Holley Sniper

[Green411]

It will be interesting to see how much of a real improvement the Sniper 2 offers. Do let us know if you get one, and what it's like. Although my first one failed (dead ECU after an hour or so's total running time from first start) I get no interference issues with my Sniper, for instance, and the basic connections are genuinely easy to follow. Possibly the major new thing is easier connection to their electronic distributor?
I haven't got to that bit on mine yet - am still using the stock distributor albeit with Pertronix kit installed. I haven't even mapped the advance curve yet.....hmm.....perhaps I should stop typing, put my laptop away and get my timing light out..........

[David C]

I think you definitely should!

I'm not sure about the 411, but the Poly engine in the early V8s has the distributor at the rear of the block so I don't think interference would be a big issue. Ford engines with the distributor right next to the ECU seemed to be the worst offenders.

The big issue for me was the number of reports of failed ECU on the original Sniper. I very much hope version 2 is more rugged. V2 also supposedly has improved throttle geometry.

The main reason I am considering a Sniper is that fitting overdrive brings the engine speed so low at motorway cruising speeds that a standard distributor doesn't have the timing range to cope. Also the Weiand inlet manifold that I have presents mixture issues at low RPM that are hard to accommodate with a standard carb and distributor. These are both marginal issues but adding a Holley Hyperspark controlled by the Sniper should bring everything into line. Add a decent tubular manifold with ceramic coating and I very much hope to have an original engine and nearly original transmission with the drivability and economy of much more recent cars.

[Green411]

Re using a Holley Hyperspark distributor: the Sniper 1 can drive the Hyperspark but I can't remember how easy the connections are. Or you can lock out the mechanical advance on the stock distributor and get the Sniper to run that. In both cases you tell it to run the distributor in the hand-held terminal's base settings menu.
Re throttle bracket geometry, Holley sell a small Mopar/Chrysler extension bracket, (Hly-20-7) which I used, to get the geometry right. Apparently Torqueflites use rods & bellcranks for managing the upshifts and kickdown and the added width of the Sniper vs a carb, plus a bit more still from the adaptor bracket meant that it seemed best to get a new top rod (the cranked one from the throttle bracket to the top bell-crank) made. This was a mirror image of the original ie the bend was in the opposite direction, but it was the same length & number of threads. It took a bit of internet research followed by a bit of playing about to get the adjustment right. Probably easier if you remember to count the visible threads on the stock setup first, which of course I forgot to do!....d'oh....

Here's a list of all the parts I used - hope it helps:
Holley: Sniper Classic gold (550-516), Drop-in Returnless Fuel Module with 255 lph pump and Hydra-mat (12-131), throttle lever extension for Chrysler (20-7);
Weiand: sealing plate 9006 for spread-bore manifold-to-square bore carb/Sniper;
Felpro: intake/lifter valley pan with blocked exhaust heat riser 1214;
Merlin Motorsport: 1/8 NPT Smiths temperature gauge sender CB-TS-18;
Bespoke: top throttle rod in mirror image of original
Bespoke: exhaust diverter housing on UK driver's side between exhaust manifold and downpipe
Small assortment of -6AN (9/16 UNF) and ¼ NPT blanking plugs and hose barbs; ¼ NPT-to-1/4 BSP adaptor if you use existing fuel feed pipe which came from the main/reserve valve; 2m of R9 fuel hose; 6 good quality efi fuel hose clips; can of Chrysler Orange engine paint; assorted gaskets; lots of tea. Then more tea. Total cost was c.£2k.

[David C]

Really useful information, thank you.

I have done a bit of reading about it and there seems to be general agreement that it's a good idea to have a post pump filter even if you are using a Hydramat.

I'm torn as to whether to go for the Hydramat. It looks brilliant if making a tank from scratch but since the Bristol tank has baffles and a sump I wonder how much advantage it gives. I think the size you have chosen along with how often the car is used will give a good few years before it clogs but I'm more inclined to let some of the small particles go through the pump and collect in a 10 micron post pump filter that can more easily be replaced. By no means a criticism of your choice. I may well decide on a Hydramat but haven't made my mind up yet.

My shopping list currently looks like this:

Sniper 2 550-510 3xx $1300
Hyperspark distributor 565-344 $400
Fuel pump 12-169 $490
Coil 556-153 $45
Filter 162-554 $120
Filter brackets 162-574 $45

Total $2400

These are not confirmed choices that will definitely work together, just the best I can do for now after a bit of on line research. I am waiting to see how well the overdrive gearbox conversion works. If it's a success I think the Sniper will follow soon after.

[Green411]

I used the Hydramat just to be on the safe side, as the stock tank baffles weren't designed for the needs of an efi electric pump. Haven't (yet!) used a post-pump filter, other than the one in the stock position near the Sniper (to disguise the conversion) which I forgot to put on the 'stuff used' list. It's a Vauxhall part and I can get the part number if you need it. I'm assuming in all this that David C is in the UK, btw.
My 411/3 has a 383 B block, so the distributor is UK driver's side, front, at 45*. I think the small block ones are like a traditional small block Chevy, in the middle, vertical, at back of intake manifold?
What transmission are you going to use David? A 4 speed o/d Chrysler one will bolt to directly to a 318/340/360 block I think, but an old 383 like mine needs an adaptor. In view of availability, need for an adaptor anyway, trans case size etc if I do get round to a trans swap then a mildly-built GM200-4R looks sensible.............(am a long way from deciding, but in any event I await the torrent of abuse from purists......)

[AndrewA]

David - if the Weiand inlet manifold causes too many issues am happy to look after it for a while......

[David C]

I am indeed in the UK.

I have gone for an A400 42RH transmission. It's a fairly straightforward bolt on replacement. Needs different flex plate and lower cover for torque converter. Also a small ear had to be removed from the block to get the starter motor to fit.
46RH are a bit easier to find and are a bit stronger. Most of the work is in modifying the gearbox crossmember and transmission tunnel. Article to follow...

The Poly engine in the 409 and 410 is internally balanced so works with the lock up torque converter without any modification. I think I previously saw that the 383 is also internally balanced but that would need to be confirmed. If so it should be fairly straightforward to bolt to a 46RH with a suitable adapter kit.

As long as the engineering is done well I don't see a problem with a GM unit. Wilcap make a suitable adapter. I think you will need an electronic adapter if the GM 'box is electronic.

It would be good to hear from others on the forum whether they would welcome an extra gear and better fuel economy or would be put off by non original gearbox. Also, once it's non original does it make any difference whether it's Mopar - developed from the original - or from another manufacturer.

[David C]

More on the Weiand inlet manifold on my 410-

For those who are interested or just need help to go to sleep there is plenty of reading on offer regarding inlet manifold arrangements, specifically square bore and spread bore. I believe 410 and 411 original manifolds were spread bore. The Weiand 7403 manifold is divided square bore. This means the Sniper should bolt straight up.
The question is whether I will get much benefit as square bore is better at higher revs but may lose torque at lower. The 42RH gearbox has a lower first gear which may offset this. I'm hoping that combined with decent tubular manifolds the improved breathing will give further improvement to fuel economy.

If it doesn't work out, Andrew is at the front of the queue for parts to make a fire breathing monster.

[Green411]

I was just reading through some earlier posts when I came upon Dezelsky's from June, when he was touring in Italy with his 411/4. I'd completely missed the photo he attached, and just had a look. Man, that is a pretty car! Perfect angle for the picture, and the combo of the wheels and colour really suit it.

[Thor]

Life is too busy, but I have acquired a Sniper kit to put on the 318 Poly in my 409. I feel very sure that at the very least a transmission with a lock-up torque converter is required. A GM 6L80 would need an adapter but there are controllers for it. I've thought about a 42RH as I had a Dodge Dakota for many years with the Magnum 318 and 42RH (I think). But if you're going to the trouble of changing the trans and have the electronic outputs from a Sniper, it's relatively easy to install 6 or even 8 gears. I have no idea whether these fit under the Bristol floor without modification.

[Green411]

Re David C's manifold intake manifold points, the Weiand design has got to be more modern (or perhaps less aged...) than the original mopar one? And I can't think why efi would need the help with fuel-atomisation of small primary bores. Am happy to be educated though if anyone knows different! Sniper is wet flow so surely avoiding the puddling of fuel in the intake matters more? The divided plenum should work ok - mine runs fine with a stock intake.
Re the transmission: I want my 411/3 to be easily(ish) returnable to stock in the future (dunno why, it just seemed important!) so part of the GM200-4R appeal is it's relatively small size. It's controlled via throttle-valve cable (like a TH700-R4) so no additional electronics to worry about - apart from TC lock-up. GM transmissions run by the ecu startd with the 4L60E and it's successors. Great trans, had one in my '95 Corvette. Additionally the 200's got a deep first gear and a lo-o-o-ong top gear. And thank you for not shouting at me for the idea of a foreign trans.....If I could find a separate conventional overdrive that fitted (not a Gear Vendors type) that would take the 383 torque then that would appeal too. Anyone got any thoughts?
You can all wake up now......

[David C]

I should really have said that the Weiand is a divided single plane whereas the original is dual plane. Supposedly the longer tracts in the dual plane allow the mixture to slow further and give a more dense charge at lower RPM providing higher torque.
Looking at the original manifold, one half turns through a right angle almost immediately on entering the manifold so common sense suggests more puddling on one side than the other. Since the Sniper only uses an O2 sensor in one of the downpipes I struggle to see how it can get the mixture just right in both banks. Hence I decided on a symmetrical manifold.

If reading this gives the illusion that I know what I'm talking about, please don't be fooled. I very much welcome input from anyone who can see through my waffle and tell me where I'm going wrong.

[Green411]

Weeelll........I actually rang Holley tech and asked them about this before I bought mine. The Sniper has 4 x 100lb/hr injectors, one in each of the 4 barrels in the throttle body. 1 x O2 sensor in one down pipe, which tells the ecu what fuel to provide. The ecu commands all 4 injectors equally and at once. So unless there is a noticeable difference in the fuel distribution to each bank (eg engine v badly worn) then each bank, and each cylinder, gets pretty much the same fuel. I used an adaptor/spacer plate, which was open with no divider, so all cylinders can draw equally-ish.
That's my understanding, and all the plugs now look roughly the same colour - a nice light tan, rather than the thick soot they had beforehand.

[David C]

I think I'm in danger of over thinking it here. The important thing is that you have a much improved system that is working well for a reasonable outlay.

With any luck a few more of us will get EFI fitted and be able to report back and fine tune what is required for those who follow.

Thanks again for sharing !

[Green411]

Well over thinking is better than no thinking, which is the hole I sometimes fall into!

[Green411]

I just had a look at some forums, including Holley's 'Sniper efi' forum. The administrator and senior members (ie the ones who know the most I reckon) generally seem to think that a dual plane intake is fine with a Sniper. My own experience supports that.
I'm no expert, and I'm a VERY long way from knowing a zillionth of what a professional mechanic/engineer knows, but I firmly belive that a successful Sniper installation needs to be in a car with properly matched engine parts on an engine in reasonably good fettle with a good battery and charging system. It won't fix basic errors in matching cam and heads, for instance. Then just follow Holley's comprehensive instructions, particularly about electrical connections, and you should be ok.

[Green411]

Howdy y'all. Hope this update is of interest.
On a recent 140 mile round trip on single-carriageway A & B roads, 18-20*c, not exceeding 65 mph, mostly at 50-60mph, but several roundabouts and junctions to accelerate away from (gently, letting the torque do the work), driving on the gently side of normally (with no hyper-miling tricks) and measuring from a hot start I got 19 mpg. From a 383! Driveability absolutely perfect.

[David C]

Brilliant! Thank you for the update.

[Thor]

That does seem like a good MPG figure. Thank you for this information. I'm hoping to get a Sniper onto my 409, and also a gearbox with lock-up torque converter. With the smaller engine I would hope to be into the 20s on MPG.

[Green411]

At first it did seem too good to be true, but I double-checked my sums and actually erred on the side of caution!
Thor, I'm sure that with a smaller engine, o/d transmission and a lock-up tc you'll beat me easily - assuming your engine is in stock/mild state of tune. On a 40 mile drive at 60-70mph, hot start, I once got 31mpg from my o/d auto '95 Corvette, which had a diff ratio of c.3.00:1 and did 2200rpm at 80mph.