From: hotrod@dixie.com (The Hotrod List)
Subject: fuel delivery
Date: Thu, 07 Jan 93 23:03:33 GMT
Organization: Dixie Communications Public Access.  The Mouth of the South.
To: hotrod@dixie.com
Reply-To: hotrod@dixie.com
Posted-Date: Thursday, Jan 07 18:03:29
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          I'm trying to plan a good fuel delivery for my 476 cid BB chevy 
          engine.  The powerplant pieces parts: 
          
          The cam is a Competition Cams 280 (at .010) and .565" lift.  The 
          intake manifold is an Edlebrock Performer RPM dual plane with a 
          claimed powerband of 1500-6000 rpms.  The heads are Chevy oval 
          ports with 2.19" and 1.88" valves.  The bowls and runners are 
          massaged.  The carb is a Brad Urban blueprinted Holly 4bbl to 
          match the induction system (750-850 cfm).  The headers are 2" 
          primaries dumping into 3" collectors, and 3" piping to the 
          mufflers.
          
          I think air will flow quite well with this powerplant.  I'm not 
          so sure what my fuel flow and pressure should be capable of 
          providing.  Should I augment a mechanical pump with an electric, 
          or just use an electric and a regulator?  Will I need more than 
          the Holly Blue Max Pressure pump (14 PSI and 110 GPH free flow 
          and 9 PSI at 70 GPH)?  Mallory makes a 250 GPH at 20 PSI with a 
          matching regulator.  I need help from a non salesperson. :-)
          
          Also, should I choose a fuel system which hase a return line back 
          to the tank?  I would like to keep the stock tank, so I suppose I 
          would need a hipo pickup.  CE makes a steel sump with a lower 
          drain port and dual pickup bungs.        
          
          I suppose you can tell that fuel delivery is not one of my strong 
          points.  All help appreciated!  Thanks.
          
          Regards,
          Eric Webb
              

[This is very easy to compute.  For the purposes of scaling fuel delivery,
assume a volumetric efficiency of 1 and an 11:1 fuel mix, and 8000 rpm.  
For your 476 cu in engine, every minute it will consume:

476 cu in * (8000 / 2) = 1,904,000 cu inches per minute or 114,240,000 cu in/
hour.  Converting this to mass using the air density conversion factor 
0.00129317 grams/cc and 16.3871 cc per cu inch, that works out to 

114E6 cu in * 16.3871 ci/cc * 0.00129317 = 2421170 grams/hr or 5537 lbs/hr.

Fuel to go with this at a ratio of 11:1 by mass works out to

485.25 lbs/hour.  

Using a typical gasoline specific gravity of 0.75, that works out to 

364 gal/hr., 6 gal/min

Notes:  1) Please check my math - I did it in one big hurry.
		2) All constants and conversion factors came from a book
		   called "Engineering Unit conversion" by Michael R Lindeburg,
		   ISBN 0-912045-29-9
		3) This is worst case; real world is probably more favorable.
		4) I have this computation in a Lotus spreadsheet on my HP95.
		   I'll put it on the famous Dixie file server when I get a
		   chance.

While I'm on the subject, anyone ever wonder why drag racers don't 
use reasonably sized pumps and accumulators instead of trying to keep
pumps large enough to supply the peak flow supplied with power?  This
would be cheaper AND a lot more reliable.  JGD]
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Posted by: ERIC WEBB 919-541-7896 <emory!epamail.epa.gov!WEBB.ERIC>
Newsgroups: alt.hotrod,wiz.hotrod