Geschrieben von inspector.kadett am 06.01.13 um 15.41:
RE: 1.2s modifikationen
Hi Elliot!
(first: the google translator is crab!)
to modify your 12 s you have quite a few possibilities. the most is mentioned when you search under "OHV Tuning" in this forum.
OHV Tuning 1,1-1,2L
hope the link works...
in short:
anything you do to the lower part of the engine helps:
- balancing the crankshaft,
- new bearings,
- bore and hone the engine,
- get new 12 S pistons (the S is important, for the higher compression is only(!!!) achieved by higher built pistons!) ,
- lighten the piston rods,
- get everything on the same weights etc (we are talking classic-tuning)
you can find a fair range of crank-shafts always depending what your goal is and what other components you want to use.
I can really recommend steffen here in the forum (name: ohv) he has a small company: reprotec (look it up) (at least for the crankshaft and a suitable exhaust system!!!)
the rest is done with the cylinder-head.
you can find heads from the later corsa a, which has gaskests on the inlet valveshafts as well as wider valves and hardened exhaust rings under the valves.
if you want higher rpm, you will need harder springs for the valves.
you can lower the head for a few mm I´m not sure how much, but it´s been dicussed in this forum.
to smoothen and widen the inlet and outlet canals in the head (widen to fit the gaskests, and there are wider inlet gaskets) gives some hp.
I have no experience with the dellorto carbs and the most recommended is the weber...
always keep in mind, that our engine has only three main bearings on the crankshaft: the higher the revs the more likely the (deadly) damage.
I think it is better to go for some steady 70-75 HP; not to change the compression ratio too much and to use a medium cam shaft, that allows an idle rev below 1000 rpm.
it is possible to get the engine to as much as 90 HP but that will only last for one or two races and these 90 HP you will find way above 6000 rpms
to have it driveable, you will need some power from below.
it is recommended to keep the original weight of the flyweel. to make it lighter, will help the engine to accellerate quicker (mainly when standing withaout a gear, which sounds impressive....)
but you will not get a single HP to the wheels by this modification. the minus is, that your idle rev will lose steadiness and going uphill forces the revs down easier.
if you are from the UK, why not look for a ohv- vauxhall chevette engine with 1300ccm? i´m not sure if this engine came with high compression ratio but too me it sounds interesting...
further questions or details/translations? just ask!
good luck
benno