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.

 

[the_mork]

Absolutely not. First of all 1g exhaust ports are exactly the same as 2g ports. Second of all making a 2g intake port match a 1g manifold will ruin the velocity that the 2g ports provide without significantly increasing potential flow because of the way that the head is designed. If you port a 2g head to match a 1g manifold you might as well throw it in the garbage because you will have combined the worst attributes of two options and not the best.

 

[JEFFREYCASTGSX]

Just to add, the intake runners on a EVO 8+ are even smaller than our 2g dsm intake ports. Just because you have BIG intake ports doenst mean the head out flows the one with smaller intake ports, real flow comes from velocity. If we were to look at all the old desings of many head designns, they also have big ports, but as they progress through there variation they get smaller. What im saying is that i would bet my money a 2g head FLOWS MORE than a 1g. ALso... Brodix HVH Big-Block Heads - Head Games - Tech - Head Velocity - Corvette Fever Magazine

 

[the_mork]

I'm fairly sure that this is incorrect. Evo ports are the same size as 2g ports. The 2g port design also isn't newer. IIRC Colts had the small port design before the 1g came out though dsmonster would have to chime in since I'm lifting his argument. That said for 90% of DSMs the small port setup is going to be better.

 

[JEFFREYCASTGSX]

I'm fairly sure that this is incorrect. Evo ports are the same size as 2g ports. The 2g port design also isn't newer. IIRC Colts had the small port design before the 1g came out though dsmonster would have to chime in since I'm lifting his argument. That said for 90% of DSMs the small port setup is going to be better.

So then just the superior design came out on top, EVO 8+ ports ARE(from experience) slightly smaller.