FYI on 403 intake manifolds. The 403 is lower then the 455. Thus the 403 can use the taller GM Olds car, aluminum or iron intake manifolds. But both end up having the carb mounting surface at the same height in relationship to the bottom of the hatch.
As to EFI systems. The Howell system IS a GM designed system that has had a Steller reputation, and service life since 1987. I put it on our 78 403. Has performed perfectly ever since the first day I installed it. Even when I didn't set the correct spark timing. The EFI system corrected my error on it's own. With the 3:70 FD, and the GM/Howell EFI. Our MPG has increase nicely. But the instant starting/stopping, smoother running, performance increase, and cleaner oil in the pan. With our GVW runs in the 17,000 to 24,000 LBS range all the time. These are qualities that I truly need. At the 17,000 GVW. Our MPG has been generally around 8.9. No headers, and the stock 2.5 tail pipe. Speeds from 60 to 65mph. We are always towing Linda's 5,000LBS handicap lift van. Or my 24 ft enclosed car hauler. With a car inside. Thus I have no idea what MPG it would get not towing. Bob Dunahugh 78 403 Royale Mouse House
________________________________
From: Bob Dunahugh
Sent: Thursday, December 27, 2018 11:46 AM
To: gmclist
Subject: RE: Fitech fuel injection and header info
I put in the GM Howell system with spark control. I had no hatch clearance issues. And I can walk into any parts store for parts. Bob Dunahugh
As to EFI systems. The Howell system IS a GM designed system that has had a Steller reputation, and service life since 1987. I put it on our 78 403. Has performed perfectly ever since the first day I installed it. Even when I didn't set the correct spark timing. The EFI system corrected my error on it's own. With the 3:70 FD, and the GM/Howell EFI. Our MPG has increase nicely. But the instant starting/stopping, smoother running, performance increase, and cleaner oil in the pan. With our GVW runs in the 17,000 to 24,000 LBS range all the time. These are qualities that I truly need. At the 17,000 GVW. Our MPG has been generally around 8.9. No headers, and the stock 2.5 tail pipe. Speeds from 60 to 65mph. We are always towing Linda's 5,000LBS handicap lift van. Or my 24 ft enclosed car hauler. With a car inside. Thus I have no idea what MPG it would get not towing. Bob Dunahugh 78 403 Royale Mouse House
________________________________
From: Bob Dunahugh
Sent: Thursday, December 27, 2018 11:46 AM
To: gmclist
Subject: RE: Fitech fuel injection and header info
I put in the GM Howell system with spark control. I had no hatch clearance issues. And I can walk into any parts store for parts. Bob Dunahugh
