To add some fuel to the fire: In this article the 1 3/4s are superior by a few HP on average. 1 5/8s produced a slighlty higher torque peak, but lower average.

http://www.chevyhiperformance.com/te...ut/hooker.html

By the way I have 1 5/8" LPEs (with a few flattened tubes due to ground clearance issues).

 

And oddly enough the 1 7/8 made more low end than all of them including the 1 1/2 shorties. Not that Im a header "expert" but that has been our exp. the bigger headers dont seem to "kill" the low end torque ,especially on the 383s with stout cams. Not race motors but street motors on pump gas. We've found thru our own exp that alot of stuff that you read cant work actually does. like 11.5:1 comp on pump gas. Heck we've built motors 12.5:1 that run on pump gas. Im not talkin what the comp "should have been" by checkin the piston part # Im talkin calculated comp ratio. Like I said before if you're trying to create torque down low, small primaries. Too bad they didnt give camshaft specs for that motor.

 

The same article also says this... "Typically, a 1 5/8-inch long-tube header is the ideal choice for street/strip engines making upward of 450 hp" -- Though the headers and engine used in this article make it rather irrelevant to this thread...

 

I think the engines relevant, its a SBC. An lt1 is still very similar in cyl head layout, bore spacing, firing order, the stuff that makes it comparable. My contention is merely that what is printed and stated as fact alot of times isnt. Do larger header tubes INCREASE low end torque? typically, no. Do they KILL low end torque? As in double digit losses? Our exp again says no. What I'm stating here isnt what I've read, heard, seen on HOTROD TV. Its what I've seen in my own shop, experienced personnally (typo?). not one time, but numerous times. going "too big" in header size doesnt seem to have the drastic (typo?) effect that too big an intake runner or manifold does.

 

The engine is making 450hp + (carb too)... at that point I too would choose larger headers than 1 5/8"... In which case it IS irrelevant to this thread... I don't think there is an arguement between 1 5/8" and 1 3/4" on that engine -- there is with most LT1/4s and this thread...

 

Especially if in all your daily driving, you don't let your rpms drop very far under the horse power peak rpm; 4800? 5200? Higher? Do you drive the dyno to work? Or the car?

RACE ON!!!

 

1: It makes its power high in the rpm band. The difference the headers are making, and what we're discussing is occuring MUCH lower
2: The fact that it has a carb really has no bearing. the engine doesnt know its not EFI, nor does the header
3: The owner of the vehicle in question stated a 383 is probably down the road, and capable of 450 flywheel HP easily. If it was his intention to stay with a smaller motor that would change my opinion of what header to use. although it would not change the fact that the bigger tubes dont seem to kill the lower end torque, as many believe.
4: Again, we're not talking about the benefit of bigger tubes at 5000, we're talking about what they do or dont do to low end torque.
5: An lt1/lt4 is a SBC gen 1 with advanced features on the OUTSIDE. The way that it processes/pumps air is nearly identical to its grandpa. Its based on cyl head config, bore spacing, and firing order. its not an LS1 where all these are different.
6: On a smaller eng (350cid) I'm sure the low end torque losses will probably be more than stated in the article, but it still wont hurt it as much as most would believe. AND the bigger tubes will still make more low end torque than the manifolds, So it would be a GAIN not a LOSS.
7: Im not saying a smaller tube is a bad choice. Anything is better that the OE manifolds. i'm merely stating that for what he wants to do in the future, the 1 7/8 tubes are a better choice AND in the meantime, on the engine he has its not going to be so severe of a power loss that " oh my gosh I should have went with the smaller tubes. What was I thinking?" Again I do this stuff everyday. On reg SBC and LT1s and LT4s andLS1s and BB chevys and so-on and so-on.

 

Again this test mule lost NO low end torque with the larger tubes. In fact it MADE MORE. And its a pump gas SMALL BLOCK. Ya'll are actin like the thing lost 30 lbs ft at 3000. I'm not talkin peak # I'm talkin LOW END TORQUE. And it didnt lose any. IT GAINED. READ PAST THE 3RD PAGE.
PS Again Im not stating that the bigger tubes boost, or increase low torque. Merely that they dont have the negative impact on it that most would believe. on the dyno or on the road.

 

The problem isn't the torque you lose with the big tubes, it is the gain you sacrifice by not using the smaller tubes. A lot of everyday driving and drag strip results have proved to me, over and over again, that just like a camshaft, more is not always better. Too many fall victim the the "Hot Rodder's Credo", "If some's good, more's better, and too much is just enough.".

RACE ON!!!

 

You may also want to look at TPiS. I went with these because they were 1 3/4, had longer collectors, and you can use the stock bolts to retain the accessories. They fit very well with no hassle. With my heads/cam I put down 405/360rw on a very hot and hummid day. I would not go less than 1 3/4, and they give room to grow.

 

I agree completely. Now, go read the article. Against conservative thinking the bigger tubes MADE MORE TORQUE IN THE VERY RANGE IN QUESTION. Get past the "1 5/8 seems to be the best choice" and look at the data. AND considering his desire to upgrade to a 383 (more is better) the bigger tubes seem like a better choice. I do agree bigger is not always better, ESPECIALLY when it comes to cams. But what I AM saying is bigger header tubes dont seem to have the ill affects that everyone seems to think they have. That article did nothing but reinforce my theory. even if they (the 1 7/8 tubes) had lost a few lbs ft, but they didnt they actually gained over ALL the headers tested. the gain of the small tube shorties was nulified by the bigger tubes. Not to say that they (the little tubes) wouldnt have better throttle response off idle, cause the test was from 3000 up. and even that (throttle response) is far more affected by intake size than exhaust. This is one of the wives tale type misconceptions that we prove wrong every day. You cant run a 12 to 1 motor on pump gas. Wanna bet?

 

Please post DATA to the contrary. Looking for double digit LOSES.

 

All I can add is that the SW products are high quality, I'm happy with mine. I wouldn't let the 1 5/8 vs. 1 3/4 make the decision. I think there are many good quality headers available from above and you should be happy with any of them. I was down to EM and SW because of their packages they offer with cats and I'm a diy in the garage guy without a welder and they went in just fine. The stainless construction won it over for me, the coating on the EMs looks sweet, but will not last forever and I don't want to have to take them off again (except for head work).

 

I think you all forgot about Hooker Super Comps. Also, Hooker makes non-Super Comps, for about half the price. If there was no benefit of the equal length scavenging, no one would buy a header that costs twice as much. IMHO, if they are not "tuned", like cheapy Hedman's, shorties, Hooker's cheap version, or those "not-so-purdy" (to me) Stainless Works, save your money and leave your stock manifolds on.
My money is going to a set of tuned, or nothing at all, regardless of the size of the primaries. Also, the torque range can be modified just by lengthening or shortening the collector, however on a car w/the exhaust components hooked up all the time, that is a moot point. Take a look at Stahl headers some time. They are really pricey, and usually only found on strictly race cars, but they go to great efforts to keep the primaries the same length.

Rich K

 

I have experimented with header sizes and posted my results, here, long before that article was written. I was happy to see it, when it came out, because it in large part, supports my observations and experiences.



I have seen 60' times and everyday drivability improve with a proper compromise of header size. Possibly you have mistaken me for a "head in the sand", or a "follow the crowd" sheep, with no practical experience. That is far from the case, here.



That isn't big enough to be better for a DD. I have experience with a 383, alcohol fueled '69 Camaro, that lost in hos 60' tomes when he want to 1 3/4" headers. The car was too heavy for the powerglide and it needed all the torque it could muster to get out of the hole.



Me too.



The "small" loss in torque was in comparison to the 1 3/4" headers, not the 1 5/8". It would be a bigger loss (or less of a gain) compared to the 1 5/8". And that is only STARTING at 3000 rpms! Most DDs don't pull 3 grand hole shots on the way to work, from every stop light. FIRST, you have to GET to 3000 rpms, if you even intend to. I repeat, do you drive a dyno to work, or your car?



Not if the exhaust is still occupying the cylinders. It works best as a balanced package. For best results, each component has to complement all the others.

RACE ON!!!

 

Hooker makes a header for the C4, other than the "Super Comp"?

RACE ON!!!

 

And that's because Stahl's are made for the pure racer crowd. Made to order, for specific racing needs, a point that I thought I had made earlier..... And I didn't forget Hooker. I said the "great headers" made for these cars. That would not include them.

 

alright alright sounds like a great debate here!!

think that alot of people here also forgot the other neat thing about headers.. the more heat you retain inside the header the higher the pressure remains and the better velocity you sustain for a longer period of time.. thermodynamics 101.. this being said.. if you have a set of uncoated stainless steel headers.. a smaller diamter primary will work better so a 1 5/8" would be my recomendation.. this is due to the absorbtion of heat the uncoated stainless will suck up cooling the exhaust charge like a radiator and dispersing it into your engine bay.

if you plan on using coated stainless " my fruit of choice" due to its ability to last, not rust and retain the coating without rusting underneath and flaking off. Then I would choose a 1 3/4" long tube with as close to equal length primaries as possible. this being said.. the exotic muscle series look like a good choice if they are made with stainless and if they are not coated.. send them off to jet hot or another known and well reputed company who can coat them inside and out! be sure ALL bungs and such are installed prior to coating as it ruins the coating if you need to drill and weld bungs on!

all in all.. about any long tube out there is going to net HUGE gains over the stock exhaust manifolds.. and arguing over 2-3 ponies and ft/lb's.. which is something no one here can feel and may show a difference of .01-.02 in the 1/4 mile...is kinda silly. go with what ya can afford.. I have 2 sets of hooker 2149's the non emissions headers.. both made excellent power on my cars.. however the durability of the coated finish on mild steel is POOR.. both sets have rusted through and the coating flaked off. I don't recommend them to anyone. go stainless steel and GOOD coating.. preferably someone with a warranty that will recoat if they flake.. this will cover you for longevity and also add power by retaining heat where it belongs.. inside the tube and NOT in the engine bay. this will extend the life of plug, wires, boots... and all in all help your engine perform better all around.

with all the work with turbocharging I have done... I can tell you that thermodynamics and heat management plays more of a role here then the primary size. an uncoated 1 5/8" oprimary will yield more output of power because of the surface area it has being less from exhaust port to collector.. it is basically like a samller radiator in which it cannot absorb as much heat as a 1 3/4" header. now coating inside and out.. this equalizes the playing field.. you should see very similar numbers through out but the larger 1 3/4" primary with work best with higher reving engine with bigger cams. this is due in part to its most efficient scavenging velocity being pushed higher in the rpm band.. so yes you may lose some availablity of power lower in the rev range but if you want big cams and heads and revs.. its the best choice!

Hope this helps!

Chris

 

Hooker's are coated on the outside, only. There are a lot of people on this forum that think the sun rises and sets in Hooker headers. I personally, believe a large amount of that is word of mouth and "following the in crowd". Hooker 2149s are the smog headers and come standard with the outside only ceramic coating. The 2151s are the same headers without smog fittings and without a ceramic coating. 2151-1 are Hooker, outside ceramic coated, 2151s. Jet Hot, and maybe others, can sell you Hookers, with their superior coating, inside and out. Personally, I like HPC coatings.

RACE ON!!!

 

Wow, I come back from a fair to a real debate. I feel honored. Seems like in the end it's a crap shoot, I'm buying the EM's because they're equal length as opposed to the unequal length others make. The EM's have been a proven performer. I'll agree 1 7/8 might be too big, the 1 3/4 will still provide some room to grow, if I don't make that extra few digits SOMEWHERE in the torque curve I could make with 1 5/8; so be it.

I have stock manifolds now, how in the world would I know if I didn't make ALL the torque, power there would to had unless I dyno each? Even then in what RPM range are we talking about. I don't really drive this car as grocery getter, it's going mostly full tilt every chance I can get.

Thank you though for all the comments, debates, it's more than interesting.