tri-y headers and smaller exhaust system

[steve cowan]

i am going to fit and test a off shelf tri-y 1 5/8 headers.these are made locally here in Australia
from Summit i received today 2 x flowmaster merge pipes,2 x venturi pipes,2 x kooks mufflers this will be 2 1/2 system.
i am going to leave the system un-welded so i can change collector lengths etc.
if i have the room i will fit a header plate so i can try and match the exhaust flange to header ports this will be tricky i think,if not i will try and get the roof,sides as close as possible and make the floor as a anti reversion barrier.
on my car at the moment i have 4 into 1 --1 3/4 headers,short collector,3 inch system to aero chamber mufflers,i made this system a few years ago when my car had the 215 dart heads,roller cam etc,ran 11.0s @ 120 plus.
this year i have been running my 383 - 10.5:1 short block with my dart 165cc heads out to 178cc and small SFT comp cam 235-242 @ 0.050'' 106 lsa .500'' lift,air gap intake.
at the moment the car runs 11.7s @ 113mph. 1.61 - 60ft. 7.4s @ 91 mph in the 1/8th.
i think 11.5s are doable with more tuning,the engine falls on its face @ 6000rpm due to intake port choke CSA.i done this on purpose to test and learn for myself on the track with time slips.
i think the smaller exhaust will help making more torque,looking for everyone's ideas so feel free to comment

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[mag2555]

You need to watch out as besides a HP loss there can come a point where at low speed the motor can't fully pump out the Exh and then the plugs get black and sooty looking and many people end up chasing what they think is a oil issue!

[NewbVetteGuy]

I can't offer an expert opinion, but I'll offer encouragement that my non-expert opinion is that I think this is moving the right direction.

383 with heads that small and that much overlap will probably gain more down low from the higher velocity exhaust than you'll lose up high. (400 and a little bit HP?)


Adam

[steve cowan]

I can't offer an expert opinion, but I'll offer encouragement that my non-expert opinion is that I think this is moving the right direction.

383 with heads that small and that much overlap will probably gain more down low from the higher velocity exhaust than you'll lose up high. (400 and a little bit HP?)


Adam

thanks Adam,
for me its about trying to learn something good or bad,i have done a fair amount of research on the exhaust side of the engine and its a tough deal.
my thinking is 1 - people dont really worry about the exhaust only the intake side.
2- people just dont understand the exhaust side of performance.
3- its all secret stuff.
yes these cylinder heads are small for this cubic inch but that was my intention from the start,but i will say it makes good torque,at 3650 pounds with me a full weight street car it leaves with the wheels a couple inches off the ground off the startline on a good track.
the exhaust port measures 1.45'' x 1.30'' wide.
it only flows 177 cfm @ 28''.
originally the airspeed was fast in the port 380 ft/sec so got a decent valve job,layed SSR down.modified guide boss a little,with a short pipe airspeed down to 320 ft/sec @ 28'' checking through a modified short pipe.turbulence was gone at lower lifts ( valve job i would think)
and was stable @ 40'' depression to 0.700'' lift.
i would think the smaller faster header would be benefit in this type of scenario,
i have been testing different converters,rocker ratios,carb spacers,carb settings for the last 3 months,i am at the track this weekend and have moved the caltrac bars to the top hole and removed lowering blocks from leaf springs to level car up,removed front sway bar as well,i just put a new set of 255/60/15 drag radials so i really hope i can go into the 1.5s in the 60ft.
i put up this thread as to try and get some feed back on collector lengths etc or should i use the venturi at the end of the collector as an example etc.
the engine will come apart at the end of the year for freshen up,port work looking at peak around 6500rpm, bigger SFT cam,more compression etc it will be rinse and repeat in testing and learning.

[77cruiser]

Those look a little different that the Doug Thorley's. Randy had good results on an EMC engine using those.

http://www.dougthorleyheaders.com/1968- ... ders_15894

[steve cowan]

Those look a little different that the Doug Thorley's. Randy had good results on an EMC engine using those.

http://www.dougthorleyheaders.com/1968- ... ders_15894

thanks for the link Jim,
if i could get a Thorley header to fit i would purchase a set but i think the left hand - right hand drive USA - AUSTRALIA configuration might not work.
yep i know Randy,CGT,Tony Knight,James (Melway) etc dyno heavy hitters use tri-y pipes
kinda where my motivation come from

[cjperformance]

Steve, that will be a positive move once you have it sorted . Another tri,y fan here.
After your collector swap i would suggest to leave the venturi pipe out and play with the length after the collector until you find what the combo likes. Then add the venturi so you can see what it does and where.
I have not played with a venturi pipe as you are using but commonly do step up and/or down in pipe size.
Running a relatively short system i will say it will prefer the venturi pipe right up at the 2 into 1 merge. BUT i have not often messed with this particular setup other than 'fit and forget'. I mainly size up full systems and have a half reasonable handle on that side if things as far as noise, drone, note and exhaust on/off performance is concerned.
Short systems can make great hp and tq but can be testy to get just right.
Always play with pipe length after the muffler too, this can make quite a difference depending on the specific muffler.

[steve cowan]

Steve, that will be a positive move once you have it sorted . Another tri,y fan here.
After your collector swap i would suggest to leave the venturi pipe out and play with the length after the collector until you find what the combo likes. Then add the venturi so you can see what it does and where.
I have not played with a venturi pipe as you are using but commonly do step up and/or down in pipe size.
Running a relatively short system i will say it will prefer the venturi pipe right up at the 2 into 1 merge. BUT i have not often messed with this particular setup other than 'fit and forget'. I mainly size up full systems and have a half reasonable handle on that side if things as far as noise, drone, note and exhaust on/off performance is concerned.
Short systems can make great hp and tq but can be testy to get just right.
Always play with pipe length after the muffler too, this can make quite a difference depending on the specific muffler.

thanks for your input Craig,
yes the venturi is the deal breaker as far as positioning.
it will be a test and see type of deal overall,having different length collectors that can be changed out will be great,my research has it as the collector has the most influence,
Craig,is there any way to get a pressure wave to work in a muffler type system without using a termination box??

[Caprimaniac]

As I tested a set of Doug T. Tri-Y headers on my car (they did not fit very well), I was told these 1 5/8" primaries were good for 500Hp, easy. Using the calc it say Your engine is sub 500 (450 crank on wallace w/o correction). 2.5" should me no problem, at least w/ straight- thru mufflers.

Yours look better; length of secondaries, collector/merge, than the D.T.'s, in my opinion. You have probably looked at of what mr. Exhausted has to say on headers. Elston is a smart guy; lot's of info there.

[cjperformance]

Steve, that will be a positive move once you have it sorted . Another tri,y fan here.
After your collector swap i would suggest to leave the venturi pipe out and play with the length after the collector until you find what the combo likes. Then add the venturi so you can see what it does and where.
I have not played with a venturi pipe as you are using but commonly do step up and/or down in pipe size.
Running a relatively short system i will say it will prefer the venturi pipe right up at the 2 into 1 merge. BUT i have not often messed with this particular setup other than 'fit and forget'. I mainly size up full systems and have a half reasonable handle on that side if things as far as noise, drone, note and exhaust on/off performance is concerned.
Short systems can make great hp and tq but can be testy to get just right.
Always play with pipe length after the muffler too, this can make quite a difference depending on the specific muffler.

thanks for your input Craig,
yes the venturi is the deal breaker as far as positioning.
it will be a test and see type of deal overall,having different length collectors that can be changed out will be great,my research has it as the collector has the most influence,
Craig,is there any way to get a pressure wave to work in a muffler type system without using a termination box??

Steve, anything that creates a change in pressure will create/enhance a pressure wave of some description. A good merge, a step up in diameter, a chambered muffler, H pipe x pipe etc all enhance the pressure wave started when the ex valve opens.
Making these work to your advantage is either a lot of physics based calculations (which im not good at) or a lot of trial and accepting/learning from the errors(i am good at! Haha). I have learnt what works in the stuff I commonly do but I dont have the crazy calc skills of some guys on here or the the range of applications that Calvin does.
The termination box is simply allowing a large sudden pressure wave to act on the collector and an area for the exhaust pulses to then soften enough to see the the rest of the system as a lessened restriction to flow.
Using multiple smaller pressure change areas can use more of the system length to create the same flow/hp outcome.

[steve cowan]

As I tested a set of Doug T. Tri-Y headers on my car (they did not fit very well), I was told these 1 5/8" primaries were good for 500Hp, easy. Using the calc it say Your engine is sub 500 (450 crank on wallace w/o correction). 2.5" should me no problem, at least w/ straight- thru mufflers.

Yours look better; length of secondaries, collector/merge, than the D.T.'s, in my opinion. You have probably looked at of what mr. Exhausted has to say on headers. Elston is a smart guy; lot's of info there.

thanks Capri,
yes i have read and re-read as much of C Elstons work on his 101 forum and also on YB,and here as well.some things that i have picked up is dont use a dual plane intake with tri-y pipes
dont use a 4-7 swap cam with standard fire tri-y pipes just to name a few,it is a extremely complex subject and could be costly in performance and the hip pocket as well if mistakes are made,i am sure i will make plenty of mistakes in this little adventure.

[steve cowan]

Steve, that will be a positive move once you have it sorted . Another tri,y fan here.
After your collector swap i would suggest to leave the venturi pipe out and play with the length after the collector until you find what the combo likes. Then add the venturi so you can see what it does and where.
I have not played with a venturi pipe as you are using but commonly do step up and/or down in pipe size.
Running a relatively short system i will say it will prefer the venturi pipe right up at the 2 into 1 merge. BUT i have not often messed with this particular setup other than 'fit and forget'. I mainly size up full systems and have a half reasonable handle on that side if things as far as noise, drone, note and exhaust on/off performance is concerned.
Short systems can make great hp and tq but can be testy to get just right.
Always play with pipe length after the muffler too, this can make quite a difference depending on the specific muffler.

thanks for your input Craig,
yes the venturi is the deal breaker as far as positioning.
it will be a test and see type of deal overall,having different length collectors that can be changed out will be great,my research has it as the collector has the most influence,
Craig,is there any way to get a pressure wave to work in a muffler type system without using a termination box??

Steve, anything that creates a change in pressure will create/enhance a pressure wave of some description. A good merge, a step up in diameter, a chambered muffler, H pipe x pipe etc all enhance the pressure wave started when the ex valve opens.
Making these work to your advantage is either a lot of physics based calculations (which im not good at) or a lot of trial and accepting/learning from the errors(i am good at! Haha). I have learnt what works in the stuff I commonly do but I dont have the crazy calc skills of some guys on here or the the range of applications that Calvin does.
The termination box is simply allowing a large sudden pressure wave to act on the collector and an area for the exhaust pulses to then soften enough to see the the rest of the system as a lessened restriction to flow.
Using multiple smaller pressure change areas can use more of the system length to create the same flow/hp outcome.

thanks for your thoughts Craig,its always appreciated,
time for the thinking cap to be screwed on,i think the flange- primary transition is going to be the hard one,the header opening height is at least 1/2 '' taller than what a standard small block chev exhaust port is looking at a felpro 1440 gasket.

[77cruiser]

I built these 5 years ago, just had them coated this winter.

[mtrhead]

Those look a little different that the Doug Thorley's. Randy had good results on an EMC engine using those.

http://www.dougthorleyheaders.com/1968- ... ders_15894

thanks for the link Jim,
if i could get a Thorley header to fit i would purchase a set but i think the left hand - right hand drive USA - AUSTRALIA configuration might not work.
yep i know Randy,CGT,Tony Knight,James (Melway) etc dyno heavy hitters use tri-y pipes
kinda where my motivation come from

I also converted/changed to smaller headers Tri-Y on my SBC. What a seat of the pants difference!

Before: 410” SBC 210cc Profiler ported heads, 1 ¾ long tubes, crower 242/252 110’ cam, 830 Holley

Now: 410 SBC 195cc ATK (profiler cast) ported heads with smaller exhaust port, 1 5/8” Dougs Tri-Y headers, Jones 236/239 cam, prosystems carb

Note the differences in these heads - Wonder what the true power difference is?
Thread on exhaust port size vs. header fitment https://www.speed-talk.com/forum/viewtopic.ph ... 1&start=30

[CGT]

I built these 5 years ago, just had them coated this winter.

Very nice. If you don't mind me asking, who coated them, how much, and are you happy with them?
Im in the process of getting mine sent out and haven't decided who to send them to.