For a SC which is better.....
08-07-2004, 02:08 PM
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For a SC which is better..... Having a forged bottom end with a larger BORE than STROKE or the opposite? or the same size for the BORE and STROKE. for example, which would be better from these two.... Having a 383CID from a 4.000 BORE 3.622 STROKE or 3.900 BORE and 4.000 STROKE or 3.935 BORE and STROKE. I know that engines with higher BORE than STROKE tend to be more flexiable with revving, but the STROKE engine gives more TQ. Any other advantages or disadvantages for the two?
08-08-2004, 10:49 AM
#4
The higher bore motor will nearly always yield a better peak HP number.
The larger stroke motor will yield better torque though (as stated above).
If you are going forced induction, IMO, it is best to go with bore being that you are already putting a torque multiplier on your engine.
As always though a properly balanced bore/stroke combo will yield the best results.
The problem with bore is getting a good block.
Stroke is probably the more reliable of the two.
-Kevin
The larger stroke motor will yield better torque though (as stated above).
If you are going forced induction, IMO, it is best to go with bore being that you are already putting a torque multiplier on your engine.
As always though a properly balanced bore/stroke combo will yield the best results.
The problem with bore is getting a good block.
Stroke is probably the more reliable of the two.
-Kevin
08-08-2004, 02:24 PM
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Originally Posted by NoGo
As always though a properly balanced bore/stroke combo will yield the best results.
So if i wanted somewhere around 383CID.... What bore and stroke u suggest? Im going to be running a D-1SC now and might go with a F1 if i need more boost later on. Also what do u think about the 4.000 bore and stroke, the one SLP came up with.... The price is really nice on that package, but i dont know about the 4.000 bore and stroke for a SC setup. From my understanding the higher the stroke the lower ur power band, which will cause u to run a really small pulley setup to max up ur blower which equal belt slippage.
If we assume that a 402CID with 4.000 bore and stroke peaks around 6K RPM then with a 7.25 Crank Pulley, 3.25 SC pulley and 4.10 step up ratio the SC will be running around 54876 RPM which is 8000 shy of the max impeller speed of the D-1SC. Now if we have a 383 CID with 4.000 Bore and 3.622 Stroke the engine can go up to 7000 RPM (Assuming the valve train is up to it). With the same pulley setup as before the blower will be running around 64000 RPM which is perfect for the whole setup.
If we go back to try to get the same impeller speed out of the blower for the 402CID setup then u will need a higher step up ratio or running a smaller blower Pulley or larger crank pulley. I dont know whats the max u can go for a LS1 Crank pulley so i will just do the calculation based on the same step up ratio and a smaller blower pulley. Ur going to need 2.75 blower pulley to get the same impeller speed(64000RPM) out of the same blower with the 402CID engine which means Slippage big time. Thats why i was wondering if a larger bore will be better for FI in general. What do u think guys?
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08-08-2004, 06:16 PM
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Originally Posted by greentahoe
Wow....
Id like to hear more about this as well. I know there are alot of guys in here running 370 and up so what route did you go and why??
Id like to hear more about this as well. I know there are alot of guys in here running 370 and up so what route did you go and why??
U can get 370CID from from a 3.900 stroke and bore which is what most are doing on a LS1. They leave the stock bore alone with just simple cleaning and upgrade to a 3.900 crank. Its great to have equal stroke and bore numbers for the extra TQ and the more usable power down low in a N/A or NOS car, but SC'd engine u need the extra RPM to avoid running a really small pulley on the SC or a really large pulley on the Crank or a really high internal step up ratio. Also is it true when u have a higher step up ratio in the blower it means more power is going to robbed from the motor? I'm not sure, but it does make sense to me.
