1 5/8 or 1 7/8?

[GodStang]

are larger diameter headers needed for 7-8xx whp or would this setup suffice? 1 5/8 stepped to 1 3/4 LT's w/ 3 inch collector, 3 inch OR/X, 3 inch catback?

IF I am looking to hit 750 1-7/8" hands down but you will 99% of the time have to run a different K-member. My 1-3/4" was fine with the stocker.

I think people say 1 5/8 are fine because then they can get Mac headers for a lot cheaper because if your going to spend the big bucks on headers might as well make it worth it and get bigger primary's.

So true. I think people want to make an excuse for why it is alright to buy the cheaper BBK or MAC. The 1-5/8" are better than stock I am not saying they are pointless I am saying if you are going through the nightmare of installing headers on the stock Kmember go correct and get Kooks or ARH and go 1-3/4".

 

[wanna_b_03]

So true. I think people want to make an excuse for why it is alright to buy the cheaper BBK or MAC. The 1-5/8" are better than stock I am not saying they are pointless I am saying if you are going through the nightmare of installing headers on the stock Kmember go correct and get Kooks or ARH and go 1-3/4".[/QUOTE]

I planned on spending my money on the good stuff. I've been there and done that with the cheap stuff.... Saving a little money isn't worth the fitment and hassle of installing inferior parts

 

[04SolidSnake]

So true. I think people want to make an excuse for why it is alright to buy the cheaper BBK or MAC. The 1-5/8" are better than stock I am not saying they are pointless I am saying if you are going through the nightmare of installing headers on the stock Kmember go correct and get Kooks or ARH and go 1-3/4".

I planned on spending my money on the good stuff. I've been there and done that with the cheap stuff.... Saving a little money isn't worth the fitment and hassle of installing inferior parts

Funny, my MAC headers fit better than my buddies Kooks headers.. "Inferior", looking at the coating on the MACs, and the flanges, they are excellent quality, and for my power goals getting headers that are more than twice the price seemed counter productive.

And based on the actual data presented, it doesn't seem like the extra cost is really worth the unknown increase in power.

 

[GodStang]

Funny, my MAC headers fit better than my buddies Kooks headers.. "Inferior", looking at the coating on the MACs, and the flanges, they are excellent quality, and for my power goals getting headers that are more than twice the price seemed counter productive.

And based on the actual data presented, it doesn't seem like the extra cost is really worth the unknown increase in power.

I have run MAC on many cars. The car I am building right now has a complete MAC system going on it (got it free). I have had many many problems with MAC headers (welds coming apart and coating coming off and rusting within 6 months). They are not the best. For the price they will do. On a 500-600rwhp no the gains are not going to be huge from a 1-5/8" to 1-3/4" but there are gains and better loss of boost. Also as your build grows you will not max out your longtubes. Having to do LTs multiple times sucks on a 4V.

 

[wesking1]

1-5/8" should not even be made for these cars. There is so so so much info on this unfortunetly most is not on this site. The tech side of this bored went years ago. One thing to think about if you do not hook up the correct catback size then headers dont matter that much. I have seen the correct complete exhaust setup gain 100+rwhp on a twin screw car.

One huge gain about adding the correct LTs on a twin screw is the boost drop that the free flowing exhaust provides. Add it back and that is more power.

How much power would I see jumping up from mac 1-5/8 to american racing 1-3/4 3" all way back? If im sitting at 672 on 18 lbs and stage 3 comps

 

[shurur]

So everybody just ignore the dyno results that I posted wher 1-5/8 outperformed 1-3/4 headers..even if you are making less that 700 RWHP???

 

[1MeanNonPI2v]

I would suggest the 1 7/8" primary with 3" collectors. American Racing Headers or Kooks are the best on the market and the only set you'll ever need to buy. I purchased ARH's for my stroked, modular Boss block build and was blown away by the quality and workmanship that went into them.

 

[sabotage]

man go big or go home do it once and dont look back or regret you didnt go with what you wanted to......

 

[shurur]

An engine is basically an air pump. The more air you can get in and out, the more power you make. 1 3/4" will be sufficient for up to 700ish, for 750+rwhp, go for 1 7/8". Below 600, 1 5/8" will give you the best torque.

Thanks for this response to my post as well. I sure would like to find some more dynos out there. So for OP...you're gonna have spend the big bucks for the big straws.

 

[wanna_b_03]

Thanks for this response to my post as well. I sure would like to find some more dynos out there. So for OP...you're gonna have spend the big bucks for the big straws.

This is true but I already planned on it anyways.

 

[04SolidSnake]

I have run MAC on many cars. The car I am building right now has a complete MAC system going on it (got it free). I have had many many problems with MAC headers (welds coming apart and coating coming off and rusting within 6 months). They are not the best. For the price they will do. On a 500-600rwhp no the gains are not going to be huge from a 1-5/8" to 1-3/4" but there are gains and better loss of boost. Also as your build grows you will not max out your longtubes. Having to do LTs multiple times sucks on a 4V.

I figure by the time I get to having to replace the headers I will have already exploded my engine and will be doing a full build anyhow

 

[wesking1]

So everybody just ignore the dyno results that I posted wher 1-5/8 outperformed 1-3/4 headers..even if you are making less that 700 RWHP???

So when do you need bigger headers. If someones making 1000whp sure that 1-5/8 would hold them back for sure

 

[shurur]

So when do you need bigger headers. If someones making 1000whp sure that 1-5/8 would hold them back for sure

recommendations for headers are very anecdotal ain't they?? I've seen contradicting opinions just in this thread alone. I've posted published dyno results. 1-5/8 < 1-3/4 < 1-7/8 == 600 < 700 < 700+ RWHP seems to be some sort of consensus. But several posters in other threads have said No to 1-5/8....ever... I'm not buying that...based on the dyno results I've shown. I just work on my car a bit and read a lot...This is yet another thead that hasn't resolved any header size questions really..because no one puts up facts..now I'm going to get a load of crap for sure...

 

[wanna_b_03]

recommendations for headers are very anecdotal ain't they?? I've seen contradicting opinions just in this thread alone. I've posted published dyno results. 1-5/8 < 1-3/4 < 1-7/8 == 600 < 700 < 700+ RWHP seems to be some sort of consensus. But several posters in other threads have said No to 1-5/8....ever... I'm not buying that...based on the dyno results I've shown. I just work on my car a bit and read a lot...This is yet another thead that hasn't resolved any header size questions really..because no one puts up facts..now I'm going to get a load of crap for sure...

You're not going to get crap from me. I'm still just as lost as you. but based off of peoples opinions alone, it sounds like for my power range all need 1 3/4. I still don't know if a 2 1/2 collector is good or if I'll need a 3" collector. so I'm pretty much just as lost as when I started this thread lol

 

[shurur]

You're not going to get crap from me. I'm still just as lost as you. but based off of peoples opinions alone, it sounds like for my power range all need 1 3/4. I still don't know if a 2 1/2 collector is good or if I'll need a 3" collector. so I'm pretty much just as lost as when I started this thread lol

I know..and didn't mean to jack your thread. But you've already seen posters in this very thread saying that 1-5/8 was crap..DESPITE the published Dyno that I posted...the same goes for CAI BTW... Intuitively it would seem that at some point 1-3/4 headers would be the direction to go. There are some dyno folks out there who could collectively get some data together...but I haven't found that thread/book yet...Some vendors don't have decent dyno data..and why should they if they can let you think Bigger and $$$ is better??

I'm going with JBA midlength because of ground clearance and cost...it only helps by ~10 RWHP...but I know it works because JBA has dyno results on their site...and I have that published dyno...and I am staying well within that dyno HP range.

I have no doubt going from OEM shorties to any size LT helps..but I never see any real comparisons between 1-5/8 < 1-3/4 < 1-7/8....apples to apples....at different HP and bore x stroke combos (4.6 < 4.75 < 5.0 < 5.1 < 5.3 break points....certainly 4.6L (3.5 x 3.5) should be a done deal by now....in terms of knowing what works.

I'm mad as hell for YOU because it is a huge investment and gamble..and it shouldn't be....these modulars (terminators) are 9 years old now!!!!!

 

[wanna_b_03]

I know..and didn't mean to jack your thread. But you've already seen posters in this very thread saying that 1-5/8 was crap..DESPITE the published Dyno that I posted...the same goes for CAI BTW... Intuitively it would seem that at some point 1-3/4 headers would be the direction to go. There are some dyno folks out there who could collectively get some data together...but I haven't found that thread/book yet...Some vendors don't have decent dyno data..and why should they if they can let you think Bigger and $$$ is better??

I'm going with JBA midlength because of ground clearance and cost...it only helps by ~10 RWHP...but I know it works because JBA has dyno results on their site...and I have that published dyno...and I am staying well within that dyno HP range.

I have no doubt going from OEM shorties to any size LT helps..but I never see any real comparisons between 1-5/8 < 1-3/4 < 1-7/8....apples to apples....at different HP and bore x stroke combos (4.6 < 4.75 < 5.0 < 5.1 < 5.3 break points....certainly 4.6L (3.5 x 3.5) should be a done deal by now....in terms of knowing what works.

I'm mad as hell for YOU because it is a huge investment and gamble..and it shouldn't be....these modulars (terminators) are 9 years old now!!!!!

Your not jacking anything bro. you contributed real data, not just an opinion!
Your setup should be a good one. Its really not to big of an investment, but when it is time to make an investment I want the best part and power money can buy based on proven testing. I guess i'm not going to get that so I guess I'll make that $1000 guess

 

[shurur]

Your not jacking anything bro. you contributed real data, not just an opinion!
Your setup should be a good one. Its really not to big of an investment, but when it is time to make an investment I want the best part and power money can buy based on proven testing. I guess i'm not going to get that so I guess I'll make that $1000 guess

My car is completely out of this league as I want 370 to whatever NA and that is it.

I do know someone with oem exhaust and 20+ # whipple..who seems stuck at 595-600+ (I'll ask him about his exhaust system next time I see him...maybe he has 1-5/8 LT) ...so...

Yes..your setup is at that tipping point for size headers..probably. Post a dyno when you get the chance...then maybe someone with a similar setup (but with 1-5/8" LT) will post and we can start to see something.

Thank You for your contribution to the cause.

 

[broke7]

I have made 744whp with mac 1-5/8th LT, 2.5" X pipe and dynomax bullets dumped.

This was on a kb 2.8h, mmr 8.5:1 bottom end, stock heads, and stock cams at about 26psi.

Here is a lil tidbit also, the ball collector on the mac necks down to about 2.25.

 

[wesking1]

I have made 744whp with mac 1-5/8th LT, 2.5" X pipe and dynomax bullets dumped.

This was on a kb 2.8h, mmr 8.5:1 bottom end, stock heads, and stock cams at about 26psi.

Here is a lil tidbit also, the ball collector on the mac necks down to about 2.25.

But if you changed your headers to say ARH 1-3/4 lt with 3" X would your horse power go up stay same or go down? 04sleeper made 714 on stock manifolds (if I remember right) and 2.3 with e85 but if he would have put long tubes on Im sure hed picked up power

 

[broke7]

But if you changed your headers to say ARH 1-3/4 lt with 3" X would your horse power go up stay same or go down? 04sleeper made 714 on stock manifolds (if I remember right) and 2.3 with e85 but if he would have put long tubes on Im sure hed picked up power

The car wouldnt lose power.....it may shift it around in the curve which is perfectly fine for a car that lives at the strip, and even on the street at 700-800HP. You cant "put" down that type of power effectively on the street anyways. The KB test showed some loss/gain under the curve in different areas.

I believe at some point an 1-5/8th is a restriction. I figured if it was a huge issue I would of seen it in my combo. My car trapped 139mph @ 3700lbs which indicates its power and held the 6spd, IRS record for over 1 year, and still is the quickest stock head/stock cam all blower 6spd/IRS car in the land.

Although, its speculation at best when throwing around 1500-2000 bux of your hard earned cash. I'm a budget minded modder and enthusiast. I exhaust every possible avenue before throwing down more coin on sketchy parts. I do value tests like KB did, hince one of the reasons I run stock rails on my car cause KB has tested them up to 1k HP in test subjects.

I am in the process of a new build after loosing an oil pump and basically the whole motor. 9:1 Teksid, new heads, with Comp Cams...so a comparison in my sake would be null and void. I have thought about installing my currrent exhaust which is 1-5/8th MAC's, 2.5" Lethal X, and 2.5" Bullets back into the car. I have realistic goals and expectations for the car due to higher compression, and more aggressive cams. If it approached 800whp uncorrected I would say the exhaust is not a huge limiting factor. More importantly, I think alot of it depends on the collector also.....which in the MAC case it is shit :nonono::nonono: I have measured it at 2.25" ID....not good when your running a 2.5" X pipe. Although most ball connectors/collectors are like this....

I will leave with this and more discussion. There is a guy who owns a 03 Cobra who has an OEM longblock, and the car has been a best of 9.06@149 and weight 3450lbs with driver. This car runs ARH 1-3/4 h eaders with 3" Collector, 3" X and 3" Mufflers.....It has made 740whp thru an autotomatic, 9" and slicks on E85. So in all reality thru a T-56 AND STREET tire it would push the 800whp area in my book.


Trust me, you are not the only one who is dabbling in this theory, I have been back and forth for a while. I think Muffler choice is key also, chambered mufflers like MAC (eventhough they claim non chambered) and flowmasters kill HP.....alot of people overlook this. Fortunately most of your companies that the 03/04 world deal with maggy, bassani, dynomax are using straight thru style mufflers.