 'X' cast into the side near the core plug. However, there is still no advantage to cutting large amounts of metal when using forged pistons. A slightly warmer cam profile will easily make up the difference in 23 inches.
The biggest 'problem' with these blocks is core shift and it can be difficult to work around.

.

 

Do not guess at the wall thickness. I've had 331 blocks that would only (I.M.O.) safely go .030 over.
Core shift IS a problem. Not with just the bores either. I've seen a fair share of these early hemi engines with rust holes to the outside of the blocks. This problem is not isolated to just marine engines.

 

Do be conservative in boring. A smaller bore with the right pistons (C/R) will net you longevity insurance, and horsepower aplenty.
Agree in spades with @bostonhemi, @73RR, & TR Waters. Conservative is always the best route with street driven Hemis.

 

Unless you are planning to go racing in a class that requires the extra cubes, the difference in a warmed up 331 and a comparable 354 for street use is negligible. Both iterations will perform admirably in street use and still showcase the 'wow' factor of a hemi. Were it not for the latter, you may as well have a 'belly button' SBC 350/383/406. Cheaper, lighter and probably equally, or more, powerful, than a 354 in street form.

Now, bear in mind, the above comments come from a guy with several Dodge and Chrysler hemi engines, and NO sbc or bbc engines in my possession. But we need to maintain perspective.

Ray

 

LOL- well received guys. I was just trying to get a little more out of the 331, having never had any real experience with an early hemi. I'm NOT against building the 331 at all- just was hoping for some input and figured the best route was with some direct feedback. Appreciate it.

Off the wall question- this motor came with the powerflite (judging by the vents in the case/ bellhousing) transmission and I'm sick of tripping over it in the garage but don't want to scrap it. I know there are a ton of variables BUT what's it worth roughly? No idea on the condition other than it was working when it was pulled supposedly.

 

The powerflight is not worth much, it's a core really.

As for overbore, go with as little as you can. I've got a 392 and I'm avoiding over boring it by doing a rering and hone. It does t have enough wear to warrant punching it out. When it does wear enough I'll have enough meat to punch it, get new Pistons and drive it even more. If you bore it out to its max, once it wears the block is junk. Not worth it imo.