Considering Holley sniper EFI for my 1969 340. Thoughts from people who have that set up?

I always say this but it makes little sense to run the Holley EFI without the Hyperspark ignition system. Being able to control the timing through the ECU software is a major benefit of the conversion to EFI. Without the timing control you will be leaving performance and drivability on the table. If you are dead set on sticking with your MSD ignition I wouldn’t even bother with the expense or hassle of the EFI, just stay with a carb.

How is the wiring in the car? Another thing I always suggest is to re-wire the car before trying to install any EFI system. You need clean power and want to avoid creating wiring situations that will increase the chances of EMI causing problems. That will definitely happen if the wiring is a mess. EMI (or RFI) will cause no end of frustration since it really has nothing to do with what the program does except that it causes it to not work right.

Don’t skimp in the fuel system either. An in-tank pump is the way to go. Also I’d sat ditch any rubber hose and worm clamps and get -AN fittings for the connections. Don’t want leaks at 60psi.

And last - consider how involved you want to get with the tune. A lot of guys won’t touch a lap top but that’s really how to get the most out of the system. Building custom fuel and ignition tables in the software goes a long way in understanding how it all works. The initial “wizard” tune is generic and is really only there to get the car started. It takes some time to figure out what the car needs.

It really does not matter what size engine you have. Eventually the program will adapt to your driving style. I had a Sniper on a mostly stock 383 for thousands of miles and there were no issues.

Again, if you think you’re just going to plug it in over a weekend and suddenly the car will run perfect don’t waste your time. Invest in all the right components and be willing put the time into the tuning process and you will get some to ing out of it. GI GO as they say.