Holley Sniper
 

Hi all, new member here with first post. It's so exciting..... I've recently bought a 411 S3 and am beginning to get over the shock of the fuel consumption. There's plenty of play in the carb throttle shaft yet it runs very rich so am assuming the carb is well worn.
Am probably going to get a Holley Sniper master kit, as I want the driveabilty of efi. So am very interested in anyone's experiences, good or bad, of them - particularly if you did it yourself, as I plan to do.
If you have one, what was fitting it like? Did you choose an in-tank or in-line pump? If in-line, what did you do for a fuel reservoir? What driveability difference did fitting it make? Etc etc.
Sorry if I've missed an existing thread about this topic.
Thanks in anticipation
Cheers Mark

Welcome! Sorry, I can't help you but I have a 408 with non-standard 360 and performance camshaft that gets horrible mileage and am considering the Sniper too. I will be interested to see how people propose fitting the fuel return into the tank.

David

I too am dismayed by the fuel my 411 & 412 use, so to that end I made a study of various fuel injection systems . Many U TUBES and articles latter these are my conclusions comparing a well set up carby verse an after market efi

1/ Your fuel economy will not improve
2/ Your motor will run more reliably(starting hot and cold, no choke issues and perform more smoothly )
3/ The cost and issues of setting it up isnt as easy as it looks
4/getting it tuned and set once again isnt that easy.
5/ Given the miles I travel in my Bristols and the cost of an EFI i decided to stick with what I have.

Do your research there is a lot on U TUBE and the US forums . Keep us informed.

I suspect you are correct and that not much, if any, economy improvements would be had and one would, at best, have to drive a lot to recoup the cost via fuel savings.

A friend of mine has suggested that I might improve my car's economy (and horrible muscle car-like idle) by reverting to a stock camshaft but I think that would be too intimidating for this home mechanic!

David

David my brother Geoffrey had a 411 mk 1 with the 383 motor which had been set up by a friend of ours in Sydney, Keith would know more about Chrysler cars and motors than any one in Australia .Geoff fitted an alloy manifold and had made a set of extractors . This car with a very mild sports cam would go like the wind and return 18 to 20 mpg.

I have spoken to Keith about my 411 and he has suggested reverting to a standard sports cam as supplied by Bristol and use either a 600 or 650 Edelbrock carbie. Edelbrock have a new range of carbies which are meant to improve economy and performance.

I had a hotter cam fitted to my car and wish I hadnt

Your car being a Mk3 had a slightly detuned motor than the Mk 1 and 2 but I have no idea what cam was used. Chrysler at the time were detuning their motors in the 70s and eventually upgraded them to the 400 motor which had low compression and no go. My 412 is very slow compared to the 411.

Morning Mark - congrats on your new acquisition - apart from the fuel consumption I hope you're pleased with your car?
There's an interesting thread on here titled Fuel Consumption where you can see what different cars are achieving.
12/13 MPG seems achievable on a big block with a new carb and everything else bang on - I'd imagine the only thing that's going to alter that dramatically is an LPG conversion.
EFI + LPG would be great and a nice winter project for you!
Cheers
Andrew

My 408 came with it. The car lost its original engine sometime in its history and the 360 from a 1978 Dodge Monaco was rebuilt by a Mopar performance expert and fitted. He fitted the following (all I can make out from the 1992 photocopy of a handwritten receipt!):

Mopar Performance Cam 4452761.
Lifters unknown.
Mopar Performance Intake Manifold P4529116.
Piston rings 4.030"
Pistons unknown
Exhaust valve 1863

It is now fitted with:

Summit Racing Carb SUM-M08600VS. 600cfm
Distributor Pertronix PNX-D141701.
Coil Pertronix PNX-45001.

The exhaust manifolds are stock cast iron things.

The cam gives the car a bit of a Muscle Car-like performance and sound. I think I'd be happier with a stock cam as I am told it would quieten the idle and improve economy but the car can certainly pick up its skirts and shift itself!

David

Andrew/David/Peter (in alphabetical order!)
Many thanks for your replies, from across the world by the looks of it. I'm intrinsically attracted to efi vs a carb from my experiences with other cars: currently I've got a '90 Chevy truck with a 5.7L/350 small chevy and a 5-speed manual, and a '95 Corvette 5.7L LT-1 auto which I'm supposed to be selling to make way for the Bristol. The truck is 2-barrel tbi, does about 19-22mpg imperial and revs at 2200 at 80mph. It weighs 100kg more than the Bristol & has worse aerodynamics. The Corvette is port injection, does 22-30mpg and has the same rpm at 80mph as the truck. Prior to the truck I had a '54 Ford Popular (Anglia to David I'd guess) with a stroked (to 6.3L/383) small Chevy, 3 speed auto and a Holley vac secondary carb, which did 11-15mpg, can't remember the gearing alas. Admittedly the Pop hot rod was a hoon-around sort of car but the truck and the 'Vette both use almost half the fuel of both the Pop and the Bristol. The Bristol revs at c.2900 rpm at 60, so with a 5500rpm red line that gives a theoretical top speed of c.120mph. I attribute the huge fuel consumption differences to 2 things: the gearing and efi. Surely even tbi will atomise the fuel much more finely, and control the mixture much more? Plus the Holley's self-learning via it's wide-band oxygen sensor (once initial paremeters are entered) suggests it will continually refine and control it's fuelling? So I'm thinking that even a modern carb will be less efficient than efi?
But I'm not an engineer - far from it, I'm just someone who's fscinated by how cars work and loves making them run better. So keep sending in the advice! I have lots to learn.....

Hello, I am an engineer (trust me !). I have spent most of my career running two companies, one of which is a well-known builder of Rover V8 engines (which were originally Buick 215 c.i.). Our most common production now is a fairly sophisticated 4.8 litre (actually 4.75, 290 c.i.) with a long-runner manifold, single motorised throttle, modern injectors, and using the best of aftermarket EFI computers. This an expensive set-up but it suits certain applications.

We have recently started using Holley Snipers on some 'cheaper' engines. So where we are not aiming to produce the rather luxurious broad torque curve of the long-runner manifold, we can let the engine be more like a sports-car engine with maximum torque and power developed at higher rpm. For this the Sniper is ideal. Where we're building 4.8 or 5.0 litre engines with around 300 bhp we use the 4-barrel Sniper on an Edelbrock manifold. For smaller engines we are a bit stuck because the 4-barrel is too large, and there aren't any 2-barrel manifolds available. We have made a very good 2-barrel manifold by modifying the standard carburettor manifold for the engine, which had 2 SU or Stromberg carbs, but the modification is quite complicated and therefore expensive.

The Sniper range seems to be intended for more highly tuned engines, as even the simplest 4-barrel is said to be adequate for up to 650bhp, and the basic 2-barrel for 350 bhp. We have found that its self-learning is very good as long as the lambda sensor is in good shape (which I suppose is obvious). The tuning control allows for you to add more information and precise parameters in certain running areas. We haven't tried the ignition timing feature at all, but as that is a fairly simple output I would be surprised if it wasn't good as well.

My Bristol 409 has the original 318 in it but with a mild cam and gas-flowed heads. It currently uses an early aftermarket programmable EFI system, but it needs a thorough up-date. I am very tempted to either use the original cast iron 4-barrel manifold or find a good aluminium one, together with a 4-barrel Sniper. The original cast-iron manifold would need to have the inlet holes re-shaped and smoothed to match up with the Sniper.

The thing that would really improve the fuel-consumption, however, is a more sophisticated gearbox. We need at least 5 gears and a lock-up torque converter. I see no reason why any of the small-block Bristols should not then comfortably exceed 20 mpg. My company frequently uses the Ford 6R80 6-speed auto in other applications. The calibration is a bit time-consuming, but we can get impressive results. It might seem a bit heretical to use a Ford gearbox on a Chrysler engine but in fact nearly all of the these modern gearboxes are fundamentally ZF designs made under licence, so I feel there shouldn't be too big a culture-shock.

SO if we're using a Sniper and a Ford gearbox, you might question why you would keep that heavy iron 318 lump, especially if you have a VERY lightweight Rover V8 at 5.0 litres to hand, but there's something rather endearing about the 'Poly-sphere' 318, so I'm inclined to keep it.

Thor makes some interesting points and he's clearly brighter than I am! in reverse order, re the trans updates, Ultrabell in the USA make bellhousings to fit anything to anything else, but in the case (pun intended...) of the TF727's successor the A-518 (small-block only) I think the old TF bellhousing has to be cut off and then the Ultrabell bolts in it's place, possibly using the A518's front pump bolts? But the A518 only has a 0.7:1-ish overdrive, and a torquey old lump like a 383 would pull a 0.5:1 with ease I think - on a light throttle my car gets into top at 20mph. On the other hand a 0.7:1 is 30% better than 1:1. Ho hum....I spoke to a very helpful chap with the improbable name of Nutty Professor Transmissions, who specialises in Mopar stuff. He says 518s are v rare in the UK so it'd be a case of being v nice to the few american contacts I have to find one from a 2wd vehicle and then get it shipped over somehow. He also thought that the controllers needed for modern 5/6 speed auto double-overdrive transmissions would be a task and a half for mortals like me, although by the sounds of it possibly less so for the no doubt mighty Thor!
Re efi, my best friend has a Lotus Carlton (drool....although it has the world's heaviest clutch). He says that they used a Bosch external fuel pump which was relatively quiet, so my latest thoughts are to buy a Spreadbore/Q-jet Sniper, but not the full Kit and get a Lotus Carlton-type Bosch pump, some hardline supply & return pipes (Holley only provide rubber one in their kit) and fittings in the UK (there's a company in the midlands who do NPT stuff), which might reduce the hammering I'm going to get from the exchange rate at the mo.
Thor, on both your customer's cars and your own 409 do you use the in-tank pump or external? If external: where & how does the supply exit the tank? What did you do about a swirl-pot? And I know what you mean about the character of american V8 engines.I'm a small-block Chevy lover myself, and am gradually getting used to mopars - took several days to get over the shock of the distrubutor rotating anti-clockwise!
Thanks to all, do please keep 'em coming
Btw, if anyone knows of a prospective buyer of good user-quality '95 Corvette auto with 80k I'd appreciate it - I need the space.

Please excuse the silly name, but many years ago, when we had the more clunky precursor to this forum, a member used the pseudonym 'Bellerophon' who was the Greek god who rode 'Pegasus' the winged horse, and hence was the driver of a Bristol car as the cars have Pegasus logos inherited from the Aeroplane Company. I thought that as an 'injunear' I would use the name Thor as one who wields a hammer.

I have considered using a later Chrysler gearbox with lock-up and more gears, but as soon as I get to the point of needing to add electronics, I feel I might as well use a gearbox for which I have the technology. There are makers of other products which claim to be easy to set up for the Ford, but again I'll stick to what we know. There are also controllers for the GM 6-speed, which is also a ZF design licensed out. You and the Nutty Professor are right, the electronic calibration set up of anything with more than 4 gears is extremely involved.

The Sniper can be bought with a fitting kit which includes a pump. The rubber hose is fine and push-on fittings are also perfectly OK at the pressure the thing runs at. It has its own internal pressure regulator valve. I don't remember the pressure just now but it is about 50 p.s.i.

So, yes, you need a swirl pot arrangement. On cars which have internal fuel pumps in the tank it is possible to modify these and do everything inside the tank, but for older cars we use a low-pressure lift pump and a swirl pot. We use the Facet Posi-Flow pumps, but mount it on very wobbly bobbins to insulate the knocking noise from the body. A good value swirl pot can be bought from someone like 'Alloy Racing Fabrications' or similar. The feed from the LP pump and the return from the Sniper go in on the upper tangential ports, the HP pump is fed from the bottom, and the top port just goes back to the tank.

If you're buying rubber hose make sure it is entirely resistant to ethanol. We always used SAE R6 type hose but we have moved on to R9 type as we have more confidence in it. With R6 we have seen the outer rubber perish quite quickly, and although to be fair the inner rubber it still OK, it doesn't seem right to have the braiding exposed.

No need to apologise for a user name, young man, they seem to be silly almost by definition! I use Lankybloke on the Classic Corvette Club site, which I thought was both descriptive, for I am both, and gently amusing too. Mrs Lankybloke, however, had firm opinions so I migrated to an equally descriptive but automotive-based one here, hence Green411.
Lots of very useful stuff in Thors post - many thanks. And I imagine that in the cold, pitiless light of a dyno test your 5.0L Rovers are going to make more hp than the '60s technology of a Mopar 383? But less torque?
Re your note on swirl pots and how you do stuff:
Could the stock chrysler mechanical pump act as the lift pump?
What volume of fuel tends to be returned to the main tank with Snipers?
I appreciate all cars are different, but where do you tend to locate the swirl pot, the HP pump and the lift pump?
I'm wary of the noise level from the Holley pump - with Snipers what HP pump do you use? How noisy is it?
I've been looking at the swirl pot/submersed pump combos from the USA, such as FiTech
https://www.vitesse-ltd.com/collecti...roducts/40004; what's your view on these?
Re Transmissions, it occured to me (ie my knowledgeable mate thought that) if Ultrabell and the various adaptor manufacturers (eg JVX Racing) make stuff to fit any USA trans to any USA engine then it would be simpler in some ways to get a more widely-available GM TH700r4 - 4 speed o/d, plentiful and relatively cheap, not electronially controlled, and provided the tv cable is adjusted correctly they seem reliable. My Corvette has the later electronically controlled version of the 700r4, the 4L60E, and that's a cracking transmission. I know it's 'un-Chrysler' and thus await torrents of abuse (or what I imagine is the Bristol owners equivalent, such as a raised eyebrow...), but it seems worth a thought if nothing else....

Torque converter
 

A huge torque converter and no lock up clutch is where a lot of power gets lost. The wonderful driving experience where the car hardly ever changes gear and proceeds so effortlessly is down to the torque converter but unless the torque converter can lock up you will always have the disappointing fuel economy.

Hi all, just a quick update on my fuel consumption and efi thoughts:
Firstly fuel - my car has averaged 13.9mpg , including a c.150 mile drive home from Warminster to near Cambridge on mostly dual-carriageway (what a wonderfully old-fashioned expression!). My intial horror at a fag-packet calculation of 10mpg came from assuming the fuel gauge was accurate, but it seems a tad on the pessimistic side. Unless it doesn't take account of the reserve?
Otherwise I absolutely luuurve the car. I adore idiosyncratic touches like the plaited leather glove-box handle, the weight of the switches, the flip-up front wings and the lovely chrome seat brackets. It's really comfortable, the ride is good now that I've got the (new) rear dampers on their softest setting, the brakes and steering are great and I've solved a lot of the (terrible) windnoise from the driver's door. I'm hoping that the rest of the windnoise (or most of the rest, in view of the age of the shape) will be solved when I get the driver's door hinges rebuilt over the winter. I haven't started on the oil leaks yet, (in a sense it's free rustproofing) so the only really annoying thing is it's reluctance to start when cold......
So I've thought long and hard about the cost/benefits of a new Carb vs an aftermarket efi, originality vs efficiency, and so on. In the end I summed it up in my mind as shotgun/carb vs rifle/efi: both are effective but the rifle is more controllable, more precise and less wasteful. With efi the fuel/air ratio is essentially commanded via sensor input, especially with a wide-band oxygen sensor covering a wider spectrum of A/F ratios. If I've understood a carb correctly the A/F is reactive - dependent on pressure drop & jet sizes. So I've pretty much decided on a Holley Sniper 550-516; and a Holley in-tank drop-in returnless fuel module with a 255lph pump and Hydramat reservoir 12-131. I hope to use the existing supply line and I won't need a return line. The engine bay will still look largely the same, especially if I leave the existing machanical fuel pump in place (without the pushrod, and with a new gasket to stop the oil leak!) so it acts as the block-off plate. Any rubber lines will be R9. So I'll have a stealthy ethanol-proof system that seems to get good reviews and is 40+ years more advanced than the worn-out Carter which is currently in place. Will order from Summit Racing and do the deed over winter. Will report back then. And yes, I will have a grown-up holding my hand in case you're worried......

Some interesting points raised here. After much research I too came to the conclusion that a newer transmission is the best way to keep the original character of the car but to significantly improve fuel economy.
For 409 and 410 the obvious upgrade is to a later Mopar 'box with overdrive and lockup. For a few glorious years there were hydraulically controlled models that can be automatically controlled with a couple of pressure switches and a vacuum switch.

Dick Peacock converted his 410, changing to an A518 / 46RH 'box. This was a straight development of the 727 Torqueflite and as far as I know mounts straight on the back of the Poly engine. In standard form the 410 would do between 18 and 20MPG on a run. Dick told me that he was getting closer to 30MPG on long continental runs. I hope the current owner of the car will chip in with some accurate up to date figures.

I discussed the subject with the gents from Classic Bristol Car Parts and they told me that for 409 / 410 the factory preferred the A500 / 42RH 'box from a 1992 to 1996 Dodge Durango. This is a development of the 904 transmission which is less robust than the above unit but is good for the output of the 410 in standard trim and can be rebuilt with more clutch plates to beef it up. The 42RH has a smaller torque converter but still bolts up directly to the Poly in the 409 and 410. The original starter motor bolts straight up as the bellhousing is different. The flex plate and dust shield from the 42RH will be needed as they different to the 727. 407 and early 408 have different crankshaft and will not directly bolt to the 42RH.

Fitting an overdrive will probably not involve modification to the tunnel but will require modification of the chassis crossmember along with shortening the prop shaft by around 3 inches. As the engines have good torque the factory back axle ratio is likely to still be suitable. Non overdrive units used 5/16" cooler pipes whilst overdrive units use 3/8" It may also be necessary to replace or augment radiator transmission cooler.

46RH transmissions can still be found in the US for reasonable money. 42RH are very hard to source but not impossible. STS imports will get a transmission from Florida to Essex for about £200 which is probably a lot less than the cost of crating and transportation to Florida from elsewhere in the States.

If trying to track down a suitable transmission it may help to know that A518 is the series with subsets 46RH (hydraulic operation) and 46RE (electronic operation) Similarly A500 has subsets among others of 40RH, 42RH, 42RE and 44RE.

Back to the topic - inlet manifolds more suitable for fuel injection adapters were made for the Poly 318 - E.g Weiand 7503 - but are very hard to find and quite pricey now.

I've got the car that was Mr P's - I get 18 mpg running around locally and around 25 mpg on a run.
That's with a 318, the gearbox with overdrive and lock up, new Edelbrock 500, rebuilt top end, electronic distributor, 2.8 rear, flat as a pancake cam and a fair amount of time on rolling road getting it all spot on.
Good luck with the efi!
Cheers
Andrew

That is a good result. By today's standards a 410 is not a heavy car and the relatively small frontal area of a Bristol makes it (quite) aerodynamic, but a 5.2 litre petrol engine has certain limitations ! With a good deal of fiddling about a Sniper OUGHT to be able to do a bit better, but it is quite a challenge.

Thanks - when the heads were off the chap that did them spent a lot of time getting them to flow as well as possible. The engine's quite poky - I'm apparently getting 245 brake at the wheels but have spent enough time with various cars on different rolling roads to know some are more generous than others!
The flat cam suits the car well btw - although the hot rodder part of me wouldn't mind a bit of lope!

A bit of lope on a cam does sound good in the right car, but as you say a Bristol may not be the right home for such a cam! Didn't Comp cams do a ' Thumpr' series which had the lope at idle but with modern lobe design?
If I had a 318/340/360 then I'd probably have a 518 in it now, on the basis of the overdrive improving cruising more than efi would. But as discussed earlier a 383 will need an adaptor, which then opens up further debate about whether to stick with Mopar and the A518/46RH or go GM TH700R4/4L60E for it's relative availability, affordability and ease of getting replacement parts.
Lots of useful specifics in David C's post - thank you!

Update
 

Hi all Just a quick update - well I bought the Holley Sniper, plus a drop-in fuel module with a 255 lph in-tank pump. Started work after getting home from a New Years Day local car show - where my car attracted a lot of interest.
Have taken my time and am now most of the way through the install. I have tried to disguise the update as much as possible so it looks original. Am writing about the job for Bodacious, and will post on here again after the big day. Will it still run? Ulp................

That's brilliant Mr. Green411, I am so looking forward to hearing how it goes.

Thank you Mr Thor (Is 'Mr' a suitable title for a God of war? Discuss...)
My current problem is trying to find a 1/8 NPT temp gauge sender with the same resistence as the standard one - the ECT sensor has to go in the top of the waterpump, where the temp gauge sender used to be. The only other available wet port for the gauge sender is a1/8 npt one on the front face of the pump, just below the old 1/2 NPT port. A £10 item that's driving me nuts......

What’s the resistance of the standard one?

So far as I can make out,
37*c = 400 ohms
40*c = 370 ohms
50*c = 250 ohms
60*c = 165
70*c = 121
75*c = 100
77*c = 91
80*c = 87
But these were done with hot air gun or hot water so not necessarily that accurate!

Update
 

Well the job's finished.
After connecting 6 wires, connecting the hand-held terminal provided, entering the basic engine data, you key-off to save the data and create the base map for starting. Then key on, check the fuel pump runs and primes the system, and start. It cranked for 5 seconds or so....... then it fired cleanly. And with not one iota of drama it immediately settled into a steady fast idle…..Whew…………….
All I’ve got to do now is hope it was worth it.
THe Sniper self-learns the fuelling as you drive (timing is still from the distributor) so I'll report back once I've driven it a bit.
There'll be an article about it in a future Bodacious, I hope.
Thanks for your interest. And patience!

The self learning sounds fun...do you teach it what foot to the floor means first or save that part of its education until later?

Encouraging progress! Do you have plans to add the Hyperspark distributor so that the Sniper can control ignition timing?

Back to other ways of improving fuel consumption - A bit of research suggests that the 383 is internally balanced so it should be fairly straightforward to adapt to a 46RH transmission with an adapter plate and spacer for the flex plate. PATC amongst others have them readily available, but at about $800.

Update - Woe, woe and thrice woe
 

Well..........

Haven't driven on the roads yet as there's not been enough rain in my area (west of Cambridge) to wash all the winter salt off the roads. So I've fired 'er up a few times and run up to temperature, mainly because it felt good and I'm still getting used to my lovely old 411 actually starting when asked to, instead of doing the automotive equivalent of saying 'Shan't' and stanping it's pretty little foot....

I noticed that tuel gauge wouldn't register so I took the sender out to check the float for a puncture and test the resistence as the float arm moved. All was ok, although there's no reading at the very bottom of the float arm's travel. In the end all I had to do was clean the sender's earth terminal and off on it's travels went the gauge needle, into the heady reaches of roughly half full.

The old 383 was happily idling away after 3rd start when it just coughed and cut out...aah....

Fuel pump wouldn't run with ignition on but ran normally when earthed. Pink ignition wire and red & black main battery connections all had power. Main Sniper fuse was intact. The HHT couldn't find the ECU when connected so the conclusion was (ie my Responsible Automotive Adult Julian said that) the ECU was dead.
I rang Holley Tech and they gave me some tests to do, all of which I'd just done under Julian's eagle eye. So Holley Tech agreed with Julian that as it was all connected correctly, power was available, then the ECU had failed. As it was less than 90 days since purchase it was down to the vendor (Summit) to replace it.
I've emailed Summit and they asked for quotes to send the unit back, which I've provided, and they're thinking about whether they want it back or not.

Anyway, at least my Anglo-saxon copulative vocabulary has had some excercise even if my 411 hasn't...
Will update further when something happens.

Thanks for the update - sorry to hear you've product issues.
Giving stuff back to the States is a real pain when it doesn't work or is not as described - hope it's sorted soon.
Great that when it was working it was idling happily.....looking forward to the next instalment.

Excellent article in the latest Bodacious with plenty of useful info for those of us considering following suit.

Very keen to get an update on driveability and any improvement in performance and fuel consumption.

I do hope someone tries out the Hyperspark distributor. It seems to me to be just as important to get the spark at the right time as to get the fuel mixture bang on.

Superb article in BODAcious, thank you. Like other people, I'm thinking of going down the EFI route for my S2 412 360.
Sorry to hear of initial gremlins, ain't that just how it goes.

A question - why did you go for the Holley Sniper? If I go onto the Summit Racing website and filter by Chrysler small block LA, then the option which comes up is the Edelbrock pro-flow.
It is a bit more expensive, but then Bristols have always been a car shaped receptacle for money.

Anyone any experience or thoughts?
Thanks

Thank you for the compliments!
I eventually got the replacement Sniper from Summit. I say eventually because I wanted an audit trail amd thus I initially emailed them. This produced lots of waiting 2 days for them to reply, which consisted of promises but little action. So I rang them and was polite and friendly but firm, whereupon stuff started happening. I kept the pressure up with daily phone calls for a few days until I got an email from their carrier confirming collection. A week or so later the package arrived safe and sound. I had to pester them to refund my £58 UPS fee for returning the dead one though. I don't think Summit were trying to avoid sending the replacement or paying the credit, but I do think that their processes could do with a bit of tighteneing up when dealing with foreign buyers who need a free replacement item. But at least they ship overseas, unlike Holley. So yes I would buy from Summit again. Since then I've discovered that I could have bought a Sniper from CM Frost of Wellingborough, Northants, who are a long standing US parts supplier. Probably more expensive, but less hassle.They keep reasonable Mopar stocks too, as they seem to supply the Jensen club.
So the replacement is fitted and I've since driven about 400 miles. Driveability is excellent, as is starting either cold or hot. Key on, wait a cople of seconds while the fuel pump primes, crank and away it goes. The first tankful gave 14 mpg, including learning, a lot of idling and many shortish journeys while I learned to trust it. The carb gave 12-14mpg and of course was subject to all the usual carb problems, including a strong smell of fuel all the time (I could find no leaks though).
I chose a Holley Sniper because it was simple-ish to fit and as it's a throttle body (ie like a 4-barrel carb but with injectors at the bottom of the barrels) with integral IACV, MAP sensor and TPS then I could disguise it. My understanding of an Edelbrock Pro-Flo is that it's a port injection system. So it's more modern and efficient, but is also more complex and couldn't be disguised. I've used Edelbrock stuff on my old V8 Ford Popular hot rod and it was very good, so I've no doubt the Pro-Flow would work as well as, or better than, the Sniper.
I'm in two minds about a fullyelectronic distributor, which the Sniper ECU could control. I know the old mech/vac advance curve works on my car, and as you'll know I've got rid of the points. Timing curves for 383s are around the internet, which could be copied and loaded into the Sniper, but the question is which one to use? So I'll probably run it as is for a year or so and see how it goes.
I'm currently checking the car over for the trip to the Le Mans Classic at the end of June. The radiator had a pinhole leak so I got it checked over and fixed (5 other pinholes found under pressure test, so it's a good job I did) by Anglia Radiators of Cambridge. They do lots of classic cars and warbird repairs for IWM at Duxford, are a proper old-fashioned place and I can recommend them. Of course one of the trans fluid cooler lines was seized so I've replaced that with Kunifer.
It'll be interesting to see what happens to the fuel 'economy' on the Le Mans trip! Will report back as & when.

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.

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.

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.

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.

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

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

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.