Hey guys, i wan to build/rebuild a daily mild a12

Just wondering what gear you recomend? Like cams, bore size, pistons, carb. Etc..

Also anything else i should consider during the build?

Cheers.

Good idea I just finished a mild a12 myself... It's lot of funneith great torque!!! I would most definitely recommend it for a daily!!!
First I would recommend putting an h89 hea on which is a higher comp than the stocker a12, it also oval ports so you can put twin side draft manifolds on....
I had my flywheel machined And lightened well it's lighter lol. I also out a Bice as of flat tops in and from memory it's bored 20 odd thou but I'm not sure.
Next is what sort or carb/s do you wanna run? You can run DHLA/DCOE, solexs, bike carbs EFI or even su's it's whatever tickles ur fancy and whatever you can afford haha.
I would also recommend getting everything balanced, rods, pistons, crank etc. I had a cam reground by wade cams. It has smooth fast idle and picks up at around the 2500 mark.
Then you cam look at head work... Double valve springs, porting, valves etc.
And when you say "gear" are u talking brands or just which way to gonkn building it? Lol I think i shouldnof starte with this question. Oh well.

Thanks mate, where abouts are you located? Im going to use the round port head due to budget and accesability of them, i might go a downdraught carb ( 38/38 DGAS or 32/36 DGV) What are your thoughts on that? I am currently in the process or machining spacers to replace the rocker shaft springs to reduce friction, also shaping rocker arms. I mean brands and sizes, machine shops(im on the gold coast), people to talk to, build tips... Anything really for me to get a better understanding of how the process works(order of machining and painting) Literally aaaaanything you can throw at me :) Zak.

use electric fan. you can free up probably 1hp.

Haha still probably like a 50% hp increase from what it is now...

You'd be surprised how hard an a12 can go!
Your best bet is to drop into a/few local mechanics and have a chat about what recommendations as they will be able to guide you the best, especially price wise...
My mechanic starts at $80. i already know before i go there it will cost me 80 dollars before he looks at it.
ACL pistons are pretty generic...
I would use all your standard rods, crank flywheel etc. It all depends how much money you wanna spend. More money means a better a12.
I would recommend having the block bored and honed, a nice set of flat tops, have the crank, rods and pistons all balanced.
Have the flywheel machined and lightened a little.
Then you can do some head work, this is all good and well but it costs money! I spent a good grand having all my machining done which included everything being balanced, had the head shaved and also had the bottom end assembled.
you can have a standard cam reground to be a little bit more lumpy but id keep it mild, as a cam tha picks up at 5-7 grand would be terrible to drive on the streets...

A much cheaper alternative is to wait a little and hunt down a cheapish a14/15... an a14 has been known to rock up from time to time for between 450 and 600 dollars... Simple conversion if you have a late model cross member. Or modifying the engine mounts isn't too hard but from memory modding engine mounts will cause an engineers cert. but dont quote me.
If you ask around for brands put a few other maybe more specific posts up to the part you're looking for on here and the gurus should be able to help as im still learning... if anything compared to some of these guys i look like nothing! haha

When it comes time to buying gasket and what not go to Auto surplus in Mitcham
http://www.autosurplus.com.au/
Let them know Eddy from here sent you. They will sort you out.
They should pretty much be able to get you anything...
Otherwise you can contact member Bige, he builds a series race engines and will be able to answer any and all of your questions much better than me!!!
One thing to keep in mind, none of this is a cheap exercise always remember that!

H89 is same compression ratio as stock A12 head, so don't waste your time there.

H89: 29-31cc
A12: 27-29cc

However, H89 makes superior power above 3000 RPM. It is highly recommended unless you don't like to rev the engine in daily use.

Yes, flat-top pistons are the best way to gain higher compression.

To make the most HP, don't worry about Compression Ratio, but instead fit larger pistons. Regular oversize pistons (0.5 mm) will gain no noticable power. A14 pistons are 3mm larger diameter, and will deliver far more power than Compression Ratio change.

Otherwise, simply put new rings in the A12 and enjoy. Most blocks do not require any machining of bores unless you are fitting larger pistons.

Oh I thought thought the H89 head was a lot higher comp, or is it a lot higher than the h75 head? O_o

I'd use the Weber 32/36 and a moderate cam with dual valve springs. If your current bores are terrible worn then go with what ever size flat tops you can find cheaply, if the bore are fine then just re-ring it. As far as the cylinder head goes you can clean up the ports, on a stock head the valve seat actually protrudes into the port about 1mm, just getting the seat flush with the port wall will increase flow a lot.

So basically if you don't need to bore the block don't, regrind the cam to a moderate spec (260 duration .375 lift), 32/36 weber, Header/extractors and larger diameter exhaust. Now as has been mentioned this will get you about 80-85HP range which is what an A14 puts out. If you can build the engine yourself than that's a plus. Also if you can find the bits used off this site or Ebay etc. then that will help as well. Even as cheap as I find stuff on the used parts market I would expect to be into the motor for $400-500.


Tom

Well said^^^ that was sorta what I was trying to get at...
Also if you can't build the engine yourself a mechanic should be able to build the bottom end for aroundte 250 dollar mark....