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What is needed to install a 6 bolt head on a 2g 7 bolt block?

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dsmGSTtuner

10+ Year Contributor
143
2
Mar 3, 2012
lexington, South_Carolina
I'm thinking of doin a 6 bolt head swap on my 7 bolt block. Just wondering what is all needed to do this and what are the advantages?

Thanks ahead of time! :D
 
I was just wondering because I was thinking about buying a 6 bolt head that has been rebuilt for $120.

Yea I should have used search. I just got out of surgery so I'm still a little loopy. my bad!!
 
If you go with 6 bolt head, You need a 6 bolt Intake as well, unless you port the hell out of the 2g intake.
The good thing on a 6 bolt head is, the runners are way way bigger, But if you have a light mod, You should stick with the 2g, which it will flow better air.
6 bolt head is more for high power (TOP END), which the bigger runners can flow more air.
 
Yes, I know that, But on very high power a 6 bolt will be the winner, I know there is some turbulence on a 6 bolt, But at the end, it will be the beast.
However, I did stated to stick with a 7 bolt which it flows better.

you might miss understood my post.
 
If I recall correctly, a 1g head will drop right on top of a 2g block. Everything originally on a 2g head should bolt up to the 1g. You'll also need to wire in a 1g cas.
 
If you go with 1G head, You need a 1G Intake as well.
The good thing on a 1G head is, the runners are way way bigger, But if you have a light mod, You should stick with the 2g, which it will flow better air.
1G head is more for high power (TOP END), which the bigger runners can flow more air.

Bigger isnt better. A 2G head will flow just as good and will actually spool faster.

Yes, I know that, But on very high power a 1G will be the winner, I know there is some turbulence on a 1G, But at the end, it will be the beast.
However, I did stated to stick with a 2G which it flows better.

you might miss understood my post.

Fixed.

Let's not get confused or continue to confuse others, folks. In terms of performance or flow, a 6-bolt head will flow the exact same as a 1G 7-bolt head. A 1G 7-bolt head and a 2G head will not flow the same. So when discussing the port sizes or air flow, there is only 1G and 2G heads, no 6-bolt or 7-bolt.

If I recall correctly, a 1g head will drop right on top of a 2g block. Everything originally on a 2g head should bolt up to the 1g. You'll also need to wire in a 1g cas.

A 2G thermostat housing will not bolt up to a 1G head and, although a 2G intake manifold will, it does not seal. The CAS issue is really only applicable to the 2Ga as a 2Gb CAS can bolt up if the appropriate intake cam is used or modified.
 
Last edited:
To answer your question, you will need:

1G Intake manifold
1G Water Pipe, you can use a turbo pipe (with provisions for water lines, if you need them. Otherwise N/T with a nipple for your water cooled-OFH is sufficient)
1G Thermostat housing
1G Throttle body, not necessary but you will want it since the 2G TB is now a restriction to you

Now keep this in mind. You MAY need to have your Intake cam drilled and tapped for your 97 CAS. If this is not something you want to to, look into getting a 1G CAS. Keeping your 97 CAS is recommended if it is possible.

Another thing to keep in mind, your throttle body elbow is going to sit about 2(?) inches further from the firewall. Be prepared to modify any existing UICP to fit, especially on a VRSF/SSAC kit.

I have done this on my car, and I have almost no low end power. I have enough for slow cruising, but since I am an auto and my car shifts itself it feels incredibly slow.

However, my butt dyno has noticed a significant amount of top end power gain.

If I had the choice in the first place to keep my 2G head, I would have. I bought a "7 bolt head" thinking it was 2G. And things just went from there. I am not unhappy with the results though.
:)
 
And if you do still decide to go with the 1G head...
Now keep this in mind. You MAY need to have your Intake cam drilled and tapped for your 97 CAS. If this is not something you want to to, look into getting a 1G CAS. Keeping your 97 CAS is recommended if it is possible.
...you could just swap the existing intake camshaft to the new head to retain the 97 CAS; no drilling or tapping involved. :)
 
And if you do still decide to go with the 1G head...

...you could just swap the existing intake camshaft to the new head to retain the 97 CAS; no drilling or tapping involved. :)

Sorry, I was assuming if the head was trashed. I probably should have read a little more into it.
:D

Side note: aren't 1G turbo cams kind of an upgrade for 2Gs?
 
A 2G thermostat housing will not bolt up to a 1G head and, although a 2G intake manifold will, it does not seal. The CAS issue is really only applicable to the 2Ga as a 2Gb CAS can bolt up if the appropriate intake cam is used or modified.

Darn I mixed up the thermostat.
 
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