1256 Superchaged

[pbottomley]

Some of us had a chat a while bac about adding either a supercharger or Turbo to a 1256cc Viva.

Well for those that were invoved look what i found on eBay, just the item we all said we would need !

http://cgi.ebay.co.uk/Shorrock-Supercharger-Austin-MG-A-series_W0QQitemZ4616176114

Ebay Item #4616176114

Thoughts welcome !

[lambaj]

Hi Paul

Got a certain plan in store for my Mrs's HA Van - my old 1280 highly tuned motor out of the black one, modified with low compression pistons from a van motor and a VNT15 turbocharger running with a blow through carb from either an MG turbo or Renault 5GTT. Should be intercooled and hopefully will handle 10psi. Will start lower and see what we get. Long duration cam may be an issue, but worst case will make it a peaky screamer. Shame!!

The Shorrock can be a bit of a headache to work with, uses oil as part of its operation and unless in excelent condition, could be a bit fragile. Also due to the "flappy paddle" design, is limited in it abilty to produce much more than about 7-8lbs of boost. I seriously researched this option for mine, but the healthy Shorrocks always went for more than most Vivas are worth! A lot of money to invest in a nice idea plus all the drive system, manifolds and plumbing will have to be custom designed and made as I'm reasonably sure that 1) shorrock did not offer the kit for the OHV, and 2) if they did, the parts are all long gone the way of the dodo!

Got the VNT15 brand spanking new on E-bay - won't say how much......
Just got to convince myself that the VNT mechanism can take the extra exhaust gas temperatures that the pertrol engine will produce over the original designed application (diesel)

Not gonna happen overnight, The HA van is a resto project - give me about 4 years and maybe I'll be getting somewhere......

Tony

[pbottomley]

Some good points chap,

I think my aim was to upgrade a Viva with period upgrades (also something that looks good and sounds wonderfull). I am not a fan off pop pop turbo stuff personally.

I think the other point is ultimate performance wasnt the aim, else i would of swap the engine out for a red top !

I feel that a supercharger is a more period upgrade, a bit like twin SU's and or Strombergs are a more period upgrade than a nice Weber DCOE ('s)...

I have an advert for the Shorock's 75 from an old magazine that does list it as a kit for a Viva, as well as the more common a' series engine (credit to the sundat night MSN crew for that one)

I admit getting the correct manifolds all set up could take ages. but its more a dream than a fact, to supercharge a viva. Biut hey wouldnt it be nice, whooshing up the road

... Not so much mad max, more Mildly Mannered Machine

[jeff66]

Personally.... I would NEVER buy a secondhand blower, unless I knew its full history.

[lambaj]

Fair points indeed. Now you mention it, I think I have seen some stuff about Viva kits. Would suite the Shorrock nicely. Triumph Heralds, MG migets, Minis, Mk1 tinas and 100E/105/109s all could be converted.

The attraction to the Shorrock originally for me was the same as yours, a nice period modification - and would be almost certainly a unique car. Heres some links you might find useful..... I expect you already have found them.
The 1st one points to a shorrock late catalogue that shows the Viva with the increased performance - 0 to 60 from 22.5 to 12.6 - that should help!

http://mk1-performance-conversions.co.u ... rchive.htm

http://www.mg-tabc.org/supercharger/Shorrock_ABC.pdf

http://www.bcsc.co.uk/info/supercharging.html

http://www.bcsc.co.uk/info/supercharging/section3b.pdf

[pbottomley]

Just for info, I wish a new kit was only the amounts shown on the advert:



http://www.vauxhallviva.com/img/super.jpg

[Chevetter]

Sorry to drag up an 'old thread' but supercharging/turbocharging is something that I've given quite a bit of thought to as well. I once spoke to Bill Blydenstein at great length regarding his 1500cc stroker motors and he said that they turboed one... and it was a dog(obviously a stroker motor has fairly low compression anyway), so he would assume the same is true of a 1256.

So Chevannes, Beagles, HAs and the like have dished pistons as opposed to larger combustion chambers?

As for supercharging (for those of us that can't afford a Shorrock supercharger) personally I'd start off with an Eaton M45 from a new mini (these are going cheap at the moment as loads of people upgrade their mini to a more powerful blower straight from the showroom) which will set you back about £150 from ebay. There are various parts available including one to make the inlet a more friendly shape and one for the outlet too so the main difficulty would be to set up the actual charger drive - obviously it needs to be driven from the crank. I think that the conclusion I've come to the conclusion that its not worth the effort...

...how about a nitrous 1256?

[lambaj]

Thought Bill B's 1500cc conversions were offset overbored, not stroked..... Maybe wrong though. HA van pistons are shorter than the chevette/1256 ones. Earlier vans used thick head gaskets in the 1159 and 1057 engines (not even sure if the 1159 found its way into the van)
About 7.6 to 1 compression, nice level. Simple enough to make the bits if you very handy with the welder, so I will be turboing mine some time in the future...... Watch space, but give me a couple of years!!
Tony

[Chevetter]

Thought Bill B's 1500cc conversions were offset overbored, not stroked...

err, pass - I had just assumed they were stroked but offset overbored would also require a custom crank and different rods wouldn't it... I think I heard somewhere that they used Saab pistons too

So does anyone know anything more about the low-compression 1256? It ran a 7.3:1 compression ratio and in the Haynes manual the mimimum head depth after refacing is 1.27mm greater than for the 9.2:1 head but only 0.36mm greater than for the later 8.7:1 head. I think I once calculated that this greater height wasn't enough to make that much difference (its a shame they don't give you the original head depth and the combustion chamber capacity) but that calculation contained a lot of assumptions.

If you look here you'll see that the headset for a Chevette is also common to a Chevanne but what's the HC for after Chevanne? High Compression? Maybe they used a thicker head gasket too... or dished pistons... or both. I just find it a bit difficult to believe that Vauxhall would have made a completely different head for the van engines... although they did sell the HA/Beagle right up until 82/83 (I think - I could have sworn I once saw a 1987 HA Van on ebay but I can't find any info to back this up) when Chevanne production ended so that means the low compression engine was made for the best part of 7 years.

[lambaj]

All HA vans were low compression.....
The 1256 engines used low compression pistons. The 1256 saloon engines came in standard and '90 tune, the '90 being higher compression acheived by effectively skimming the head, but also the valves and cam were different. The standard and 90 bottom ends are the same (apart from the cam)

Your correct about the Saab 99 pistons. These can only be made to fit the block by offsetting the bore positions. The crank is the same, the rods I believe are the same, just the piston sits a little to one side on the gudgeon pin. Not sure if the 1500cc is worth the trouble and risk of thin walled bores and the limited life the offset gudgeon pin will see

If you want to "blow" a 1256, find a set of van pistons, a 90 head for the bigger valves, do an unleaded conversion to look after the exhausts and give it some welly! Oil cooler would be a good idea, and limit to about 6500rpm max if all fully balanced and matched. Basically a good blueprinted bottom end should take serveral pounds of boost for a good increase in torque and a reasonable increase in top end HP