Long tubes and midpipe.

[rudeone707]

In the beginning of april i want to order my headers and midpipe. I was looking at MAC LTs and the shorty prochamber. Whats the difference between 1 3/4" vs 1 5/8" HP wise? Would 1 3/4 be over kill? also For the midpipe is 3" to big? my cat back is 3 inch and i kinda wanted to keep it all the same.

Also will MAC headers work on GT40P heads?

 

[Joes95GT]

Rude, you can get a MAC P-specific header that will fit on the stock E7 head. MAC LT's do not have a bung welded into them, and they will probably not pass the strict CA emission laws. I would stay with the 1 5/8" primaries and a 2 1/2" collector. 3 inch tubing is huge and will kill low end torque due to lost back pressure. I would get a 2 1/2" Prochamber - that will bolt right up to the 3" catback. Are you sure the Magnaflow kit is 3", mine is 2.5" all the way through.

Joe

 

[rudeone707]

Rude, you can get a MAC P-specific header that will fit on the stock E7 head. MAC LT's do not have a bung welded into them, and they will probably not pass the strict CA emission laws. I would stay with the 1 5/8" primaries and a 2 1/2" collector. 3 inch tubing is huge and will kill low end torque due to lost back pressure. I would get a 2 1/2" Prochamber - that will bolt right up to the 3" catback. Are you sure the Magnaflow kit is 3", mine is 2.5" all the way through.

Joe

i was pretty sure that it was 3 inch catback with 3 1/2" tips.

emissions are not too much of a concern for me. I know someone, and if worse comes to worse i will just put the stock stuff back on.

 

[GTJake]

MAC LT's do not have a bung welded into them, and they will probably not pass the strict CA emission laws.

Joe

My MAC's and everyone else that I've heard from had the EGR bung on them. MAC long tubes will fit P heads also. Killer95 has them on his car with P heads.

Jake

 

[final5-0]

Rude

My 94-95 Mac lt's had a bung for egr.

IMHO the 1 3/4 lt's would cause a low end loss of torque.

Later
Grady

 

[GTJake]

How much of a difference can 1/8" make? Grady, you talking about how the ports of the AFR's were a little covered up by the 1 5/8" have got me thinking if 1 3/4" would have been a better choice. But on stock E7's 1 3/4" would be a little too much IMO. I noticed little to no low end loss on my car with the LT's.

Jake

 

[Joes95GT]

I'm not calling you guys wrong, but I never saw a set of MAC headers with an EGR bung on them, but then again, the last set I installed was more than a year ago.

Jake, remember that we are not just talking about a flat 1/8 inch, we are talking about 3 feet of an 1/8 inch difference. Don't worry about the headers covering the exhaust ports, tons of people are running LTs with AFRs and look at their numbers - they don't seem to be affected at all. They probably only cover 1/16 on each side, and if you were that set on getting the flange to match the exhaust port, you could dremel out the flange on the header. I doubt you would gain anything by it though.

Joe

 

[rudeone707]

Next year i want to drop in a DSS 331 w/ AFR 185s with a blower. So i didnt really want to have to buy 2 sets of headers for my car.

 

[final5-0]

How much of a difference can 1/8" make? Grady, you talking about how the ports of the AFR's were a little covered up by the 1 5/8" have got me thinking if 1 3/4" would have been a better choice. But on stock E7's 1 3/4" would be a little too much IMO. I noticed little to no low end loss on my car with the LT's.

Jake

I based the low end loss of larger headers due to various times in the past I have seen this happen when the exhaust system is too big for the combo.

Have you ever heard that 1&1/2 inch is better than 1&5/8 inch for very mild combos with small stuff like, just pulleys or just a K&N etc.

If the car will be modded with many parts in the future then yes, the 1&5/8 size would be a better choice.

Then there is the weight of our cars also. If the car is light, like a fox coupe, then the time spent in the lower rpm range is significantly less than a heavy car like ours. Low end torque loss is recovered quicker with less weight. Perfect example of why gears with a ratio of at least 3.73 is so important in our heavy cars. (NA by the way)

The larger header will make more power in the upper rpm range but the low end will suffer. IMHO, not good for a heavy street car.

Again, a few things I've seen happen with street cars in the past.

Later
Grady

 

[mo_dingo]

94-95 5.0L V8, GT/Cobra,
4x9x14" Muffler, 2.5" Tubing, Rear Exit, 3.5" Tip 15638 $566.78

From Magnaflow's website. The mid-pipes are generaly 2.5 inches in diameter. I saw a dyno run on headers on a near stock mustang. I will see if I can find it.

But here is what I remember. The LT's with the bigger primaries gained HP in the upper RPM's, and the LT's with smaller primaries gained HP in the low-mid RPM's.

IMO, if you want your car to perform at the track or when racing, the you want the bigger primaries (1 & 3/4").
Scott

 

[rudeone707]

what else is needed for installation? im assuming that the headers will come with the gaskets needed should i use those or by my own? I am going to by new 02's will i need 02 extenders?

 

[GTJake]

I would get some Fel-Pro 1415's for the exhaust gaskets. I got O2 extenders from Brothers. Also, get some header studs or Stage 8 locking header bolts.

Jake

 

[final5-0]

You can use the extenders.

I just extended the length of my car's harness.

I used 1415's for gaskets as those that were supplied with headers were too small.

A cheap and effective way to keep header bolts tight is thin stainless steel lock washers from a bolt & nut supply. Been doing it for years. Works great.

Later
Grady

 

[VibrantRedGT]

MAC LT's do have the EGR bung. BBK's didn't for a long time until like a year ago and I here those are scarce. I bought the O2 extenders from Brothers for $40 (it's plug and play). I also used the copper gaskets that came with the headers from MAC. Just wanted to try them out and I've had them on and off the car with zero problems.

 

[rudeone707]

thanks guys, im pretty sure ill have some questions when i get ready to install.

 

[Killer95Stang]

Here's a couple pics I took during my install of Ceramic Coated LT's, on GT40P heads...

Also, I recommend getting O2 extensions, because it just makes it easier...

 

[Joes95GT]

Killer, have you passed CA emissions with those headers? Do you just put a catted H on when you're about to go to DMV? I've heard of cars that don't come close to passing with LT's, thats why my shop doesn't mess with 'em.

Joe

 

[Killer95Stang]

I'm not even gonna bother trying to make it pass... I'm lucky enough to know a few shops in the LA area that will make sure it passes.... *wink* *wink*...

 

[rudeone707]

Killer, have you passed CA emissions with those headers? Do you just put a catted H on when you're about to go to DMV? I've heard of cars that don't come close to passing with LT's, thats why my shop doesn't mess with 'em.

Joe

In CA exhaust shops cannot remove or relocate the cats. Nobody will touch them. i guess there is like a $10,000 fine if you do.

 

[Killer95Stang]

Actually, if you pass a car that is obviously not emissions legal, you lose your license, have a butt load of fines, and can get a 6month to 1 year jail sentence.... a lot of risk for a couple hundred bucks... life sucks here in CA... If I do decide to get legal with the car again, I figure I will just register it in AZ... because I'm not pulling those longtubes off, unless its with a cutting torch...