[jellish]

Hey guys! I finished up installing a Sniper w/HyperSpark on my 390 last week, so I thought I'd show the video of how it went.

 

[PSIG]

Nice, using the instructions and basic principles to get it done. BTW, you can put a new timing mark and pointer anywhere, and sometimes I'll put a stiff wire pointer under a bolt or screw head under the engine, with a matching mark. Set your crank to the exact timing on your original pointer that you want to read from underneath (0°TDC, or multiple marks, whatever) and set your mark to your new pointer. Kinda weird laying under the front bumper or other location to set timing, but whatever works! 😎

 

[DesertXL]

Hey guys! I finished up installing a Sniper w/HyperSpark on my 390 last week, so I thought I'd show the video of how it went.

Hello jellish,

Thank you for sharing the video. I do agree with you on some points in favour of TBI over a carburetor. It however is possible to get just as good fuel mileage with a carb under a constant set of meteorological and fuel conditions with a properly tuned carb and properly realized ignition timing map. In other words the big problem with carburetors is you can tune them just as well as fuel injection but only at one fixed temperature, one fixed elevation or atmospheric pressure and with a constant chemical fuel source. Alter any one of those and the performance and or fuel mileage starts to suffer. Also for people living at high altitudes (> 5000 ft MSL) on hot days, especially with the air con running (adding additional engine bay heat) most carb's like a Holley based or even the older Autolite 2100 or 4100 can start to boil the fuel right in the bowl and everything goes south at that point and that's with an engine running with a 160 degree F stat and keeping around 170-180 degrees under those conditions.

The latter half of last summer and fall I was able to tune (both carb and ignition timing map) my '68 XL with a Z-390 and a energy vampire of a C6 coupled to an another energy vampire heavy duty (large bearing) Ford 9" to get 18 MPG in a rural setting (so a mix of town and highway) and that was with the factory air con running and no spirited driving. Then the government changed to the winter formulation gasoline come late fall and with the temperature dropping (aka density altitude) that all went out the window because: carburetor.

The one problem however with TBI fuel injection, as GM knew but delayed sequential multiport mass production (GM used TBI on many vehicles for many years) is you're still using a wet manifold and fuel distribution still isn't really equal and some cylinders burn lean and some burn rich and that can change under loading and RPM variations. I am just curious why you didn't go with a sequential multiport fuel system for the FE for all that work? Plus with sequential multiport fuel injection and with an appropriate controller you should be able to adjust the phasing of the injector pulse with respect to crank angle for maximum fuel atomization (no puddling of fuel sitting on the closed intake valve) under low and medium power levels for increased efficiency of the engine.

Please do not misunderstand, anything that improves fuel mixture adjustment on the fly is a good thing and that carburetors do have their place such that if you live closer to sea level under more temperate conditions they should work very well if you understand and are willing to work with their idiosyncrasies (setting the choke on cold starts and such).

Anyway nice to see you have your FE running with fuel injection.

Cheers

 

[PSIG]

Agreed to all those points, generally. Improvements are incremental, and the biggest gains are usually chosen first. Electronic control, easy sharp tuning, automated functions and corrections for conditions are the big gains, while fuel distribution from MPFI is good, but smaller gains. Get what you can with the time, funds and skills you have.

Injection timing (fuel squirt end-point) is adjustable on most MPFI setups, but it is interesting that most OEMs and most performance tuners do the opposite of your description. This is of course tested while tuning, but depending on many factors from injector angle to spray pattern, injecting on a closed valve promotes better fuel vaporization. Weird, as gut instinct first says to inject while the valve is open, right? But, even the newest systems try to enhance vaporization using stuff like dual-injection per-cycle or injection start at valve-close, in order to promote this "cooking" vaporization, and tighter-stream spray to the back of the valves, instead of the fog patterns we like to think are better.

For me, this is what makes tuning so much fun, as you don't really know what is going to work best until you get in there and try it. A surprise in every box!

 

[My427stang]

Sorry I didn't have time to watch, but if you haven't upgraded your handheld, laptop (if you use one) and the ECM, recommend you get the latest from Holley. I have seen great improvements in behavior on the Snipers, and not sure why, but they always seem to deliver with an old software version. It's very easy to do

Nice work, I like the Snipers and Terminator throttle bodies, just hid one inside a Vortech blow 347, couldn't ask for a nice behaving engine

 

[jellish]

Hey guys, thanks for the comments! I went to TBI (Sniper EFI) simply because it was the most straightforward and easiest path to EFI. MPFI on a FE (from the research I did) is not nearly as simple or cost effective. If I was going to a HP motor I'd go that route for sure, but this is a convertible cruiser.

@My427stang yeah that helped a ton! I updated to the latest firmware and it fixed the only issue I was seeing, which was random stalls at idle.