Bore and stroke ?
07-13-2011, 10:48 AM
#2
LT1s can be bored up to .060", but there's no real point in going that big. You should only bore it out as much as it needs for the cylinder walls to be cleaned up, since the added cubes are minimal and the further you go right away the less material you have for future builds, of needed. I.E., if you go .060" right away and blow the motor, the block is toast. A .020" leaves plenty of room for future rebuilds.
The three most common strokes for LT1s are 3.48" (stock), 3.75" (when used with a .030" overbore results in a 383), and 3.85" (when used with a .030" overbore results in a 396).
It seems as though you may be under the impression that displacement = power, but that is not the case. I mentioned in your other post that the VALVETRAIN needs to be the primary focus.
The three most common strokes for LT1s are 3.48" (stock), 3.75" (when used with a .030" overbore results in a 383), and 3.85" (when used with a .030" overbore results in a 396).
It seems as though you may be under the impression that displacement = power, but that is not the case. I mentioned in your other post that the VALVETRAIN needs to be the primary focus.
07-13-2011, 11:17 AM
#3
4.125-inch stroke....421 cubes! I remember reading about these in the late 90's 
http://www.vetteweb.com/features/vem...rankshaft.html
http://www.vetteweb.com/features/vem...rankshaft.html
07-13-2011, 11:28 AM
#4
4.125-inch stroke....421 cubes! I remember reading about these in the late 90's
http://www.vetteweb.com/features/vem...rankshaft.html
http://www.vetteweb.com/features/vem...rankshaft.html
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07-14-2011, 09:08 AM
#9
I put a 3.875" crank in a LT1 Corvette 4-bolt main block and there was quite a bit of machining that had to be done. My machinist said he felt he could get a 4" crank in there with a little more work. When you start to push the limits of stroke, then you run the risk of hitting the water jacket and you run out of room in the oil pan rail for clearance.
Also at that point you have to start picking parts that will allow you the most clearance such as smaller rod bolt heads. Then you have to remove some metal on the rods, and sometimes you'll run into issues with clearing the camshaft.
If you are really chasing cubes, put a big block chevy in there. If you are chasing horsepower, up the compression and run race gas or go power adder. If you just want to be unique, be prepared to pay your machinist.
Also at that point you have to start picking parts that will allow you the most clearance such as smaller rod bolt heads. Then you have to remove some metal on the rods, and sometimes you'll run into issues with clearing the camshaft.
If you are really chasing cubes, put a big block chevy in there. If you are chasing horsepower, up the compression and run race gas or go power adder. If you just want to be unique, be prepared to pay your machinist.
07-14-2011, 09:35 AM
#10
Village Troll 
iTrader: (2)
I believe those engines are dry sump so you'd need to buy all the hardware for that which would cost a buuuuuuuuunch more.
Last edited by SS RRR; 07-14-2011 at 09:41 AM.
in just machining for a 421 cube LT1....then the heads can't flow enough and they tend to not last very long. 575 WHP isn't bad though, until a LS car beats you with just heads and cam for less than half the money invested
07-14-2011, 11:07 AM
#13
head....don't hate cuz I got 383 cubes of LT1 glory and a LS1 car. In case you didn't notice, this website is called "ls1tech.com"....you can GTFO if you don't like talk of LS motors. I've owned a LT1 f-body since 1996 dude and have nothing but respect for the LT platform....I'm just not an ignorant 
like yourself who thinks LT1 is the second coming of Christ. 
07-14-2011, 01:47 PM
#14
another LS1 tech thread that has spiraled out of control...........
OP....for a DD listen to RAMAIR up there......hes absolutly correct......bore it as little as possible.... .030 is 90% of the time the case.....a 383 with a good cylinder head an cam combo will make big power..........
as for massive stroke motors they are good sometimes but sometimes they are not..........
big stroke does give more cubic inch obviously.......however it comes with draw backs.....
#1 The crankshaft and rotating asssembly weight increases......as does the leverage point on the crank where the rod attaches.........which puts a much greater load on not only the rotating assembly but also the block and mains.....
#2 The piston comes down the bore more which makes the piston skirt try to "Drive" itself into the wall even more when its ascending up the cylinder from bottom dead center.......
Those are two of the main issues along with a Piston pin that becomes located very far up into the piston creating ring issues........those two factors limit the rpm and horsepower capability of the motor while directly affecting durability as well........
Horsepower is a function of CFM and RPM, which is why you see cup cars running around at 9000+rpm.......which is also why you see alot of big bore short stroke NA combos.....
when i built my LT motor i could gain more from revving it 8000+rpm as a 3.75" stroke motor versus a 3.875+ stroke motor at a lower rpm.......the LT block is strong but IMO is not capable of properly controling cylinder wall and block twist at very high rpm and horsepower levels with a very large stroke crankshaft......IMO i would never attempt to go over the 3.875" stroke in these blocks, its just downright irresponisble to design something like that with the platform we have to work with......
as for LS to LT motors, its an argument that will go on for ages........the LS is a better platform because of one thing.......cylinder head valve angles........us in LT land are limited to a 23* angle with our "stock" style heads........The LS are down in the 18* to 15* range or less.........you can make an LT motor make serious power even with a 23* if done properly.......they do have alot of capability in them even with the 23* head.....
OP....for a DD listen to RAMAIR up there......hes absolutly correct......bore it as little as possible.... .030 is 90% of the time the case.....a 383 with a good cylinder head an cam combo will make big power..........
as for massive stroke motors they are good sometimes but sometimes they are not..........
big stroke does give more cubic inch obviously.......however it comes with draw backs.....
#1 The crankshaft and rotating asssembly weight increases......as does the leverage point on the crank where the rod attaches.........which puts a much greater load on not only the rotating assembly but also the block and mains.....
#2 The piston comes down the bore more which makes the piston skirt try to "Drive" itself into the wall even more when its ascending up the cylinder from bottom dead center.......
Those are two of the main issues along with a Piston pin that becomes located very far up into the piston creating ring issues........those two factors limit the rpm and horsepower capability of the motor while directly affecting durability as well........
Horsepower is a function of CFM and RPM, which is why you see cup cars running around at 9000+rpm.......which is also why you see alot of big bore short stroke NA combos.....
when i built my LT motor i could gain more from revving it 8000+rpm as a 3.75" stroke motor versus a 3.875+ stroke motor at a lower rpm.......the LT block is strong but IMO is not capable of properly controling cylinder wall and block twist at very high rpm and horsepower levels with a very large stroke crankshaft......IMO i would never attempt to go over the 3.875" stroke in these blocks, its just downright irresponisble to design something like that with the platform we have to work with......
as for LS to LT motors, its an argument that will go on for ages........the LS is a better platform because of one thing.......cylinder head valve angles........us in LT land are limited to a 23* angle with our "stock" style heads........The LS are down in the 18* to 15* range or less.........you can make an LT motor make serious power even with a 23* if done properly.......they do have alot of capability in them even with the 23* head.....
07-14-2011, 06:10 PM
#15
another LS1 tech thread that has spiraled out of control...........
OP....for a DD listen to RAMAIR up there......hes absolutly correct......bore it as little as possible.... .030 is 90% of the time the case.....a 383 with a good cylinder head an cam combo will make big power..........
as for massive stroke motors they are good sometimes but sometimes they are not..........
big stroke does give more cubic inch obviously.......however it comes with draw backs.....
#1 The crankshaft and rotating asssembly weight increases......as does the leverage point on the crank where the rod attaches.........which puts a much greater load on not only the rotating assembly but also the block and mains.....
#2 The piston comes down the bore more which makes the piston skirt try to "Drive" itself into the wall even more when its ascending up the cylinder from bottom dead center.......
Those are two of the main issues along with a Piston pin that becomes located very far up into the piston creating ring issues........those two factors limit the rpm and horsepower capability of the motor while directly affecting durability as well........
Horsepower is a function of CFM and RPM, which is why you see cup cars running around at 9000+rpm.......which is also why you see alot of big bore short stroke NA combos.....
when i built my LT motor i could gain more from revving it 8000+rpm as a 3.75" stroke motor versus a 3.875+ stroke motor at a lower rpm.......the LT block is strong but IMO is not capable of properly controling cylinder wall and block twist at very high rpm and horsepower levels with a very large stroke crankshaft......IMO i would never attempt to go over the 3.875" stroke in these blocks, its just downright irresponisble to design something like that with the platform we have to work with......
as for LS to LT motors, its an argument that will go on for ages........the LS is a better platform because of one thing.......cylinder head valve angles........us in LT land are limited to a 23* angle with our "stock" style heads........The LS are down in the 18* to 15* range or less.........you can make an LT motor make serious power even with a 23* if done properly.......they do have alot of capability in them even with the 23* head.....
OP....for a DD listen to RAMAIR up there......hes absolutly correct......bore it as little as possible.... .030 is 90% of the time the case.....a 383 with a good cylinder head an cam combo will make big power..........
as for massive stroke motors they are good sometimes but sometimes they are not..........
big stroke does give more cubic inch obviously.......however it comes with draw backs.....
#1 The crankshaft and rotating asssembly weight increases......as does the leverage point on the crank where the rod attaches.........which puts a much greater load on not only the rotating assembly but also the block and mains.....
#2 The piston comes down the bore more which makes the piston skirt try to "Drive" itself into the wall even more when its ascending up the cylinder from bottom dead center.......
Those are two of the main issues along with a Piston pin that becomes located very far up into the piston creating ring issues........those two factors limit the rpm and horsepower capability of the motor while directly affecting durability as well........
Horsepower is a function of CFM and RPM, which is why you see cup cars running around at 9000+rpm.......which is also why you see alot of big bore short stroke NA combos.....
when i built my LT motor i could gain more from revving it 8000+rpm as a 3.75" stroke motor versus a 3.875+ stroke motor at a lower rpm.......the LT block is strong but IMO is not capable of properly controling cylinder wall and block twist at very high rpm and horsepower levels with a very large stroke crankshaft......IMO i would never attempt to go over the 3.875" stroke in these blocks, its just downright irresponisble to design something like that with the platform we have to work with......
as for LS to LT motors, its an argument that will go on for ages........the LS is a better platform because of one thing.......cylinder head valve angles........us in LT land are limited to a 23* angle with our "stock" style heads........The LS are down in the 18* to 15* range or less.........you can make an LT motor make serious power even with a 23* if done properly.......they do have alot of capability in them even with the 23* head.....
** Just to correct very slightly... hoersepower is a function of CFM. Ci, rpm and Fi are just ways to get more of it.
Last edited by Nastyc4; 07-14-2011 at 07:50 PM.
07-14-2011, 07:44 PM
#16
He started it! 
I was just trying to illustrate why NOBODY builds 421 strokers anymore due to durability and cost/hp ratio reasons. Did anybody notice that article was from the 90s....how many 421 stroker owners we got out here now in 2011? (crickets chirping) But some people sooo sensitive here...jeeez. 
