Tbi swap build thread

[rfmaster]

You will need the DRAC to convert AC 4000 ppm signal coming from VSS. The DRAC will provide correct 2000 ppm square wave signal to the 7747 ECM. You do not need 90+TPI ECM. DRAC will also provide 4000 ppm square wave signal to the electronic instrument cluster from 90 burban. Alternative to DRAC is a dakota digital SGI-5 can do the same without DIY alteration of the DRAC to account for tire size, rear end gear ratio and VSS reluctor gear.

Problems

Crane cam 100052 has duration @0.050 216/216 with LSA of 110. This is a good carburetor camshaft, but it will make MAP sensor very unhappy! I am going to guess your idle vacuum is only 12 to 13 in-Hg at 700 RPM with plenty lopping. Even modified 7747 will have problems at idle. The kicker is 216 duration and tight 110 LSA. If budget permits go for a cam with duration around 210/210 and LSA more than 112 deg. You'll loose a little bit of top end power, but your idle will smooth out.

Close alternatives are Comp Cam 12-365-4
Lift I/E .499/.493
Duration @0.050 216/220
LSA 113 deg

If you heads can not take this much lift Speed Pro CS1013R can be a good candidate
Range 2000-4500 RPM
Duration @.050 214 intake/224 exhaust,
Lift I/E 0.443 /0.465
LSA 112

Disabling EGR is straightforward in EPROM. To get the full power of this engine expect to DIY tune. Please be aware that Vortecs do not require too much timing ~ 32 deg maximum at 3000 RPM vs 36+ for conventional heads. Thirdgen.org has extensive articles that covers this in fine detail.

//RF