I have an older 2 barrel Holley Pro-Jection System that surges at low rpm's. When the A/C is engaged the problem magnifies. I had a local Hot Rod mechanic take a look. He believes this Holley is not delivering the volume needed for the 455 engine and is recommending to change to a 4 barrel Edelbrock 1406 carburetor. He has concerns about technology involved with a new Holley Sniper EFI, especially if something fails while traveling. I have also seen recommendations to use a professionally rebuilt Rochester Quadrajet carburetor. When I inquire with ChatGBT and Claude AI they recommend Quadrajet and then the Edelbrock.
Based upon my research, my Holley system seems to be prone to the surging issue.
Any thoughts?
Thank you.
Those injectors do not flow enough fuel for the Olds 455 (or 403). Holley changed from 80 pound per hour (PPH) to those 60pph injectors about 15 years ago and caused a lot of issues within the GMC motorhome communiity. 60pph injectors can not flow enough fuel when you get near wide open throttle.
However I assume your system was running fine and this is a new issue. Surging generally is caused by a lean mixture. The Holley Throttle Body (TB) was designed for a fuel pressure of 12-13 PSI. There is an adjustable fuel pressure regulator built into the TB (the round cylinder between the injectors).
Your problem could be the fuel pressure regulator has gone out of adjustment and dropped the fuel pressure. check the fuel pressure with a gauge. It can be adjusted from the Allen screw on top of the regulator. Low fuel pressure usually causes other issues like stalling when you step on the accelerator.
Also check for vacuum leaks.
Another issue could be the butterflies are closing too far causing the idle control to open more which leads to a lean mixture at idle.
Your mechanic is correct in his concerns with aftermarket EFI kits leaving you at the side of the road. They are mostly proprietary systems and with any failure the manufacturer wants you to ship the system back to them for repair. That is fine for hot-rodders and classic cars who generally don't go far from home. But not so much in a motorhome you drive days and weeks away from home.
An EFI system based on GM parts, such as Howell, is a better choice since parts are readily available and mechanics have knowledge with them. I'm not sure how Howell has addressed the smaller injectors. I changed from the Holley TB with the small injectors to a Rochester TB with larger 80pph injectors and have no issues with my Howell (EBL eqipped) EFI system.
