The exhaust testing results were published in the Nov-Dec 2020 issue of The Y-Block Magazine. There were some additional tests in that article that were not published in this particular thread. Because this thread was quite old, the pictures of the various exhausts did not transfer when the website changed servers. The article as it was published in the YBM has been made available on the Eaton Balancing website. Here’s the link.
Y-Block Exhaust Testing
Have now completed running an assortment of headers and exhaust systems on the 312 dyno mule. The mule engine is the same +060 over 312 that’s been used in a variety of other tests. Specifics for this engine are cast pistons being 0.025” in the hole, ECZ rods, a Crower Monarch camshaft with 238° dur @ 0.050” and 0.459” lift at the valve after lash, an unmodified Mummert intake, and 750cfm Holley on top of a 2” carb spacer. A set of mildly ported G heads that have been heavily milled brings the compression ratio to 9.6:1 . Originally being unposted G heads, a pair of posts were installed into each head prior to using them for this series of tests. With the mill and the porting, these heads were roughly worth 18HP over a set of stock G heads that had a measured static compression ratio of 9.2:1. With the mild port job, consider these heads a Stage I port job. There’s over 300 dyno pulls now on the mule engine and the bottom end is still holding up fine other than the rear main has started leaking. Although the oil from the rear seal is not pouring out, it’s enough to remind you that this engine is now marking its territory.
Mufflers were tested on most of the exhaust combinations and only with the EMC headers did the HP & TQ numbers actually improve with the addition of mufflers. All other systems did not particularly like the mufflers. Different inlet sized chambered mufflers were used and which ones being used was determined by the exhaust sizing going into them. The test range for this series of tests was 2300 to 5500 rpms. The test range was lowered down to 2300 rpms for the exhaust system testing to get the engine rpms down to that critical lower rpm range that would be seen on a daily driver. Many of the exhaust systems were tested with varying extension pipe lengths and with & without mufflers.
For simplicity while also providing a quick overview of how each system performed, here’s the charted summary based on the best score for each system that was tested. Scoring is calculated by adding the average torque and horsepower for the test range, multiplying by 1000 and dividing by the cubic inch. I’ll add that the best score didn’t necessarily give the best peak HP or TQ values but scoring does gives a better indication of how the ‘as tested’ exhaust system will work in regards to overall performance. On this chart, the peak HP and peak TQ values are those that belong with the score while the ‘Testing configs” column tells how many variants of that particular exhaust system were actually tested.
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 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 |
Sanderson 1½” T-Bird header w/2” pipes | 1724 | 290 | 346 | 236 | 319 | NO | 4 |
Sanderson 1½” T-Bird header w/2¼” pipes | 1726 | 289 | 346 | 236 | 320 | NO | 4 |
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 header w/2½” pipes | 1751 | 297 | 350 | 240 | 324 | NO | 3 |
Sanderson 1½” Pickup headers w/2½” pipes | 1751 | 300 | 350 | 240 | 324 | NO | 5 |
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 |
EMC headers 1.75”/1.875” stepped | 1780 | 310 | 349 | 244 | 329 | YES | 4 |
Unfortunately the individual numbers don’t tell the whole story. The torque curves could be manipulated with different lengths of exhaust pipes or the point in which the muffers were inserted into the system. I’ll work on some graphs down the road which will better illustrate this.
A big Thank You to all of you that contributed parts or pieces for this exhaust test. For those of you that sent manifolds or headers for testing, email me and let’s work on getting those pieces back to you. My email address is under contact info at the following site: www.eatonbalancing.com
Lorena, Texas (South of Waco)