Notices
C4 General Discussion General C4 Corvette Discussion not covered in Tech

377 vs 383

 
Old 02-04-2019, 07:09 PM
  #21  
Cool Runnings
CF Senior Member
 
Cool Runnings's Avatar
 
Member Since: Jan 2017
Location: Minneapolis MN
Posts: 1,917
Thanked 35 Times in 34 Posts
Default

Originally Posted by C409 View Post
A Wise Old Man (the wise part rules me out) once said " There is NO Replacement for Displacement" I believe him ! ..


<<<<< 421 <<<<<
Turbos and Superchargers ..
Cool Runnings is online now  
Old 02-04-2019, 08:07 PM
  #22  
Vette5311
CF Senior Member
 
Vette5311's Avatar
 
Member Since: Mar 2018
Location: Golden Colorado
Posts: 1,010
Thanked 121 Times in 116 Posts
Default

Really should stick to OP original question. Throwing LS etc into it is apples and oranges. Different mains and many other items affect this. Keep it to 400 destroked or 350 stroker for comparisons. JMHO.
Vette5311 is offline  
Old 02-04-2019, 08:33 PM
  #23  
MatthewMiller
CF Senior Member
 
MatthewMiller's Avatar
 
Member Since: Aug 2015
Location: St. Charles MO
Posts: 1,984
Thanked 283 Times in 237 Posts
Default

Originally Posted by Vette5311 View Post
Really should stick to OP original question. Throwing LS etc into it is apples and oranges. Different mains and many other items affect this. Keep it to 400 destroked or 350 stroker for comparisons. JMHO.
Just trying to respond to absolutist statements that an engine with a 3.75" stroke can't possibly be as reliable as one with a smaller stroke. The fact is that we can make a short block reliable with any piston speed that's reasonably attainable in a SBC short block, especially for a street motor. I didn't even delve into the fact that for a given power, a bigger engine can hit the goal at a lower rpm and be more reliable than a smaller-stroke engine. But that's also the case. With extra displacement you can either make the same power more reliably or more power just as reliably.

As already noted, it would be stupid to destroke a 400 unless a race class's rules require a lower displacement limit. If the OP wants to keep his block and is willing to spring for a 3.75" crank, then he will definitely get more power and great reliability out of it. If he is willing/able to start his build with a 400 block, then by all means he should build it as a 400 (or go even bigger with a longer stroke). When seeking power, there is never, ever a case where more displacement isn't better as long as the rules allow it. I assume that the OP (who, btw, hasn't come back to his own thread in 35 hours) is just doing a street build, where rules don't apply. For him, a 377 is stupid. A 383 is good, a 396 is better, and a 400+ is even betterer.
MatthewMiller is online now  
Old 02-04-2019, 09:41 PM
  #24  
KyleF
CF Senior Member
 
Member Since: Jun 2018
Posts: 218
Thanked 17 Times in 17 Posts
Default

Originally Posted by Tom400CFI View Post
I'm wondering what the point is here? How does this relate to this thread? You are totally right; With enough age and miles weak links show up that may never be an issue in the first 5-10 years. Ayuh. But....(?)


Dtto here. What's this got to do with a 377 (destroked 400) vs. a 400 crank in a 350?


Who disputed that...or even brought it up? Talk about making your own issue to debate!

well I quoted the reference to the 8000 RPMS.

There is discussion up above about stroke vs. Bore and RPM.

Matthewmiller was stating his case based on the fact production cars have a certain capability, I was pointing out there have been lots of designs that work initially and don't stand the test of time.

Seem you have a bit of a problem. There is an ignore function. Feel free to use it.
KyleF is offline  
Old 02-04-2019, 09:44 PM
  #25  
KyleF
CF Senior Member
 
Member Since: Jun 2018
Posts: 218
Thanked 17 Times in 17 Posts
Default

Originally Posted by Cool Runnings View Post
Turbos and Superchargers ..
That does not replace displacement. When someone says "all things being equal" that is just what it means.
A supercharged 400 with the same heads, cam, pistons and so on as the supercharged 350 setting next to it will make more power.
KyleF is offline  
Old 02-05-2019, 12:43 AM
  #26  
Tom400CFI
CF Senior Member
 
Tom400CFI's Avatar
 
Member Since: Aug 2004
Location: Park City Utah
Posts: 13,808
Thanked 586 Times in 520 Posts
Default

Originally Posted by KyleF View Post

Seem you have a bit of a problem. There is an ignore function. Feel free to use it.
Likewise.

BTW, I'm quite problem free, but thanks for the free "diagnosis".
Tom400CFI is offline  
Old 02-05-2019, 12:46 AM
  #27  
383vett
CF Senior Member
 
383vett's Avatar
 
Member Since: Apr 2003
Location: moraga ca
Posts: 15,731
Thanked 657 Times in 486 Posts
Default

Originally Posted by Tom400CFI View Post
Doesn't a 383 have the same stroke as a 400? Aren't there 400's out there that rev decent/make good power/have a usable RPM range?
Yes Tom, they both have the same stroke, but a 400 has a lower stroke to bore ratio which allows it to rev higher.


Originally Posted by MatthewMiller View Post
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.
What you are not taking into account is stroke to bore ratio which is important in determining rpm limits and longevity of a motor. Sure a 427 has the same 3.75 stroke as a 383 and can rev to 7000. But its larger bore makes for a more square stroke to bore ratio allowing it to rev easier. An extreme example is a formula 1 motor. It can rev to 18,000 rpm because it's stroke is only 1.566" while it's bore is only about 1/8" smaller than a 350 block. This allows it to achieve 8000 hp with 2.4 liters. I'm not saying a 383 can't be made to rev to 8000rpm, but the bearing friction increases due to the speed and weight of the piston and reliability becomes compromised. That is why a 383 is considered a motor more for the street or heavy duty applications than a motor commonly found at the track. Don't get me wrong, I am in no way knocking a 383 motor; I ran one for years at the strip and shifted at 6200 rpm. I am now running a 406 and shifting at 6700.

Last edited by 383vett; 02-05-2019 at 12:51 AM.
383vett is offline  
Old 02-05-2019, 01:04 AM
  #28  
Tom400CFI
CF Senior Member
 
Tom400CFI's Avatar
 
Member Since: Aug 2004
Location: Park City Utah
Posts: 13,808
Thanked 586 Times in 520 Posts
Default

I don't see how the stroke to bore ratio affects longevity*. Piston speed, rod angle, side loading....is all about the same, for the same stroke (all else equal). Going from a 383 to a 400....how does the 400's bigger piston make it "more reliable" or longer lasting? Is a 350 more reliable or longer lasting than a 305? They both have the same 3.48" stroke, but the 350 has a better bore/stroke ratio. What am I missing, here?

*As it relates to this discussion. I "get it" that a short stroke engine -one with say, a 2" stroke is going to create less wear and stress at a given RPM...here we're talking about 383's and 400's...both of which have 3.75" stroke.

Last edited by Tom400CFI; 02-05-2019 at 01:25 AM.
Tom400CFI is offline  
Old 02-05-2019, 01:04 AM
  #29  
MatthewMiller
CF Senior Member
 
MatthewMiller's Avatar
 
Member Since: Aug 2015
Location: St. Charles MO
Posts: 1,984
Thanked 283 Times in 237 Posts
Default

Originally Posted by 383vett View Post
What you are not taking into account is stroke to bore ratio which is important in determining rpm limits and longevity of a motor. Sure a 427 has the same 3.75 stroke as a 383 and can rev to 7000. But its larger bore makes for a more square stroke to bore ratio allowing it to rev easier. An extreme example is a formula 1 motor. It can rev to 18,000 rpm because it's stroke is only 1.566" while it's bore is only about 1/8" smaller than a 350 block. This allows it to achieve 8000 hp with 2.4 liters. I'm not saying a 383 can't be made to rev to 8000rpm, but the bearing friction increases due to the speed and weight of the piston and reliability becomes compromised. That is why a 383 is considered a motor more for the street or heavy duty applications than a motor commonly found at the track. Don't get me wrong, I am in no way knocking a 383 motor; I ran one for years at the strip and shifted at 6200 rpm. I am now running a 406 and shifting at 6700.
The only thing that determines average piston speed is stroke and rpm. The rod length has a minor effect on peak piston speeds and acceleration. Bore has nothing to do with it at all. In fact, the engine with the bigger bore will have the heavier piston even if the rods are identical, so it will actually place more stress on the bearings and piston pin due to the higher reciprocating mass. Your 406 has the same stroke as your 383 did, so the piston speeds are the same for any given rpm.
MatthewMiller is online now  
Old 02-05-2019, 10:53 AM
  #30  
KyleF
CF Senior Member
 
Member Since: Jun 2018
Posts: 218
Thanked 17 Times in 17 Posts
Default

Originally Posted by Tom400CFI View Post
*As it relates to this discussion. I "get it" that a short stroke engine -one with say, a 2" stroke is going to create less wear and stress at a given RPM...here we're talking about 383's and 400's...both of which have 3.75" stroke.
Same stroke is the same piston speed at a given RPM, So no change. All the same loading except the piston weight. Looking at a bore to stroke ratio for reduced stresses wouldn't be between two different displacements utilizing the same stroke. It would be to say, as I mentioned above, there are two ways to get a 377.
350 block with a 400 crank or a 400 Block with a 350 crank. Same displacement, different stroke lengths.
The 350 with the 400 crank would lend itself to be a higher torque lower rpm motor
The 400 with the 350 crank would lend itself to be a higher horsepower engine that would rev easier.

That is not to say both couldn't run 7500-8000RPMs, both built well with quality parts and proper clearances should last.

There is the anecdotal reliability we all need. Which is will the motor serve us well and will not fail on us. Then there is reliability testing. Both engines mentioned are more than likely capable of lasting many years, hours, or miles of use. I would say, if both motors were put on a dyno and ran at 7500RPMs to failure, the 400 with a shorter stroke should last longer. However, I believe there are way too many variables long term that affect reliability other than just stresses on the bottom end. Especially in a boosted application where detonation can blow a hole through a piston. There are a lot of things that can go wrong and cause a motor failure. Neither a stroked 350 or destroked 400 are pushing the extremes where wither is failure prone. So if the destroked 400 can last 500K hours at 7500RPM and the stoked 350 can last 450K hours... are either a bad motor? No Are either considered prone to failure? No.
KyleF is offline  
Old 02-05-2019, 11:08 AM
  #31  
Tom400CFI
CF Senior Member
 
Tom400CFI's Avatar
 
Member Since: Aug 2004
Location: Park City Utah
Posts: 13,808
Thanked 586 Times in 520 Posts
Default

Originally Posted by KyleF View Post
Same stroke is the same piston speed at a given RPM, So no change. All the same loading except the piston weight. Looking at a bore to stroke ratio for reduced stresses wouldn't be between two different displacements utilizing the same stroke. It would be to say, as I mentioned above, there are two ways to get a 377.
350 block with a 400 crank or a 400 Block with a 350 crank. Same displacement, different stroke lengths.
Yes...I "get it". The reason I was asing ***** is b/c he said bore/stroke ratio, about a 383 and a 400. At least, that's the way I read his post. I couldn't understand where he was going w/that b/c they both have the same stroke. The more "favorable" bore/stroke ratio that the 400 has doesn't make it more reliable.


Originally Posted by KyleF View Post
There is the anecdotal reliability we all need. Which is will the motor serve us well and will not fail on us. Then there is reliability testing. Both engines mentioned are more than likely capable of lasting many years, hours, or miles of use. However, I believe there are way too many variables long term that affect reliability other than just stresses on the bottom end. Neither a stroked 350 or destroked 400 are pushing the extremes where wither is failure prone. So if the destroked 400 can last 500K hours at 7500RPM and the stoked 350 can last 450K hours... are either a bad motor? No Are either considered prone to failure? No.
Exactly. And I believe that is what MM was saying.

For the purpose of this discussion, the OP is fine with either. Destroking a 400 to a 377 for the sake of reliability is Worryin' about chit that ain't worth worryin' about. SO....if the OP's friend thinks that a 3.48 stroke 400/377 is going to be "more efficient and reliable" than a 3.75 stroke 350/383....then the friend is up in the night, and the OP should either:
1. reuse the 350 block that he already has or
2. take that same 400 block that he would have to acquire to build the 3.48 stroke 377 and build a 3.75 stroke 400 and enjoy ALL 400 cubes, for a long, long time.


.

Last edited by Tom400CFI; 02-05-2019 at 11:09 AM.
Tom400CFI is offline  
Old 02-05-2019, 11:45 AM
  #32  
383vett
CF Senior Member
 
383vett's Avatar
 
Member Since: Apr 2003
Location: moraga ca
Posts: 15,731
Thanked 657 Times in 486 Posts
Default

For your reading enjoyment...

Tech Talk #53 – Big Bore or Long Stroke: Which Is Better?

By David Reher, Reher-Morrison Racing Engines

“An engine produces peak torque at the rpm where it is most efficient.”

Recently I’ve had several conversations with racers who wanted to build engines with long crankshaft strokes and small cylinder bores. When I questioned them about their preference for long-stroke/small-bore engines, the common answer was that this combination makes more torque. Unfortunately that assertion doesn’t match up with my experience in building drag racing engines.

My subject is racing engines, not street motors, so I’m not concerned with torque at 2,000 rpm. In my view, if you are building an engine for maximum output at a specific displacement, such as a Comp eliminator motor, then the bores should be as big as possible and the stroke as short as possible. If you’re building an engine that’s not restricted in size, such as a heads-up Super eliminator or Quick 16 motor, then big bores are an absolute performance bargain.

I know that there are drag racers who are successful with small-bore/long-stroke engines. And I know that countless magazine articles have been written about “torque monster” motors. But before readers fire off angry e-mails to National DRAGSTER about Reher’s rantings on the back page, allow me to explain my observations on the bore vs. stroke debate.

In mechanical terms, the definition of torque is the force acting on an object that causes that object to rotate. In an internal combustion engine, the pressure produced by expanding gases acts through the pistons and connecting rods to push against the crankshaft, producing torque. The mechanical leverage is greatest at the point when the connecting rod is perpendicular to its respective crank throw; depending on the geometry of the crank, piston and rod, this typically occurs when the piston is about 80 degrees after top dead center (ATDC).

So if torque is what accelerates a race car, why don’t we use engines with 2-inch diameter cylinder bores and 6-inch long crankshaft strokes? Obviously there are other factors involved.

The first consideration is that the cylinder pressure produced by the expanding gases reaches its peak shortly after combustion begins, when the volume above the piston is still relatively small and the lever arm created by the piston, rod and crank pin is an acute angle of less than 90 degrees. Peak cylinder pressure occurs at approximately 30 degrees ATDC, and drops dramatically by the time that the rod has its maximum leverage against the crank arm. Consequently the mechanical torque advantage of a long stroke is significantly diminished by the reduced force that’s pushing against the piston when the leverage of a long crankshaft stroke is greatest.

An engine produces peak torque at the rpm where it is most efficient. Efficiency is the result of many factors, including airflow, combustion, and parasitic losses such as friction and windage. Comparing two engines with the same displacement, a long-stroke/small-bore combination is simply less efficient than a short-stroke/big-bore combination on several counts.

Big bores promote better breathing. If you compare cylinder head airflow on a small-bore test fixture and on a large-bore fixture, the bigger bore will almost invariably improve airflow due to less valve shrouding. If the goal is maximum performance, the larger bore diameter allows the installation of larger valves, which further improve power.

A short crankshaft stroke reduces parasitic losses. Ring drag is the major source of internal friction. With a shorter stroke, the pistons don’t travel as far with every revolution. The crankshaft assembly also rotates in a smaller arc so the windage is reduced. In a wet-sump engine, a shorter stroke also cuts down on oil pressure problems caused by windage and oil aeration.

The big-block Chevrolet V-8 is an example of an engine that responds positively to increases in bore diameter. The GM engineers who designed the big-block knew that its splayed valves needed room to breath; that’s why the factory machined notches in the tops of the cylinder bores on high-performance blocks. When Chevy went Can-Am racing back in the ’60s, special blocks were produced with 4.440-inch bores instead of the standard 4.250-inch diameter cylinders. There’s been a steady progression in bore diameters ever since. We’re now using 4.700-inch bores in NHRA Pro Stock, and even bigger bores in unrestricted engines.

Racers are no longer limited to production castings and the relatively small cylinder bore diameters that they dictated. Today’s aftermarket blocks are manufactured with better materials and thicker cylinder walls that make big-bore engines affordable and reliable. A sportsman drag racer can enjoy the benefits of big cylinder bores at no extra cost: a set of pistons for 4.500-inch, 4.600-inch or 4.625-inch cylinders cost virtually the same. For my money, the bigger bore is a bargain. The customer not only gets more cubic inches for the same price, but also gets better performance because the larger bores improve airflow. A big-bore engine delivers more bang for the buck.

Big bores aren’t just for big-blocks. Many aftermarket Chevy small-block V-8s now have siamesed cylinder walls that will easily accommodate 4.185-inch cylinder bores. There’s simply no reason to build a 383-cubic-inch small-block with a 4-inch bore block when you can have a 406 or 412-cubic-inch small-block for about the same money.

There are much more cost-effective ways to tailor an engine’s torque curve than to use a long stroke crank and small bore block. The intake manifold, cylinder head runner volume, and camshaft timing all have a much more significant impact on the torque curve than the stroke – and are much easier and less expensive to change.
383vett is offline  
Old 02-05-2019, 11:57 AM
  #33  
Tom400CFI
CF Senior Member
 
Tom400CFI's Avatar
 
Member Since: Aug 2004
Location: Park City Utah
Posts: 13,808
Thanked 586 Times in 520 Posts
Default

Ayuh.

Copy all of that. Still not seeing the 383/400 diff as it relates to reliability... but I see the big pic of bore/stroke.
Tom400CFI is offline  
Old 02-05-2019, 12:49 PM
  #34  
pologreen1
CF Senior Member
 
pologreen1's Avatar
 
Member Since: Dec 2007
Posts: 15,773
Thanked 189 Times in 182 Posts
Default

Picking the cubes is the easy part....matching the intake, cam, heads, rr's, headers, exhaust, gears, flywheel, trans, tune, etc, etc, etc... is the real heart of the matter.

Then you have to ask your self was it all worth 450-500hp? (maybe more, but is it streetable) in a C4....

Will the car like to stop going faster? Will it accelerate straight with more power? Will it hook? Will you be comfortable with more power in it? Will your tires accommodate? Will your other parts hold up in the driveline?

Power sounds fun. it is expensive one way or another. A motor swap is one thing, a build in another.

Last edited by pologreen1; 02-05-2019 at 12:51 PM.
pologreen1 is offline  
Old 02-05-2019, 01:48 PM
  #35  
ghoastrider1
CF Senior Member
 
ghoastrider1's Avatar
 
Member Since: May 2006
Location: indy indiana
Posts: 7,120
Thanked 174 Times in 156 Posts
Default

that estrocked 302 engine was a damn good engine.
ghoastrider1 is offline  
Old 02-05-2019, 02:21 PM
  #36  
mtwoolford
CF Senior Member
 
Member Since: Jan 2009
Location: folsom california
Posts: 3,186
Thanked 120 Times in 116 Posts
Default

Assuming that you can find an original 400 c.i. block, and at this late date, good luck with that, or you're willing to pony up for a large bore aftermarket block, which solves a lot of other problems, like providing priority oiling, 383 / 400 pistons, unless you use the oem short 400 rods, as the rod length goes up to 5.7 or 6.0 inches the piston skirts become much shorter, and, especially with 6.0 inch rods, the ring pack is compressed to the point that I would question it's effectiveness in a street engine; blasting down the strip a quarter mile at a time, okay, regular, extended use on the street, maybe not so desirable.
mtwoolford is offline  
Old 02-05-2019, 02:26 PM
  #37  
dmaxx3500
CF Senior Member
 
dmaxx3500's Avatar
 
Member Since: Jan 2008
Location: chicago
Posts: 24,108
Thanked 436 Times in 345 Posts
Default

just put a ''BIG BLOCK CHEVY'' in it,,454-632ci,,it will get out of its own way then


or go find a ''SB2'' ex nascar engine,,if you look around there for sale for $5-10k

Last edited by dmaxx3500; 02-05-2019 at 02:28 PM.
dmaxx3500 is online now  
Old 02-05-2019, 03:24 PM
  #38  
KyleF
CF Senior Member
 
Member Since: Jun 2018
Posts: 218
Thanked 17 Times in 17 Posts
Default

Originally Posted by pologreen1 View Post
Picking the cubes is the easy part....matching the intake, cam, heads, rr's, headers, exhaust, gears, flywheel, trans, tune, etc, etc, etc... is the real heart of the matter.

Then you have to ask your self was it all worth 450-500hp? (maybe more, but is it streetable) in a C4....

Will the car like to stop going faster? Will it accelerate straight with more power? Will it hook? Will you be comfortable with more power in it? Will your tires accommodate? Will your other parts hold up in the driveline?

Power sounds fun. it is expensive one way or another. A motor swap is one thing, a build in another.
I was once told by a very experienced drag racer "You build the car from the back to the front". As to some of the things you are mentioning, the best engine in the world is worthless if you can put the power to the ground and control it.

I am still not buying the original more efficient statement. I still think more displacement is king except for when weight becomes and issue. I wouldn't opt for a big block just to get more cubes in a street car, but I would always opt for the bigger small block displacement.
KyleF is offline  
Old 02-05-2019, 03:29 PM
  #39  
Tom400CFI
CF Senior Member
 
Tom400CFI's Avatar
 
Member Since: Aug 2004
Location: Park City Utah
Posts: 13,808
Thanked 586 Times in 520 Posts
Default

Originally Posted by mtwoolford View Post
Assuming that you can find an original 400 c.i. block, and at this late date, good luck with that,
I have two in my garage. Bought one for $150 (this past summer) the other was free.

Skirt length has nothing to do with rod length.
Tom400CFI is offline  
Old 02-05-2019, 04:15 PM
  #40  
pologreen1
CF Senior Member
 
pologreen1's Avatar
 
Member Since: Dec 2007
Posts: 15,773
Thanked 189 Times in 182 Posts
Default

Originally Posted by KyleF View Post
I was once told by a very experienced drag racer "You build the car from the back to the front". As to some of the things you are mentioning, the best engine in the world is worthless if you can put the power to the ground and control it.

I am still not buying the original more efficient statement. I still think more displacement is king except for when weight becomes and issue. I wouldn't opt for a big block just to get more cubes in a street car, but I would always opt for the bigger small block displacement.
I'll trade my 434 SBC for 502-632 any day.

Last edited by pologreen1; 02-05-2019 at 04:15 PM.
pologreen1 is offline  

Thread Tools
Search this Thread
Quick Reply: 377 vs 383


Sponsored Ads
Vendor Directory

Contact Us - About Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: