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Exhaust Tube Sizing: I did your Arithmetic for you!!

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What about trying to achieve a specific sound? The affect of an H pipe, the affect of an X pipe, chambered muffler vs straight through.


Any thoughts on these links?






Is it possible to "tune" the exhaust so that the v8 will sound like a v6? I think so to a point based on the configuration. From what I can tell the 4.3 vs the 5.7 sbc will sound the same with the correct exhaust seeing that a 4.3 is a 5.7 with 2 cyl lopped off. The difference I have found is the larger displacement tends to create a deeper tone.





They give off a similar type of exhaust tone BUT the v8 5.0 is just simply deeper.


That in mind what would one need to make a sbc sound like that 5.0? short headers, and h pipe and a particular muffler? To me it sounded like he used an x pipe because it sounded as if the pulses were equaled out. Seeing that an H pipe was used I would assume that the LSA on the cam was higher in the 112-115+ range making the vehicle idle better.


Personally I am attempting to find the smallest diameter primaries I can use until it chokes the engine, also I am curious on if my plan to use shorter headers for sound alone is going to dis-benefit my motor. The header I found has equal length primaries at 17.5 inches which according to the headers by ed equation is too short with a 1 5/8s inch diameter primary (assuming 1 5/8s inch primaries are as small as I can go with out choking the motor). The recommended size is 34 inches.


The motor is a 333ci motor, 195cc intake ports, team g single plane manifold, the cam will run from 2300rpm-6900rpm.


Any thoughts or suggestions there?


Btw great thread learned more by reading these three pages than I have for the past 3 weeks on the subject.

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Dyno Testing a 260Z - Part 2


This is an analysis based on my dyno testing from yesterday (9-8-12).

Test Parameters


The reason behind testing was to baseline the Nissan Motorsports header/dual pipe exhaust against the stock manifold/single 2.5" that I baselined on page 2. Also tested was the same setup with advanced (from stock) timing, then with air cleaners removed, and finally with EDIS/Megajolt controlling ignition.


The settings are as follows:


  • early 260Z with 1972 L24/E88 that was installed by the previous owner
  • stock cam and internals
  • triple 40DCOE-18 Weber carbs with K&N-style filters (no heat shield)
  • Cannon long-runner manifold
  • Nissan Motorsports header with crush-bent true dual 2" pipes
  • Mobil1 synthetic 10W-30 in engine, Redline 75W-90 in transmission (GL-4) and differential (GL-5)
  • Stock 260Z distributor or Ford EDIS run by Megajolt for ignition

Testing was done at Dito's Motors in South San Francisco on a Dynomite load-bearing dyno. Robert and David are great guys to work with!




Test Settings: Same as page 2, but with a Nissan Motorsport header and 2" twice pipes









SOLID lines are the initial baseline

DOTTED lines show the new exhaust


post-3287-036349600 1347292205_thumb.png


The new setup made a peak of 130.5lb-ft @ 3350rpm and 115.8hp @ 5600 rpm, compared to the initial baseline of 136.3lb-ft @ 4100rpm and 120.8hp @ 5150rpm.




The results are not unexpected, the single 2.5" did better than the separate duals. It is worth to note that the Nissan Motorsport header brought the torque peak down by about 750rpm when compared to the stock manifold and 2.5 pipe setup! This is caused by the header's very long primaries. The powerband feels like a mini-V8, gobs of torque down low, but still likes to rev. However, mid-range torque took a definite hit.

Final Thoughts


The twice pipe system does not have a merge collector, which would give gains across the board. Integrating a merge collector can also shift and improve the torque peak. The next iteration of the engine will be jetting the carbs (more for partial throttle cruise, WOT AFR is 11-12), putting in a more aggressive cam to take advantage of the header and to let the engine breathe better at higher rpm. I'd also like to build a single-pipe system utilizing this header. Eventually, I will build up an L28 to drop in.


Other Notable Data (not exhaust related):

  1. Advancing distributor timing gave peak gains of 2.1lb-ft (132.6lb-ft) and 4.3 hp (120.1hp)
  2. Removing the dirty air cleaners gave additional gains of 3.4lb-ft (136.0lb-ft) and 4.2hp (124.3hp)
  3. Using EDIS/Megajolt to tune the spark curve gave another additional 4.4lb-ft (140.4lb-ft) and 3.6hp (127.9hp)

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Are you saying you were 11-12 AFR's WOT on this pull?

Seems a bit rich-losing a bit of HP there?

Don't give the up the duals man!

Yeah, a bit rich so I'm probably losing a few more horses. I'll try to rejet for 12.5-13:1 AFR and see where it gets me.


Don't worry, the duals will stay for now!140lb-ft at 3500rpm from an L24 on an load-bearing dyno is pretty healthy, nonetheless.:D

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