Different Strokes

[EFISYSTEMS at aol.com]

Hi David,
       It has been my experience that it does take less time for the engine to
accelerate with a shorter stroke,,,but like you said the larger cu in will
give more streetable torque and that would probably be the trade off I would
take if I already had the parts as you do.....The biggest downfall of the 4"
arm is the fact that you have very little(if any...was this 350 mains or 400?)
journal overlap and if you are planning to make alot of hp(1000+) and/or
rpm,,expect this crank to crack probably after 30 1/4 mile blasts.....just
some experience....hth's
-Carl Summers


In a message dated 1/29/99 3:34:37 PM Pacific Standard Time, dsagers at ci.west-
valley.ut.us writes:

<< Subj:	 Different Strokes
 Date:	1/29/99 3:34:37 PM Pacific Standard Time
 From:	dsagers at ci.west-valley.ut.us (David Sagers)
 Sender:	owner-diy_efi at efi332.eng.ohio-state.edu
 Reply-to:	diy_efi at efi332.eng.ohio-state.edu
 To:	diy_efi at efi332.eng.ohio-state.edu
 
 I'm building a twin turbo small block chevy for a 1981 Corvette, auto trans
and all the power accessories.  It'll be used for a hotrod street car,
primarily on weekends and sunny days.
 
 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 block I have is
already clearanced for the 4" stroke so the additional cost of preparing the
block isn't a factor.   I already own the 4" crank and rods, and the crank can
be traded out for a shorter stroke without any additional cost.
 
 The builder said that a short stroke engine will respond better to a turbo as
it'll rev faster.  So I'm looking for someone with knowledge and experience
with turbo engines.   Do I go with the shorter stoke that'll rev faster, or go
with the 4" stroke that makes a lot of torque, especially in the low RPM
ranges.  Low RPM torque seems to be important as this is going to be a street
engine generally run in the lower RPM ranges.
 
 Some of the things I want from the engine are throttle response and low rpm
power.  I was hoping that by going with the big 434 ci engine I could over
come some of the slow acceleration associated with turbo lag in small engines.
 
 
  >>