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2005 Cadillac CTS-V
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Discussion Starter #1
I read on the LS1 page that a guy had installed LS7 exhaust manifolds on his LS6/Z06 corvette (or maybe it was a CTS-V, I'm not sure). He said he dynoed before and after and picked up 15rwhp just by making the switch from the factory LS6 manifold to the factory LS7 manifold. I presume the bigger diameter exhaust manifold of the LS7 accounts for the power pick-up/better breathing. Anyway, assuming this is basically doable, does anyone know of anyone who has done this performance mod on their 2004-07 CTS-V? I'm prepared to pick up some used LS7 stock manifolds and have a muffler shop fabricate/attach these to my Random Technology high flow cats if the LS7 manifolds do indeed attach to my LS6 heads. Anyone know? Please advise.
 

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2005 CTS-V
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I looked at this briefly, but decided not to pursue it.

Based on threads in the Corvette forums, I believe the LS7 manifolds will indeed bolt up to 243 cast heads on LS6s and LS2s. I do not know how well the ports match up, but the reported gains (some accompanied by dyno graphs) suggest that the port matching is okay.

The issue I could not resolve had to do with the shape of the LS7 manifold compared to the shape of the CTS-V manifolds. Specifically, based on pictures alone, it looked to me like the shape of LS7 manifold was sufficiently different from that of the stock CTS-V manifold that my Random Tech cats would not bolt up without modification and there might be a number clearance issues with the frame, starter, and lower steering column/shaft.
 

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2005 Cadillac CTS-V
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134 Posts
Discussion Starter #3
Thanks Darkman - it seems like a nice idea but I agree on the unknown fitment issues. I guess until someone says they did this mod to their 2004-07 CTS-V it'll remain an unproven mod.
 

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2005 CTS-V
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Thanks Darkman - it seems like a nice idea but I agree on the unknown fitment issues. I guess until someone says they did this mod to their 2004-07 CTS-V it'll remain an unproven mod.
Well, I didn't mean to talk you out of it, I just wanted you to know why I chickened out.
 

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2005 Cadillac CTS-V
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134 Posts
Discussion Starter #6
I agree on the HP gains - 15rwhp is significant. I don't have the set-up/tools/guts to be the guinea pig on this one but if I learned that someone had done it on their CTS-V (i.e. discovered they could clear the obstacles in the engine bay) I would do it. I saw some used LS7 exhaust manifolds on eBay for $100. Add in some exhaust shop fabrication work and cost-wise it still looks a whole lot better than dumping $1,500 on headers and high flow cats. That's coming from a guy who just added up his receipts and gulped when he discovered he had spent $5,000 on his car in 2014.
 

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'05 CTS-V
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^^^ That's why you never add up the receipts!! :D

Just based on the pics I've seen, I think it's a long shot for the LS7 manifolds to work. I think passenger side might be OK, but on the driver side I think the steering shaft would be right in the way. I've got Camaro/G8 shorty headers from JBA on my car, and I had to have the driver side one modified to clear the steering shaft. The LS7 manifolds appear to move the flange forward, so it would be even more of an issue.

If you can get them for $100, though, it might be worth taking a look. If I had known about the LS7 manifolds a while ago I might have given them a shot.
 
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