Difference between 6 and 7 bolt head?

[mindset]

I need to know the differences between the 6 and 7 bolt head. My buddy just recently bought a 1990 Eagle Talon Tsi AWD. The guy claims it has a 7 bolt head, but we're unsure. Just so you guys know, he also has a 6 bolt head. Feel free to post pics to help me understand.

 

[PIMking]

why would they put a less flowing head on the 1g car? 2g heads dont flow as well.

 

[mindset]

why would they put a less flowing head on the 1g car? 2g heads dont flow as well.

Yea I understand that, but what are the physical differences? Besides how big the intake side holes are. I dont know why they would do that though. Just how he bought it.

 

[95blackGsTurbo]

1g intake ports are bigger but the 2g has better casting so take it for what it's worth. Other than that you can switch them as long as your use the right intake manifold. I have seen people try to use a 2g manifold on 1g head or the other way around and it doesn't work. They don't match up flange wise and create HUGE boost leaks. And the difference is 1g and 2g heads not 6 bolt and 7 bolt. The 7 bolt 1g still had the larger port head.
http://www.dsmtuners.com/forums/newbie-forum/123568-answer-quikk-difference-1g-2g-head.html

 

[Redfwdsm]

1g intake ports are bigger but the 2g has better casting so take it for what it's worth. Other than that you can switch them as long as your use the right intake manifold. I have seen people try to use a 2g manifold on 1g head or the other way around and it doesn't work. They don't match up flange wise and create HUGE boost leaks. And the difference is 1g and 2g heads not 6 bolt and 7 bolt. The 7 bolt 1g still had the larger port head.
http://www.dsmtuners.com/forums/newbie-forum/123568-answer-quikk-difference-1g-2g-head.html

sweet i just pulled a head off a blown 7 bolt 1g and was unsure if i could use it now i have a head to send out for port and polish and all the other goodies i can afford

 

[98 Mits GS-T]

If you take the exhaust manifold cover off you can see the manifold-to-head studs. If it is a 2g head all the studs will be the same size, if it is a 1g head the two end studs will be bigger than the rest.

 

[Dsm_Roly]

Go to VFAQ Site - Visual Frequently Answered Questions. You can tell if it's a seven bolt or six by the way the oil pan looks.

Oops, didn't realize we we're talking about heads?

 

[the_mork]

The 2g heads have a higher velocity intake charge in comparison to the 1g head. The 1g head can flow more but doesn't necessarily depending on conditions. Specifically in apples to apples comparisons a 2g head should generally have better part throttle and mid range response while the 1g head should have a higher flow potential at high RPMs.

At least that is the way that I understand it.

 

[the_mork]

As for identifying a 2g head you can start with this post I made in a discussion of intake manifolds. It contains pictures of the intake side of a 2g head as well as pictures of potential intake manifolds that might be attached to it.

http://www.dsmtuners.com/forums/bol...take-manifold-tb-options-3.html#post151695004

As for identifying the head you can identify the intake manifold which should tell you which head it is since the 1g and 2g manifolds are not interchangeable. A 2g manifold has a small rectangular black sensor on the top of it which is called the MDP sensor

 

[redyute1]

Carefull the 7 bolt head uses smaller diameter heads bolts,you can use it but to make it work you would have to drill the bolt holes to make it work with the bigger 6 bolt head bolts.

 

[mindset]

Okay, thanks guys. This helps a lot. On my other buddys car, 1993 Talon Tsi, the guy put on a 2g manifold on a 1g head and the holes were all "not aligned" i guess. Ill have to talk to my friend and see if he's got any more questions. Thanks

 

[DSM_PWR]

To give you an idea of how much bigger the ports are,

Here's a pic of a 1g intake gasket on a 2g head

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[98GST6BOLT]

ya they intake holes are the only way i could tell what gen there off of.

 

[ZLODEY]

a) still not clear for me if it is possible to put 1G 6bolt head on 2G 7bolt block or I should find only 7bolt 1G head for it?
b) is it possible to use 2G stock intake and exhaust manifold together with 1G 7bolt head or 6bolt?

 

[ZLODEY]

can anyone clarify this once and for all, please?

 

[JusMX141]

a) still not clear for me if it is possible to put 1G 6bolt head on 2G 7bolt block or I should find only 7bolt 1G head for it?

1G 6-bolt and 7-bolt heads are the same. You can use a 1G head on a 2G block, yes.

b) is it possible to use 2G stock intake and exhaust manifold together with 1G 7bolt head or 6bolt?

You should not mix-and-match intake manifolds between the 1G and 2G cars. If you're running a 1G head, use a 1G intake manifold.

Any exhaust manifold will fit / work. The 2G manifolds are cast with thicker webbing than 1G manifolds, making them more durable. A 2G manifold is the same dimension as an Evo III manifold with a smaller (6cm2) collector.

 

[ilco187]

1g top/2g bottom

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[jrohner]

If you take the exhaust manifold cover off you can see the manifold-to-head studs. If it is a 2g head all the studs will be the same size, if it is a 1g head the two end studs will be bigger than the rest.

You got that backwards.

 

[Blitz_86]

easiest way to tell on the car with out taking anything off is if all the nuts on the exhaust manifold are the same size if so its a 1g head, the 2g head the 2 lower outer studs are 10x1.25 instead of 8x125 , and the end nuts are 14mm instead of 12mm easiest way to tell.

 

[92_talon_awd]

easiest way to tell on the car with out taking anything off is if all the nuts on the exhaust manifold are the same size if so its a 1g head, the 2g head the 2 lower outer studs are 10x1.25 instead of 8x125 , and the end nuts are 14mm instead of 12mm easiest way to tell.

I have a 1g head with a 2g manifold and my end nuts are the 14mm ones. Just throwing that in there to point out this method isn't 100% foolproof.

 

[Blitz_86]

hmm weird, guess i was wrong i have never seen a 1g with that tho. but thanks for informing. guess the only way to tell for sure is the ports and the water neck housing

 

[ZLODEY]

I have a 1g head with a 2g manifold and my end nuts are the 14mm ones. Just throwing that in there to point out this method isn't 100% foolproof.

this is probably 1G 7bolts head with M10x1.25 (14mm) nuts on both sides, same as 2G 7bolts head...

 

[deflator]

can anyone clarify this once and for all, please?

Let me try, anyone feel free to add to this or correct anything...

Applicable Differences

1G head
-Bigger intake ports
-12mm head studs (1.25 pitch?)
-Hall or optical effect CAS on intake cam, passenger side
-Slightly more aggressive stock cams

2G head
-Smaller, higher-velocity intake ports
-11mm head bolts (pitch?)
-95-96 CAS is underneath the intake cam gear on, on passenger side on 97+
-Detuned cams

Misc Differences
-Different thermostats
-Some brackets on the 2g absent on the 1g

 

[stevestevesteve]

couldnt you just port a 2g head to match the 1g intake and exhuast?

 

[donniekak]

couldnt you just port a 2g head to match the 1g intake and exhuast?

If you had a flow bench. Porting out 4 intake runners within a few % of each other by estimation is impossible. If 1 runner flows more than the other 3 it will run leaner, and that can cause major problems.