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.