Holley Sniper

[Green411]

They're all very good figures, especially for 50+ year old cars with (by modern standards) poor aerodynamics.
If only we could help DWomby with his dismal consumption! If I recall correctly David struggles to get into double figures with a 360 cid engine? Makes my own tribulations seem small. I looked up the cam specs of his Mopar Performance 4452761 and they don't seem too outlandish.
So wrong timing/timing curve? Vacuum advance missing/not working? Cam incorrectly installed? Carb leak? Other leak? Fuel evaporating? Engine fault? Over-rich carb? Blocked air filter?

[dwomby]

Originally Posted by Green411

They're all very good figures, especially for 50+ year old cars with (by modern standards) poor aerodynamics.
If only we could help DWomby with his dismal consumption! If I recall correctly David struggles to get into double figures with a 360 cid engine? Makes my own tribulations seem small. I looked up the cam specs of his Mopar Performance 4452761 and they don't seem too outlandish.
So wrong timing/timing curve? Vacuum advance missing/not working? Cam incorrectly installed? Carb leak? Other leak? Fuel evaporating? Engine fault? Over-rich carb? Blocked air filter?

You do recall correctly although most of my driving is suburban. So higher numbers may be possible on longer runs. Unfortunately, my car has been off the road since late last year while the front suspension is out (see the saga so far here: http://www.bristolcars.info/forums/8...r-removal.html

I expect to start reassembly in another week or two when temperatures and humidity here have made working in the garage possible. I hope to get her back on the road before Christmas and the fuel consumption/tuning issue will no doubt need addressing then and I'll welcome all help!

David

[AndrewA]

As everything beds down I'm finding 25 mpg relatively easily achievable and a nearer 30 on long runs driven sensibly.
I do however enjoy making full use of kickdown when running around locally - it's difficult to resist - and then I'm back in the high teens.

[dezelsky]

These are great results. Thank you for sharing. All the more reason for us to enjoy our cars!

[David C]

A bit more reading on Mopar forums about Sniper upgrades has led me off on a bit of a tangent. Changing to EFI requires a fuel pump that can draw up to 20 Amps. Air conditioning can add about another 15 Amps.

These two upgrades alone can double the original current draw. The easy fix is to upgrade to a newer high output one wire alternator and do away with the original external voltage regulator. This is great but leaves the ammeter in circuit, wired with cable which isn't adequate for the new load and now a fire risk.

Maybe the best solution is to do away with the ammeter and find a period voltmeter to replace it.

Another option if keeping the original charging system would be to fit LED headlamps and wire the air conditioning to disable the heated rear screen when in operation.

[Green411]

Interesting point DavidC makes, so I checked my own car. My '73 411/3 has a voltmeter, albeit a slow-reacting one. As a precaution I'd renewed the separate solid-state regulator at the time I fitted the Sniper. Alternator looks original-ish and there's no sign of an upgrade or replacement in the history file.
I checked the charging with my voltmeter, and with fans on (and electric fuel pump obviously) it charges at 12.75v (shows just over 13v on the dash gauge) and 12.25v with the headlights on main beam, as well as the fans. Normal running shows c.15v on the dash gauge, which reads a bit high in relation to my multi-meter. Exec summary: it seems to work.

Referring to David C's earlier post about intake manifolds I experimented by trying my car without the (Holley-reccomended) divider-less Wieand sealer plate between the stock cast-iron spreadbore divided manifold and the square bore Sniper. I used a gasket with a divider strip. It ran ok at first but soon developed an air-leak that I couldn't cure so I went back to the original setup of open sealer plate with a gasket above & below, and it's running fine again. Whew....