991 gt3 header fit our Gt3's?
05-24-2018, 01:18 PM
#1
Rennlist Member
Thread Starter
991 gt3 header fit our Gt3's?
I know that the 997 GT3 header will fit on our 996 Gt3's, curious if the 991 version will fit. Any install issues like clearance or port fitment? I would be building a custom exhaust from the header flange to exit.
Thanks guys for your input.
Thanks guys for your input.
05-25-2018, 02:01 AM
#2
Rennlist Member
Doubt it... The M96/79 and M97/76(77) are effectively the same cylinder blocks and the MA175 is just a different thing altogether.
Besides fit, you also have to consider scavenging efficiency when you move to wider-bore headers.
Besides fit, you also have to consider scavenging efficiency when you move to wider-bore headers.
05-25-2018, 09:28 AM
#3
Rennlist Member
Thread Starter
I understand exhaust flow issues associated with bore diameters in primary and cats. That being said I see that 997 and 991 headers are being marketed as an interchangeable part from a number of sources.
Knowing the 997 fits the 996 I was trying to wrap my head around what the actual differences were with a 991 model as it relates to the geometric properties of these headers.
Knowing the 997 fits the 996 I was trying to wrap my head around what the actual differences were with a 991 model as it relates to the geometric properties of these headers.
05-25-2018, 12:58 PM
#5
Rennlist Member
I don’t recall exactly, but when I was doing this research before I bought a 997 system I was also under the impression the 991 units would fit a 996. Which was surprising LOL
05-28-2018, 12:40 PM
#6
Different spacing on the flange for the bolt holes between 997 and 991. I ran into a fitment issue once back when I was at Fabspeed when we sent a set of their 991 GT3 Race Headers to a fellow overseas with a 991 Cup. Turns out early year 991 Cups were still using the 997 generation engine and couldn't get it to work...oops!
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05-29-2018, 09:55 PM
#8
Rennlist Member
Well known fact that the 991.1 Cups (up to MY2016) ran the Mezger engine. Different story with the street cars though--all 991 GT variants are all on the 9A1 architecture.
Off the top of my head the bore spacing doesn't even line up if you put two sets of headers side by side.
Off the top of my head the bore spacing doesn't even line up if you put two sets of headers side by side.
05-29-2018, 11:03 PM
#9
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Do the opposite, get the 991 Center Muffler and built custom headers to the OEM exhaust.
__________________
Instagram :Swine11 | TitanMotorsports
Swine11 ReBoot - 964 / 993 Shift Boot Trim Panel
2004 996 GT3 | 1986 Carrera 3.2 (future Keen Project) | 2016 Cayenne Diesel
Instagram :Swine11 | TitanMotorsports
Swine11 ReBoot - 964 / 993 Shift Boot Trim Panel
2004 996 GT3 | 1986 Carrera 3.2 (future Keen Project) | 2016 Cayenne Diesel
05-30-2018, 10:07 AM
#10
Well known fact that the 991.1 Cups (up to MY2016) ran the Mezger engine. Different story with the street cars though--all 991 GT variants are all on the 9A1 architecture.
Off the top of my head the bore spacing doesn't even line up if you put two sets of headers side by side.
Off the top of my head the bore spacing doesn't even line up if you put two sets of headers side by side.
06-01-2018, 01:53 AM
#12
Rennlist Member
Your best compatibility may be the 997.1 GT3/RS/Cup headers coz they're made to flow with a 3.6.
FWIW, 997 cup headers are mated with [200] cell cats. Could be 100 I dunno. More free-flowing and louder but defo has lifing issues if you're buying them used. Had to replace mine when the engine was rebuilt at ~150 hours... also I think the 996 cats reside in the muffler (I think)... your conversion will be more extensive than just a header swap.
06-02-2018, 09:03 PM
#13
RL Community Team
Rennlist Member
Rennlist Member
It fits, and agree that in comparison the 996 headers look like toilet rolls taped together
Your best compatibility may be the 997.1 GT3/RS/Cup headers coz they're made to flow with a 3.6.
FWIW, 997 cup headers are mated with [200] cell cats. Could be 100 I dunno. More free-flowing and louder but defo has lifing issues if you're buying them used. Had to replace mine when the engine was rebuilt at ~150 hours... also I think the 996 cats reside in the muffler (I think)... your conversion will be more extensive than just a header swap.
Your best compatibility may be the 997.1 GT3/RS/Cup headers coz they're made to flow with a 3.6.
FWIW, 997 cup headers are mated with [200] cell cats. Could be 100 I dunno. More free-flowing and louder but defo has lifing issues if you're buying them used. Had to replace mine when the engine was rebuilt at ~150 hours... also I think the 996 cats reside in the muffler (I think)... your conversion will be more extensive than just a header swap.
06-02-2018, 10:04 PM
#14
Race Car
I’d encourage you all to look at the FVD (M&M) offerings they have available. They are well made with good size primaries and even without the Rennlist discount they are very well priced. I modified a set for my custom exhaust and couldn’t be happier with them. They have multiple figments some that I’d bet would take very little fab work to fit with center exit exhaust setups
06-04-2018, 09:21 AM
#15
RL Community Team
Rennlist Member
Rennlist Member
I’d encourage you all to look at the FVD (M&M) offerings they have available. They are well made with good size primaries and even without the Rennlist discount they are very well priced. I modified a set for my custom exhaust and couldn’t be happier with them. They have multiple figments some that I’d bet would take very little fab work to fit with center exit exhaust setups