360 to 408, or 340 to 410?

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The bigger bore helps unshroud the valves but if your
using a 2.02 valve it doesnt matter... I use 340
blocks because all my stuff has the small mains...
I went with a 416ci for my street/strip

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Use which ever one you want, for what your doing there won't be a nickel's worth of difference. My 408 made around 550 hp, there is no way I would've noticed any difference if it had been built on a 340 block. Build it and enjoy, 4" motors are a hoot.

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If you have an uncut 340 and the bores clean-up at .020 you wind up with a standard 4.06" bore which has lots and lots more piston and ring pack choices readily available. Plus you get to save the block for additional incremental bores later...If I can I go 4.06 I will and I'll save for a possible need for 4.07 down the road.

Valve shrouding is IMO more of a concern on Big block Mopar Wedges than on small blocks due the SB superior valve angle, on-center valve/bore placement, the limiting factor on SBM's is generally port cross section and pushrod pinch shrouding.

all else being equal a 340 stroker will have a bit less frictional losses at the mains due to its' smaller bearing diameter....a 360 will also be a bit heavier due to those thicker crank mains (steel is heavier than cast iron)

360s are a lot more plentiful though

As for why mopar went to a 360 instead of just a 4" bore 318 block, I suspect cost cutting with the longer 3.58 stroke allowed for cheaper but still strong cast crank production and external balancing saving millions ofver the mass production multi-year run of the engine. As evidence of that, (to my knowledge) there was never a steel or internally balanced 360 made. The 360 was also intended as a gap bridger for trucks and the big C bodys between the 318 and the (was 383, now 400).

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also thought there was a SCCA / NASCAR cubic inch rule change involved there. The 340 was always touted as the "performance engine", mostly because of when it came on board (1970)and of course the performance options available. When the 360 showed up ( 1971 - with a 2-barrel only ) the performance party was on the way out. On the market, that 340 is probably worth 2-3 times what the 360 is worth.

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I would look at it this way...
start shopping for a crank.. look for the best deal.. and depending if its a large main or small main that would dictate which block you use..
yr back I had a 340 block I sold off to use the money to build a 385 cui class rule engine.
and planned on using a early 360 block.
as soon as I sold off the 340 block all I could find deals on for cranks was for 340 mains..
some killer deal on a k1 3.79 stroke crank came available but It was a 340 main..
I didn't have the 340 anymore so couldn't take advantage of the killer crank deal.
shop for a crank first ....that will dictate which block to use.
that's my

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Stroker kit prices for both engines is almost identical ( 360 is actually a little less - Hughes engines prices ). Shopping for used stroker cranks will show no advantage ( one engine over the other) either. Selling the 340 and building the 360 will definitely net you a $ advantage for your shopping fun. Did I mention the smaller bore of the 360 will have less friction than the larger bore 340. The larger main journal on the 360 will have more journal overlap making it stiffer. Since none of this is much of a concern with the OP's application and very difficult to measure, it gets down to $ - which is definitely measureable - IMO. Did I mention that I have a stock journal size ( E58 motor ) 360 crank for sale?

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I think it all comes down to personal preference. I have one of each, and I have decided that if I build anymore stock block strokers, they will be 360 main.

Definitely get with Rod Bloomer, BPE on here. His stuff is top notch!

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