1.2 head on 1.3 block?

[mowgli]

So i use the 1.2st block, 1.3 pistons rods and crank, 1.2 head? Sounds tempting!

115mph (real not pub mph) 35mpg......no injection to annoy you.....

I am tempted to do it myself again

[Novasport]

So i use the 1.2st block, 1.3 pistons rods and crank, 1.2 head? Sounds tempting!

Yes thats correct, I have not tried it myself but I assured it works by someone that has done it.
The 12ST is short stroke thats why they rev so well and the are a larger bore than the 13SB(Same as 1.4). So combine the longer stroke of the 1.3 added to the larger bore of the 1.2 and you have 1400CC:D .
Externally it looks standard aswell unles you fit twin carbs etc. The 1.2 head is actually different & I have been told its better but not sure if that is true.
I was also told a few years ago that a Sierra 1.8 carb fits(Poss a Pierburg?) and is good as twin 40's to a certain extent but not sure if thats correct.
Prob best to get a Weber carb meant for a 1.4SR if you can, should go quite well then.
Also whack in a F13CR with a 4.18 final drive in from your F10

[mowgli]

As I have already said, I got my pistons pocketted to lower the compression a bit. apart from that, it is really easy.

[John]

Yes thats correct, I have not tried it myself but I assured it works by someone that has done it.
The 12ST is short stroke thats why they rev so well and the are a larger bore than the 13SB(Same as 1.4). So combine the longer stroke of the 1.3 added to the larger bore of the 1.2 and you have 1400CC:D .
Externally it looks standard aswell unles you fit twin carbs etc. The 1.2 head is actually different & I have been told its better but not sure if that is true.
I was also told a few years ago that a Sierra 1.8 carb fits(Poss a Pierburg?) and is good as twin 40's to a certain extent but not sure if thats correct.
Prob best to get a Weber carb meant for a 1.4SR if you can, should go quite well then.
Also whack in a F13CR with a 4.18 final drive in from your F10

Thanks rich, most helpful as usual! I have both engines sat in the shed, so won't cost me anything to do. I'll use a 1.3 inlet with a twin choke weber on. What'll the 4.18 fd give, better acceleration?

[John]

As I have already said, I got my pistons pocketted to lower the compression a bit. apart from that, it is really easy.

Don't suppose you can remember how much you removed?

[novaxe235]

Thanks rich, most helpful as usual! I have both engines sat in the shed, so won't cost me anything to do. I'll use a 1.3 inlet with a twin choke weber on. What'll the 4.18 fd give, better acceleration?

yes thats right better acceleration

[mowgli]

Don't suppose you can remember how much you removed?

I took about 5mm from the crown out. but it was 17 years ago & I'd measured the thickness of an old head gasket, the crown volume & the head volume then calculated the compression ratio. it came out quite high & I worked out what volume was needed to get 10:1 & got a engineering shop to machine them. they never charged me for doing it because they wanted no comeback.... I will try & find the diameter out for the machining, it was based on stock pistons, and (amazingly) a photo in a back issue of CCC mag feature on tuning baby vauxhalls.

I have looked up the piston catalogue specs. the 1200 piston has a flat outer lip. that is the limit of where to machine it. the valve cutouts are at about 4.5mm depth. I remember that the cutouts were removed so the 5mm figure is about right. I got the engineer to put a nice radius in the corner so it would have been about 2mm.

[Novasport]

I took about 5mm from the crown out. but it was 17 years ago & I'd measured the thickness of an old head gasket, the crown volume & the head volume then calculated the compression ratio. it came out quite high & I worked out what volume was needed to get 10:1 & got a engineering shop to machine them. they never charged me for doing it because they wanted no comeback.... I will try & find the diameter out for the machining, it was based on stock pistons, and (amazingly) a photo in a back issue of CCC mag feature on tuning baby vauxhalls.

I would be interested in finding out more info on that CCC feature aswell

Thanks rich, most helpful as usual! I have both engines sat in the shed, so won't cost me anything to do. I'll use a 1.3 inlet with a twin choke weber on. What'll the 4.18 fd give, better acceleration?

Yes that FD will give a better accelleration, the F13 & 4.18 FD will give the same ratios as an F15CR from a Corsa Sport so you can use either.

Wish I had kept my 12ST from the 28k mile swing I broke, and the bloody bump strips I now need for the SR!!!

[mowgli]

it was based on a conversion done by peter maiden components from tamworth. they were the men when it came to nova tuning in the late eighties. there was a copy on ebay a year or so ago, but I never got it...

[Novasport]

Do you know the issue number?