Stroked 340 vs Stroked 360

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JGC403

JGC403

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If a stroker 340 and stroker 360 were built exactly the same. Would there be a measurable power difference between the 2 engines? The 340 has smaller main journals than the 360, so I would think the 340 would have a slight advantage, but how much power would this equate to?
 
The advantage would only be slight and only if you were turning your stroker 8000 rpm. Most stroker don't see over 6500

360 is easier to find, cheaper.

Build what you have.
 
Eight cubic inches, 416 vs 408 would have to make some difference? Not much though.
 
Bearing speed, slight bore difference, a few cubes, etc......Slim to none. I actually think weather conditions or different dyno's would show more difference then the build itself. My thought goes back to the initial cost to obtain the building block? 99% of the time you'll spend way more for a 340 then a 360.
 
I figured there would be some measurable difference. I have seen other engine builds that the rods journals are small "Honda" size. But I guess that is for weight reduction to.


BrianT said:
Eight cubic inches, 416 vs 408 would have to make some difference? Not much though.
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Well if the engine is producing 1- 1.5 hp per cubic inch. Thats 8- 12 horsepower, lol.
 
Bigger bores always require less pressure to move the piston. In the case of a stroked motor we can't say that there's only 8 cubic inches of difference. Mainly because we're talking about the only difference here being diameter. That's where our comparison lies. In a 340 we have 102.49 square inches of piston area with a standard bore. In a 360 we have 100.48 square inches of piston area with a standard bore.
That's 2% more piston area so it will take 2% less pressure to do the same work at the crankshaft.
While not a lot we can put it into perspective. Would you like to add 2% to your car budget this year??
 
OP

If a stroker 340 and stroker 360 were built exactly the same. Would there be a measurable power difference between the 2 engines? The 340 has smaller main journals than the 360, so I would think the 340 would have a slight advantage, but how much power would this equate to?
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Then the bore size would be the same.

He is asking if the "Journal side" will make a difference.
I still say no.
 
Only real difference is the 340 block cost more to buy. But then you can say you have a 340 block which sounds cooler. Best choice is a roller cam 360 block.
 
Cudafever said:
OP



Then the bore size would be the same.

He is asking if the "Journal side" will make a difference.
I still say no.
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Exactly. I was just curious if the smaller bearings in the 340 would be a noticeable power advantage.
 
skrews said:
X2 on the 360 roller block

Real world power difference between 340 and 360 mainline dia. next to nothing.
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if that is indeed the case why do all race blocks use smaller/ 340 bearing size?
 
K.O. SWINGER said:
if that is indeed the case why do all race blocks use smaller/ 340 bearing size?
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Not all race blocks use the 340 main dia.
http://www.hughesengines.com/TechArticles/1ritterracingsmallblocks.php
here's a link about the Ritter block. Comes with 340 or 360 main line dia.

Most of the earlier race blocks were designed with the 340 mains, because back in the day most of the quality cranks were designed with 340 main size. This was because most of the people racing small blocks 20+ years ago used 340s (cuz dem dar 360s was nuttin but truck motors).
 
You will probably spend 5 to 10 times as much to buy a rebuild able 340 block for less displacement...why would you. Even if you already had the 340 - if it is not numbers matching sell the thing and finance the 360 stroker build..
 
I have a couple of 360s one running one not , I would be happy to trade them
straight across for any bodies 340s and then you can build your self a nice 360
stroker. yah whoo.
 
I thought a bigger bore unshrouds the valves more for a slightly better flow into the combustion chamber. Smaller main bearing should make for a slightly lighter crank. And you have 8 more cubic inches. I think theoretically those all are a benefit. How much?, seems to be very small, but each one is a tiny improvement.

I paid $200 for my std bore 340 block. Easier to find at the swap meet than a 360 or 360 LA roller block. There was another 340 block for $300 at the same Spring Fling swap meet.

Rod journals have a larger swing (reciprocating) weight on the crank. And can allow lighter rod too. So any weight there is more dramatic than in the center where the main journals are.

Would be cool if Scat made their cranks across the board with Chevy 2.100 rod journal style so we could run Chevy rods and save some money.
 
JGC403 said:
If a stroker 340 and stroker 360 were built exactly the same. Would there be a measurable power difference between the 2 engines? The 340 has smaller main journals than the 360, so I would think the 340 would have a slight advantage, but how much power would this equate to?
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built the same.........nill to none
 
360-based stroker main bearings will last a little longer since they're bigger. Chrysler engineers made them bigger for a reason, the longer stroke of a 360 puts more stress on the main bearings and that's only .27" more stroke than a 340 compared to .69" more for a 4" stroke. Of course we're talking 100,000-mile durability here, power-wise there's little difference.
 
the larger mains on a 360 are no longer a issue with bearing speed with the new oils out there. and back in the day when they were being raced competively this was still not a issue unless you were running circle track(sustained rpms at 7000 and higher). it still was not a issue if you ran a oil cooler and provided oil block mod that were still need for the 340 engine.if everything were built exactly the same a engine dyno could not see the difference,thats how small a difference a larger main make. there are instraments out there that could measure it but what a waist of time.save your self money and help a restoration and get a 360. or get a origanal 340 car and go faster then stock and you can say i have a 340 and your car is a 340 origanal.
 
Depends on the 340 block. If you can score a good deal on a 340 TransAm block, do so. This one has thicker webs to allow for 4-bolt mains.

One of the problems I have with the 360 vs 340 main discussion is that, at least in showroom trim, we never got to see a high compression 360 4 bbl with a forged crank. They also changed bore and stroke. So we have no good basis for comparison between the two in a factory HP configuration.

Over in the Chevy camp, the discussion is pretty much settled. The 327 was known as a high-winding runner. The bottom end was suspect. When Chevy came out with the 350 in 1967, it was essentially a stroked 327 with LARGER main journals. (FWIW: Chevy continued to use the 327 in 68-69 models but with a large journal crank.) This provided more power but also cleared up a lot of the bottom end problems.

Based on the Chevy experiences, I would think that a 360 would work better. However, the small journal LA does not have the gimpy bottom end reputation that the original mouse motor had, it may not be that big of a deal. Given that the upper end will be the same and cranks are the same except for main size, the ability to rev is going to be determined by the stroke and the balance that is necessary for the piston/rod combination that is used.
 
Forged cranks are heavier than cast. Build a 340 forged stroker and a 360 cast stroker, both internally balanced (strokers normally dont see very high RPM's) and Im thinking the lighter cast 360 would rap faster all other things considered. Not in the original question though.
 
pishta said:
Forged cranks are heavier than cast. Build a 340 forged stroker and a 360 cast stroker, both internally balanced (stokers normally dont see very high RPM's) and Im thinking the lighter cast 360 would rap faster all other things considered. Not in the original question though.
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you can buy a cast crank for the 340 mains also...only weight difference would be the bore size of the piston you choose....being that a 340 block has .040 larger bore from the get go.
 
I like my 340 with its super light Ross racing forged aluminum pistons.
 
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