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C4 Upgrade Air Management to Improved Fuel Delivery - Got Air?

Samuel James Mar 2, 2010
Corp_0801_01_z C4_air_management_fuel_delivery Air_fuel_upgrade 2/39

Here are the induction system parts we'll be replacing in this job. Shown are thenew intake manifold and runners, throttle body (and box), mass air flow (MAF) sensor,EGR insulation, and manifold gaskets that we had to purchase separately asthey were, surprisingly, not included with the manifold.

LAST time, our "Got Fuel?"(August 2007) story detailed the proceduresfor upgrading fuel injectors andthe fuel-pressure regulator. This month,we will explain air-managementupgrades to take the best advantage ofthe improved fuel delivery.

More fuel is usually better. But only ifmore air is available to make most efficientuse of the enhanced fuel/air mixture.After all, if properly managed,more air/fuel mixture translates intomore ponies to the pavement. Havingupgraded our fuel injectors and fuelpressureregulator, we decided now wasthe time to install a high-performancethrottle body, runners, and intake manifoldin our project '87.

Once again we turned to the folks atMid America Motorworks to see whichpieces they recommended to complementthe modifications made previously. Theyrecommended Accel's trio of throttlebody, intake runners, and intake manifold,so we ordered up these parts andwent back to re-read the previous storyon fuel-system upgrades because all ofthose pieces would have to come backoff for this job. Certainly it makes senseto do both jobs at the same time if yourcheckbook can withstand the shock. Butif not, we think doing the fuel upgradesfirst is both more affordable and lessintimidating, so when you're ready totackle the manifold and runner job, you'llbe more confident.

We'll say right up front that this jobdid not go as well as previous jobs for anumber of reasons. Access to bolts andparts was, in some cases, difficult. Andwe learned the hard way that manypieces had to come off and go back on ina very specific order, so trial fitting duringreassembly is critical. Further, althoughthe instructions with the manifold advisethat some modifications might be necessaryfor everything to fit right, we weresurprised and disappointed at the sometimesobvious interference points that wefelt should have been engineered betterbefore the final design was released.

And, finally, there were areas like theport size in the new runners that weremuch larger than the ports in the originalplenum, leaving what we felt was a tooabruptchange in diameter. We addressedthat matter by milling the ports in theplenum to match those of the new runners.And the passage for the cold startenrichment injector (the so-called ninthinjector) was simply machined in thewrong place and in the wrong shape. Asa result, we ended up spending time onour machinist's Bridgeport making modificationsthat shouldn't have been necessary.Finally, we found that the new intakemanifold did not come with manifold-tocylinderhead gaskets, so they had to bepurchased separately.

Nevertheless, the finished job is handsome,and looks like it should producenoticeable improvements in quarter-miletimes. We'll report on those improvementsafter our next run down the ol' 1320.

This job involves the usual cautions,including relieving the fuel pressure asdescribed in the previous article andwearing suitable eye protection. Andwhile the previous story includes particularsabout working your way down toremoval of the plenum, runners, and fuelrail, we'll start with a reminder or twojust to put you in the proper mindset forthe job to come.

ANYONE'S PROJECT | no tools required...................... N
BEGINNER | basic tools.......................................... N N
EXPERIENCED | special tools ................................ N N N
ACCOMPLISHED | special tools and outside help ...... N N N N
PROFESSIONALS ONLY | send this work out......... N N N N N


From Mid-America Motorworks catalog:

>> Accel high-flow intake manifold,PN 618-589
>> Accel high-flow intake runners,PN618-587
>> Accel high-flow plenum, PN 618-583
>> Edelbrock throttle body, PN 609-093
>> Adjustable MAF sensor, PN 622-622
>> EGR Tube Insulation
From local speed shop:
>> Mr. Gasket manifold/runner gasket setPN 5851
From local Chevy dealer:
>> IAC connector
>> TPS connector

In addition to everyday handtools suchas screwdrivers, wrenches, and sockets,you'll also need:

>> 5⁄8-inch line (flare) wrench
>> 3⁄4-inch line (flare) wrench
>> 8mm socket
>> 10mm socket
>> T20 torx socket
>> T40 torx socket
>> T45 torx socket
>> 3⁄8-inch16 tap (for chasing cylinder headbolt holes)
You may also want to use:
>> Snap-on ball-type hex and torx driver set
>> Snap-on wire connector pigtail remover
>> Teflon tape (for pipe fittings)
>> Silicone sealant (for front and rear ofintake manifold)
>> Thread sealant

38 Final step in this job was adjusting theThrottle Position Sensor (TPS) using a DigitalVolt/Ohm Meter (DVOM) to achieve the properspec of 0.54 +/- 0.08 volts. CF



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