View Full Version : Reboring a 1.4 to take 1.2 pistons?
Yo, have just read on a listing on ebay that if you rebore a 1.4 engine to take 1.2 pistons it will increase the accleration. Is this true or just the usual ebay Bollocks? quite interested in doing it if it is. any feed back appreciated :)
http://www.ebay.co.uk/itm/1988-VAUXHALL-NOVA-MERIT-BLUE-/220805298487?pt=Automobiles_UK&hash=item3369057937
matt_vaughan
02-07-11, 05:39 PM
Its a lot of hassle. It can be done but it's worth just tuning the 1.4.
EDIT: My original post wasnt very helpful, and I felt guilty.
However, now I've told you it CAN be done, you're best properly researching the methods and ideas behind the conversion yourself.
Take a look on this site at the Engine specs and you'll soon realise what's required.
http://www.opel-corsa-a.com/index_e.php
If you're struggling, PM me with any questions.
ah right, was just intrueged as i have a 1.2 and a 1.4 engine here, but done some more research and you have to use a few bits off a 1.3 too
matt_vaughan
02-07-11, 06:04 PM
Best to start with a 1.3 pal. The 1.4 isn't much use in this conversion. You do end up with a quick engine, that says 1.3 on the block, but its lots of hassle and not particularly value-for-money unless you're restricted by a motorsport class, to which end you would then be cheating anyway.
insurance is what restricting me haha,
The normal conversion is to stick a 1300 crank and rods in a 1200. The 1300\1400 stroke is the same so IMHO you'd be better off boring the 1400 +40, decking the block and skimming the head to bring up the CR.
as one of the few people who have done this conversion....i had a 1.3 bottom end in dire need of a rebore, so i got it bored to take the 1200 pistons, and had the crank reground, block cleaned, and a new set of oil pump gears. but, and this is important imho, i also machined the piston crowns so i could use normal fuel.. it certainly had some guts, and with a std f10 4 speed box would pull from 15 to 115 (indicated on the autobahn on the way to dusseldorf) in top.
i would only recommend doing it if you need a rebuild, but it was great fun to do & great fun to drive.
as for doing a 1.2 with a 1.3 crank & rods, you still need to rebore it cos there is a wear lip from the shorter throw crank, and of you don't, i'd give the rings a week.
another thing to note. the 1200 & 1300 use 20mm gudgeon pins, and the later stuff uses 18mm pins.
as one of the few people who have done this conversion....i had a 1.3 bottom end in dire need of a rebore, so i got it bored to take the 1200 pistons, and had the crank reground, block cleaned, and a new set of oil pump gears. but, and this is important imho, i also machined the piston crowns so i could use normal fuel.. it certainly had some guts, and with a std f10 4 speed box would pull from 15 to 115 (indicated on the autobahn on the way to dusseldorf) in top.
i would only recommend doing it if you need a rebuild, but it was great fun to do & great fun to drive.
as for doing a 1.2 with a 1.3 crank & rods, you still need to rebore it cos there is a wear lip from the shorter throw crank, and of you don't, i'd give the rings a week.
another thing to note. the 1200 & 1300 use 20mm gudgeon pins, and the later stuff uses 18mm pins.
Yeah i have a 1.4 which i was going to rebuild anyway but then heard about this. & What do you mean about machining the piston crowns too?
Ive read that you need the 1300 crank and con rods, but could you use the 1400 ones instead?
read my post.... the 1.3 & 1.4 share cranks, but you need 1300 rods, cos the little end, as in the end the piston gudgeon pin goes into, is a different size between the 1300 & the 1400, and only the 1300 type will fit the 1200 pistons.
re machining the pistons, if you just fit the pistons as they come from the factor, you end up with really high compression, (like12:1) which is fine on german racing fuel, but on uk pump fuel, you need to get it down to about 10.5:1, this means physically removing some of the top of the piston (the crown) by means of sticking them in a lathe & cutting some out.
now, if you want to actually build an engine up from scratch for the exercise of doing it & for the technical challenge, this is great fun, as you get to actually measure all the chamber sizes, gasket thicknesses etc, so you get it all to work.. then you end up with about 90hp.
this engine was great back in the early 90's before the 1.4 & 1.6mpi engines started to get popular as it genuinely produced a great improvement over the std 1.3 & 1.4. with 40's & a head/cam, you will be looking at a good 120-130hp with torque and reliability
C612DNM
04-07-11, 04:51 PM
Some people no listen!
Another thing to note is the rise in compression ratio by using 1.2 pistons in an over-bored 1.3 block (note: 1.3) - unless you're going to use a rally or race cam, just don't go there.
If you do, use MAHLE pistons, they're stronger and better (and cost more).
Some of the stuff on eBay is spoken by people who appear to have hair around their lips, and their breath smells of fish.
C612DNM
04-07-11, 04:59 PM
The normal conversion is to stick a 1300 crank and rods in a 1200. The 1300\1400 stroke is the same so IMHO you'd be better off boring the 1400 +40, decking the block and skimming the head to bring up the CR.
Gary, that won't work. The 1300 stroke is that much longer that the pistons will emerge from the top of the block. 1300=75x73.4 1200=77.9x62.9 = 11mm difference in stroke, thats 5.5mm of piston poking out of the top of the hole.
Some twonk on MiGweb was jibbering on that you could do it, but you can't.
The 1.4/1.6 engines have different bore/strokes again - with smaller wrist/gudgen/piston pin diameters. The rods are feeble compared to the old 1300 rods which will take a fair bit more power before saying sayonara and exiting stage left.
read my post.... the 1.3 & 1.4 share cranks, but you need 1300 rods, cos the little end, as in the end the piston gudgeon pin goes into, is a different size between the 1300 & the 1400, and only the 1300 type will fit the 1200 pistons.
re machining the pistons, if you just fit the pistons as they come from the factor, you end up with really high compression, (like12:1) which is fine on german racing fuel, but on uk pump fuel, you need to get it down to about 10.5:1, this means physically removing some of the top of the piston (the crown) by means of sticking them in a lathe & cutting some out.
now, if you want to actually build an engine up from scratch for the exercise of doing it & for the technical challenge, this is great fun, as you get to actually measure all the chamber sizes, gasket thicknesses etc, so you get it all to work.. then you end up with about 90hp.
this engine was great back in the early 90's before the 1.4 & 1.6mpi engines started to get popular as it genuinely produced a great improvement over the std 1.3 & 1.4. with 40's & a head/cam, you will be looking at a good 120-130hp with torque and reliability
Okay nice one thanks thats what i wanted to know, lucky im trained to use lathes then lol
Gary, that won't work. The 1300 stroke is that much longer that the pistons will emerge from the top of the block. 1300=75x73.4 1200=77.9x62.9 = 11mm difference in stroke, thats 5.5mm of piston poking out of the top of the hole.
Some twonk on MiGweb was jibbering on that you could do it, but you can't.
The 1.4/1.6 engines have different bore/strokes again - with smaller wrist/gudgen/piston pin diameters. The rods are feeble compared to the old 1300 rods which will take a fair bit more power before saying sayonara and exiting stage left.
i did mine in 1990/1 and i used an article in CCC mag that showed Peter Maiden doing it as a conversion, there was a photo of the pistons with machined crowns, i actually used a vernier on the pic to get a rough idea on what needed doing.. then started measuring lots of things.
once i mentioned it on here a few years back, the amount of BS that has arisen is incredible.... every few months, someone pm's me to ask a heap of questions about it, and most involve some piece of misinformation a mate/relative/mechanic has told them.
ps.i asked Steve(Duick) at billing if there is much 1300 stuff left on the continent. and its no better than over here...
C612DNM
09-07-11, 05:23 PM
I did my first one in '88.
I contacted PMC on recommendation of Peter Sowray at Atkinsons Motorsport, looking for a stronger headgasket for a "1200" as at that time, the 1300 gasket wasn't big enough for the overbore, and the 1200 was weaker.
They asked "why", I opened my trap without thinking that nobody else had done it before..... I said "because I've bored my 1300 out to 77.8mm and fitted Mahle Nova 1200 pistons because a bore got mashed when it dropped a valve, and beyond a 60thou overbore, so I'd looked at the catalogues, and decided to give it a go. The factory gasket for the 1200 Nova wouldn't last much more than a week due to the raised compression ratio, and the 1300 gasket was only about 76mm at that time.
At the time, the Astra 1200 was based on the old 1256 pushrod engine from the Viva, and it took a little discussion to talk through the issues.
About three months later, PMC started to offer 1400 kits.......
The solution was to use the new GTE gasket which was for up to an 80mm bore.
The older I get, the better I used to be!!
i machined my KS pistons in a similar fashion to the pmc photos in the CCC article, and fitted an elring 1200 oe spec gasket and that was that till i sold it...a bloke bought it for an astramax he'd sold, then rang me up to ask what the hell had i done to it....i bet that van went bloody well...
C612DNM
09-07-11, 05:40 PM
I think back, and it was the Elring gasket that was the tough one. The Payen ones weren't very strong (as I found out!).
My engine went to a sprinting competitor in the Bath area who was running a Nova, and they'd increased the class limit to 1400cc.
Some time later, I built another one for my brother's Sport. 132@wheels on Pete Baldwin's roller. 8 class wins in 1992, should have won the championship with it, but had to miss a couple of rounds due to work.
its about time one of the day dreamers actually did this and then photo it and write it up as a guide.
C612DNM
10-07-11, 10:12 AM
Bring me a TARDIS and I'll go back to 1988 to do it especially for you.
In those days, before digital cameras / camera phones, you didn't just take photos on every whim. Film cameras cost more money to run than beer, so were low priority.
Back then a 36 exposure film cost about a tenner to buy and get processed. That bought a chicken vindaloo, rice, naan, and a pint, with some change. Now which is more important?
correct... mine was built to be driven on the road, i never took a single photo of my first 4 novas.
as c612dnm & myself have stated, this was a good mod, but the bits are very rare these days. a decent 1300 bottom end as a donor is going to set you back at least a hundred quid, then new pistons, another hundred or so, then machining & gaskets, and before a head or cam, you are £500 down, even more if you want to pay to get it put together.
LOL, rather that you two I was thinking more of someone that comes on asks loads of questions, then just disappears as fast as they arrived! I have sold one crank and set of rods to someone who was talking about doing it.
C612DNM
11-07-11, 09:20 PM
One over-bore job I was looking at in the early 90's was an attempt at the biggest engine we could achieve using a 1200 crank/block - to make a short stroke screamer.
With the same bore/pistons I used with the 1764cc smallblock job, I seem to remember we got to about 1361cc. If my copper headgasket manufacturing had been better, I'm sure we would have had a go at it.
All about charge velocity, charge cooling, and whizz!
I wish I had more time to play with things like this again. All work and no racing engines makes Rob a dull boy! Plus I have two little V8's that need my attention first.
fast forward 2+ years...
A donor x14sz block bored to suit said 12st pistons... (has been decked too, dont ask how much because that was over a year ago..)
http://i255.photobucket.com/albums/hh160/bodmin344/DSC01436_zpse76a48ec.jpg (http://s255.photobucket.com/user/bodmin344/media/DSC01436_zpse76a48ec.jpg.html)
1300 Crank and rods...
http://i255.photobucket.com/albums/hh160/bodmin344/DSC01565_zpscf624f69.jpg (http://s255.photobucket.com/user/bodmin344/media/DSC01565_zpscf624f69.jpg.html)
new mahle 12st pistons on said rods..
http://i255.photobucket.com/albums/hh160/bodmin344/DSC01522_zpse5897888.jpg (http://s255.photobucket.com/user/bodmin344/media/DSC01522_zpse5897888.jpg.html)
http://i255.photobucket.com/albums/hh160/bodmin344/DSC01527_zps4c5431df.jpg (http://s255.photobucket.com/user/bodmin344/media/DSC01527_zps4c5431df.jpg.html)
http://i255.photobucket.com/albums/hh160/bodmin344/DSC01526_zps66090e8f.jpg (http://s255.photobucket.com/user/bodmin344/media/DSC01526_zps66090e8f.jpg.html)
http://i255.photobucket.com/albums/hh160/bodmin344/DSC01525_zps132fa7b9.jpg (http://s255.photobucket.com/user/bodmin344/media/DSC01525_zps132fa7b9.jpg.html)
It works. as you can see the pistons are pretty much flush with the deck...
I worked out 12.5:1CR with a C16se head. Not running yet because i cant decide wether to go carbs and dizzy or bike tb's and mappable ignition...
So theyre you go. one of the dreamers did it.
turbojolt
03-03-14, 01:40 PM
love it, fair play mate
I vote carbs
love it, fair play mate
I vote carbs
Half thinking Bike TB's with ignition control, to get the most out of it. got to be really careful with my money right now though :(
turbojolt
03-03-14, 02:07 PM
carbs look right in a nova engine bay, like a period modification
well done... i can't wait to see this working..
well done... i can't wait to see this working..
Thanks for the help/advice mike :)
Jake have you got the head cc for the 1.2 head?
jimbob-mcgrew
03-03-14, 06:51 PM
does the 1.4 and 1.6 share the same bottom end ? as theres a fair amount of meat left in the block there, even after the re-bore
+ good job by the way :thumb: ... I guess it works out something like a 1.5 now ?
Jake have you got the head cc for the 1.2 head?
havent got a 1.2 head, i have a 1.3 i can do for you if you want mate
does the 1.4 and 1.6 share the same bottom end ? as theres a fair amount of meat left in the block there, even after the re-bore
+ good job by the way :thumb: ... I guess it works out something like a 1.5 now ?
1420cc i think, its not a massive rebore
jimbob-mcgrew
03-03-14, 11:18 PM
that's only 31 cc !
I guess the majority of the power comes from the compression hike.
could you not get similar results by giving the original head an aggressive skim ?
Novaload_Nick
04-03-14, 09:03 AM
Love this, I want to do a similar thing with my 1.2, crazy thoughts of trying to get 100bhp out of the 1.2 :cool:
Peredur
04-03-14, 10:33 AM
Cool Stuff Jake! I'm hoping to get cracking on my hybrid 1200/1400 experimental build once the shell is done.
that's only 31 cc !
I guess the majority of the power comes from the compression hike.
could you not get similar results by giving the original head an aggressive skim ?
bit boring though int it! plus i wanted to prove everyone wrong lol
compression is where its at.
what did you get the 1400 out of?? is it a nova one with the smaller flywheel?
jimbob-mcgrew
04-03-14, 10:30 PM
bit boring though int it! plus i wanted to prove everyone wrong lol
its something different, which makes a nice change, rather than the usual 20xe + 5 spoke rims I see all over the net. hopefully runs well too :thumb:
+ even tho its only a small change, you've got the stronger 1300 rods in there to take more abuse. in future if you get bored, you could always skim the pistons down, and turbo it for a laugh lol
compression is where its at.
what did you get the 1400 out of?? is it a nova one with the smaller flywheel?
x14sz out of a corsa which has the f13 flywheel, i did look for a 14nv block but everyone wanted too much for them! £50 delivered for the 14sz so i didnt really moan
its something different, which makes a nice change, rather than the usual 20xe + 5 spoke rims I see all over the net. hopefully runs well too :thumb:
+ even tho its only a small change, you've got the stronger 1300 rods in there to take more abuse. in future if you get bored, you could always skim the pistons down, and turbo it for a laugh lol
1600 8v turbo next, got a pretty good idea of how im going to do it.. :)
Novasport
07-03-14, 02:27 PM
I measured a 14NV block and again, it is shorter than the 13SB block.
what is the height of the block you used?
I measured a 14NV block and again, it is shorter than the 13SB block.
what is the height of the block you used?
Didnt measure it, will do it tonight when i go to the workshop if i remember, next worry is valve clearances.
jake. the valve clearances should be ok, unless you go for a real crazy camshaft.
jake. the valve clearances should be ok, unless you go for a real crazy camshaft.
Several engine builders ive spoke too have advised 12mm liftlol i dont really dare make the cutouts any deeper either
you could try a dummy build with an old head gasket, and some really weak springs.
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