CNC 415ci, 412 rwhp, 444 rwtq(?), unknown brand of tri Y, replaced with 1 7/8 long tubes, cam unknown but mild (sounds kinda choppy, but power curve indicates it’s not radical), standard size valves for AFR 220 heads. Engine was spec’d by prior owner.

Probably close in hp to your new engine.

My point is that tri Y headers don’t necessarily mean more low end torque. Long tubes usually win down low, tube diameter effects top end.

 

My point is that appropriately sized tri-y headers vs. a 4:1 with a big cam / a lot of overlap means more low-end torque (anti-reversion props up the torque down low; whether than comes from AR chambers a few inches off of the heads and a traditional header or tri-ys).

1 5/8" headers were way undersized for your motor. You've got way more motor/ HP than me. I'm really hoping for 350 RWHP (440 fly wheel *0.8 (autotrans)).


Adam

 

I’ve never seen a powerful, fast car with tri Y headers.

I agree, 1 5/8” is too small, but a larger tube on a tri Y would only help top end. There is no tri Y solution for my engine that would make more power anywhere in the powerband versus properly sized long tubes.

I’ll just add, that when I replaced the tri Y with ARH headers, my engine stopped fouling plugs. I believe it was due to far better scavenging by using a better header. IMO

You need a set of stainless 1 3/4” headers. 1 5/8” long tubes would work too, but would shift your power band down some.

 

You've never watched Winston Cup NASCAR?!?

Calvin Elston is undisputedly one of the best professional header builders on the planet and was behind many Winston Cup-winning teams starting in 1996 (That Dale Earnhardt guy, that Jeff Gordon guy & Hendrick Motorsports, etc...); he's also the co-developer of the merge collector.

His direct quote on Tri-Y headers: "Done correctly, they are a better header for anything operating under 8500 rpms as a general rule." (The higher the RPM, the shorter primaries and total header length; obviously none of the off-the-shelf tri-ys are made for even close to this RPM, though.) He's clarified his statement that he feels that TRI-Ys would continue to be better beyond that RPM, it's just that it's not physically possible to build them short enough to reach higher RPMs.


http://elstonheaders.com/


Adam

 

I have 1 5/8" coated long tubes currently, but with 3" collectors and they're pretty "blah" headers with pretty crappy coating but they were stupid cheap, at least.

Calvin Elston has essentially his own "school" of thought on headers. It's essentially that exhaust VELOCITY is king; it's kind of an exhaust version of what we see on intake ports in the best modern 23 degree SBC heads where the focus is on VELOCITY and is pushing back on the "an engine's just a dumb air pump" philosophy. He talks about "blowdown length" a lot -how far you can shoot the exhaust gases down the header tubes before reversion starts to try to suck it back into the engine. You get more blowdown length when you have a higher velocity out of the head- the smallest tube possible at the head for your power level is how you do this.

Calvin can make 550 HP in a broad powerband with 1.5" OD tubing and 590 HP in a narrow powerband with that same 1.5" OD tubing. (Because he's doing header steps within at most 10" of the head; Larry Widmer does the same for his extreme Honda engines, too. (Yes, this isn't a normal header.)

When he builds 4:1 headers he's always using a modern merge collector (he buys them from Burns Stainless vs. making his own) but with a shockingly small diameter merge collector to keep the velocity up (same idea as with his Tri-Ys), then he adjusts the primary tuned length for the RPM target.


One of the reasons he PREFERS the Tri-Ys is that they can do their magic in a very broad RPM band because the Tri-Ys don't utilize reflective pressure waves they actually dissapate / attenuate the pressure waves so the header works equally well across the full RPM range.

Cool Calvin Rules of Thumb: "Every 1/8" increase in primary tube size you raise the torque peak 500-1,000 RPM; every 1/2" increase in collector size you raise the torque peak by 250-500 RPM".

Diameter to HP Table for TRI-Ys using the Elston philosphy (shocking #'s really):
§ 1.5″ OD 18ga tubing off a port can handle 430hp in broad powerband, (BP) and 475 in tight powerband, (TP)
§ 1.63″ tubing is good to 550 in BP and 590in TP.
§ 1.75″ tubing is good to 700 in BP and 780 in TP. <---780HP out of a 1 3/4" primary tube?!?!?!
§ 1.88″ tubing is good to 875 in BP and 1000 in TP
2.00″ tubing is good to 1000 in BP and 1200 in TP



Adam

 

Do you race in the Winston Cup?

My point stands, but I’ll add “in the real world” I’ve never seen a powerful car use tri Y headers. The short primaries might be good for extreme high rpm NASCAR, but not Street or drag racing NA engines.

 

You’re WAY overthinking this.

 

[Deleted unnecessary snarky comment that used to be here.]


I never said short primaries would be good for the street; the point of the quote from Calvin Elston is that properly sized and designed tri-ys are better at all RPMs up to 8,500. For typical street builds this includes longish primaries. The benefit is not seen at peak HP but in improved low to mid RPM torque improvement and a broadened torque curve. -This is primarily beneficial on the street. A street driven motor with a big cam or a good bit of overlap and a low stall TC is most likely to benefit from a Tri-Y to support the low to midrange RPM torque.



Adam

 

He may not build Winston Cup motors, but he, like many members of this forum, has experience building and modifying 1968-82 Corvettes.

I switched header brands because of his review (and am very thankful he posted it!).

 

Fair enough. I'm the weirdo who has a hard time weighting anecdotal evidence of something working one time in one instance vs. anecdotal evidence supported by multiple cases and a supporting explanation of WHY.

(If I had two sides of an argument placed before me and one just said "I did this one time and I got result X" and someone else said "I've done this multiple times and I got result Y and this is why I saw this result", I'd probably agree that the 2nd approach was the right one, even if it wasn't. Possibly a flaw in how I evaluate information but it has tended to be right more times than not so I'll stick with it.)

-I realize that theory sometimes doesn't play out in reality but on this issue, I think there's enough evidence that there's a LOT of really poorly matched engine +header combos out there, which skews the results. If you've got a primary diameter and lesser so a primary length that's wrong for your combo, you're going to have crappy results regardless of whether it's a Tri-y or a 4:1.

Getting a header that's well matched to your combo is first and foremost and header type is distant secondary concern, but I'm still convinced an engine with a big lopey cam with lots of overlap will have its bottom-end and mid range torque supported by a tri-y due to better scavenging and the anti-reversion abilities inherent to a Tri-Y / 4:2:1 design. (Yes this first and foremost assuming that the primary diameter and lengths are appropriate; if that's incorrect then you can't come to any conclusions about tri-y vs 4:1.)

There's also this popular urban legend that TRI-Ys can't make power because most of the off-the-shelf old school TRI-Ys are of the small diameter and long length variety. These tri-ys are not making power up top because they're not designed to; not because Tri-Ys just can't make as much power as a 4:1. When you see WINNING Winston Cup engines using Tri-Ys at high RPMs, it becomes blatantly obvious that TRI-Ys can make power and the off-the-shelf Thorley's-style TRI-Ys aren't limiting upper RPM HP simply because their TRI-Ys, it's because their ID or length is inappropriate to support those RPMs at that power level.



Adam

 

99% of time you not at WOT or at max RPM. Those 2 facts alone would negate nay benefit, real or perceived, of try-Y's below 8500.

@6000rpm does any sub 400 cid sbc move enough air to see any benefit from tri-Y's?

 

I'd think the difference between off the shelf and custom headers would play the biggest part. Don't expect to get custom tri-Y header results from off the shelf headers.

 

I'm confused. If the primary benefits of the tri-y is the increased air velocity and decreased reversion at low to mid RPMs (increased low to mid RPM torque) and the fuel economy improvement that results, then why the discussion on high RPMs?

If you're saying that a TRI-Y designed for 8,500 RPM wouldn't help a street engine at normal RPMs and driving conditions, then I agree completely; that would be dumb. But a TRI-Y designed for 6,000 RPM vs. a 4:1 designed for 6,000 RPM, the TRI-Y is going to see more low and mid RPM torque and they'll have the SAME HP at the peak. That's what you want in a street motor- a broad torque peak and people like me want the fuel economy, too.


Adam

 

The bigger question I have is can a tri-Y be built with good primary tube diameter, correct tube length to all the junctions *and* fit inside a C3 frame?

I'd bet in most cases we'd have to go custom to do this - if it's possible at all. The guys that are putting that much consideration into C3 builds are not using stock steering boxes, may not be using stock steering pans, hopefully aren't using stock oil pans, etc.

The budgets and amount of fabrication talent available to a Nascar team greatly eclipses ours.

 

Thanks for the “snarky comment” delete. I’m only trying to help you.

I’ll just say if tri Y headers were the best, the aftermarket would be full of them for sale. You could argue that in a specialized nascar race engine they have some benefit, but we’re talking about a Street hipo engine you’re building.

If you really want the best header for your car, buy a set from ARH, like I did. They have merge collectors, high quality stainless construction, and fit perfectly.

Call them and have a talk, they’ll explain this better than most.

 

Here’s the link to my ARH install. Pics and side by side pics versus the tri Y.

https://www.corvetteforum.com/forums...stall-diy.html

 

Jeepers. The Winston Cup left NASCAR years ago.

 

Unless the Tri-Y you're looking at already has the diameter and length that's appropriate for your combo.

Somewhere I had a quote on a 400-450 HP SBC on the RPM that the Doug Thorley 1 5/8" tri-ys start becoming a restriction (I want to say 4,500 RPM). I had have this number for the slightly shorter Stan's 1 5/8" tri-ys and it was more like 5,500 RPM. (For my build with my long-runner FIRST intake my HP peak is supposed to be at 5,800 RPM, anyway.) Edit for Clarity: I think the Stan's 1 5/8" Tri-Ys are right for the majority of C3 SBC 350s and 383s; for the 350 and lower HP SBCs the Thorleys longer length might be better (but there's fitament issues for some people); I can admit there's not great off-the-shelf TRI-Y options for the 500hp-550hp motors that I've found. At some point the 1 7/8" Thorleys become a good option, but how many people have SBCs that hot and street drive them?

Strokerengine.com has some some residual info on a back-to-back dyno test of a 1 5/8" stans tri-y vs a 4:1 on a 383 (doesn't detail the lenghts, though) and it showed the Tri-Ys beating a 4:1 by 27 ft lbs from 3,600-5,200 RPM and the 4:1 having the advantage from 5,200 RPM to the redline. People have since analyzed the results because he had some weirdness in the lower RPMS up to 3,600 RPM and they're saying that the results were due to overscavening at the low RPMs and sucking fuel out the exhaust. -This can be compensated for by tuning in an EFI motor and the TRI-Y should see improved torque from off idle to that 5,200 RPM.


My build is focused on TORQUE and MPG and trying to get as much HP as I can at 6,000 RPM. IMHO, a 1 5/8" Tri-Y seems to have a significant advantage from idle to 5,000- 5,500 RPM ish even if it'll lose HP from 5,500 to 6,000. I'll happily trade 27 ft lbs from idle to 5,000 for what I lose up top where I'll rarely drive. --If I want the most impressive dyno numbers, I think my current 4:1 would do that, but I still think the torque and MPG advantage of the Tri-Y makes it the way to go.

There's some way bigger and better off-the-shelf Tri-Y headers for the LS motors but our SBCs seem to be able to get either 1 5/8" TRI-Ys or you have to go up to 1 7/8" which would be too big for my 440 FWHP and give up the torque that I want down low.


Adam

 

This makes no sense. Tri-Ys should be an easier fit than a standard 4:1 and "correct" tube diameter and length is dependant upon the output, at 400hp and below 1 5/8" is the right diameter and they're readily available from Stans.

From a fitament perspective TRI-Ys have the added benefit of essentially all being "step" headers so they can start at a smaller diameter near the head where the space is at a premium and then at the first "y" they step up to the next largest size but you've only got 2 tubes vying for 3 dimensional space.


Adam

 

The best doesn't sell. The best marketing and bragging rights and big HP #'s at mostly unused RPMs sells. (You think people buy soft metal Comp Cams sewing machine cams and rebranded springs of questionable origin because they're "Best"?!? You think people buy tiny, tinny Chinese paper cone Bose speakers because they're "best"?!?)

The market largely defines "best" as highest HP at max RPM; the SBC market adds "at the cheapest price" to that demand, so that's what you see in the marketplace.

HP #'s at max RPM sell; ft lbs at low to moderate RPMs doesn't (but should); the aftermarket and especially the historical SBC aftermarket shows people often making TERRIBLE trade-offs to get bragging rights for max HP at the cost of useable, streetable torque.

"An engine is just an airpump; make everything bigger and you'll go faster" -is far too prevalent an opinion. A blunt instrument philosophy for blunt instruments. -The market is asking for the wrong thing, so the market is full of the wrong product for most street motors, IMO.

Ton of motors out there with oversized cams, oversized heads, and oversized headers with lazy bottom ends.

Too many people underthinking it for far too long.


The LS market has a lot more Tri-Ys in lot more diameters and lengths available and the good ones show good gains.

Adam