Holley Sniper

[dezelsky]

Thank you Mr Green411 for sharing your experiences with the Holly setup.

I am currently on the return leg of a trip to Italy in my 411 S4, It is not directly comparable to yours - with the later series 400ci engine + torqueflite. It also has a 603 rear axle with longer top-gear ratio, and MSD ignition kit both fitted by Martin Barnes several years ago. I bought an Edelbrock ‘Performer’ 750cfm from Summit to replace the worn out Thermoquad with electronic choke. This worked pretty well immediately out of the box, and fits with the original air-cleaner. I took it for a rolling-road tune up but no adjustments were required. Almost certainly over-carbed, but seems to suit it well, with easy starting and good kick-down when needed.

I had not bothered to check fuel consumption up until now, fearing the worst. However having covered 1700 miles on this trip so far, my back-of-fag-packet calculations tell me it is returning just over 16mpg. This is using regular 95 fuel and sometimes 98 super when conveniently available. Whilst It is still undoubtedly a very thirsty machine, it is slightly better than I was expecting. Seems happiest on long motorway runs between 2500-3000rpm where it averages 17-19mpg. On days with more stop/start and mountain driving it returns 12-13mpg.

I have occasionally flirted with the idea of fitting an LPG conversion, but based on other forum comments the downsides appear to outweigh the upsides, unless the car is used for everyday substantial mileages, so have rejected that idea.

[Green411]

Dezelsky, thank you for thanking me!
Much respect for driving your car such a long way - had any problems? I'm not a fan of LPG conversions myself, although I'm not sure why. Maybe too complicated thus too many opportunies for a failure to proceed? (on the assumption that a Bristol would never do anything so vulgar as to break down....)
As soon as I have any proper empirical-ish fuel consumption results (yes, good or bad!) I'll let y'all know. But so far I can say that starting, idling stability, part throttle driveability and general crispness are much better.

[dezelsky]

Just under 3000 miles for the trip in total. No problems, and no oil or coolant top-ups required. Comfortable and fast enough to keep up with anything modern on the autoroutes - a real Grand Tourer as it was originally intended, I guess. The total fuel cost is painful, so best not to think too hard about it.

[Green411]

Hi all
Got back from the Le Mans Classic on Monday, and after an 872 mile round trip at last I've got some empirical fuel consumption results.
When I drove my new car home from the dealers last September it was about 170 miles of mostly 60-80mph (indicated, officer....) on dual carriageway plus some stop-start crawling and took almost a full tank of E5, working out to 13.6mpg. At the current UK E5 average price of £1.59/L (RAC) that's 53p per mile.
The car just didn't have the performance one would expect, it smelled of fuel and it was a very reluctant starter, hot or cold.
The car now has Pertronix electronic ignition and, of course, a Holley Sniper with an ethanol-proof fuel system. As I've said in recent posts it now runs very well, starts quickly hot or cold, has a rock steady idle and rpm's cleanly with no hesitation or fluffing aparrent. The plugs are the right tan colour instead of being caked in soot.
After fitting but before the Le Mans trip it did 14mpg on E10, which at the current UK average of £1.45/L (RAC) that's 47p per mile = 6p per mile reduction.
On the Le Mans trip the car started full, used 3.5 tanks and so had half a tank left when I got home. Filling it up to get back to where I started brought the total fuel used to 250.5L/55.2 gallons. Thus the overall fuel consumption for the 872 mile trip was 15.8mpg, on E10 = 42p per mile at current UK average.
The detail by tankful is:
1st tank 14.2mpg (lots of crawling on UK M11, M25 & Eurotunnel plus 70-80mph on autoroute Calais-Abbeville)
2nd tank 15.8mpg (almost entirely 70-80 mph/3-3500rpm on autoroute to Le Mans with slow stop/go drive through Rouen)
3rd tank 16.7mpg (as above)
4th tank 17 mpg (50 miles of 70-80mph on autoroute, queues at Calais Eurotunnel, 100 miles of 60-70mph in UK plus 5 miles of crawling at Dartford crossing).
So in round figures I've spent c.£2000 to save roughly 10p per mile, which is a 20k mile payback or roughly 7 years. However, and it's a big however, the improvements in overall driveabilty are such that even if there was no improvement whatsoever in 'economy' (if that's the right word....) other than the move from E5 to E10, I'd do it all again. I accept that a more refined aftermarket system - Edelbrock's Pro-Flow, for example - would probably yield more efficiency, but the entry cost is higher. And a new carb would be cheaper, better than the old carb but not as good as a throttle-body efi like the Sniper. EFI = rifle, carb = shotgun. So ya pays ya money and takes ya choice.
And I haven't even thought about refining the target fuel/air ratios in the Sniper's ECU map yet........
Thanks for your interest in my little adventure.

[dwomby]

Thanks for the detailed results.

I think, given our lower US full prices and my low annual mileage, the investment is not worth it to me. I will keep tinkering with the carb and Pertronix ignition once I get the car back on the road.

David

[David C]

Great to hear all well. Thank you for taking the time to share.

[David C]

I have just spotted that Holley have released the Sniper 2 EFI kit. Hopefully this deals with most of the issues they had with the original. Really tempted now but will wait for a few home user reports.