Valve Train noise

[John Hess]

I would rather not quote my source;  however, if one looks at the flow 
characteristics of the stock TPI one finds that it flows approximately 
435 CFM.  Making slight mods as follows causes significant changes to 
this.
Cut the screens off the MAF increases the flow to 512 CFM
Install a throttle body air foil increases the flow further to about 
530 CFM (Still not in the realm of what one would consider for even a 
moderate performance 350).
Opening up the filter cover and putting a K&N filter in gets us into 
the 560 CFM range.
Modifying the MAF (Cutting and polishing the heat sink inside) gets us 
up to about 585
As you can see, there is room for much improvement without ever 
getting out of the air intake.

The MAF, itself flows about 529 CFM stock.  Taking the screens out 
gets it up to over 700 CFM.  Modifying the heat sink and cleaning up 
the inside gets it up to about 750 CFM.

Note that all this data is corrected to 20.4 inches of water (What 
Holley rates their carburetors at).

Since this is a "dry" flow system (no fuel in the air stream), the 
equivalent to a carbureted engine is about 650 CFM.  NOW we are in the 
realm of a solid 350.  Further improvements may now be realized by 
mods to the throttle body, plenum, runners, and base.


----------
From:  Scot Sealander[SMTP:Sealand at clarityconnect.com]
Sent:  Saturday, January 18, 1997 7:47 PM
To:  diy_efi at coulomb.eng.ohio-state.edu
Subject:  Re: Valve Train noise

John Hess wrote:

> The original TPI was designed for the 305 engine
> and is woefully inadequate for even a mildly built 350.

Do you have a source for this?  How do you know it was designed for 
the 305,
and not the 350?


> To state that these parts are fraudulent or that the people
> who sell them are liars is irresponsible and/or stupid..

Maybe not.  Just what does that "air foil" do anyway... ;-)  As far as 
aftermarket PROMs, the three I have looked at did not do much.  Delay 
TCC lock
up by several mph, maybe reduce the ESC attack rate (makes sure of the 
need
for 93 octane!)  Change fan turn on temp.... One completely zero'd 
every EGR
location..... Basically no ignition or fuel changes.  Not a lot for 
the 150
bucks or so they charge!  That is close to fraudulent in my book, and 
points
out that GM tunes them pretty well from the factory.

I am sure that some of the aftermarket is great stuff, but the 
consumer must
understand what he is buying.  The TPI is a great low/mid RPM intake 
system,
and that may not be clear to all consumers.  So if you make changes to 
your
350 that increase airflow requirements at higher RPMs, the TPI will 
not work
well for you.

Scot Sealander    Sealand at clarityconnect.com