Finally installed the GMMG
07-06-2009, 06:02 PM
#1
Finally installed the GMMG So last month I posted some pics of when I polished the used GMMG cat-back that I picked up----> https://ls1tech.com/forums/generatio...shed-gmmg.html
Well, I finally installed it a few days ago. My friend Jamie and I cut the Flowmaster off that came on my car when I bought it and clamped the GMMG into place. The guy I picked the GMMG up form had welded it and cut it off his car so my clamp wasn't very secure. The next morning after the initial install I took it and had the clamp removed and the over-the-axel pipe welded along with my old stainless tips. With the flowmaster only (stock lid) I dyno'd @ 306rwhp. I definitely feel the difference and the day I installed it I ran my friend's 99 SS with LT's, ORY, LM1, and 3500 stall and drag radials. He has a best of a 12.9 and I beat him by 2 cars; I was suprised at how my car felt. Next I think I may pick up a lid. I hope I can feel a difference again when I get rid of this stock lid. Let me know what you guys think!
Old cat-back with Flowmaster
Polished GMMG waiting for install
GMMG installed without tips
GMMG after tips
Well, I finally installed it a few days ago. My friend Jamie and I cut the Flowmaster off that came on my car when I bought it and clamped the GMMG into place. The guy I picked the GMMG up form had welded it and cut it off his car so my clamp wasn't very secure. The next morning after the initial install I took it and had the clamp removed and the over-the-axel pipe welded along with my old stainless tips. With the flowmaster only (stock lid) I dyno'd @ 306rwhp. I definitely feel the difference and the day I installed it I ran my friend's 99 SS with LT's, ORY, LM1, and 3500 stall and drag radials. He has a best of a 12.9 and I beat him by 2 cars; I was suprised at how my car felt. Next I think I may pick up a lid. I hope I can feel a difference again when I get rid of this stock lid. Let me know what you guys think!
Old cat-back with Flowmaster
Polished GMMG waiting for install
GMMG installed without tips
GMMG after tips
Last edited by rob69zombie; 07-06-2009 at 06:08 PM.
07-06-2009, 07:53 PM
#5
Thanks. He was racing at WOT. We did a 3 honk at 50mph. I started in 2nd and we shut down when I was at the top of 3rd @ 90 with me out front by 2. I'm glad I raced him though because he just installed his MS4 today and now I have NO chance, lol. I thought I was going to get drug and so did he. I think that's why installed his cam earlier than he had planned and I'll admit it; if we raced at the track I would have been beat. I'm sure of it, especially in the 60' with his stall and tires.
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07-06-2009, 09:20 PM
#9
Thanks Jamie, but I beg to differ. Art is at *****'s right now, lol. *****'s working late tonight, hahaha. 7plagues, I've never raced my friend before so I couldn't tell you what it would have been like before, but I've seen several cars drop a couple of tenth's with a nice cat-back. I'm in no way saying I've dropped that much, but I'm not sure what you're trying to say about 2 lengths.
07-06-2009, 09:29 PM
#10
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i can relate to the 2 car lengths. my car was a whole new animal when i went from stock to my lm2 catback and lid, next you should try to get you're tb ported if you haven't already...
07-07-2009, 12:07 AM
#14
Thanks guys. 
I actually don't know what brand tips they are but they were welded on to the flowmaster. The guy I bought it from didn't opt for the premium oval tips and I didn't like the slash cut tips they came with. Overall I am extremely happy with it for now. I hope it sounds good with LT's and a Polluter 
I actually don't know what brand tips they are but they were welded on to the flowmaster. The guy I bought it from didn't opt for the premium oval tips and I didn't like the slash cut tips they came with. Overall I am extremely happy with it for now. I hope it sounds good with LT's and a Polluter
07-07-2009, 12:19 AM
#15
Thanks guys. I actually don't know what brand tips they are but they were welded on to the flowmaster. The guy I bought it from didn't opt for the premium oval tips and I didn't like the slash cut tips they came with. Overall I am extremely happy with it for now. I hope it sounds good with LT's and a Polluter
I actually don't know what brand tips they are but they were welded on to the flowmaster. The guy I bought it from didn't opt for the premium oval tips and I didn't like the slash cut tips they came with. Overall I am extremely happy with it for now. I hope it sounds good with LT's and a Polluter 
07-07-2009, 12:27 AM
#16
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Thanks Jamie, but I beg to differ. Art is at *****'s right now, lol. *****'s working late tonight, hahaha. 7plagues, I've never raced my friend before so I couldn't tell you what it would have been like before, but I've seen several cars drop a couple of tenth's with a nice cat-back. I'm in no way saying I've dropped that much, but I'm not sure what you're trying to say about 2 lengths.
im just saying 2 cars is quite a bit, I raced my roomie when he would pull maybe a 1/4 car on me and then i installed longtubes and i ended up around 2 cars infront, maybe a tad more. that was after i had a catback and lid too. but im glad you got some power either way haha
(sorry OP)
07-07-2009, 10:21 AM
#19
im just saying 2 cars is quite a bit, I raced my roomie when he would pull maybe a 1/4 car on me and then i installed longtubes and i ended up around 2 cars infront, maybe a tad more. that was after i had a catback and lid too. but im glad you got some power either way haha
