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Exhaust test to end all tests?

Posted By Ted 13 Years Ago
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ScottY
Posted 13 Years Ago
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           Thanks all for your comments/replies, the use of round pipe was never in question, it was the point of using a "square" port flange and re-shaping the pipe to suit. Why all the extra effort, when the relevant sized tube for the port would be so much simpler/cleaner. When in dedicated racing use, more often than not, that is exactly what is done. Now I realise horses for courses, which brings me back to the line of thought, that there must be a valid advantage/reason. Sorry if I seem dumb, or sound like a broken record, but could try explaining again.                                                           

                                            Thanks again, Scotty!

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Ted
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Scotty (3/30/2011)
Thanks all for your comments/replies, the use of round pipe was never in question, it was the point of using a "square" port flange and re-shaping the pipe to suit. Why all the extra effort, when the relevant sized tube for the port would be so much simpler/cleaner. When in dedicated racing use, more often than not, that is exactly what is done. Now I realise horses for courses, which brings me back to the line of thought, that there must be a valid advantage/reason.
Looks like I’m going to do another of those lengthy explanations here. For the most part, if you can put a dollar sign to the question, you’ll find the answer. In this case, it costs much less for the header manufacturer to utilize round ports at the header flange as these are much easier to produce than the ‘square’ ports at the flanges. That’s the dollar sign answer.

.

But the essence of your question boils down to laminar flow versus turbulent flow at the exhaust port exit. With a round header port matching up to a square exhaust port at the head, there will be more turbulent flow at that point and part of that is due to ‘eddies’ that are being produced at the edges of the port. Those ‘eddies’ come about due to the extreme irregularity of the two different shaped ports being mated up to each other. When both the exhaust port and the header/manifold are similar in shape, then the flow becomes more laminar and as such, overall flow potential is increased simply due to the reduction of eddy currents in the air flow where the header meets the head.

.

Besides the flow properties of a square or rectangular port on the head going to a similar shaped port on the header being an improvement over that of a round port, space utilization at the exit area on the head with a square or rectangular port is also better. An example is a 1.625” round port will have a square surface area of 2.074 inches. A square port that’s 1.44” X 1.44” will have the same cross-sectional flow area at 2.074”. Although the cross-sectional areas are the same, the non-round shaped port will have a greater flow capability than the perfectly round port.

.

On the stock heads, round ports at the headers are typically not a serious detriment in regards to flow obstructions or gasket sealing as the corners of the ports on the heads are still within the boundaries of the round port at the header. When increasing the head exhaust port sizes beyond stock, then the outside boundary of the round header port size can be exceeded which makes for a flow inhibiting obstruction for the exhaust to make its way past. At this point, the square ports become a necessity if the ports at the heads retain the overall square configuration.

.

I’ll also add that the exhaust port gasket sealing area on a rectangular head exhaust port is substantially increased when using a similar shaped header port. Going to a round port on the exhaust manifold or header where the head port exit is rectangular will minimize gasket sealing on the vertical and horizontal centerlines at the edge of the ports.

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Here’s a link to the thread showing some various ports and how the gasket sealing area is affected when doing a rectangular versus round port at the head. Obviously with a round port at the head, it’s also going to take a round port at the header as it would be a monster sized square port to compensate for the round port size.

http://forums.y-blocksforever.com/Topic46226-3-2.aspx

Lorena, Texas (South of Waco)


ScottY
Posted 13 Years Ago
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Hi There Again Ted,

                    Thanks very much for your extra time in rehashing my question. that is much appreciated I assure you. Your answer is pretty much along the lines i had in mind also, but couldn't quite  rationalise it to myself. so again, thanks. Also, how did those heads ported to round exhausts perform on your tests? I had a bit of a search for it but didn't find it. As Aussie Bill said he had done that back in the day, so to had an Uncle of mine, though not on a Y-Block.

                    Hope all is well with you n yours, and another congrats on the EMC Project, fantastic result!

                                                                                                                                        yours Scotty!

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Y-BLOCKS ROCK!!!!!

jardine
Posted 13 Years Ago
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Ted has hit the nail on the head as to port match. The whole anti reversion theory is simply a band aid for a screwed up header to start with. How much time and money do you spend to blueprint the intake to head? The same should apply to exhaust port. It's even more critical as the exhaust pulses are traveling way faster. This week I'm building a set of headers on a 632ci drag car. The customer supplied the flanges with a 2.5" round port. The port is actually happy with a 2" tube. I spent a lot of time sleaving it down to 2". The collector is 2 3/8". The 2" at the port cones out to 2 1/4".

Thanks,

Jerod.


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Ted
Posted 13 Years Ago
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ScottY (4/7/2011)
........ Also, how did those heads ported to round exhausts perform on your tests? I had a bit of a search for it but didn't find it. As Aussie Bill said he had done that back in the day, so to had an Uncle of mine, though not on a Y-Block.
That particular pair of heads with the round exhaust ports exhibited middle of the road performance gains when tested against other heads with conventional exhaust ports.  Here's the graphs showing how that particular set of heads did with three different sets of headers.

   

Lorena, Texas (South of Waco)


ScottY
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Thanks again Ted,

                    Reasonably impressive wouldn't you say Though well up there in rev range, and I would assume to though, that all these headers had the square port flanges still wouldn't they, and if so, surely none would have been large enuff to uncover/restrict, the ports?

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Ted
Posted 13 Years Ago
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ScottY (4/10/2011)
......I would assume too though, that all these headers had the square port flanges still wouldn't they, and if so, surely none would have been large enuff to uncover/restrict, the ports?

The fenderwell headers were the only set of headers of the three sets used in the round port head test that actually had round ports at the header flanges.  The round ported heads themselves were actually ported back in their day to match up to this particular set of headers.  The EMC and Sanderson headers have rectangular ports that were actually smaller than the ports at the heads and as a result, both sets had some flow obstructions taking place as a result of the mismatch at the heads.  But to look at the torque graph, the EMC headers outshined the other two sets of headers in the lower rpm band regardless of the port mismatch.

 

But as usual, there’s much more happening here than just a head to header flange port mismatch. The large dip in torque seen with the fenderwell headers has since been attributed to the collector size on that particular set of headers as being way too large.  Had this been recognized at the time of the round port head test, the fenderwell headers would have performed much better with downsized collectors.

 

Since doing that particular cylinder head test, the fenderwell headers have been tested again with a different set of heads on the engine but also with collector extensions that brought the collector sizes down from 4” to 3”.  With that change, much of the pronounced dip that was evident with the 4” collectors was removed from the lower rpm band of the curve.  Here’s the torque graph where the round ported fenderwell headers were tested on the mildly ported G heads that have rectangular exhaust ports.

 

Lorena, Texas (South of Waco)


pegleg
Posted 13 Years Ago
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Now THAT'S interesting! the mufflers did just exactly the opposite of what my intuition would have expected. More top end HP (TQ) and lower readings in the midrange. Splain that Lucy.w00t

Frank/Rebop

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Ted
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Gary R. (site member) had very recently shipped to me the latest Reds header offering for the ‘55/56 car chassis.  This new header is a four tube header design feeding into a very short 2½” collector.  Overall it’s still a shorty header but fares much better than the older two tube version that was tested.  Scoring is still calculated starting at 2300 rpms and ending at 5500 rpms.  I’ll add that this is also the best scoring chassis header that is designed to fit into the mid-fifties Ford cars.  All the other headers that outscored this particular set are either race car or dyno specific.  Here are the detailed results for this particular header. 

 

Reds 55/56 car 4 Tube 1.625” headers

Score

Peak

HP

Peak

TQ

Avg

HP

Avg

TQ

Mufflers

2” pipes 68” long w/mufflers

1690

287

338

231

313

Yes

2” pipes 66” long w/ no muffs

1730

290

344

236

321

No

2” pipes 24” long w/ no muffs

1726

303

344

237

319

No

 

2½” pipes 75” long w/mufflers

1729

292

345

237

320

Yes

2½” pipes 75” long w/ no muffs

1753

295

347

240

325

No

2½” pipes 28” long w/ no muffs

1746

307

349

240

322

No

2½” pipes 20” long w/ no muffs

1740

309

343

239

321

No

2½” pipes 12” long w/ no muffs

1721

304

332

236

318

No

 

 

And here is the revised chart showing the ‘best’ score for each exhaust system tested thus far. Keep in mind that the best score does not necessarily produce the best peak horsepower or peak torque values.

Description.

Score

Peak

HP

Peak

TQ

Avg

HP

Avg

TQ

Mufflers

Testing configs

Single exhaust with crossover pipe

1484

239

303

202

276

NO

2

1955/56 Dual Exhaust manifolds

1629

274

327

223

301

NO

4

Reds/Hedman two tube headers

1635

278

327

224

302

NO

3

1957 Dual Exhaust manifolds

1650

279

330

226

305

NO

4

Fenton cast iron manifolds

1663

282

332

228

308

NO

2

Tri-Y stepped shorty Tbird headers non-firing order specific - GB

1675

294

332

230

309

NO

4

Ram Horns w/2”into 2¼” pipes

1683

283

337

230

312

NO

2

Shorty 1.625” w/box collectors - DC

1693

284

336

231

314

NO

1

JC 4 tube car chassis shorty headers

1739

296

347

238

322

NO

6

Tri-Y pickup headers firing order specific-CC

1739

297

347

238

322

NO

5

Sanderson 1½” T-Bird headers w/2½” pipes

1751

297

350

240

324

NO

11

Sanderson 1½” Pickup headers w/2½” pipes

1751

300

350

240

324

NO

5

Reds 1.625” 4 tube hdrs for 55/56 car

1753

295

347

240

325

NO

8

Fenderwell headers 1.75” tubes - MW

1768

306

344

242

327

NO

5

Fenderwell headers 1.625” tubes

1769

308

346

243

327

NO

5

KC 4 tube Maxton Mile 1 5/8” headers

1775

310

351

244

328

NO

4

Rdstr 4 tube 1.75” gattling collector hdr

1778

309

355

244

329

NO

2

EMC headers 1.75”/1.875” stepped

1780

310

349

244

329

YES

4

FPA T-Bird hdrs 1.625”/1/75” stepped

1780

311

342

244

329

NO

13

 

Lorena, Texas (South of Waco)


Ted
Posted 13 Years Ago
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pegleg (4/16/2011)
Now THAT'S interesting! the mufflers did just exactly the opposite of what my intuition would have expected. More top end HP (TQ) and lower readings in the midrange. Splain that Lucy.w00t
Frank.  Those are the headers designed for the EMC competition and these actually work best with the mufflers in place.  Part of this has to do with the muffler inlet/outlets being larger than the actual collector size.  There is a 3” merge collector inside the 3½” header collector and the muffler sizing is 3½”.  This particular header and muffler combination ends up being a very nicely tuned exhaust system for the dyno and has thus far worked very well on a multitude of different Y combinations.

Lorena, Texas (South of Waco)




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