377 vs 383
#1
377 vs 383
I am going to do a rebuild next year, my best friend who has been building cars his entire life suggested I do a 377 vs a 383 on my 86. His reasoning was that the 377 is more efficient and reliable than the 383. Im curios about the feedback from the corvette community...
#2
Drifting
If the 377 is a 400 block with a 350 crank, why ? Just go 400 and be done with it. A 383 can be built out your block or a common 350 core. That 377 is an aftermarket block to start with and cost goes up from there. Build (or buy) what you want but a 383 is a great value.
#3
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#4
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St. Jude Donor '05
Destroking any street car is kind of going backwards. That longer stroke is what pushes you back in the seat.
Last edited by cv67; 02-03-2019 at 02:42 PM.
#6
Drifting
The 383 as must know is taking a 350 and putting a 400 crank. Both of the above replies are correct, since both the 350 and the 400 are on the same archetecture, once you take a 350 and put a 400 crank in it, it is just a bore difference form being a 400. There are difference in the blocks overall, so you can't just bore your 350 .120" over.
You end up with a 377 because the block isn't bored. A 350 with a 400 crank is a 377 (376.8)... .030 over bore = 383 (382.47).
a .030 is pretty standard and common. When a 350 is rebuilt, this is a common re-bore size and net a 355. Shouldn't be cause for concern.
Typically as the bore to stroke ratio goes up, you make more HP. Longer stroke is more torque.... this is for motors with relatively the same displacement as shorter stroke motors tend to like to rev higher since the piston doesn't have to accelerate as much per stroke.
All things being equal, the 383 should make more average torque and HP across the RPM range due to the added displacement. What is his reasoning to say it is more "efficient". More fuel efficient, or makes more power?
I don't want to insult your best friend, but there is a difference between an opinion from someone putting things together for a long time that work... even those that work well, and a well researched, tested, and documented fact.
You end up with a 377 because the block isn't bored. A 350 with a 400 crank is a 377 (376.8)... .030 over bore = 383 (382.47).
a .030 is pretty standard and common. When a 350 is rebuilt, this is a common re-bore size and net a 355. Shouldn't be cause for concern.
Typically as the bore to stroke ratio goes up, you make more HP. Longer stroke is more torque.... this is for motors with relatively the same displacement as shorter stroke motors tend to like to rev higher since the piston doesn't have to accelerate as much per stroke.
All things being equal, the 383 should make more average torque and HP across the RPM range due to the added displacement. What is his reasoning to say it is more "efficient". More fuel efficient, or makes more power?
I don't want to insult your best friend, but there is a difference between an opinion from someone putting things together for a long time that work... even those that work well, and a well researched, tested, and documented fact.
Last edited by KyleF; 02-03-2019 at 02:56 PM.
#7
Le Mans Master
…… A Wise Old Man (the wise part rules me out) once said " There is NO Replacement for Displacement" … I believe him ! …..
<<<<< 421 <<<<<
<<<<< 421 <<<<<
Last edited by C409; 02-03-2019 at 07:55 PM.
#8
Race Director
377s are used more for racing applications where the motor needs to wind and maintain higher revs for instance coming into and out of turns. For a street car, a 383 is the practical way to go. A buddy of mine ran a 377 for the strip. That thing was fast and could really spin.
#9
Le Mans Master
The 383 as must know is taking a 350 and putting a 400 crank. Both of the above replies are correct, since both the 350 and the 400 are on the same archetecture, once you take a 350 and put a 400 crank in it, it is just a bore difference form being a 400. There are difference in the blocks overall, so you can't just bore your 350 .120" over.
You end up with a 377 because the block isn't bored. A 350 with a 400 crank is a 377 (376.8)... .030 over bore = 383 (382.47).
You end up with a 377 because the block isn't bored. A 350 with a 400 crank is a 377 (376.8)... .030 over bore = 383 (382.47).
To the OP, there's no difference between the two engines in reliability or efficiency. There's been talk over the years that the 400 could suffer cooling issues due to its siamesed bores. It appears that this is not really true, however, based on the many people who have used it successfully.
PS - C409, is your engine a 400 bored 0.040 over?
#11
Platinum Supporting Vendor
It all depends on what RPM he wants to run. If you are wanting to go RPM then big piston short stroke is the way to go. There is a limit to the piston speed so there are physics at play in engine building, you can't just go huge bore and stroke and then decided you want to be able to rev it to the moon. For the street, you can't beat a 383 or 406.
#12
Le Mans Master
It all depends on what RPM he wants to run. If you are wanting to go RPM then big piston short stroke is the way to go. There is a limit to the piston speed so there are physics at play in engine building, you can't just go huge bore and stroke and then decided you want to be able to rev it to the moon. For the street, you can't beat a 383 or 406.
Last edited by MatthewMiller; 02-04-2019 at 09:18 AM.
#13
Race Director
It's true that there are differences in piston speeds at a given rpm between the two builds, due to their strokes of 3.5" (377) and 3.75" (383). But that doesn't cause any practical limitation on rpm. The limitations to engine speed are always going to be found in the valvetrain first, .
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Melting Slicks
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#16
Le Mans Master
Right, a 383 and a stock 400 both use the same crank with a 3.75" stroke. All I can say is that the empirical evidence suggests that in the year 2019, there are plenty of engines with much longer strokes than 3.75" that are revving to the moon. As Tom mentioned, plenty of 3.75" SBCs rev safely way above 8000rpm. Chevy's own LS7 had a 4" stroke and came in mass-produced vehicles with a 7000rpm redline and a warranty. And companies like HPR routinely sell LS engines with 4.25" strokes (and more!) that can safely go past 8000rpm.
There's simply no good reason for a 3.75"-stroke engine to be rpm-limited by its rotating assembly. This obviously depends on the parts one specifies: a stock 400 rotating assembly isn't good for 8000rpm, but then neither is a stock 350 rotating assembly. I'm going out on a limb to suggest that any build the OP is considering would not entail rpms that a stock 400 rotating assembly couldn't handle. It's probably going to be kept to a 6000rpm redline, and that is uber-safe for any of these assemblies.
There's simply no good reason for a 3.75"-stroke engine to be rpm-limited by its rotating assembly. This obviously depends on the parts one specifies: a stock 400 rotating assembly isn't good for 8000rpm, but then neither is a stock 350 rotating assembly. I'm going out on a limb to suggest that any build the OP is considering would not entail rpms that a stock 400 rotating assembly couldn't handle. It's probably going to be kept to a 6000rpm redline, and that is uber-safe for any of these assemblies.
#17
Drifting
Right, a 383 and a stock 400 both use the same crank with a 3.75" stroke. All I can say is that the empirical evidence suggests that in the year 2019, there are plenty of engines with much longer strokes than 3.75" that are revving to the moon. As Tom mentioned, plenty of 3.75" SBCs rev safely way above 8000rpm. Chevy's own LS7 had a 4" stroke and came in mass-produced vehicles with a 7000rpm redline and a warranty. And companies like HPR routinely sell LS engines with 4.25" strokes (and more!) that can safely go past 8000rpm.
There's simply no good reason for a 3.75"-stroke engine to be rpm-limited by its rotating assembly. This obviously depends on the parts one specifies: a stock 400 rotating assembly isn't good for 8000rpm, but then neither is a stock 350 rotating assembly. I'm going out on a limb to suggest that any build the OP is considering would not entail rpms that a stock 400 rotating assembly couldn't handle. It's probably going to be kept to a 6000rpm redline, and that is uber-safe for any of these assemblies.
There's simply no good reason for a 3.75"-stroke engine to be rpm-limited by its rotating assembly. This obviously depends on the parts one specifies: a stock 400 rotating assembly isn't good for 8000rpm, but then neither is a stock 350 rotating assembly. I'm going out on a limb to suggest that any build the OP is considering would not entail rpms that a stock 400 rotating assembly couldn't handle. It's probably going to be kept to a 6000rpm redline, and that is uber-safe for any of these assemblies.
Physics dictates that it is easier on a block and rotating assembly to have a shorter stroke if you want to rev high. This also has less inertial losses as with the pistons moving and accelerating less, less power is consumed to move them. GM did not start with a blank slate. They started with their LS architecture. All products of mass production are a result of a series of compromises. I suggest you read the book "Car guys vs. Bean Counters" by Bob Lutz. Just because it is built, doesn't mean it is the best way to do it.
I didn't see anywhere in the thread that anyone said a SBC couldn't spin to 8000RPMs either. You are making your own issue to debate. A properly built and balanced SBC should be able to rev to 8000RPMs and not spontaneously explode. Doesn't mean it will be as reliable over years of service as one that stops at 6500RPMs.
Last edited by KyleF; 02-04-2019 at 04:46 PM.
#18
Team Owner
Pro Mechanic
You are glossing over why. You are also glossing over the fact that a lot cars have long term issues that do not show up when they are fairly new. The 3000GT/Dodge Stealth come to mind. The output shafts from the transmission to the transfer case almost always eventually fail. Same with opti sparks, the ash tray lid on Fox Body 'Stangs, Spark Plugs breaking in Triton heads, dash pads cracking, electronic dashes going out...this list goes on. With enough age and miles weak links show up that may never be an issue in the first 5-10 years of ownership.
Physics dictates that it is easier on a block and rotating assembly to have a shorter stroke if you want to rev high. This also has less inertial losses as with the pistons moving and accelerating less, less power is consumed to move them. GM did not start with a blank slate. They started with their LS architecture. All products of mass production are a result of a series of compromises. I suggest you read the book "Car guys vs. Bean Counters" by Bob Lutz. Just because it is built, doesn't mean it is the best way to do it.
I didn't see anywhere in the thread that anyone said a SBC couldn't spin to 8000RPMs either. You are making your own issue to debate. A properly built and balanced SBC should be able to rev to 8000RPMs and not spontaneously explode. Doesn't mean it will be as reliable over years of service as one that stops at 6500RPMs.
#19
Le Mans Master
You are glossing over why. You are also glossing over the fact that a lot cars have long term issues that do not show up when they are fairly new. The 3000GT/Dodge Stealth come to mind. The output shafts from the transmission to the transfer case almost always eventually fail. Same with opti sparks, the ash tray lid on Fox Body 'Stangs, Spark Plugs breaking in Triton heads, dash pads cracking, electronic dashes going out...this list goes on. With enough age and miles weak links show up that may never be an issue in the first 5-10 years of ownership.
Physics dictates that it is easier on a block and rotating assembly to have a shorter stroke if you want to rev high. This also has less inertial losses as with the pistons moving and accelerating less, less power is consumed to move them.
I didn't see anywhere in the thread that anyone said a SBC couldn't spin to 8000RPMs either. You are making your own issue to debate. A properly built and balanced SBC should be able to rev to 8000RPMs and not spontaneously explode. Doesn't mean it will be as reliable over years of service as one that stops at 6500RPMs.
#20