Need some explaining about corsa pistons in a cga3 with cg head

[.Maarten]

Ive read some stuff about boring a cga3de bottom end to 72.5 and put corsa pistons in. Ive read somewhere this would give a compression of 8:1. I also read you could bolt a cg13 head to it so it would be ideal for a turbo swap for a 1.3.

Is this correct? And if so from what engine do i need the corsa pistons? X12XE? And is the compression indeed 8:1?

Another question. I also read somewhere you could redrill the cg flywheel and bolt a ga16 190mm clutch to it. Is this also correct?

 

[frank]

its the pre twinport 1.0 and 1.2 pistons maarten, and paul,s (polly) has a redrilled flywheel iirc

 

[.Maarten]

Thanks frank. That should be the X12XE or Z12XE then. Do you also happen to know if it indeed brings the compression to 8:1?

 

[frank]

i forget now mate, the deck height is 4mm less iirc, but the CGA pistons have a deep dish tho
9:1 maybe ? the twinport pistons are about 74mm ? http://www.micra.com.au/community/message.php?messageid=75745

 

[.Maarten]

Thats with the CG13 crank? Or with the CGA3 crank? My guess would be with the CG13 one.
Lovely threat by the way. Lots of info.

 

[frank]

yes cg13 crank, and 3mm less deck height on a cga, so its not much different to the deep dish.
this was the high comp corsa piston build (decked block and headskim and shortened lower chain)
http://www.micra.com.au/community/message.php?messageid=69926

 

[.Maarten]

That high comp block looks nice. Although a bit to much for my goals of being a reliable daily with some power to at least have some fun when i want to. Thats why there will be a turbo fitted but i dont really fancy swapping the engine every few months. Thats why i want to lower the compression. Boost wise im aiming at something like 0.8 - 1 bar.

After reading all those links i think this should work and give me a compression ratio between 8:1 and 9:1:

CG13 crank
CGA3 block
CG13 head
Corsa X10XE Pistons (The X10 have the dish and the X12 are the flat top)

 

[frank]

how about 73.4 z14 twinport pistons maarten ? dished
a rally member has used custom 74mm pistons for a while

 

[.Maarten]

They look good but do they fit in a CGA3 bottom? If they do they are surely a good option. And prolly stronger than the older X10XE ones.

 

[frank]

or 72.5 1.4 turbo ones ?
https://www.ebay.co.uk/itm/Vauxhall-Corsa-Meriva-Astra-1-4-turbo-Piston-A14NET-A14NEL-EURO-5/162853583042?fits=Model:Corsa&hash=item25ead478c2:g:KigAAOSw2LZanobU:rk:26f:0

 

[frank]

Manufacturer Part Number: 3970220RMP
Compression Height: 25.870 MPN: 3970220RMP
Bolt length: 47,5 EAN: 4044197687497
Recess Depth 1: 2.904 Other Part Number: 87-437400-00
Recess Diameter: 54.780 Function: Piston
Valve pocket depth 1: 2.100 Length: 44.180
Production Number: 07279-212 Additional Information 2: for keystone connecting rod
Valve pocket depth 2: 1.870 Component Number: 08-437400-00
Reference OE/OEM Number: 87-437400-00 Cylinder Bore: 72,5

 

[.Maarten]

Turbo pistons would prolly be alot stronger and wont have a problem with something like 150-175 horsepower seeing that they chip those Opels to 180hp.
But the main question is would they fit? The pin is 18mm so that should fit. Just like the bore of 72.5.

I also found this picture from the A14NET pistons:

Edit:

They look very tempting. Strong enough atleast

 

[.Maarten]

So i found this for the A14NET pistons:
https://www.ksmotorshop.com/article-detail/view/en/108033/piston-87-437400-00-nural
They are a bit shorter than the X10XE pistons but the compression height also is higher. Correct me if im wrong but this would mean the compression is higher than the X10XE pistons in a CGA3 bottom?

Still the A14NET has a stock compression of 9.5:1 and the pistons are made for a turbo engine so they would be alot stronger then the CG13 or CGA3 ones and it would prolly still drop a bit due to using a cg13 crank with a cga3 bottom.

Frank do you recon the A14NET pistons would fit without much hastle? Like only giving the block a bore to 72.5 without further modifications.
(To make this combination: CG13 head, cga3 bottom, cg13 crank, A14NET pistons)

 

[frank]

i dont see why they would,nt fit mate, and the compression height is about the same as CGA, so you would need the CG13 crank to drop the c/r eh.
but i would go for the CGA crank personally
https://www.micra.org.uk/threads/piston-info.41514/#post-431632

 

[.Maarten]

Cool that looks very good! Ill go with the A14NET ones with a CGA crank then. Ill keep you updated about it.

 

[frank]

might be best to try 1 piston first maarten ? to test the fitment

 

[.Maarten]

Yeah im picking up a CGA3DE next week and them i can compare both pistons and see the differences. Or i just drop the engine off at the builder to check if they indeed fit before i buy 4

 

[frank]

a search shows circlips holding the pin, but no sign of little end bearing, so i,m guessing its the same interference fit in the rod but circlips added also
so centralising the pin will need to be precise

 

[.Maarten]

I saw that circlip on some pictures. The pin also was 18mm so same as CG/CGA. Should fit right? Yeah ill leave that to the engine builder. He's the one with far more experience than me. Its just way to costly to have him figure everything out. Id rather spend the money on parts that on him googling stuff.

 

[frank]

yes 18mm, and the cg rod bore is 1" thou less (17.98 mm) so you have to heat the rod to remove or fit the pin
i think the a14 pin is fully floating, but it should,nt be a problem tho, you could use the interference fit and/or circlips

 

[.Maarten]

Good to know. Ill let the builder decide how he wants to do it. Heating shouldnt be a problem. But ill ask him to make some pictures.

 

[.Maarten]

Small update. The engine builder is looking for a suitable headgasket atm. He told me the compression ratio is around 9.8:1. We are currently looking for ways to bring it down a bit and see what gasket we are going to use.


I asked them to check if swapping to the cg13 crank lowers the compression ratio and if so how much.

 

[.Maarten]

Another small update. Kinda stuck at the moment.

The engine builder told me he couldnt use the CG13 head gasket because the bore would be to small. And that he had to use the Nismo 73mm bore and 0.5mm thickness one due to the overbore for the pistons. He told me he needed a 73mm bore gasket. The Nismo one would bring the compression ratio to about 10:1. A bit high but still doable on low boost. We tried the Reinz CGA3DE 73.5mm 0.6mm head gasket but that one doesnt fit because it has no oil return holes but the cga3de bottom end has them so thats kinda wierd. (According to my engine builder)

Does anybody have some tips for a head gasket?

Btw swapping to the cg13 crank would mean a compression ratio of around 8.2:1.

 

[frank]

sounds like you have one of those wrongly listed k12 gaskets maarten ? is it a 2 skin pressed steel gasket ?

 

[.Maarten]

Yep we are 90% sure thats the case. Victor reinz has the wrong one in their catalog.. Its a MLS one yeah

 

[frank]

i would just use the stock 72mm gasket mate

 

[.Maarten]

Thanks ill tell him that.

Here are some images he send me.

 

[.Maarten]

Small update. Engine is ready for pickup and the engine builder send me some pictures:

Luk Ga16 clutch

Fidanza GA16 flywheel. They made a bush to fit the smaller crank

Finished engine:

Finished engine 2:

 

[.Maarten]

Another update. The engine is in and is running. It still has a vacuumleak and i had to fit the stock intake manifold due to the bolt spacing being a bit off on the other intake. thats all getting sorted now. Gave me some headaches before i found out it was the intake.

Still doubting about swapping to a 1.4 gearbox with 1.4 starter and drive shafts. The longer box should be nice when the turbo is fitted. And my guess would be it would fit with the ga16 flywheel. But have to measure of just try it.

 

[Low Rider]

The 1.4 gearbox isn't long on a turbo and I'm always wishing there was a 6th gear to be honest.

 

[.Maarten]

Yeah true. But i think its longer then the stock 1.3 gearbox. As far as i know there isnt a 6 speed that would fit without alot of hassle

 

[Low Rider]

Ratios are below FYI.

There is some discrepancy over 5th being 0.733 vs 0.756 but I've never had my box open to count the teeth. The JDM spec cars list 0.756 as does the UKDM Almera with the QG15DE engine, which supposedly shares the same gearbox. It's still a shorter top gear overall compared to a 1.3 box. Not much difference in cruising speed but it does take a bit off the top end due to a shorter final drive.

CG13DE
1st 3.333
2nd 1.955
3rd 1.286
4th 0.927
5th 0.756
FD 3.895

CGA3DE
1st 3.333
2nd 1.782
3rd 1.207
4th 0.902
5th 0.756*
FD 4.167

 

[mullen]

In the process of wanting to build a engine that can hold a decent ammount of boost. in the end did you end up going with the A14NET pistons and a standard 72mm headgasket? did the pistons fit on cg13 rods? then u ran the cg13 crank correct?

 

[.Maarten]

I went with a nismo headgasket but id advise the aspect head gasket as they sell one thats 2mm thick. Im using a cga3 bottom end. Not the cg13.

 

[MicraMake]

Hmm very interesting post! I think can I use this setup:
-1.0 cga bottom end with cg13 crank
-cg13 rods
-a14net pistons
-cg13 head and cams

 

[Clara_2512]

What rods did you use in the end?

 

[.Maarten]

I think they used the cga3 ones

 

[Paul T 6640]

This is the route I took CGA3de bored to 72.5mm with vaux corsa 1.4 net pistons. CGA3 rods and crank. Pistons need machining so conrod goes in between for gudgin pin. also made them fully floating
The block was decked about 1 mm. I have 73 mm head gasket 1.2 mm thick from Matt Humphies.