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Old 06-30-2019, 11:34 AM
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sbc 671 blower anyone running holley sniper efi

looking to go with HOLLEY Super SNIPER EFI 4150 2X4 kit on
sbc with 671 blower old school street rod

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Old 07-15-2019, 10:12 AM
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Holley Sniper EFI

I would talk with Holley Tech support.

I just finished a 57 Chevy with the single 4150 unit. Attached pics below.

As with anything, fuel to air flow through all rpm ranges is the concern.

Sniper ECU does a good job of optimizing the AFR, but obviously at the physical/mechanical level, everything has to be properly matched.

The unit I installed included the tank with pump and sender, the Hyperspark Distributor/Coil package, 4150 (550-511), and later the Hyperspark CD Box.

We were still having run-abilty and start issues, so then picked up the USB connector and downloaded the software for the laptop.

The only thing not purchased was the fuel line kit and in hindsight would have been better to have done that. I made a 3/8 hardline supply and used the flex inch line that was from the carb setup as the return. Eventually this return line will need replaced. For all the flex I did, I used Earl's 250 PSI FI 3/8th line. I did not build the car, so don’t know quality of the inch line that they had put in.

Depending on which Sniper setup you get, you most likely will have to update the firmware, so you will need some computer/internet abilities here.

Basically down load the update from Holley, save to the supplied SD Card, and place in the control unit and upload it. The Sniper ECU will finish it out.

In the area of Computer/Internet savvy … I would suggest getting the USB connector and down loading the tuning software to your laptop.

The main issue we had was fixed when we pulled the engine and discovered the original builder “expert” had placed 30 over pistons and rings setup or nitrous, in a 40+ over engine that had not been properly bored. Cylinder three was the worst, which was .047 over, which puts the bores on this SBC 400 @ 4.158 to 4.172, running a 4.155 piston and gaps of about .034 to .037…

The Sniper system can correct a badly running engine when the issue is carburation. Yet, it can’t fix a poorly built or mechanically damaged engine.
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Name:	1957 Chevy EFI Holley Sniper Roughed in Engine 002A.jpg
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Name:	1957 Chevy EFI Holley Sniper Roughed in Engine 001B.jpg
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Last edited by Foperfoauto; 07-15-2019 at 10:15 AM. Reason: line spacing
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