Modifications to a 1256

[griffonmark]

When I was a teenager, when you could buy a new Viva, I used to dream about go faster Vivas. As I got older I realised it was a waste of money trying to get them to go faster. I did have an HB which I fitted with a 1256 engine, upgraded with the SL90 twin downpipe exhaust, stromberg carb, cam and worked on head, but even in those days it cost more than it was really worth, just to get an extra 15hp. I came to the conclusion that it was easier to get secondhand parts from a higher performance model in the same range, ie get all the bits off a magnum 2300, or do the most sensible thing and buy the higher performance model. Look for a pre 1974 2300 with twin carbs, keep it standard (who really needs more than 128hp) and use the money you save on free tax to pay towards 4 star. I did the stupid thing and bought a kitcar. Now I spend every weekend trying to work out what the bit that has just packed up comes from. Regards, Mark

[Chevetter]

Just a bit more info on tuning a 1256:

I've been fortunate enough to come across an artticle from and old copy of Autocar in which a 1500cc Chevette was tested. The car had been specially built by Blydenstein for an economy run but sadly lost out to a 1600cc Avenger.

The engine contained a custom steel crank and matching rods produced by Gordon Allen which increased the stroke from 60.96mm to 72mm. Oversize 81.75mm Hepworth's Powermax pistons were also used (standard are 80.98mm) making the final capacity 1511cc. There was a DTV sportpart stage II cylinder head and also Lumenition but apart from these mods everything was standard. The result of this was that the 0-60 time was reduced to 13 seconds from 15.1 and the standing 1/4 to 18.6 from 19.8 while the overall fuel consumption rose from 30.4mpg to 34.0mpg. Blydenstein engineering sold short engines which were limited to a rate of 1 per month at a cost of £450 exchange or £650 exchange fitted.

I've yet to find a mention of the offset overbore engine that Tony mentioned in another thred.

I also read another article on tuning the 1256 (which I can't seem to lay my hands on right now) which advocated the use of pistons from a ford pre-crossflow 1500cc motor (standard bore 81mm) to raise the compression ratio of the engine. These can be fitted to the engine with the help of a floating gudgeon pin set-up but the crowns need machining down. The result of this modification was a compression ratio of 11.5:1 iirc and coupled with a Weber sidedraught carb, exhaust manifold, cam and modified head yielded an output of roughly 100bhp.

I also read on a forum somewhere the other day that some guy had managed 115bhp from a Kadett 1196cc engine although I have seen no evidence to substantiate this claim.

[Dave1300GLS]

if your interested in a CHEAP easy to fit mod that will transform your ohv unit bolt on a nikki twinchoke carb you can usually find them on ebay for between 30-50 quid it will liberate your viva.

Hope this helps coz it helped me

Dave