Dyno & Bench Racing Forum - okay guys help me out here

Car: 1999 Trans Am M6

Mods: Baby Comp Cam XR265HR (212/218 - .522/.529 - 114), Mac mids with ORY, Cutout, LS6 Intake, Slp lid, UD pulley, Flowmaster, 3.73's, BMR LCA's, Panhard, and STB, mild tune.

These mods netted me somewhere around 345 / 350 cutout closed and 366 / 369 cutout open (cant find the dyno graph from the run with cutout closed). My question for the board is what kind of gains over the graph with the cutout closed could I get by swapping the Mac mids for LT's and throwing a 3" catback like a Magnaflow on there? Im trying to get opinions to see if swapping out the exhaust would be worth it monetarily. Thanks!

Also curious what some of you think the car might be capable of at the track with the current mods :)

Car: 1999 Trans Am M6

Mods: Baby Comp Cam XR265HR (212/218 - .522/.529 - 114), Mac mids with ORY, Cutout, LS6 Intake, Slp lid, UD pulley, Flowmaster, 3.73's, BMR LCA's, Panhard, and STB, mild tune.

These mods netted me somewhere around 345 / 350 cutout closed and 366 / 369 cutout open (cant find the dyno graph from the run with cutout closed). My question for the board is what kind of gains over the graph with the cutout closed could I get by swapping the Mac mids for LT's and throwing a 3" catback like a Magnaflow on there? Im trying to get opinions to see if swapping out the exhaust would be worth it monetarily. Thanks!

Also curious what some of you think the car might be capable of at the track with the current mods :)

Gains would be minimal.. .1 and MAYBE 2mph, but that would be pushing it IMO..

Low to mid 12s@113 or so? I don't guess M6 times very well at all.

Thanks for your input Lemons....before posting this I went through a thread in search that was a big debate about Mac mids and LT's. Some argued that gains would near 15-20 HP, especially lower in the curve with the LT's. They talked about how LT's "scavenge" better? Others said gains would be minimal up top. I dont have much experience with dynos, your thoughts on that?

Thanks for your input Lemons....before posting this I went through a thread in search that was a big debate about Mac mids and LT's. Some argued that gains would near 15-20 HP, especially lower in the curve with the LT's. They talked about how LT's "scavenge" better? Others said gains would be minimal up top. I dont have much experience with dynos, your thoughts on that?

The place you would see gains would be up top (peak power), under the curve will not be affected nearly as much.. If anything you might lose a little bit down low, although the gain you get up top would offset it. 15-20hp up top would be good for .1 and almost 2mph.. Although that would be in the best situation IMO..

If you had a larger cam you would see more gains but having that size cam it will not effect much.

Car: 1999 Trans Am M6

Mods: Baby Comp Cam XR265HR (212/218 - .522/.529 - 114), Mac mids with ORY, Cutout, LS6 Intake, Slp lid, UD pulley, Flowmaster, 3.73's, BMR LCA's, Panhard, and STB, mild tune.

These mods netted me somewhere around 345 / 350 cutout closed and 366 / 369 cutout open (cant find the dyno graph from the run with cutout closed). My question for the board is what kind of gains over the graph with the cutout closed could I get by swapping the Mac mids for LT's and throwing a 3" catback like a Magnaflow on there? Im trying to get opinions to see if swapping out the exhaust would be worth it monetarily. Thanks!

Also curious what some of you think the car might be capable of at the track with the current mods :)

Welp....I'll give this a shot. You went from 345/350 to 366/369 by opening up your exhaust. So obviously your car needs a better flowing exhaust. By "cutout" I assume you mean you still have the headers going into a Y then back. I would start out by going to a dual 2.5" or 3" exhaust. I think you would gain more there over a set of longtubes. Seems the headers aren't whats holding you back exhaust wise.

But hey, what do I know. I'm a Ford guy, the only time my car had a Y pipe in the exhaust was when it was turned around backwards and the car had a snail in front of it. :devil:


And boy is that one itty bitty cam for a 346cid motor! Bet that thing sounds milder than it did stock!

Welp....I'll give this a shot. You went from 345/350 to 366/369 by opening up your exhaust. So obviously your car needs a better flowing exhaust. By "cutout" I assume you mean you still have the headers going into a Y then back. I would start out by going to a dual 2.5" or 3" exhaust. I think you would gain more there over a set of longtubes. Seems the headers aren't whats holding you back exhaust wise.

But hey, what do I know. I'm a Ford guy, the only time my car had a Y pipe in the exhaust was when it was turned around backwards and the car had a snail in front of it. :devil:

And boy is that one itty bitty cam for a 346cid motor! Bet that thing sounds milder than it did stock!

Stopsign is correct, it is not the headers holding you back. It is the muffler, but a cutout bypasses that so no need to worry about it.

I would stay away from a TD setup unless you want to spend money, it is not cheap but sounds SOOOOOOO GOOD!!!!!!!! :lol:

Welp....I'll give this a shot. You went from 345/350 to 366/369 by opening up your exhaust. So obviously your car needs a better flowing exhaust. By "cutout" I assume you mean you still have the headers going into a Y then back. I would start out by going to a dual 2.5" or 3" exhaust. I think you would gain more there over a set of longtubes. Seems the headers aren't whats holding you back exhaust wise.

But hey, what do I know. I'm a Ford guy, the only time my car had a Y pipe in the exhaust was when it was turned around backwards and the car had a snail in front of it. :devil:


And boy is that one itty bitty cam for a 346cid motor! Bet that thing sounds milder than it did stock!Ya I had a much bigger cam in it before my motor blew :(

Since dad was paying for the rebuild, he got to choose the cam. I wasnt happy about it but I couldnt afford to do what he did so I just went with it. Yes it does sound stock (my previous cam had big lope, etc). :(

Also, thanks for your input as well. The cutout is at the beginning if the I pipe, so I guess we see how restrictive the rest of my exhaust is.

The restriction is behind the cutout. Need to do something about that. I hate how GM did the F-bodies like that.

I would stay away from a TD setup unless you want to spend money, it is not cheap but sounds SOOOOOOO GOOD!!!!!!!! :lol:

Have you ever gotten a quote on TD's? I went to a shop and got them made (mandrel bent) with mufflers for $200. Its actually cheaper to go with a TD set up unless you start going with an over the axel, out the back set up.

Have you ever gotten a quote on TD's? I went to a shop and got them made (mandrel bent) with mufflers for $200. Its actually cheaper to go with a TD set up unless you start going with an over the axel, out the back set up.

I had True Duals.. Before the axle is cheap but most people on a DD don't want them before the axle, hence the reason I said not cheap.

I had True Duals.. Before the axle is cheap but most people on a DD don't want them before the axle, hence the reason I said not cheap.

I hear ya. Under the axle is pretty cheap as well, its the over the axle that can get expensive.

Most people need to quit being sissys. lol

I hear ya. Under the axle is pretty cheap as well, its the over the axle that can get expensive.

Most people need to quit being sissys. lol

Under the axle? :suspiciou That sounds smart.

I had True Duals.. Before the axle is cheap but most people on a DD don't want them before the axle, hence the reason I said not cheap.

You are a pussy if you need tail pipes. :gay:

Under the axle? :suspiciou That sounds smart.

it actually works out very well, and some members on here have been runnin them for quite a while with excellent results. if i wanted tips and cared about loudness thats the way i would go with my setup, but i prefer the looks/sound of it being dumped on mine personally :devil:

Under the axle? :suspiciou That sounds smart.

Well, it doesn't sound stupid either. People do it all the time with no issues what so ever. You are at just as much of a risk going above the axle, if not more... think about it. There isn't a whole lot of room to go over the top, so thats why its so expensive. :cheers:

I appreciate everyones input so far. I think I am going to replace the Macs with some Ebay stainless or Pacesetters if I find a good deal on some used ones. Then I am going to have the exhaust place run 3" back through a magnaflow and keep the cutout in the new I pipe. Speaking of that...will I need a new one since id be running bigger pipe? Also if you guys know of a more aggressive sounding muffler than Magnaflow I would probably try it. This will just be a temp setup until Im out of college and then Ill move towards Kooks, ARH, etc :drive:

You are a pussy if you need tail pipes. :gay:

Don't need them, I want them! :cheers:

:lol:

I appreciate everyones input so far. I think I am going to replace the Macs with some Ebay stainless or Pacesetters if I find a good deal on some used ones. Then I am going to have the exhaust place run 3" back through a magnaflow and keep the cutout in the new I pipe. Speaking of that...will I need a new one since id be running bigger pipe? Also if you guys know of a more aggressive sounding muffler than Magnaflow I would probably try it. This will just be a temp setup until Im out of college and then Ill move towards Kooks, ARH, etc :drive:

If it were me I would probably put your money somewhere else.. But it is up to you.

This is why I just run 12" extensions off my headers now :lol:. Sounds so good with the 110lsa :D

This is why I just run 12" extensions off my headers now :lol:. Sounds so good with the 110lsa :D

That would be LOUD. It would be fun every now and then, buy I don't know if I could deal with that. I bet that thing sounds scary with that 110lsa and basically no exhaust.

Don't need them, I want them! :cheers:

:lol:



If it were me I would probably put your money somewhere else.. But it is up to you.any suggestions? :drive:

Ive had the Macs since 2003 and I bought them used at that point....so no telling how many miles total there are on them. Im here a "clicking" noise when I accelerate and once that started is when I began thinking of getting new headers. Any ideas as to what that clicking sound might be if not an exhaust leak of some kind?

That would be LOUD. It would be fun every now and then, buy I don't know if I could deal with that. I bet that thing sounds scary with that 110lsa and basically no exhaust.

It's not my daily driver so it's all good :). It's my bracket car that I can drive on the street if I ever feel like it :razz:

any suggestions? :drive:


If it were me I would get a cam..

Something like a 226 would still be very streetable but give you a nice increase..

You need cam/springs/pushrods/oil pump.. If you didn't do that stuff already..
But I would rather fund that than a new exhaust setup. Just depends on what you want.