350vs400 mains
09-26-2007, 10:07 PM
#1
Team Owner
Thread Starter
Member Since: Jan 2006
Location: Hampton, VA Yea, i'm a redneck... but you love it
Posts: 26,598
Likes: 0
Received 0 Likes
on
0 Posts
Cruise-In 8-9 Veteran
aka/Trunk Monkey/Banned For Life/Corvette For Life
350vs400 mains
what is the difference in cranks... what should I get for a 383 stroker? Pro's and con's of each?
09-26-2007, 10:44 PM
#2
Team Owner
Member Since: Sep 2001
Location: Athens AL
Posts: 59,651
Received 1,401 Likes
on
1,017 Posts
C7 of the Year - Unmodified Finalist 2021
C4 of Year Finalist (performance mods) 2019
The usual 383 is a 350 block bored over .030" with a crank from a 400.
new flywheel
09-27-2007, 07:57 AM
#5
Le Mans Master
Member Since: Aug 2000
Location: Sydney Australia
Posts: 8,837
Likes: 0
Received 30 Likes
on
29 Posts
This is the classic way of building a 383;
requires the mains of the 400 crank to be cut down to 350 size.
With the aftermarket cranks available now , you just buy a 3.75 stroke crank to fit a 350 making 383 with a 30 over rebore.
Plus you get the choice of cast iron , cast steel or forged depending on your requirements whereas 400 cranks are cast .
My Scat 3.75 crank fitted stock L98 Vette pan without clearance problems
09-27-2007, 07:59 AM
#6
Instructor
A 400 crank has larger main journals. Go to SCAT or Eagle for their 383 crank, it will drop in. (you may have to grind some of the con rod bolt ends for cam lobe clearance) I would recommend having the assembly balanced.
09-27-2007, 08:26 AM
#7
Race Director
09-27-2007, 09:10 AM
#8
Safety Car
The specific difference in cranks is the stroke and the main journal diameter.
350 = 3.48 stroke with 2.45 mains
400 = 3.75 stroke with 2.65 mains
So if you use a stock GM 400 shaft in a stock GM 350 block you will have to have the mains ground down.
Wheter or not you have to grind, notch, and/or hammer anything else in (or on) your engine depends on what Connecting Rods you use. The stock 400SBC didn't have any of these things done to it. Depending on what crank you buy (external or inernal balance) decides whether or not you have to buy a new flywheel.
Pros of each?
Given the choice I"ll build a 3.75 stroke motor evertime over a 3.48 stroke. More cubic inches. Its easier to make more power with a bigger motor. There really is no Pro about using a 3.48 stroke crank (if you have the choice) unless you already have a useable 350SBC and don't want to spend any $$$ on a new crankshaft.
Cons of each?
Considering the cost of a new crank varies from $189.00 to whatever you want to spend (upwards of $3,000.00), things could get costly in a hurry, espc when you tack on a few higher end componets (rods and pistons) to go with your shiney new crankshaft. A 3.75 stroke will create higher side loads on the piston because it increases rod angle over the 3.48 stroke (and yes you can offset this to a point by using longer rods but everything has its practical limits as there is only so much available space in a SBC). This limits RPM relative to the QUALITY of the parts you use. Also to take advantage of all those extra cubic inches you just gained, a long stroke engine should have better heads and induction.
Theres alot more to this than what I've said and frankly there are books written soley on this subject so I couldn't possibally explain it in detail here. There are members here who have both 350's and 383's that run very well. Both can be built to do what ever you want to do, it all depends on how much $$$ you want to spend.
What you should get for 383 stroker?
Everything is in the ENGINE COMBINATION. First decide how much performance you expect out of your engine and car. Second find a member here (or a professional engine builder) who's engine/car meets that expectation and ask them what it took to get there.
Will
350 = 3.48 stroke with 2.45 mains
400 = 3.75 stroke with 2.65 mains
So if you use a stock GM 400 shaft in a stock GM 350 block you will have to have the mains ground down.
Wheter or not you have to grind, notch, and/or hammer anything else in (or on) your engine depends on what Connecting Rods you use. The stock 400SBC didn't have any of these things done to it. Depending on what crank you buy (external or inernal balance) decides whether or not you have to buy a new flywheel.
Pros of each?
Given the choice I"ll build a 3.75 stroke motor evertime over a 3.48 stroke. More cubic inches. Its easier to make more power with a bigger motor. There really is no Pro about using a 3.48 stroke crank (if you have the choice) unless you already have a useable 350SBC and don't want to spend any $$$ on a new crankshaft.
Cons of each?
Considering the cost of a new crank varies from $189.00 to whatever you want to spend (upwards of $3,000.00), things could get costly in a hurry, espc when you tack on a few higher end componets (rods and pistons) to go with your shiney new crankshaft. A 3.75 stroke will create higher side loads on the piston because it increases rod angle over the 3.48 stroke (and yes you can offset this to a point by using longer rods but everything has its practical limits as there is only so much available space in a SBC). This limits RPM relative to the QUALITY of the parts you use. Also to take advantage of all those extra cubic inches you just gained, a long stroke engine should have better heads and induction.
Theres alot more to this than what I've said and frankly there are books written soley on this subject so I couldn't possibally explain it in detail here. There are members here who have both 350's and 383's that run very well. Both can be built to do what ever you want to do, it all depends on how much $$$ you want to spend.
What you should get for 383 stroker?
Everything is in the ENGINE COMBINATION. First decide how much performance you expect out of your engine and car. Second find a member here (or a professional engine builder) who's engine/car meets that expectation and ask them what it took to get there.
Will
Last edited by rklessdriver; 09-27-2007 at 09:13 AM.
09-27-2007, 10:47 AM
#9
Team Owner
Member Since: Sep 2001
Location: Athens AL
Posts: 59,651
Received 1,401 Likes
on
1,017 Posts
C7 of the Year - Unmodified Finalist 2021
C4 of Year Finalist (performance mods) 2019
This is the classic way of building a 383;
requires the mains of the 400 crank to be cut down to 350 size.
With the aftermarket cranks available now , you just buy a 3.75 stroke crank to fit a 350 making 383 with a 30 over rebore.
Plus you get the choice of cast iron , cast steel or forged depending on your requirements whereas 400 cranks are cast .
requires the mains of the 400 crank to be cut down to 350 size.
With the aftermarket cranks available now , you just buy a 3.75 stroke crank to fit a 350 making 383 with a 30 over rebore.
Plus you get the choice of cast iron , cast steel or forged depending on your requirements whereas 400 cranks are cast .
09-27-2007, 11:12 AM
#10
Team Owner
Thread Starter
Member Since: Jan 2006
Location: Hampton, VA Yea, i'm a redneck... but you love it
Posts: 26,598
Likes: 0
Received 0 Likes
on
0 Posts
Cruise-In 8-9 Veteran
aka/Trunk Monkey/Banned For Life/Corvette For Life
09-27-2007, 08:21 PM
#11
Safety Car
Most 1 pc rear seal cranks are set up to use the stock 153 tooth counterweighted FW and an internal (neutral) balancer, just like the stock L98/LT1.
However the 2pc rear seal cranks can be either external balance (counterweighted) or internal (neutral) on the both FW and balancer sides (ie 2 different cranks). Eagle and Scat have 2 differnt PN's depending.
Looking on Ohio Cranks' site I noticed they do not specify whether their 2pc rear seal cranks are internal or external balance. Best to call and ask them what FW and Balancer to use with their cranks.
I will also just caution you gently about Ohio Crank. They are well know for balance problems and inconsistant machine work. Hey everybody has a bad day (Eagle, Scat, even Bryant or Kings occasionally) but Ohio is know for having "more than a few". If you do buy from them make sure you have it mic'd by a competent machinest.
Will
