Headers too big??

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Re: Headers too big??

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cjperformance wrote: Thu Mar 15, 2018 6:51 am
BILL-C wrote: Thu Mar 15, 2018 6:45 am I have a set of 1.75 x32long primary x 3 " collector dyno headers that always perform very well with combinations like yours. I would expect that hooker number to have a 3" collector also.
With a full street exhaust system behind them?
No , just 3" pipe into 3" hooker aerochamber mufflers then into twin 8" dyno pipes and mufflers.
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Re: Headers too big??

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I think world says to use 1 3/4 with the sportsman II's, if you measure the exhaust port(provided the porter didn't enlarge it) it would need a 1 3/4 circle to not obstruct it. Otherwise you'd have to taper a smaller 1 5/8 header flange, so unless your willing to weld up n taper a 1 5/8 header flange 1 3/4 is the way to go with those heads.
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Re: Headers too big??

Post by digger »

Simply change the header primary pipe by itself 1/8" imo won't do much without some other changes especially on a full exhaust
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Re: Headers too big??

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wilson1970 wrote: Thu Mar 15, 2018 9:11 am Thanks for the responses. The reason why I ask is I have these headers from a previous project. Can i get away with these or will I regret using them. These thing were quite expensive. And yes this is a street engine looking for power to be done around 6200.
If you have them use them, they are not what I would buy if starting from scratch but why spend more $ if you dont need to, it will still go fine.
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Re: Headers too big??

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digger wrote: Thu Mar 15, 2018 5:44 pm Simply change the header primary pipe by itself 1/8" imo won't do much without some other changes especially on a full exhaust
From 1-5/8" to 1-3/4" pipes , loosely based on .0625" wall tube, CSA 1.76" v 2.07" , Thats 17/18% increase in CSA !
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Re: Headers too big??

Post by digger »

cjperformance wrote: Thu Mar 15, 2018 6:48 pm
digger wrote: Thu Mar 15, 2018 5:44 pm Simply change the header primary pipe by itself 1/8" imo won't do much without some other changes especially on a full exhaust
From 1-5/8" to 1-3/4" pipes , loosely based on .0625" wall tube, CSA 1.76" v 2.07" , Thats 17/18% increase in CSA !
That's area but what will it translate to in the torque output with nothing but a diameter change ?
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Re: Headers too big??

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IMHO, matching primary pipe size to overhang cookie cutter exhaust ports.. often used on several different sized CC intake runner heads.. is a mistake on a wider powerband application(such as a moderate sized street engine). But as some are rightfully pointing out.. it's neither here not there for this application and $$$. Still makes me wonder.. have we learned nothing from Calvin Elston through his many posts around here?

Velocity and blowdown length is everything when it comes to "shutting the back door quicker", as he used to say. Even at the expense of primary pipe overlapping the exhaust port in some cases.

http://www.exhausting101.com/?p=37


Then there's guys like Ed Henniman(headers by ed) who quite literally made a business out of shrinking cookie cutter exhaust ports down in size to better match specific applications. Even when said pipe size was smaller than the exhaust ports exit size. He once told me that many guys, even professional engine builders and racers, can go through an entire lifetime and never figure out it's the velocity immediately coming out of the exhaust port that impacts the engines powerband characteristics. Get that closer to right and the collector can be used to further tune the powerband. Get it closer to wrong and you'll need to crutch the shortcomings in some other manner. Merge collectors work really well at shoring up big primary pipes sluggish performance. Asking yourself why that is will potentially make your parts combinations better in the long run.
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Re: Headers too big??

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groberts101 wrote: Thu Mar 15, 2018 7:42 pm IMHO, matching primary pipe size to overhang cookie cutter exhaust ports.. often used on several different sized CC intake runner heads.. is a mistake on a wider powerband application(such as a moderate sized street engine). But as some are rightfully pointing out.. it's neither here not there for this application and $$$. Still makes me wonder.. have we learned nothing from Calvin Elston through his many posts around here?

Velocity and blowdown length is everything when it comes to "shutting the back door quicker", as he used to say. Even at the expense of primary pipe overlapping the exhaust port in some cases.

http://www.exhausting101.com/?p=37


Then there's guys like Ed Henniman(headers by ed) who quite literally made a business out of shrinking cookie cutter exhaust ports down in size to better match specific applications. Even when said pipe size was smaller than the exhaust ports exit size. He once told me that many guys, even professional engine builders and racers, can go through an entire lifetime and never figure out it's the velocity immediately coming out of the exhaust port that impacts the engines powerband characteristics. Get that closer to right and the collector can be used to further tune the powerband. Get it closer to wrong and you'll need to crutch the shortcomings in some other manner. Merge collectors work really well at shoring up big primary pipes sluggish performance. Asking yourself why that is will potentially make your parts combinations better in the long run.

It's not that what Calvin says isn't learned. It's that at times it just isn't applicable. I've seen many more failures with merge collectors, steps, chokes and all that. Unless the entire system is designed around the header, most times that stuff is a loser.
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Re: Headers too big??

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statsystems wrote: Thu Mar 15, 2018 8:13 pm
groberts101 wrote: Thu Mar 15, 2018 7:42 pm IMHO, matching primary pipe size to overhang cookie cutter exhaust ports.. often used on several different sized CC intake runner heads.. is a mistake on a wider powerband application(such as a moderate sized street engine). But as some are rightfully pointing out.. it's neither here not there for this application and $$$. Still makes me wonder.. have we learned nothing from Calvin Elston through his many posts around here?

Velocity and blowdown length is everything when it comes to "shutting the back door quicker", as he used to say. Even at the expense of primary pipe overlapping the exhaust port in some cases.

http://www.exhausting101.com/?p=37


Then there's guys like Ed Henniman(headers by ed) who quite literally made a business out of shrinking cookie cutter exhaust ports down in size to better match specific applications. Even when said pipe size was smaller than the exhaust ports exit size. He once told me that many guys, even professional engine builders and racers, can go through an entire lifetime and never figure out it's the velocity immediately coming out of the exhaust port that impacts the engines powerband characteristics. Get that closer to right and the collector can be used to further tune the powerband. Get it closer to wrong and you'll need to crutch the shortcomings in some other manner. Merge collectors work really well at shoring up big primary pipes sluggish performance. Asking yourself why that is will potentially make your parts combinations better in the long run.

It's not that what Calvin says isn't learned. It's that at times it just isn't applicable. I've seen many more failures with merge collectors, steps, chokes and all that. Unless the entire system is designed around the header, most times that stuff is a loser.

Don't buy that for a millesecond. Blowdown length is ALWAYS important and probably moreso on a predominately low piston speed application. Headers are one of the biggest cookie cutter bolt on issues I see. Then we're forced to bandaid many other things and compromise the tune to compensate for a lazy pipe and/or collector.

case in point.. my little 310" SBF motor DESERVES a 1.5" primary pipe off the little RHS 165 head. But guess what?.. the stupid "one size fit all" exhaust port mentality means they cast it the same as heads one used on much bigger stroker motors. So, what do I do? make sure I put a 1.75" primary pipe that covers the exhaust port out of for fear of a step down in size leading into the primary? Nope!.. I weld it smaller and put the pipe the MOTOR WANTS.. not some arbitrary size based on what some lazy R&D department decided to use to make production cheaper. Same can be said about the OEM's too.
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Re: Headers too big??

Post by wilson1970 »

Thanks for the all of the responses. I will keep what I have and yes they have 3" collectors. The big downfall to these is that the back tubes wrap around the frame which affects turning radius with street tires. :(
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Re: Headers too big??

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groberts101 wrote: Thu Mar 15, 2018 8:20 pm
statsystems wrote: Thu Mar 15, 2018 8:13 pm
groberts101 wrote: Thu Mar 15, 2018 7:42 pm IMHO, matching primary pipe size to overhang cookie cutter exhaust ports.. often used on several different sized CC intake runner heads.. is a mistake on a wider powerband application(such as a moderate sized street engine). But as some are rightfully pointing out.. it's neither here not there for this application and $$$. Still makes me wonder.. have we learned nothing from Calvin Elston through his many posts around here?

Velocity and blowdown length is everything when it comes to "shutting the back door quicker", as he used to say. Even at the expense of primary pipe overlapping the exhaust port in some cases.

http://www.exhausting101.com/?p=37


Then there's guys like Ed Henniman(headers by ed) who quite literally made a business out of shrinking cookie cutter exhaust ports down in size to better match specific applications. Even when said pipe size was smaller than the exhaust ports exit size. He once told me that many guys, even professional engine builders and racers, can go through an entire lifetime and never figure out it's the velocity immediately coming out of the exhaust port that impacts the engines powerband characteristics. Get that closer to right and the collector can be used to further tune the powerband. Get it closer to wrong and you'll need to crutch the shortcomings in some other manner. Merge collectors work really well at shoring up big primary pipes sluggish performance. Asking yourself why that is will potentially make your parts combinations better in the long run.

It's not that what Calvin says isn't learned. It's that at times it just isn't applicable. I've seen many more failures with merge collectors, steps, chokes and all that. Unless the entire system is designed around the header, most times that stuff is a loser.

Don't buy that for a millesecond. Blowdown length is ALWAYS important and probably moreso on a predominately low piston speed application. Headers are one of the biggest cookie cutter bolt on issues I see. Then we're forced to bandaid many other things and compromise the tune to compensate for a lazy pipe and/or collector.

case in point.. my little 310" SBF motor DESERVES a 1.5" primary pipe off the little RHS 165 head. But guess what?.. the stupid "one size fit all" exhaust port mentality means they cast it the same as heads one used on much bigger stroker motors. So, what do I do? make sure I put a 1.75" primary pipe that covers the exhaust port out of for fear of a step down in size leading into the primary? Nope!.. I weld it smaller and put the pipe the MOTOR WANTS.. not some arbitrary size based on what some lazy R&D department decided to use to make production cheaper. Same can be said about the OEM's too.
Did you back to back test the headers?
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Re: Headers too big??

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statsystems wrote: Thu Mar 15, 2018 9:13 pm
Did you back to back test the headers?
Seems like a waste of time considering there are smaller cid sbf road race engines far more potent than mine making well over 500 horsepower through a 1.625" primary and 2.25" collector choke turning 8000 rpm.
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Re: Headers too big??

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groberts101 wrote: Thu Mar 15, 2018 8:20 pm...
case in point.. my little 310" SBF motor DESERVES a 1.5" primary pipe off the little RHS 165 head. But guess what?.. the stupid "one size fit all" exhaust port mentality means they cast it the same as heads one used on much bigger stroker motors. So, what do I do? make sure I put a 1.75" primary pipe that covers the exhaust port out of for fear of a step down in size leading into the primary? Nope!.. I weld it smaller and put the pipe the MOTOR WANTS.. not some arbitrary size based on what some lazy R&D department decided to use to make production cheaper. Same can be said about the OEM's too.
Port sleeving might be a possibility. Short lengths of 1-5/8" or 1-1/2" tube ground/tapered to a near-knife edge on the OD of the inboard end, heated to red and pounded in to form to the port contour and then trimmed flush with the flanges.
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Re: Headers too big??

Post by 77cruiser »

Seemed to work on a certain EMC deal.


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Re: Headers too big??

Post by groberts101 »

MadBill wrote: Fri Mar 16, 2018 12:21 am
groberts101 wrote: Thu Mar 15, 2018 8:20 pm...
case in point.. my little 310" SBF motor DESERVES a 1.5" primary pipe off the little RHS 165 head. But guess what?.. the stupid "one size fit all" exhaust port mentality means they cast it the same as heads one used on much bigger stroker motors. So, what do I do? make sure I put a 1.75" primary pipe that covers the exhaust port out of for fear of a step down in size leading into the primary? Nope!.. I weld it smaller and put the pipe the MOTOR WANTS.. not some arbitrary size based on what some lazy R&D department decided to use to make production cheaper. Same can be said about the OEM's too.
Port sleeving might be a possibility. Short lengths of 1-5/8" or 1-1/2" tube ground/tapered to a near-knife edge on the OD of the inboard end, heated to red and pounded in to form to the port contour and then trimmed flush with the flanges.
Thanks for the idea, Bill. I took the much longer harder traveled path with tig rod and molten aluminum. Had to buy a small specialty #24 water cooled torch just to access the port for the SSR fill. Only goes to 180 amps though.. so it's a slow process. Now I fully understand why more people don't weld up their own ports. #-o
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