How much compression do you think my EA81dc (dual carb/different heads) could take? I am looking at custom pistons. I was thinking something like 12:1...

 

This is ofcause not turbo'd and I am not planning on turboing/SC it.

 

Also there are 3 types of custom pistons. I have no idea what the differenced do. I will look into it tomorrow, but can anyone tell me what is better for what? Flat Top, Dome Top, Reverse Top...

I think you could go dome top.Slight dome that is.I think Ram performance or Wiseco pistons would be the best bet for that.I know that both companies can do custom work.Would be fun to try.

i made the pistons in my ea81 they're all right with my set up but i think what help the most welding up the area head

but i think what help the most welding up the area head

Sorry, but could you please tell me what the area head is? I'm not too familier with the terms of the internals of the engine and how they make a difference as yet.

While you're at it, could you clue me in on the process you used to make the pistons?

are you going to upgrade the rods and valvetrain? what about interference/noninterference? (a dome piston would almost certainly need to be sculpted around the valves and spark plug)..

are you going to upgrade the rods and valvetrain? what about interference/noninterference? (a dome piston would almost certainly need to be sculpted around the valves and spark plug)..

Seems the heads I have already have big valves, and I don't want them to crack either, I figured I might leave them alone. A polish might be useful though. And because it is already the performance dual carb engine the cam is also pretty good. As stock it should have 108hp. I'd like to see something like 135hp. I'll look into better rods, although I have bearly heard of problems with them (only once in the 2 and a bit years of interneting Subies.) I kinda figured it being a pushrod motor and the likeliness of bending a valve from a rod failure being a couple of million to one I didn't need to worry too much about interference or not. I just won't compression that is through the roof. Something that needs the 102 octane fuel

Seems the heads I have already have big valves, and I don't want them to crack either, I figured I might leave them alone. A polish might be useful though. And because it is already the performance dual carb engine the cam is also pretty good. As stock it should have 108hp. I'd like to see something like 135hp. I'll look into better rods, although I have bearly heard of problems with them (only once in the 2 and a bit years of interneting Subies.) I kinda figured it being a pushrod motor and the likeliness of bending a valve from a rod failure being a couple of million to one I didn't need to worry too much about interference or not. I just won't compression that is through the roof. Something that needs the 102 octane fuel

 

I would just get the heads decked down like .050"(not sure what that is in mm).You already have the higher compression pistons than the stock hydro lifter ones in you dually carbie engine.Just need to muck around a bit with your intake manifold holes so they fit.I think then you would need 100 octane!

You already have the higher compression pistons than the stock hydro lifter ones in you dually carbie engine.

See here lies a problem.. The block on of my engine can't be a dual carb block (engine number is one from around the 87, 88, 89 period.) I know it has the dual carb cam, but I don't know about the pistons.. And the whole Idea of higher compression is so I don't feel like I need to supercharge it. I also like high compression power over boosted power, it feels better.

And really, 9.5 to 1 just isn't enough for me.. I want crazy power

Plus custom pistons means forged, which is lighter, so more power straight away.

Talking about that, what else could I get custom for lighter internals? (remember, this isn't for offroad, its for 8K RPM+ power )

I would get the crank knifed(profiled)to shave off some rotating mass since you said it is meant to sing up in the upper rpms.Also go with some stronger valve springs and stainless valves.I bought my high strength valve springs from RAM performance.

I think a email to SUB4 is in order... Maybe I should wait til the new EJ is in my car and working..

I don't know how thick an OEM head gasket is, but if you had one made out of metal that was very thin that could also raise compression a little, and be stronger too.

I don't know how thick an OEM head gasket is, but if you had one made out of metal that was very thin that could also raise compression a little, and be stronger too.

I'd say the head gaskets I use are about 1.5mm to 2mm thick at a guess. I really should know because I've had to pull the head off this engine more then 4 times, for things not related to the head gaskets. I was thinking laser cut copper gaskets..

Give J+P pistons in Adelaide a buzz if you haven't already, they will copy anything you want, l have vintage motorcycle piston's made there, (have done so for the last 20 years), and have found the quality of the pistons to be excellent and always on the size you give them. Their price is also compareable but their better service has always won me over, good luck.