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355 vs. 377 or even 377 vs 406 SBC?

 
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Lil_Jimmy_John
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1992 Chevrolet Blazer

PostPosted: Mon Jun 02, 2008 9:37 pm    Post subject: 355 vs. 377 or even 377 vs 406 SBC? Reply with quote

Just a question Ive been asking myself? If one had two engines,,,a 377 and a 355, Identical internals ( compresion, cam, heads ect...) Only difference here would be the bore size. What would the difference be in HP and Torque #'s? at say 6500 rpm. Would the the 377 make more power from the difference in bore size alone? Or change it up a little bit....Same deal 377 or 406? would the 406 make more power only because the stroke is longer? Often wondered..never asked!! Lets hear what you think guys.
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af2
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1933 Willys Coupe

PostPosted: Mon Jun 02, 2008 9:56 pm    Post subject: Reply with quote

At 6500 the 400 wins hands down. At 8500 the 377 will shine. Very Happy
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clay
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PostPosted: Tue Jun 03, 2008 12:07 am    Post subject: Reply with quote

I would say cubic inches always wins. 377 has 37 c.i. over the 350 plus the bigger bore size. All things being equal, I would expect the 377 to have 35 - 40 more h.p. than a 350. The 406 has 29 more c.i. than a 377 and the same bore size so I would expect around 30 - 35 more h.p. I know at some point that parasitic losses increase to a point of diminishing returns on stroke increases, but there isn't really a drastic difference in the strokes. A more interesting test I have seen is a 377 vs. a 383. They used the same compression, same cam, same heads, intake, carb, headers, etc. The trend you would expect was there, but it was very subtle. The 383 made 3 - 5 more ft. lbs. torque in the lower rpm ranges and the 377 made 3 - 5 more h.p. in the upper rpm ranges. Now sure you could change cam, intake, headers, etc. to help each combination show it's true characteristics, but this was a bore vs. stroke test and it was pretty good. Clay
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af2
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1933 Willys Coupe

PostPosted: Tue Jun 03, 2008 12:17 am    Post subject: Reply with quote

That is very true! But the cam was the same. Confused The best thing with the 377 is cam it. 383 will be close with a 400 lobe. Rpm is the main difference! Cool
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squeeezer
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PostPosted: Tue Jun 03, 2008 8:34 am    Post subject: Reply with quote

im pretty sure i have a book with that same comparo
and they reved to what 6500 or 6700
did they use street friendly mid port tfs heads and cam

anyway who would build a street 377??????

it would have been a sweet test with more aggressive comp ratio heads cam etc.

for the street the 383 in that comparo was the victor imo
build a purpose built 377 and it wouldnt be a street motor
and if you want to unshroud the valves for the street build a 406

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Big Dave
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PostPosted: Wed Jun 04, 2008 4:48 pm    Post subject: Reply with quote

AF2 nailed it! Horse power is a derived figure; which is torque applied over time. The higher you can wind a motor the more power the shorter stroke motor can bring to the table. This is because RPM has minutes being the deciding factor. The more strokes (even though it isnít making as much energy per cycle as the longer stroked engine), it is overwhelming the longer stroke engine by making more cycles in a given unit of time.

This is why a 500 cubic inch Pro Stock motor shifts at 10,000 RPM. They could have chosen to run a 4.5" stroke instead of a 3.4" stroke. They chose the shorter stroke and make up for the lack of swept cylinder displacement offered by the longer stroke by choosing a monster bore.

Big Dave
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96capriceMGR
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PostPosted: Wed Jun 04, 2008 7:15 pm    Post subject: Reply with quote

The "there's no replacement for displacement" crowd is always fun, amazing the variety of excuses they come up with when a smaller motor done RIGHT mops them up. Shocked

Power is in the topend, the bottomend really only has to be able to handle the rpms needed to move that air.

Problem with bench racing is there are FAR more poorly spec'd/machined/assembled setups out there than good ones which makes it hard to compare things.
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10sec.et
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PostPosted: Wed Jun 04, 2008 9:42 pm    Post subject: Reply with quote

96capriceMGR wrote:
The "there's no replacement for displacement" crowd is always fun, amazing the variety of excuses they come up with when a smaller motor done RIGHT mops them up. Shocked



yeah, this n/a street driven show car would be much faster with a small block Rolling Eyes http://www.smokemup.com/bb/viewtopic.php?t=3969

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clay
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PostPosted: Thu Jun 05, 2008 12:17 am    Post subject: Reply with quote

Look at it this way, if you applied the same careful parts selection, assembly and tuning to a 377 or a 400 that you do to a 350, do you still think the 350 will make more power? I'm not saying that blindly adding cubic inches are the answer, other things have to go with them to gain the benefit. If we were talking about a 1" stroke difference like Big Dave said, there would be other factors to consider, but in the original question, I don't think 0.250" of stroke difference is huge. Bottom line, with the RIGHT person specing the parts and doing the tuning, I think the bigger motor will win every time. Clay
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af2
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1933 Willys Coupe

PostPosted: Thu Jun 05, 2008 12:17 am    Post subject: Reply with quote

Wait a minute! Laughing Never mind!!! Very Happy

A friend of mine runs a 355 and is 1 second behind my times and weighs 1000# more. FWITW Very Happy
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FRITODAVE
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PostPosted: Thu Jun 05, 2008 10:36 am    Post subject: Reply with quote

Power is in the topend, the bottomend really only has to be able to handle the rpms needed to move that air.


That is the key to unlock a performance/race engine.
96capriceMGR said it all.

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