hi
i first installed on 65 with 289 and auto about 6 years ago. the holley carb on there would go through a full tank between sydney and canberra without any spirited driving. with the sniper, the cold starts are excellent and fuel economy is much better. the first attempt was challenging. called holley helpline (had to wait until about midnight AU) and they send a whole new system. the highlight of the first system was the ceasing of the 02 sensor in bondi one sunday morning, which caused over fuelling and wouldn't start. i got it home, eventually, after smoking out the entire of the sunday brunch scene.
the second unit was fine, the 02 sensor was ok, however i didn't get too stuck into the tuning etc part of it. driving it wasn't great and it was frustrating. i didn't do the sensilbe things though - like check the voltage at the coil (pertronix coil and electontic ignition) so I wasn't having the best time while driving it. i forked out $800 to get a tune on a dyno in QBN near canberra, that made a lot of difference, and the tuner locked the tune so that the holley sniper didn't update fuel etc. there was a backfire through the throttle body at around 2200rpm, which sounded awful and used to scare me when it happened.
This year i've replaced the dash, had found that the immobilser had shorted itself and so re-wired the dash completely. I kept the ballast resistor wire, however added a relay to the coil. i had found that the coil was only getting 6-7 volts, which wasn't great.
The dyno graph showed the timing moving about, as the timing changed in the distributor. was a bit annoyed the operator didn't mention, or didn't pick it up.
I did invest in the sniper fuel tank and the hyperspark coil, box and distributor, as i thought these were problems, causing the backfire. as soon as i added the relay, the backfire ceased, and it has been excellent to drive. throttle response was great, cold starts a breeze (i'm in highlands nsw and no probs on those frosty winter mornings) the car goes through the gears and rev range without issue now.
if i was starting again, i would be concious of the below:
- not installing on jack stands, if possible, it is a pain to try and drill the bung into the exhaust while its on the ground, or on stands - and make sure the bung is close enough to the collectors
- RESEARCH!! i looked at fueltech and holley - i went with holley as they have been around and i had used before. There is a guy name Joe Simpson who is based in the states, he has excellent information on tuning holley systems on you tube and a course if you want to get overwhelmed
- seek help where needed. i had spent $3k or so on a master kit - another $800 to get it running perfect was money well spent
- don't be discouraged if its not great day 1. see point 2. learn about it, appreciate the complexities and lean on the holley notice boards if you need to
- if your 02 sensor fails, there is no need to buy a holley sniper replacement. check the plug, the wires and look for alternatives. i was on my 5th 02 sensor before i figured this out. i hadn't adjusted the cold start enough which put too much fuel in and made the start up dirty, which fouled the sensor
- try and score yourself an invite to donnie's mustang rescue, who has did 95% of the work on this for me
overall, much better than the carb, however much harder to get correct