[Gmecm] TBI for 455 Olds

[Aaron]

First I should mention, all my experience comes from installation and some light tuning on two KITS sold for the 73-78 GMC Motorhomes.

Howell EFI and Turbo City.

http://howellefi.com/tbi-kit-455-gmc-motorhome-1973-78.html

Turbo City may be out of business.

They used GM part with the GM 7747 ECU. It made finding parts on the road easier than customer EFI.

 

That Motorhome community is still very strong and active. 

http://www.gmcmotorhomes.com/clubs/directory.html

Here is a Tech. webpage from the Eastern States GMC Club. It includes two articles on TBI for the 455 in these motorhomes.

http://www.gmceast.com/technical/

 

The good news about the distributor is the size. The 455, 403, 350 and 307 all used the same distributor shaft dimensions. The only difference that I ever noticed was the cap clocking position. Meaning the HEI cap has a tab that fits into a notch on the aluminum distributor housing. Some Olds had the notch on the passenger side, some on the driver side. The housing can be notched to make the cap ?clock? to the position that fits your needs. On the Motorhome, the HEI module to coil wires were longer than normal to reach the other clock position. This was the case in both the standard HEI and EST (Electronic Spark Timing) distributors. We would buy rebuilt distributors from Napa or AutoZone or Rock Auto for a mid to late ?80?s Olds V8 that had the 7 pin module. 

The bad news is the Distributor to ECU wiring harness does not come with the rebuilt or new parts. We always searched the junk yards for those. V6 or V8 HEI distributors with the EST system all had the same harness. 

Page 131 - 133 on this PDF shows the pictures of what I?m talking about. http://www.gmceast.com/technical/Waters_Howell_TBI_Installation.pdf

 

 

As mentioned by another post, BEWARE of the Quadrajet to TBI adapter. One of the rear bolts in under the IAC passage AND it LEAKS !!!  A LOT !!!! AND I spent way too much damn time looking for it !!!!

Page 47 on this PDF shows the location. http://www.gmceast.com/technical/Waters_Howell_TBI_Installation.pdf

 

As for the code, I think it started as the ?89 Chevy C2500 .

But I?ve can?t research it any more now.

Aaron

 

 

 

 

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