Throttle Body Mods
This is a simple way to increase the airflow of the TB
offering mild performance gains on the Magnum motors.
This mod really makes some power as better breathing
items are added to the motor. Not everyone will have
the tools or facilities to perform this mod, so make
use of your local machine shop buddies. The SBEC will
adjust for the new airflow after a few days by opening
the fuel injector pulse width further to match the optimum
A/F ratio it requires.
- First, remove the air cleaner assy then disconnect the
electrical imputs, throttle and 4 bolts that hold down
the TB, it can now be removed to the shop bench.
- Notice that the bracket in the center for the air cleaner
hold down blocks a 1/4-1/3 of each venturi. Remove this
bracket and replace it later with a piece of threaded
rod bent to align up with the air cleaner.
- Now the top of the TB has 1 inch tall nodules what I can
only describe as Stonehenge blocks that line up the air
cleaner. These need to come off, my way was in a vise with
a hacksaw to remove the major parts of them (sounds crude
"hacksaw the carb in half Joe...") Then I had access to a
flat table grinder which most machine shops have. Have them
mill the top of the TB flat till the Stonehenge blocks or
Holley emblem just dissappear. Be sure to clean up with carb
cleaner and air.
- If you decide to open the venturis as I did, then proceed
to remove the butterflies which are connected each by 2 bolts
with loctite. Opening the bores this way is in no way precise
as a flow bench should be used to balance the air flow of both
sides. I chose the unbalanced eyeball method of equal removal.
I used an air dremel to open the upper half only (from the shaft
to the top) and polished it with the wire wheel fitting and rouge
compound afterward. I removed and contoured aproximately 1/8 of
each venturi bore. I then R2'd the butterfly bolts with smoother
hardware that recess into the shaft better.
- Before putting the butterflys back on, I milled them flatter on
the flat bench then polished them the same way as the bores. I
used loctite to secure the hardware on the shaft holding the
butterflys. Clean the complete TB with compressed air and carb
cleaner to ensure that no metal shavings remain. Pretty simple eh?
Reinstall the TB and drive for a few hours to teach the SBEC it's
new readings. I put my truck in 5th gear at 40mph and floored the
throttle. When I did, it stumbled for air momentarily then pulled
(air bogged). Next day, it didn't air bog but pulled only. As usual,
if there are any questions, contact me at
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