383 magnum versus 383 big block

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qkcuda

qkcuda

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I have been thinking about building a reliable street engine for a heavy car, running A/C, power steering and brakes, throttle body fuel injection, and some form of O/D transmission. I used to run a 400 with a 222/234 cam, pocket ported heads (250 cfm), dual plane intake, 1 3/4 headers. It made 415 HP and 450 TQ, and was a nice street motor. If you put a 4 inch stroker crank in a 318 magnum you are right about 383 cubes. I am wondering about how the right combo would compare with the big block 383. I am thinking EQ heads or Eddies, but no idea on cam choice. The beauty of the magnum is factory roller lifters and the ability to use a factory O/D transmission. For the purposes of the discussion, I want it to be a 383, so don't say why not use a 360 block for more cubes..
 
Yes I agree the big block has more ultimate power potential. I just wondered if the long stroke small block might be more efficient, with the small bore and high velocity heads, while achieving the same power levels? I learned form my stroker big block that torque is what to look for on the street.
 
Interesting comparison. The cubes being very close between the two I would bet on the stroked 318 for the street but I plugged in some generic pieces into the desktop dyno and got almost the same hp and torque between the two. It's a wash!
 
toolmanmike said:
Interesting comparison. The cubes being very close between the two I would bet on the stroked 318 for the street but I plugged in some generic pieces into the desktop dyno and got almost the same hp and torque between the two. It's a wash!
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That's what I was thinking. Where did the torque peak on the two engines?
 
There was an article many years ago talking about this very issue. The bottom line was that it comes down to volumetric efficiency. Basically, cubes matter, and the rest is "tuning" for application. A small block vs big block, cube for cube, will have the same potential as long as the engine can breath. "Where" it makes is power is a discussion, but you all probably know book loads more about that than I do.
 
qkcuda said:
That's what I was thinking. Where did the torque peak on the two engines?
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The 318/390 torque was at 3500. The 383 was at 3000. The torque and horsepower was almost identical at 2000 rpm where you start accelerating on the street wit the 318/390 having 3 lb/ft more.
 
toolmanmike said:
The 318/390 torque was at 3500. The 383 was at 3000. The torque and horsepower was almost identical at 2000 rpm where you start accelerating on the street wit the 318/390 having 3 lb/ft more.
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Interesting, I might have thought it the other way around, with the long stroke engine having the lower torque peak.
 
It doesn't show up in the dyno numbers, but overall a LA small block will have roughly 75 less pounds to haul around than a low deck big block!
 
qkcuda said:
Interesting, I might have thought it the other way around, with the long stroke engine having the lower torque peak.
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Long stroke, more torque at a lower rpm.
 
toolmanmike said:
Long stroke, more torque at a lower rpm.
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So at what point does the rod length to stroke issue come into play? My understanding is a longer rod, "dwells" at TDC and BDC longer affecting cam choices, but I'm not sure in what way exactly. Thoughts?
 
qkcuda said:
The beauty of the magnum is factory roller lifters and the ability to use a factory O/D transmission.
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I think you answered your question right there.

I'm kicking myself with my truck for that reason alone, I went 460 (Ford) for displacement (low end torque) where a 408 Windsor (or Cleveland) would have given me an overdrive and roller cam options.
 
dano said:
I think you answered your question right there.

I'm kicking myself with my truck for that reason alone, I went 460 (Ford) for displacement (low end torque) where a 408 Windsor (or Cleveland) would have given me an overdrive and roller cam options.
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Clevelands are the bomb
 
toolmanmike said:
Interesting comparison. The cubes being very close between the two I would bet on the stroked 318 for the street but I plugged in some generic pieces into the desktop dyno and got almost the same hp and torque between the two. It's a wash!
Click to expand...
my question would be... whats the compression like on that small block to get those numbers in comparison to the B series 383?

I would actually say go with the Big Block 383 is the power level is going to be the same. The big block is gonna be making the same power, with less stress and less cost than the 318 stroked., in theory anyway.
 
dukeboy_318 said:
my question would be... whats the compression like on that small block to get those numbers in comparison to the B series 383?

I would actually say go with the Big Block 383 is the power level is going to be the same. The big block is gonna be making the same power, with less stress and less cost than the 318 stroked., in theory anyway.
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I used 9.5/1 as a baseline for both.
 
dukeboy_318 said:
my question would be... whats the compression like on that small block to get those numbers in comparison to the B series 383?

I would actually say go with the Big Block 383 is the power level is going to be the same. The big block is gonna be making the same power, with less stress and less cost than the 318 stroked., in theory anyway.
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From an economy standpoint, I depends what the engine is replacing. Small block out, small block in would be pretty simple. If you switch to big block, the cost will add up quick.
 
toolmanmike said:
From an economy standpoint, I depends what the engine is replacing. Small block out, small block in would be pretty simple. If you switch to big block, the cost will add up quick.
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true, but it also depends on what is done to the big block.

a stroked 318, bored and all the parts and such, especially a grand in the heads alone, all adds up too. Where as if you're taking a stockish 383 with maybe a small cam and intake upgrade, but with the stock heads and making the same power, then that grand from the heads, goes towards the transmission adapter plate and cooling. it becomes mute.
 
toolmanmike said:
Yes, Stock heads on the stroker as well but with 383 size valves.
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can you fit Big Block sized valves in a small block head? I would think the bore size would limit that on the 318
 
dukeboy_318 said:
Ahh, i assumed you went with the Eddy heads he stated he was going to put on the stroker.
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D Dyno doesn't have much for specifics there. I would have to look up all the specs and build a head to mimic the Edelbrocks. I just used "2 valve,open chamber, wedge,low performance,stock ports"
 
dukeboy_318 said:
can you fit Big Block sized valves in a small block head? I would think the bore size would limit that on the 318
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I used 1.800 int. 1.600 exhaust valves. I didn't look up the stock 383 valve size. Their intakes are possibly closer to 2.000" but I might be suprised.
 
ran a b383 in my dart , no issues . a little nose heavy . had air but the rad clearance and my clutch fan would not clear it . so i backed off the air , and never looked back .
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toolmanmike said:
I used 1.800 int. 1.600 exhaust valves. I didn't look up the stock 383 valve size. Their intakes are possibly closer to 2.000" but I might be suprised.
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383, depending on the head castings, should have a 2.08 and at minimum a 1.74 exhaust, except for the early heads which were a 1.60 exhaust.
 
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