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1G 2g head swap!

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TK9er

Proven Member
168
16
Jun 1, 2014
lincoln, Nebraska
Hey, everyone. I know that this has been done a lot, but i am struggling to find info on the 1g cas in a 2g head. Everything I am finding deals with wiring a 6bolt into a 2g car and using the 1g cas.

Maybe i'm over thinking it...

Putting in a 91 GSX

I just bought a head off of a 95 tsi. It is the one that doesn't have a traditional cas. My question is, can i just put the old cas off my 1g head on the 2g head??? and then remove the 2g stuff?

Also, For the swap. I have read a lot of stuff on the swap, but it seems like every one gets into the weeds on what does and doesn't need to be done.

As of right now, I am only planning on opening up the head bold holes and doing the oil port mod... it looks like my tstat will bolt up. I am going to be using a 2g intake manifold, and possibly a 1g throttle body (i am open to suggestion on this one). I'm sure i'll find out when the manifold gets here, but does the 1g fuel rail bolt up??? anyway, my main question is about the cas.

Thanks for your time!
 
1g fuel rail bolts up but the 2g regulator wont go on it you would need the 1g, the bolt holes for the regulator are north south vs east west. The 1g cas will go right on as long as you have the intake cam slotted for the sensor (use a 1g intake cam or aftermarket), then just wire it as a 6 bolt in a 2g.
 
Thanks for the reply. I'll have to check if it has the slotted cam.

I'm kind of confused about the wiring... if I can use my cas, why can't I just plug it back in as if it where a normal 1g head going back on? To clarify, it is going in a 1g car. Or maybe I'm not understandin you.
 
1g fuel rail bolts up but the 2g regulator wont go on it you would need the 1g, the bolt holes for the regulator are north south vs east west. The 1g cas will go right on as long as you have the intake cam slotted for the sensor (use a 1g intake cam or aftermarket), then just wire it as a 6 bolt in a 2g.
OP said it' a 91. You don't need to change any wiring. Just use it as stock.
 
Oh, that's good news! I was hoping it would be that simple. Just kinda freaked out when I got the head and it didn't have a cas at all!
 
You don't seem to know the differences. Are you also aware the head bolt holes are smaller, the intake ports are smaller, the outer exhaust man studs are bigger.

Why are you stating 91 when your profile says 90?
 
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Yeah, in my original post I said I'm opening up the bolt holes on the head. I'm using a 2g intake manifold. Not sure what I'm doing for the throttle body. I see people porting there 2g intake to match, but I don't like the idea of that. What would you suggest.

And as for the difference, what I am aware of is the 2g head is a more efficient design. It will bump my compression, have better mid range torque do to the port size and velocity. Also, how the air entering the cylinder is a better design for a street able use.

I am not saying I know a lot, but I am trying to learn. I've been reading a lot on here, it can just get to be a lot. I am open to suggestions as well as corrections.

As for the 91 and 90... that's a long story. I bought the 90 with a spun bearing... well, it turned out to have a giant hole in the block. So, I was able to find a local guy who had a completely stock 91 gsx that jumped timing. And bought the whole car for a good price. The body of the gsx is junk! So, I pulled the head, sure enough it had bent valves. So, instead of fixing up the 1g head, I got a 2g head from a salvage yard. I plan on putting the 2g head on the 91 and making sure everything work and I don't have any surprises (making sure the transmission is good. I plan on using the trans out of the 91 since it is a 23 spline and the motor was never modded). Then, pulling everything and sending it off to a machine shop. Once everything is done, I plan on putting it in the 90... long, confusing story, but it makes sense to me
 
Yeah, in my original post I said I'm opening up the bolt holes on the head. I'm using a 2g intake manifold. Not sure what I'm doing for the throttle body. I see people porting there 2g intake to match, but I don't like the idea of that. What would you suggest.

And as for the difference, what I am aware of is the 2g head is a more efficient design. It will bump my compression, have better mid range torque do to the port size and velocity. Also, how the air entering the cylinder is a better design for a street able use.

I am not saying I know a lot, but I am trying to learn. I've been reading a lot on here, it can just get to be a lot. I am open to suggestions as well as corrections.

As for the 91 and 90... that's a long story. I bought the 90 with a spun bearing... well, it turned out to have a giant hole in the block. So, I was able to find a local guy who had a completely stock 91 gsx that jumped timing. And bought the whole car for a good price. The body of the gsx is junk! So, I pulled the head, sure enough it had bent valves. So, instead of fixing up the 1g head, I got a 2g head from a salvage yard. I plan on putting the 2g head on the 91 and making sure everything work and I don't have any surprises (making sure the transmission is good. I plan on using the trans out of the 91 since it is a 23 spline and the motor was never modded). Then, pulling everything and sending it off to a machine shop. Once everything is done, I plan on putting it in the 90... long, confusing story, but it makes sense to me

how does a 2g head bump your compression? it has the same combustion chamber size as the 1g.
 
I don't know... maybe I am wrong on this. I thought it was higher... I am not claiming to be right, just saying what I believe is true. Again, if I'm wrong, I have no problem with that. I'm wrong a lot! Not here to argue
 
how does a 2g head bump your compression? it has the same combustion chamber size as the 1g.
Because he's going to resurface the head ;)

I don't know... maybe I am wrong on this. I thought it was higher... I am not claiming to be right, just saying what I believe is true. Again, if I'm wrong, I have no problem with that. I'm wrong a lot! Not here to argue
You arguing, punk? JK, I'm about to start my 2g head swap today. A lot of people just run the 1g throttle body and port out the 2g intake manifold inlet. I decided to go with a ported Curt Brown evo3 intake manifold. I also chose to reinforce the welds on the manifold because god forbid I blow the welds out on a sick pull because of too much nos.
 
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You arguing, punk? JK, I'm about to start my 2g head swap today. A lot of people just run the 1g throttle body and port out the 2g intake manifold inlet. I decided to go with a ported Curt Brown evo3 intake manifold. I also chose to reinforce the welds on the manifold because god forbid I blow the welds out on a sick pull because of too much nos.
That's so funny! We just watched that scene at work yesterday! Don't forget to tighten your diamond plate floor boards down!

I'll probably go with the 1g throttle body like you said. Thanks for the help. I did notice that most of head bolt fit fine from my 1g to 2g head. I only opened up one hole. I remember reading that you only have to open them up if using head studs, is that right?

I believe it's the 2G pistons that are responsible for the compression bump over the 1G's.
Thanks! I must of gotten them mixed up in my head.
 
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That's so funny! We just watched that scene at work yesterday! Don't forget to tighten your diamond plate floor boards down!

I'll probably go with the 1g throttle body like you said. Thanks for the help. I did notice that most of head bolt fit fine from my 1g to 2g head. I only opened up one hole. I remember reading that you only have to open them up if using head studs, is that right?
No. They fit through but it's
Tight.
 
That's so funny! We just watched that scene at work yesterday! Don't forget to tighten your diamond plate floor boards down!

I'll probably go with the 1g throttle body like you said. Thanks for the help. I did notice that most of head bolt fit fine from my 1g to 2g head. I only opened up one hole. I remember reading that you only have to open them up if using head studs, is that right?
The bread and butter setup for DSMs is ARP head studs and having a machine shop enlarge the 2g stud holes to 13mm to accommodate the studs.
 
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