Should I use Tri-Y Headers on my 347?

Ferf · Apr 15, 2011

I have a 347 stroker and the place that built my motor recommended using headers with 1 3/4" or 1 7/8" primaries. I am looking at a set of Doug Thorley Tri-Y headers (p/n 289Y-C) but they only have 1 1/2" primaries.

Will I see a noticable difference in power using the smaller diameter primaries? What are the advantages / disadvanatages of using a Tri-Y header over a regular 4-Tube header? Any other comments and recommendations are appreciated.

blown65 · Apr 15, 2011

1 1/2 is awefully small. 1 5/8" is common on LT headers and Accufab sells some 1 3/4" headers. 1 7/8" will have to be a totally custom deal and super tight in a 65 with stock front suspension parts.

Ferf · Apr 15, 2011

blown65,

Forgive me but I am a totaly noobie when it come to this stuff. Looking back on it, I believe that the headers were to stepped from 1 3/4" to 1 7/8". As for Doug Thorley's headers, it may be a misprint on the site as I have seen the same headers listed a 1 5/8" primaries.

What are the differences in using a 4-to-1 header vs a Tri-Y header?

blown65 · Apr 15, 2011

Ferf said:
blown65,

Forgive me but I am a totaly noobie when it come to this stuff. Looking back on it, I believe that the headers were to stepped from 1 3/4" to 1 7/8". As for Doug Thorley's headers, it may be a misprint on the site as I have seen the same headers listed a 1 5/8" primaries.

What are the differences in using a 4-to-1 header vs a Tri-Y header?

If you look at the pictures of a tri-y vs 4-1 its pretty simple to see the difference in them.

Just for a point of reference for you, I went from 1 5/8" headers to 1 3/4" headers. Same basic length on the tubes, 4-1 headers. Gained 0 at the track. This was on a 347 making 535hp flywheel and spinning to 8000 rpm. Unless your doing something along those lines I'd save your $$ and purchase a set of 1 5/8" LT 4-1's.

Ferf · Apr 15, 2011

blown65 said:
If you look at the pictures of a tri-y vs 4-1 its pretty simple to see the difference in them.

Just for a point of reference for you, I went from 1 5/8" headers to 1 3/4" headers. Same basic length on the tubes, 4-1 headers. Gained 0 at the track. This was on a 347 making 535hp flywheel and spinning to 8000 rpm. Unless your doing something along those lines I'd save your $$ and purchase a set of 1 5/8" LT 4-1's.

Blown65,

I know the appearance looks different but what about the performance?

I spoke with Doug Thorley's and thier Tri-Y (p/n 289y) has 1 1/2" primaries. They recommended using p/n 268-C which is a 4-1 long tube header that has 1 5/8" primaries.

I also spoke with the engine builder and he stated that while he recommended 1 3/4" primaries since my car will be a street car and I am not looking to get every bit of HP out of the motor 1 5/8" primary headers will work well. As for Tri-Y headers, he stated that he has never ran them on the motors that he has put on the dyno so he can't really comment on exactly how well they will perform.

With all that said, I found a set of Doug's Headers (not Doug Thorley's) that are a Tri-Y design AND have 1 5/8" primaries. Given that I will be using a set of headers that have 1 5/8" primaries what would I be sacraficing by going to a Tri-Y design over the 4-1 headers?

blown65 · Apr 15, 2011

I don't have a good answer there for ya. I would think you would give up some HP but probably gain some low end TQ.

Personally I'd just go with the 1 5/8" deal.

Ferf · Apr 15, 2011

blown65 said:
I don't have a good answer there for ya. I would think you would give up some HP but probably gain some low end TQ.

Personally I'd just go with the 1 5/8" deal.

Blown65,

Sorry to be a pain but I am assuming that you are referring to the 1 5/8" Tri-Y headers to go with, correct?

blown65 · Apr 15, 2011

LOL, sorry. I have zero experience with the Tri-Y's. I believe they are supposed to give more low end tq.

Maybe someone else can chime in on the 1 5/8 4-1 header VS a 1 5/8" TRI-Y header. I thought you wrote that they were 1 1/2" where I would say no to that.

Ferf · Apr 15, 2011

Blown65,

Doug Thorley's Tri-Y headers are 1 1/2" primaries.
Doug's Headers Tri-Y headers are 1 5/8" primaries.

I just spoke with Pertronix who manufactures Doug's Headers and he stated that you can start to feel their Tri-Y's start to drop off in HP around 5500 RPM.

Doug's Headers do make a 4-1 header for my car but it is a 3/4 length header with a 1 5/8" primary. This header was their recommendation. Will I notice a difference between a 3/4 length vs a full length header?

Sorry for all the questions but this is my first time learning about this stuff.

blown65 · Apr 15, 2011

This is what I ran. I have no idea between mid and full length how it would stack up.

I cant remember if it was hooker or hedman headers though but pretty sure it was hooker.

Hooker Headers 6111-1HKR - Hooker Super Competition Headers - Overview - SummitRacing.com

1 5/8" LT headers.

Edster · Apr 15, 2011

I guess comes down to splitting hairs, on the street it won't be that big of a deal, race yes. A 347 may benifit a little more w/ the 1 5/8 a little more on the street but I reckon the difference may not be much. If ya got the dough (if the bigger set is more $$) then spend it, if not get the 1 1/2 primaries. I think it won't make much difference on the street.

Ferf · Apr 15, 2011

After talking to a number of different resources, I will definitly be going with the 1 5/8" primaries. Now it boils down to Tri-Y or 4-1 headers. From what I am gathering since my car will be street drivin' 99.99% of the time it won't make much of a difference what type of header that I go with.

blown65 · Apr 15, 2011

Ferf said:
After talking to a number of different resources, I will definitly be going with the 1 5/8" primaries. Now it boils down to Tri-Y or 4-1 headers. From what I am gathering since my car will be street drivin' 99.99% of the time it won't make much of a difference what type of header that I go with.

X2

PoppyMod · Apr 16, 2011

Hi Guys,

This is my take on the LT vs. TRI-Ys.
It has long been stated, TRI-Ys are a "TQ" building header and LTs for HP at higher Rs.
My junk (333 cu.in.) makes 392 RWHP at 6000 and a RWTQ of 401 at 4400 and has a rev limit of 7K. MY rig is a street warrior. A 347, if designed properly, is going to really shine at the higher RPMs. Doesn't mean it want perform well on the street, but the additional cubes give it an HP advantage.
So, if your rig is going to be a street warrior, you want that bigger "kick" in the seat of your pants feel, go for more TQ. After all, except for " blistering out of the entrance ramp onto the freeway, you are not going to be cruising at 4500-6500 Rs from stop light to stop light. Obviously, your rear gear is going to speak to some of this, as well.
Not to mention, TRY-Ys hug the body better and have less fitment issues. So, If I were shopping and I considered the 347 build myself, I wold go with the larger TRY-Ys.
Anyway, this is how I view it all.
Happy Trails!

Ferf · Apr 18, 2011

I think I have my purchase narrowed down to two options. My car will be street drivin' 99.999% of the time.

1. Doug's Headers P/N D665 - 4-1 Style 3/4 Length Header, 1 5/8" Primary, 3" Collector

2. Doug's Headers P/N D690YS - Tri-Y Style Full Length Header, 1 5/8" Primary, 2.5" Collector

The place where I purchased my motor recommended a 2.5" exhaust so I am not sure if the 3" will be a benefit or not. I can get a great deal on the Tri-Ys but if they are going to cause a considerable amount of HP loss on the top end then I will go for the 4-1 headers.

What would you purchase?

Ferf · Apr 18, 2011

Just heard back from the engine builder and my 347 red lines at 6000 RPM. Since I won't be pushing very high RPMs, I think the Tri-Ys will have less of an impact on HP loss. Thoughts?

PoppyMod · Apr 18, 2011

Ferf said:
Just heard back from the engine builder and my 347 red lines at 6000 RPM. Since I won't be pushing very high RPMs, I think the Tri-Ys will have less of an impact on HP loss. Thoughts?

The benefits of the TQ building qualities are going to be more beneficial at the RPM ranges your are more apt to see than a couple HP at 6200. As i mentioned, My 333 puts out 392 RWHP at 5900-6000 (Redlines at 7K) and it's running TRI-Ys into a 2.5" "X" over exhaust. The problem with running 3" is fitment and clearance. My suggestion is go with the TRY-Ys.
Happy Motoring!

HDTony · Apr 22, 2011

Ferf said:
2. Doug's Headers P/N D690YS - Tri-Y Style Full Length Header, 1 5/8" Primary, 2.5" Collector

?

Well I just ordered those after reading all this. and I'm also ordering a 2.5 inch flowmaster exhaust out the back.

hipo_p51 · Apr 22, 2011

Go with what you like. I mean its your car. Put the parts on it your like. Are you going to race it? or just look cool and drive up and down the BLVD? I have the HIPO manifolds on my 331, and the car is a SCREAMER! I have these on my car because they look cool and are period correct.

PoppyMod · Apr 23, 2011

HDTony said:
Well I just ordered those after reading all this. and I'm also ordering a 2.5 inch flowmaster exhaust out the back.

Hi,

I think you'll be happy with the choice. I'm running "Z" bar clutch system, TRI-Ys, and 2.5" exhausts. It all fits and runs well.
I'd be interested in the quality and fitment of Doug's Tri-Ys
Happy Motoring!

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