Different Strokes

[Chill4 at ix.netcom.com]

On 01/29/99 16:34:36 you wrote:
>
>I'm building a twin turbo small block chevy for a 1981 Corvette, auto trans 
>and all the power accessories..... 
>In a conversation with the machine shop this afternoon the engine builder 
>said I should consider going with a shorter stroke.  I can build a 4" 
>stroke 434 ci, a 3.75" 406 ci, or a 3.48" stroke 355 ci engine.....  
>The builder said that a short stroke engine will respond better to a turbo 
>as it'll rev faster.....  
>Low RPM torque seems to be important as this is going to be a street engine 
>generally run in the lower RPM ranges.

To keep this as short as possible I'll start by saying that for the reasons 
you were given (quicker revving, will work better with a turbo?) I 
completely disagree with your builder. Torque is king on the street and 
there will be a huge difference between a big engine and a smaller one in 
the lower rpm's. Now, I personally don't recommend the 41/8" bore engine for 
other reasons, and since you said you can build either a 434(4.155x4.00), 
406(4.155x3.750), or a 355(4.030x3.480), if that is the case you should have 
two blocks a 4" & a 4&1/8", I personally would consider an engine based on 
the 4" block. Anyway given the same size turbocharger, a larger engine will 
see much less turbo lag, and provide more bottom end torque, and once the 
boost comes in you'll be amazed at how fast the engine revs. However if you 
size the hot sides correctly even the smaller engine can get similar boost 
response (you can virtually have boost start when you want it to), but since 
you said you already have the crank and rods build the big engine and I 
think you'll be very happy with the performance. By the way I have a TT 355 
SBC and have no problem with boost response or turbo lag at all. I will be 
switching over to a single turbo (class rules) and I will size my torque 
converter and the turbine side to make sure I have proper spool up and 
response. I can help with turbo sizing for virtually any vehicle as I have 
experience in this area and I am also a distributor for turbochargers and 
other performance items for a few major manufacturers, if you or anyone else 
is looking for a good deal on some turbochargers or need more assistance on 
sizing or anything else email me directly.

Chris
Advanced Performance
Chill4 at ix.netcom.com