[Diy_efi] Adding headers to GM TBI system

[Jason M.]

I'd say go for it.  I did.

Put a set of summit headers on my 92 caprice with TBI 305.  The headers were 
actually for monte carlo/cutlass/malibu so I had to cut the collector off 
the driverside to change the angle.  and flatten part of a tube and the 
collector on the passenger side to get them to fit.  Also had to make my own 
Y-pipe (two 2.5'' U-bends).

Seems to have lost a little bit of low end torque but now has more top end. 
Pre-headers it had nothing after 4200 rpm.  Post-headers it will pull strong 
to 5000 rpm.

I also gained 1mpg and dropped 3 tenths off my 1/4 mile ET, gained 3mph.

As far as what the ecm sees, I've hooked up auto x-ray and all data looks 
just like before.  No trouble codes set.  In my application the only things 
that the engine should really see a change on is less egr flow since the 
valve needs back pressure to open, and the oxygen sensor moves from the 
front of the exhaust manifold collector to the rear of the headers 
collector.

I've heard some estimates/opinions that the stock TBI system can handle 
about 25-30 hp gains through cam/intake/exhaust before the stock tuning is 
so far out that it won't run right.  Of course with tuning you'd probably 
get a few more hp out of that mechanical gain.

At any rate, just change it, worst thing that can happen is you have to do a 
little tuning.
----- Original Message ----- 
From: "Scott Scott" <scott_o_matic at yahoo.com>
To: <diy_efi at diy-efi.org>
Sent: Friday, June 30, 2006 12:48 PM
Subject: [Diy_efi] Adding headers to GM TBI system


>I have a Ford 302 with a GM TBI system on it.  I'm
> thinking of adding hedders but I have heard that,
> because the TBI is a speed denisty system, adding
> hedders can screw up the system.
>
> Is this true, or can I just go for it?   Anyone know
> who can help me with chip programming near Sacramento,
> CA?
>
>
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