Can someone explain to me exactly how a 383 and a 377 work
06-08-2002, 04:40 PM
#1
Registered User
Thread Starter
Join Date: Jan 2000
Location: Calgary, Ab, Canada
Posts: 731
Can someone explain to me exactly how a 383 and a 377 work
Hey guys. I know that basically a 383 is a 350 Chevy with a 3.75" Crankshaft. But, when you pick pistons, do you pick them for a 350, or are they 383 specific?
And a 377 is basically a 400 with a 3.48" crank. Now, for this motor, you need either spacer bearings to run the smaller journal OR an Eagle aftermaket 3.48" stroke crank for a 400, correct? What about pistons for this setup? And, I know that 400s sometimes have rod-cam clearance problems with 5.7" rods, do 377s as well or not 'cause of the smaller stroke.
And finally, the general rule is 383s and 406s like low and midrange 'cause that is where they make power, and I heard 377s dominated 4000 RPM and up over either of these motors. What about over a 350? Are these assumptions correct? I have decided to make most use of my .040 over 350 bottom end for now (got a solid roller cam to install into it, plus a few other things), but once that wares out, I am thinking ether 406, 383 or a 377. Thanks.
------------------
1981 Olds Delta 88 455/th400/3.23 posi
1988 Trans Am WS6, 355/T5/3.27 posi; RPM heads and Intake; Crane Fireball cam; Holley 750 carb; soon Comp RXE294H; th350 & 10" converter.
1994 Trans Am LT1/T56, no cat; Hooker CB; Hotch. SFC and STB; Ripper shifter; Poly mount; Lakewood LCA; K&N FIPK; Hypertech Airfoil; soon to port&polish MAF; Sprint springs & Bilstein shocks; GM Motive 4.10; Hypertech PowerTuner III
And a 377 is basically a 400 with a 3.48" crank. Now, for this motor, you need either spacer bearings to run the smaller journal OR an Eagle aftermaket 3.48" stroke crank for a 400, correct? What about pistons for this setup? And, I know that 400s sometimes have rod-cam clearance problems with 5.7" rods, do 377s as well or not 'cause of the smaller stroke.
And finally, the general rule is 383s and 406s like low and midrange 'cause that is where they make power, and I heard 377s dominated 4000 RPM and up over either of these motors. What about over a 350? Are these assumptions correct? I have decided to make most use of my .040 over 350 bottom end for now (got a solid roller cam to install into it, plus a few other things), but once that wares out, I am thinking ether 406, 383 or a 377. Thanks.
------------------
1981 Olds Delta 88 455/th400/3.23 posi
1988 Trans Am WS6, 355/T5/3.27 posi; RPM heads and Intake; Crane Fireball cam; Holley 750 carb; soon Comp RXE294H; th350 & 10" converter.
1994 Trans Am LT1/T56, no cat; Hooker CB; Hotch. SFC and STB; Ripper shifter; Poly mount; Lakewood LCA; K&N FIPK; Hypertech Airfoil; soon to port&polish MAF; Sprint springs & Bilstein shocks; GM Motive 4.10; Hypertech PowerTuner III
06-09-2002, 03:22 PM
#2
Registered User
Join Date: Sep 2001
Location: Lewiston, ID
Posts: 133
<font face="Verdana, Arial" size="2">Originally posted by IgorT.455/406:
Hey guys. I know that basically a 383 is a 350 Chevy with a 3.75" Crankshaft. But, when you pick pistons, do you pick them for a 350, or are they 383 specific?
get 383 pistons! if you put 350 pistons on a 3.75" crank, they'd stick .125" out of the block at TDC!
And a 377 is basically a 400 with a 3.48" crank. Now, for this motor, you need either spacer bearings to run the smaller journal OR an Eagle aftermaket 3.48" stroke crank for a 400, correct? What about pistons for this setup?
377 pistons. 350 pistons would be the right height, but they are .125" too small in diameter
I've never heard of a 350 crank with 400 mains, but that would work. Bearing spacers are only $50, and then you can use any standard-main 350 crank
And, I know that 400s sometimes have rod-cam clearance problems with 5.7" rods, do 377s as well or not 'cause of the smaller stroke.
383's also sometimes have problems with cam/rod interference. The issue is the length of the stroke - the longer stroke puts the rod big-end closer to the cam when the crank throw is straight up.
Thus, a 377 will have no more problem with rod/cam contact than a 350 would.
And finally, the general rule is 383s and 406s like low and midrange 'cause that is where they make power, and I heard 377s dominated 4000 RPM and up over either of these motors. What about over a 350? Are these assumptions correct? I have decided to make most use of my .040 over 350 bottom end for now (got a solid roller cam to install into it, plus a few other things), but once that wares out, I am thinking ether 406, 383 or a 377.
383/406 motors are longer stroke, so most people build them for lower rpm's to take it easier on the rods, pistons, piston rings, etc. That longer stroke means higher piston speeds, and more piston G's for the same rpm. They make more midrange power because that's how they are built.
People who build a 377 usually build it for high rpm's because it has a shorter stroke than a 383/406 (thus is easier on parts), but has more cubes than a 350.
Now, I know of people who have build 3.75" stroke motors to run at 8000rpm all day long. It isn't really that hard - good rod bolts, etc. It IS harder on the motor, but the SBC is more than up to it!
At the end of the day, what makes the most power is more cubes, and the highest RPM you can run them at. A 377 or a 383 will be just about even. The 377 does have the advantage of a larger bore, so you can run larger valves. Both a 383, and a 377 will give you more power than a 350 though.
BUT, an equally-built 406 will beat a 383, 377, or 350 any day. That's an extra 29 cubes there. About the same as going from a 355 to a 383.
If you have a choice between the three - get the 406!
Personally, I'd like a 6" rod 406! There are plenty of companies selling cam-clearanced rods out there that will clear most combos. with a longer rod, the piston is shorter, thus lighter (the longer rod is also heavier, but the weight savings from the piston more than offset this). With some lightweight KB pistons, light tool-steel wristpins, and 6" rods, you can make a heck of a light 406 rotating assembley.
Then stick some AFR 220 heads on top with a solid roller, tunnel-ram intake, and some big headers.
That's a recipie for some serious power! Don't worry about the tunnel-ram killing the low-end. A 406 has low-end torque to spare!
[/B]</font>
Hey guys. I know that basically a 383 is a 350 Chevy with a 3.75" Crankshaft. But, when you pick pistons, do you pick them for a 350, or are they 383 specific?
get 383 pistons! if you put 350 pistons on a 3.75" crank, they'd stick .125" out of the block at TDC!
And a 377 is basically a 400 with a 3.48" crank. Now, for this motor, you need either spacer bearings to run the smaller journal OR an Eagle aftermaket 3.48" stroke crank for a 400, correct? What about pistons for this setup?
377 pistons. 350 pistons would be the right height, but they are .125" too small in diameter
I've never heard of a 350 crank with 400 mains, but that would work. Bearing spacers are only $50, and then you can use any standard-main 350 crank
And, I know that 400s sometimes have rod-cam clearance problems with 5.7" rods, do 377s as well or not 'cause of the smaller stroke.
383's also sometimes have problems with cam/rod interference. The issue is the length of the stroke - the longer stroke puts the rod big-end closer to the cam when the crank throw is straight up.
Thus, a 377 will have no more problem with rod/cam contact than a 350 would.
And finally, the general rule is 383s and 406s like low and midrange 'cause that is where they make power, and I heard 377s dominated 4000 RPM and up over either of these motors. What about over a 350? Are these assumptions correct? I have decided to make most use of my .040 over 350 bottom end for now (got a solid roller cam to install into it, plus a few other things), but once that wares out, I am thinking ether 406, 383 or a 377.
383/406 motors are longer stroke, so most people build them for lower rpm's to take it easier on the rods, pistons, piston rings, etc. That longer stroke means higher piston speeds, and more piston G's for the same rpm. They make more midrange power because that's how they are built.
People who build a 377 usually build it for high rpm's because it has a shorter stroke than a 383/406 (thus is easier on parts), but has more cubes than a 350.
Now, I know of people who have build 3.75" stroke motors to run at 8000rpm all day long. It isn't really that hard - good rod bolts, etc. It IS harder on the motor, but the SBC is more than up to it!
At the end of the day, what makes the most power is more cubes, and the highest RPM you can run them at. A 377 or a 383 will be just about even. The 377 does have the advantage of a larger bore, so you can run larger valves. Both a 383, and a 377 will give you more power than a 350 though.
BUT, an equally-built 406 will beat a 383, 377, or 350 any day. That's an extra 29 cubes there. About the same as going from a 355 to a 383.
If you have a choice between the three - get the 406!
Personally, I'd like a 6" rod 406! There are plenty of companies selling cam-clearanced rods out there that will clear most combos. with a longer rod, the piston is shorter, thus lighter (the longer rod is also heavier, but the weight savings from the piston more than offset this). With some lightweight KB pistons, light tool-steel wristpins, and 6" rods, you can make a heck of a light 406 rotating assembley.
Then stick some AFR 220 heads on top with a solid roller, tunnel-ram intake, and some big headers.
That's a recipie for some serious power! Don't worry about the tunnel-ram killing the low-end. A 406 has low-end torque to spare!
[/B]</font>
06-11-2002, 08:17 AM
#3
Guest
Posts: n/a
A 377 is a standard 350cid (4.00") bore, with a 3.75" stroke.
A 383 is a 0.030" over bore (4.030") with a 3.75" stroke.
Either way you have to get new pistons otherwise the piston will come out the top of the cylinder due to the increased stroke.
-Dave C. '97 Z28
A 383 is a 0.030" over bore (4.030") with a 3.75" stroke.
Either way you have to get new pistons otherwise the piston will come out the top of the cylinder due to the increased stroke.
-Dave C. '97 Z28
06-11-2002, 09:01 AM
#4
Registered User
Join Date: Apr 2002
Location: Chi-town
Posts: 183
<font face="Verdana, Arial" size="2">Originally posted by Dave C. '97 Z28:
A 377 is a standard 350cid (4.00") bore, with a 3.75" stroke.</font>
A 377 is a standard 350cid (4.00") bore, with a 3.75" stroke.</font>
06-12-2002, 10:23 PM
#5
Registered User
Join Date: May 2001
Location: Fullerton, CA, USA
Posts: 202
Most of the time when people refer to a "383" motor, it means they have increased the stroke on a 350 small block and bored it over .030" to achieve approximately 383 cubic inches. <B>Most</B> of the time when someone refers to a 377 cubic inch chevy, they are talking about a de-stroked 400 using a 350 crank with spacer bearings or an aftermarket piece with the larger journals.
06-13-2002, 07:11 PM
#6
Registered User
Join Date: Feb 2002
Location: Houston, TX USA
Posts: 706
The piston you buy will depend on the rod length you settle on
A budget 383 using the 400 crank and 5.65 rods uses off the shelf 350 pistons for whatever bore you are using
you also have the choice of 5.7, 5.85 or 6" rods, which all take different pistons, it depends on what rod ratio you want. Normally, on two or three of the rod bolts come close to the cam.. if you use aftermarket rods with cap screws they will usually clear, you can also run a small base circle cam for more clearance
A 377 has the same bore/stroke ratio as the old 327, so it likes to rev, but you have the added cubes, so it will make more torque than a 350..but usually not as much as a 383. But it all depends on your cam, heads, intake, compression and about a milion other things. Car Craft did a comparison a couple years ago, built two identical motors, same everything, except the bore and stroke. One 377 and one 383.. the power difference was a wash, within the variables of the dyno. But, if each was optimized for it's bore/stroke, then who knows? Just remember, that torque moves the car.. horsepower is a fictional number that is calculated from the torque x rpm curve. HP sells magazines, but torque wins races..
------------------
Texlurch - 68 Camaro (Just a little ol' LT1 with a Hot Cam, I SWEAR
" a little spray never hurt anyone, spank you very much!"
or the old standby:"I came here to race, not sell real estate. You ain't scared, is ya?"
A budget 383 using the 400 crank and 5.65 rods uses off the shelf 350 pistons for whatever bore you are using
you also have the choice of 5.7, 5.85 or 6" rods, which all take different pistons, it depends on what rod ratio you want. Normally, on two or three of the rod bolts come close to the cam.. if you use aftermarket rods with cap screws they will usually clear, you can also run a small base circle cam for more clearance
A 377 has the same bore/stroke ratio as the old 327, so it likes to rev, but you have the added cubes, so it will make more torque than a 350..but usually not as much as a 383. But it all depends on your cam, heads, intake, compression and about a milion other things. Car Craft did a comparison a couple years ago, built two identical motors, same everything, except the bore and stroke. One 377 and one 383.. the power difference was a wash, within the variables of the dyno. But, if each was optimized for it's bore/stroke, then who knows? Just remember, that torque moves the car.. horsepower is a fictional number that is calculated from the torque x rpm curve. HP sells magazines, but torque wins races..
------------------
Texlurch - 68 Camaro (Just a little ol' LT1 with a Hot Cam, I SWEAR
" a little spray never hurt anyone, spank you very much!"
or the old standby:"I came here to race, not sell real estate. You ain't scared, is ya?"
06-13-2002, 08:31 PM
#7
Registered User
Join Date: Sep 2001
Location: Lewiston, ID
Posts: 133
<font face="Verdana, Arial" size="2">Originally posted by texlurch:
A 377 has the same bore/stroke ratio as the old 327, so it likes to rev</font>
A 377 has the same bore/stroke ratio as the old 327, so it likes to rev</font>
Really, a fully optimized 377 should be able to make more power/cube than a 383, because ther larger bore allows bigger valves, and more airflow.
Thread
Thread Starter
Forum
Replies
Last Post
dbusch22
Forced Induction
6
10-31-2016 11:09 AM