GM TPI in the 400 SBC

[Mark Romans]

TPIS's book, insider hints, on page 17 shows a chart with a 383 w/airflow
research heads, big mouth intake ported plenum, 58mm throttle body and
modified maf using for comparison purposes the stock runners, slp cast,
lingenfelter cast, tpis extruded and tpis siamesed runners.  Obviously the
stock runners at 1.470 diameter id were down from the others oh hp and but
torque was similar but at 700 to 1000 lower rpm band.  With the stock
runners it made 469.6 ft lbs at 3750 rpm's and 390 hp at 5750. The biggest
jump was to the siamesed runners (Which are no longer made by tpis) at 462ft
lbs at 4250 (Actually down) and 427.7 hp at 5750 rpms.  So the stock runners
are not that much of a limitation.  The whole thing works as a system.

I would recommend that anyone wanting to do any playing with a tpi system
buy the tpis book.  They have exhaustive flow tests on every component
documented in this book.

A 406 with a tpi ought to be a really fun combination.

Mark
-----Original Message-----
From: ECMnut at aol.com <ECMnut at aol.com>
To: diy_efi at efi332.eng.ohio-state.edu <diy_efi at efi332.eng.ohio-state.edu>
Date: Saturday, January 16, 1999 6:36 AM
Subject: Re: GM TPI in the 400 SBC


>Skip this post if you could care less about 400 SBCs
>or drag racing..
>
>With such a low RPM torque peak, some conservative
>rear-end gears (3.55-4.10) will probably work well.
>Peter mentioned traction linitations in a previous post.
>I couldn't agree more.  IF you can keep it connected
>to the pavement, the car should provide big fun..
>The 400 SBC makes lots of torque without such a
>TPI intake amplifying the issue.  With the stock runners,
>it should REALLY make torque by 3,500 RPM.
>Some years back, I had a 2700 lb bracket car with
>a 350 SBC, 5.13 gears decent heads, very mild hydraulic
> cam and a box-stock 750 Holley.  It turned 11.70s all
>day long.  It idled as smooth as a hoover vaccuum cleaner.
>Eventually, I replace the 350 shortblock with a 13:1 400
>shortblock, reusing the heads, cam & everything possible..
>I reduced the rear-end gear from 5.13 to 4.10 because I was
>nervous about turning the "strokey" short-rod 400 too hard.
>The first day out with the 400, it idled perfectly smooth at
>15 inches of vaccuum, and the car turned 10.80s....
>Almost a full second improvement over the 350..
>Even with the gear reduction, the car left the starting
>line much harder than before.  A hard throttle stab
>from a fast idle would pick the front tires up almost
>a foot.  The car was a small Vega with a 3 link suspension
>and 14 inch wide slicks, so traction was usually available.
>If I could have EFI'd this thing, I'm sure it would've been
>faster and cleaner.  Even with a carb, I considered
>getting a tailpipe emmisions test done, but never found
>the time.  The engine stayed in the car until two years
>later, when I sold everything..
>The 400 is really impressive as long as you keep the
>RPMs low (below 6,000?)..  That includes the burnout.
>Despite my persistent warnings about hi RPM death,
>the rookie that bought my car liked the sounds of 8,000
>RPM in the burnout area, and put a rod through the
>oil pan his first day at the track..
>Good luck, I bet the 400 TPI combo will be fun..
>Mike V
>