1 5/8 long tube headers
07-23-2014, 12:53 PM
#1
1 5/8 long tube headers Is there anyone who makes good 1 5/8 long tube headers that will fit my 96 lt1 m6? Everyone seems to make only 1 3/4 headers which I don't want. I think the 1 5/8 is all you need on a Lt1 under 400hp and it will help keep low end torque better than the 1 3/4. In the distant future if I get a cam it will be one that produces low-mid range power under 6000rpm.
I would love to find some that are ceramic coated or stainless. Then I plan on adding a y-pipe with high flow cats. I would like to keep some of the stock exhaust sensors too if I can. Any suggestions??? I am getting ready to spend some money!
Also my catback is already deleted, it is straight pipe into duals after the bulletmuffler on the I-pipe. The car is already loud but sounds good.
I would love to find some that are ceramic coated or stainless. Then I plan on adding a y-pipe with high flow cats. I would like to keep some of the stock exhaust sensors too if I can. Any suggestions??? I am getting ready to spend some money!
Also my catback is already deleted, it is straight pipe into duals after the bulletmuffler on the I-pipe. The car is already loud but sounds good.
07-23-2014, 01:19 PM
#2
I don't think you'd be sacrificing any low end torque with a 1 3/4 long tube plus I've never seen a 1 5/8 long tube for the 4th gen. If you get some gears or a cam with 1 3/4 long tubes you'll have more low end than you'll be able to use on street tires.
07-23-2014, 05:19 PM
#4
TECH Regular
You don't save any low end torque by getting smaller headers.
But to answer your question, I think MAC makes their midlength in 1 5/8. Individual flanges on them are prone to leak though, after you take them on and off a couple times to replace gaskets. It's not worth the trouble, just do a quality set of longtubes.
But to answer your question, I think MAC makes their midlength in 1 5/8. Individual flanges on them are prone to leak though, after you take them on and off a couple times to replace gaskets. It's not worth the trouble, just do a quality set of longtubes.
07-23-2014, 10:50 PM
#5
Everything I have read about headers says that a 350 does better with 1 5/8 if under 400 hp and u might lose a couple hp top end but keep more low end torque?
But you guys have did the 1 3/4 headers and have the real world experience. Peak torque is @ 2400-2500rpm on the stock lt1 which I love. I am just afraid that going with big headers will move that torque peak up to maybe 4000?
I am 100% I want to do long tubes and not mids. If I can't find the 1 5/8 headers I will have to go with some stainless 1 3/4 and hope for the best.
I am hoping to feel some power increase after doing these mods over the winter.
TB bypass
PCM for less tune
Long Tubes
Y-pipe with high flow cats
I already have the CAI and catback delete.
I am hoping for maybe 280 rear wheel hp out of my m6 with these mods, and get into the 13's with street tires. Do you think these goals are realistic???????????
But you guys have did the 1 3/4 headers and have the real world experience. Peak torque is @ 2400-2500rpm on the stock lt1 which I love. I am just afraid that going with big headers will move that torque peak up to maybe 4000?
I am 100% I want to do long tubes and not mids. If I can't find the 1 5/8 headers I will have to go with some stainless 1 3/4 and hope for the best.
I am hoping to feel some power increase after doing these mods over the winter.
TB bypass
PCM for less tune
Long Tubes
Y-pipe with high flow cats
I already have the CAI and catback delete.
I am hoping for maybe 280 rear wheel hp out of my m6 with these mods, and get into the 13's with street tires. Do you think these goals are realistic???????????
07-23-2014, 11:58 PM
#6
Village Troll 
iTrader: (2)
IMO 1 5/8" headers are useless, especially on an OBDII car. I was running Edelbrock 1 5/8" shorties with the stock y-pipe including cats with the LPE setup and was running 12.5's at 110. Switched to LT's with ORY and was able to run 12.1's/12.2's at 115mph. Torque and power curve dramatically improved across the RPM band. A lot of that I credit to just getting rid of the cats. One of the largest improvements you can make on a stock 350cid is getting rid of the cat(s). With what you have listed you should be flirting with 300rwhp.
07-24-2014, 12:06 AM
#7
I think I may pass on the high flow cats then! I am thinking the ceramic coated pacesetters and y pipe are the best fitment for the price that I can see? I would like to keep the EGR and air sensors intact. 300 rear wheel hp would be impressive considering that the lt1 stock only makes around 300 crank!
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07-24-2014, 05:04 PM
#9
IMO header primary length/diameter and headers in general are grossly over benchraced.
SS RRR Edelshit is an awful product you proved that but I wouldn't say you proved anything about primary diameter.
Header benchracing often neglects things like what clears a chassis, or what leaved decent plug access so those get changed often enough. I know dynos show all sorts of things with headers especially engine dynos, but what fits in a chassis and what is perfect are different things.
I have had three different sets of headers on my car and never saw a big difference from 1 5/8" mids to 1 5/8" tri-Ys to 1 3/4" longtubes. I can tell you the plugs were a hell of a lot easier to change with the 1 5/8" tri-Ys and the car ran in the 11s with all three sets.
Fairly certain some of bowtienut's 10.9 NA stock shortblock passes have been on 1 5/8 tri-Y, but every kid wanting to run 12s with a lighter car will swear 1 3/4 is the only way to go, not directed at Richard
and you need a TH400 and an opti delete and a 9"................................................ ..................
SS RRR Edelshit is an awful product you proved that but I wouldn't say you proved anything about primary diameter.
Header benchracing often neglects things like what clears a chassis, or what leaved decent plug access so those get changed often enough. I know dynos show all sorts of things with headers especially engine dynos, but what fits in a chassis and what is perfect are different things.
I have had three different sets of headers on my car and never saw a big difference from 1 5/8" mids to 1 5/8" tri-Ys to 1 3/4" longtubes. I can tell you the plugs were a hell of a lot easier to change with the 1 5/8" tri-Ys and the car ran in the 11s with all three sets.
Fairly certain some of bowtienut's 10.9 NA stock shortblock passes have been on 1 5/8 tri-Y, but every kid wanting to run 12s with a lighter car will swear 1 3/4 is the only way to go, not directed at Richard
and you need a TH400 and an opti delete and a 9"................................................ .................. Last edited by 96capricemgr; 07-24-2014 at 08:39 PM.
07-24-2014, 08:05 PM
#10
TECH Addict
Some posters here need to learn some fluid dynamics before giving advice.
The difference in power from a 1-5/8" LT and 1-3/4" LT on the same engine in the same car with the same shape and same collector length and diameter will depend on head flow and cam timing.
Typically though, the smaller primaries will increase low end torque (which equals small gains in horsepower) due to better scavenging. Those same smaller primaries will also become a choke point at higher RPM's. The larger Diameter primaries will scavenge better at higher RPM's, but will lack enough velocity to match the smaller primaries scavenging at lower RPM's.
The big advantage of 1-3/4" primaries over 1-5/8" primaries is that horsepower equals torque times RPM divided by 5252. That means a bigger gain in torque at lower RPM's is needed to net the same gain in horsepower at higher RPM's. Therefore, the 1-3/4 primaries will have a greater horsepower output than the smaller primaries simply because they increase torque through scavenging at higher RPM's.
But wait there's more. If the cam is set up for low RPM operation it is not wise to use headers that are designed to operate higher than the cams capability. This typically isn't an issue nor the case with LT1's or LS1's in performance cars. On the flip side using small tubes on a high revving cam profile is bad too, worse so than the other way around when it comes to peak horsepower.
So, generally speaking yes the 1-3/4" primaries will give more high end power than 1-5/8" primaries of equal length on an LT1 in an F-Body, but it will sacrifice some low end power to the smaller tubes too. The gain up high is typically more than the loss down low.
But the overall difference between the two are probably not noticeable without a dyno.....
The difference in power from a 1-5/8" LT and 1-3/4" LT on the same engine in the same car with the same shape and same collector length and diameter will depend on head flow and cam timing.
Typically though, the smaller primaries will increase low end torque (which equals small gains in horsepower) due to better scavenging. Those same smaller primaries will also become a choke point at higher RPM's. The larger Diameter primaries will scavenge better at higher RPM's, but will lack enough velocity to match the smaller primaries scavenging at lower RPM's.
The big advantage of 1-3/4" primaries over 1-5/8" primaries is that horsepower equals torque times RPM divided by 5252. That means a bigger gain in torque at lower RPM's is needed to net the same gain in horsepower at higher RPM's. Therefore, the 1-3/4 primaries will have a greater horsepower output than the smaller primaries simply because they increase torque through scavenging at higher RPM's.
But wait there's more. If the cam is set up for low RPM operation it is not wise to use headers that are designed to operate higher than the cams capability. This typically isn't an issue nor the case with LT1's or LS1's in performance cars. On the flip side using small tubes on a high revving cam profile is bad too, worse so than the other way around when it comes to peak horsepower.
So, generally speaking yes the 1-3/4" primaries will give more high end power than 1-5/8" primaries of equal length on an LT1 in an F-Body, but it will sacrifice some low end power to the smaller tubes too. The gain up high is typically more than the loss down low.
But the overall difference between the two are probably not noticeable without a dyno.....
Last edited by hrcslam; 07-25-2014 at 11:27 AM.
07-24-2014, 08:54 PM
#11
Everything you wrote is pure "perfect theory" and ignores real world variables like the exhaust system behind the headers, or cam overlap and it's affect on how exhaust sensitive the engine is, and then there is the fact that I don't think anyone here has proven where the hp/tq graphs would intersect.
We do know Pat's car has run 10.9 at 3770lbs NA with a 1 5/8" tri-Y which according to your bench racing wisdom is all wrong for a motor turning 7000rpm, and it puts down 425rwhp which is above the supposed 400hp mark being tossed out, and he has a 4200stall in the thing so he isn't using a lot of lowend.
I pissed away a lot of money trying three different sets of handbuilt b-body headers. Going forward fit and plug access would be my deciding factors much more than primary length/diameter.
We do know Pat's car has run 10.9 at 3770lbs NA with a 1 5/8" tri-Y which according to your bench racing wisdom is all wrong for a motor turning 7000rpm, and it puts down 425rwhp which is above the supposed 400hp mark being tossed out, and he has a 4200stall in the thing so he isn't using a lot of lowend.
I pissed away a lot of money trying three different sets of handbuilt b-body headers. Going forward fit and plug access would be my deciding factors much more than primary length/diameter.
07-24-2014, 11:27 PM
#12
Village Troll
iTrader: (2)
I didn't see the "long tubes" part in the title. Whoops. Regardless, OP, you will not suffer any drivability issues with 1 3/4" LT's with stock heads/cam. People have been doing this since Hooker first made them available for the f-body back in the late '90's nary a complaint about low end torque loss. You'll be fine, and if you ever decide to increase and change the breathing characteristics of the engine you don't have to drop more money on headers.
07-25-2014, 12:12 AM
#13
I would have to say that hrcslam's opinion is the one that I have believed and read about with headers. On the other hand I don't really have a choice because they don't make a 1 5/8 longtube for the LT1 so I don't have a choice but get 1 3/4's. But I do believe that the low end torque lose with the 1 3/4 most likely wont be noticeable, but the extra 25 crank hp in the mid to high rpm's will! Plus I haven't heard of anyone complaining that they lost low end torque with headers.
My other problem is figuring out if I want high flow cats so my exhaust doesn't stink and I heard that high flow cats make the exhaust tone deeper which I would like. I wouldn't think that high flow cats would lose more than 1-2 hp?
My other problem is figuring out if I want high flow cats so my exhaust doesn't stink and I heard that high flow cats make the exhaust tone deeper which I would like. I wouldn't think that high flow cats would lose more than 1-2 hp?
07-25-2014, 03:09 AM
#14
07-25-2014, 08:45 AM
#16
TECH Addict
Everything you wrote is pure "perfect theory" and ignores real world variables like the exhaust system behind the headers, or cam overlap and it's affect on how exhaust sensitive the engine is, and then there is the fact that I don't think anyone here has proven where the hp/tq graphs would intersect.
We do know Pat's car has run 10.9 at 3770lbs NA with a 1 5/8" tri-Y which according to your bench racing wisdom is all wrong for a motor turning 7000rpm, and it puts down 425rwhp which is above the supposed 400hp mark being tossed out, and he has a 4200stall in the thing so he isn't using a lot of lowend.
I pissed away a lot of money trying three different sets of handbuilt b-body headers. Going forward fit and plug access would be my deciding factors much more than primary length/diameter.
We do know Pat's car has run 10.9 at 3770lbs NA with a 1 5/8" tri-Y which according to your bench racing wisdom is all wrong for a motor turning 7000rpm, and it puts down 425rwhp which is above the supposed 400hp mark being tossed out, and he has a 4200stall in the thing so he isn't using a lot of lowend.
I pissed away a lot of money trying three different sets of handbuilt b-body headers. Going forward fit and plug access would be my deciding factors much more than primary length/diameter.
Both will out perform stock manifolds. And using one over the other really won't make to much of a difference in ET as ET has much to do with average horsepower as it does with peak horsepower and traction.
Also note I did say that cam and many other factors can change the outcome. But generally the larger 1-3/4 primaries work better in most scenarios. They are also cheaper and allow room for growth.
In short the thoughts that the OP had are true regarding primary diameter. But the difference is as you said, minimal and not worth the money unless you are racing professionally and that extra hundredth is needed.
Last edited by hrcslam; 07-25-2014 at 03:39 PM.
07-25-2014, 11:18 AM
#17
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Hedman 65375 LT have 1&5/8" primaries. They have great looking collectors too. Problem is no emissions hook ups (AIR & EGR or even an O2 bung) if u need them. Can u special order from Headmen Headers w/AIR & EGR & O2 fittings? I dont know. Plenty of companies that will ceramic coat nearly anything for u.
I share your ideas Goundpounder, higher velocity in the primary exh extracts more spent gas from each cyl and the 1&5/8" primary matches a 350 at low rpm better. And more so the shorter the cam duration. Would it be worth the effort - in this case if u need to mod the headers for emissions probaly not on $/hp basis.
As for hi-flow cats i've had no luck with them passing CA emissions for NOx. They just dont seem to be able to do the job for NOx but can pass on CO and HC. Many states dont even monitor for NOx but nothing in your profile to help us help u so only u will know.
Good luck and please post your results,
cardo
I share your ideas Goundpounder, higher velocity in the primary exh extracts more spent gas from each cyl and the 1&5/8" primary matches a 350 at low rpm better. And more so the shorter the cam duration. Would it be worth the effort - in this case if u need to mod the headers for emissions probaly not on $/hp basis.
As for hi-flow cats i've had no luck with them passing CA emissions for NOx. They just dont seem to be able to do the job for NOx but can pass on CO and HC. Many states dont even monitor for NOx but nothing in your profile to help us help u so only u will know.
Good luck and please post your results,
cardo
07-26-2014, 10:54 AM
#19
Launching!
I think the 1 5/8 is all you need on a Lt1 under 400hp and it wil
Dont buy into the equal length bs on a street car either its not worth it.
07-26-2014, 03:54 PM
#20
not even close to that on a stock cam LT1.
On my high rpm h/c motor, I gained about 15 going from 1-5/8" Tri-Y's to 1-3/4" conventional longtubes. I'd expect less than 10 at peak with a stock cam LT1.
But you are correct that you'll never notice a difference, other than on the dyno, with 1-3/4 versus 1-5/8 at lower rpm's. I saw no gain back on the stock motor going from 1-3/4 shorties to the 1-5/8" Tri-Y's. Maybe with a stock converter, I would have.
The bottom line is just buy a quality built header that fits well and offers decent spark plug access, just as 96Caprice already mentioned a few posts back.
On my high rpm h/c motor, I gained about 15 going from 1-5/8" Tri-Y's to 1-3/4" conventional longtubes. I'd expect less than 10 at peak with a stock cam LT1.
But you are correct that you'll never notice a difference, other than on the dyno, with 1-3/4 versus 1-5/8 at lower rpm's. I saw no gain back on the stock motor going from 1-3/4 shorties to the 1-5/8" Tri-Y's. Maybe with a stock converter, I would have.
The bottom line is just buy a quality built header that fits well and offers decent spark plug access, just as 96Caprice already mentioned a few posts back.