Felix C

I was reading a few posts and Tri-Ys seem popular as do 1-5/8" ID primary tubing.

Also saw this header test from 2005:

This is reproduced from a Headers Test Carried out by Sams Performance, Sydney, Aus. for a magazine couple of years ago:-

.....................Un-tuned...........Tuned
Pacemaker......hp lbs/ft..........hp..lbs/ft

1.5" Tri-Y.........339 349.......... 364 373
1.625" Tri-Y......353 357.......... 370 379
1.5" 4>1 ..........309 341.......... 364 379
1.375"..............339 354.......... 360 374
1.625" 4>1........349 355.......... 368 378
1.75" 4>1.........340 344.......... 371 381


Sams Brand XX

1-5/8 t-y&2.5"....352 358........ 376 383
1-5/8 4>1..........344 354........ 374 380

Genie

1-5/8 4>1..........347 353....... 368 377
1-5/8 Tri-Y........345 355........ 374 382

HM Headers

1-5/8 & 2.5........349 355......... 370 379
1-5/8 & 2.25......343 352........ 372 381

Hurricane

1- Tri-Y.........346 356......... 363 375
1-5/8 Tri-Y.......350 358......... 369 380

DiFilippo
4>1..................343 356........ 374 381

HSV
4>1..................340 349........ 365 373

CAPA
4>1 .................356 356........ 371 377

Wildcat
1-5/8...............346 353........ 370 376

Advance
1-5/8 T-Y.........355 358........ 373 382

Hi-Tech
1-5/8...............352 357........ 372 380

Std Manifold
.....................347 349........ 367 372

NOTE:] A bog stock LS1 out of a 2001 VX series I Commodore with 30,000kms on the clock was used. It had the P.A.S. pump, alternator, a-c compressor and water pump fitted & operational. Along with the complete stock intake system and a full road-going 72mm twin exhaust system with identical layout (same type of offset as fitted to the car) mufflers.
The knock retard was limited to a maximum of 4 degrees total.

We do not do Tri-Y nor 1-58" tubing here for the GTO,(nee' Monaro), typically 1-3/4" and 1-7/8" for heads+cam upgraded ones. Due to use in the F-body and Corvette.

Jase01

G'day mate,

I'm familiar with that test but not fully, I might be wrong but I think it only showed the peak numbers on the stock engine, not graphs or tables of power through the range which is what I'd prefer to see.

I would say that most over here in Aus with LS1 powered Monaros/Commodores would probably use 1 3/4" 4 into 1 with a dual 2.5" or possibly 3" aftermarket exhaust system and some form of high flow cat converters. Some go the 1 7/8" header but probably more so with the bigger 6 and 6.2 litre LS variants, no where near as many as in the U.S from what I can gather though. The 1 5/8" do get used a bit but I think the 1 3/4" would be more popular.

I recently swapped 1 5/8" tri-Y's (bought for a stock engine at the time with no plans to mod) to an 1 3/4" 4 into 1 on my now modified LS1 Commodore but I haven't had it dyno'd yet to see what (if any) improvement it makes, hopefully something decent as it wasn't a cheap exercise.

Best wishes,
Jason.

Felix C

Do wonder what the tube and collector sizing on those Tri-Ys was.

Jase01

Which ones specifically?

I think most have 1 5/8" primaries into twin 1 3/4" or maybe 2" secondaries and then a 2 1/2" collector. One company over here used to do an 1 3/4" primary tri Y but they don't list them anymore.

P.S. I did a bit more research on the test you quoted and in the magazine they did show dyno graph comparisons for the different headers but apparently they were very small and not easy to read. I haven't been able to find them on the web anywhere and the links on Sam's Performance web page no longer work.

Jason.

Felix C

I was searching on LS1.com.au and found the above. Posted out of interest.

I use 1-3/4"x3" 4-1 as is typical in the USA.

Used Tri-Y in previous car with lower rpm engine. Made power below 5000rpm