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2.5 Exhaust On A 330HP 327

 
Old 02-03-2019, 10:53 AM
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Originally Posted by 6T2Vette View Post
Good reading, but more specs than I can relate to. From what I could understand, I'm on the right track using 2.5" pipes with a 330ci, with 330HP engine, but 2.25" could work just as well. Don't know about the size of the crossover, but I would think 1.5" would be OK.
Bob
Bob, you are absolutely on the right track. When I dropped the LS in my Defender (sourced from a 2012 Camaro), I spent a lot of time researching before buying a bunch of stainless 2.5” straights and mandrel bends and welding up a custom exhaust using a single Magnaflow Tru-X muffler (internal crossover). A non-mandrel bent 90 degree bend reduces flow by up to 25%. Also, saying that larger diameter equals more power is fundamentally flawed. Your exhaust system should be considered as part of your overall engine build. Some engines really benefit from a more restrictive exhaust, pushing the torque band into the most used rpm range and making the car “feel” more powerful. However, an engine with intake, exhaust and cam shaft parameters that can flow X maximum, will not benefit from an exhaust system that can flow 2X. It would also not achieve its potential if the exhaust could only flow .5X.





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Old 02-03-2019, 10:56 AM
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Originally Posted by Drothgeb View Post
Are you going with stainless or aluminized?
Steel. I'm trying to keep the original semblance. Here's a pic of my new fuel pump that resembles the original. I like the look.
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Old 02-03-2019, 11:19 AM
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Originally Posted by Factoid View Post


Bob, you are absolutely on the right track. When I dropped the LS in my Defender (sourced from a 2012 Camaro), I spent a lot of time researching before buying a bunch of stainless 2.5” straights and mandrel bends and welding up a custom exhaust using a single Magnaflow Tru-X muffler (internal crossover). A non-mandrel bent 90 degree bend reduces flow by up to 25%. Also, saying that larger diameter equals more power is fundamentally flawed. Your exhaust system should be considered as part of your overall engine build. Some engines really benefit from a more restrictive exhaust, pushing the torque band into the most used rpm range and making the car “feel” more powerful. However, an engine with intake, exhaust and cam shaft parameters that can flow X maximum, will not benefit from an exhaust system that can flow 2X. It would also not achieve its potential if the exhaust could only flow .5X.





Thanks Factoid. That's one reason I'm thinking that using 2.5" non-mandrel bent pipes might be OK, but if I do go with 2.25 exhaust, I do want it to be a true 2.25" exhaust and not reduced to 2.0" at the bends. I would like an "X" crossover, but I may have to settle for an "H" which will be OK.
Great looking exhaust by the way.
Bob

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Old 02-03-2019, 11:48 AM
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Thanks, I loved the sound! On my mutant fat boy build I’m going with a 3” exhaust into a Magnaflow (same muffler, but 3”). With the new rear end set up and no spare tire carrier, I should have just enough room.
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Old 02-03-2019, 03:58 PM
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If youre shooting for the original type exh sound no crossover is best but a small H shouldnt alter it much if at all.
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Old 02-03-2019, 04:48 PM
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Originally Posted by 6T2Vette View Post
Thanks Factoid. That's one reason I'm thinking that using 2.5" non-mandrel bent pipes might be OK, but if I do go with 2.25 exhaust, I do want it to be a true 2.25" exhaust and not reduced to 2.0" at the bends. I would like an "X" crossover, but I may have to settle for an "H" which will be OK.
Great looking exhaust by the way.
Bob
Almost NO horsepower gain using either an "X" pipe or "H" pipe vs NO crossover...
In my opinion the TV show "Engine Masters"...is the MOST informative and ACCURATE engine based show on TV!....Mark

https://www.dailymotion.com/video/x5s8nr8

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Old 02-03-2019, 09:28 PM
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2 1/2" exhaust manifolds with 2 1/2" side pipes would eliminate a lot of questions, and was & still is available as it was originally GM equiptment
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Old 02-03-2019, 09:59 PM
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Originally Posted by sidepipe seeker View Post
Almost NO horsepower gain using either an "X" pipe or "H" pipe vs NO crossover...
In my opinion the TV show "Engine Masters"...is the MOST informative and ACCURATE engine based show on TV!....Mark

https://www.dailymotion.com/video/x5s8nr8
I found it difficult to respond to your post, as you're stating as fact the results of your favorite commercial TV show. That's fine. We're all entitled to our opinion, based on our set of facts.
Me, I'll stay with tradition and go with what I know. I have a '56 Chevy with a 300hp 327 and dual 2,25" "H" type exhaust. I love the 327 BelAir with the throaty sound and excellent response with a 3sp with OD. I also have a '55 Nomad with a 300hp 350 with a 2.5" "X" type exhaust. It has a very mellow sounding exhaust. It has a 700R4 transmission. That's cool too. No one looks at Nomads as hot rods. they both have the same cam, and the same 14" Dynomax Super turbos. The BelAir has the same Rams horns as the Vette. The Nomad has Sanderson shorty headers.
My C1 is different from these two. It has a high 385# torque at 3700rpm, 330hp 327 engine. I wanna sit in this car and when I turn it on, I wanna be reminded it is not my BelAir or my Nomad. Sound, vibration and response are gonna do it for me, and right now the "H" pattern 2.5" is gonna help me get that feeling.
Different strokes for different folks Sidepipe. That's what makes this hobby so diverse and fantastic.
Thanks for your input, I enjoyed the video.
Bob
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Old 02-03-2019, 11:12 PM
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Originally Posted by Dennis 613 View Post
2 1/2" exhaust manifolds with 2 1/2" side pipes would eliminate a lot of questions, and was & still is available as it was originally GM equiptment
I have the 2.5" manifolds, but my '62 didn't come with side pipes.
Bob




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Old 02-03-2019, 11:47 PM
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Originally Posted by 6T2Vette View Post
I found it difficult to respond to your post, as you're stating as fact the results of your favorite commercial TV show. That's fine. We're all entitled to our opinion, based on our set of facts.
Me, I'll stay with tradition and go with what I know. I have a '56 Chevy with a 300hp 327 and dual 2,25" "H" type exhaust. I love the 327 BelAir with the throaty sound and excellent response with a 3sp with OD. I also have a '55 Nomad with a 300hp 350 with a 2.5" "X" type exhaust. It has a very mellow sounding exhaust. It has a 700R4 transmission. That's cool too. No one looks at Nomads as hot rods. they both have the same cam, and the same 14" Dynomax Super turbos. The BelAir has the same Rams horns as the Vette. The Nomad has Sanderson shorty headers.
My C1 is different from these two. It has a high 385# torque at 3700rpm, 330hp 327 engine. I wanna sit in this car and when I turn it on, I wanna be reminded it is not my BelAir or my Nomad. Sound, vibration and response are gonna do it for me, and right now the "H" pattern 2.5" is gonna help me get that feeling.
Different strokes for different folks Sidepipe. That's what makes this hobby so diverse and fantastic.
Thanks for your input, I enjoyed the video.
Bob
H pipes were never intended for additional horsepower but rather to balance out the exhaust from left and right banks to give a quitter more pleasing sound rather than the back down rap it has without it. Any h.p. gain derived no matter how minimal from it was just a bonus.
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Old 02-04-2019, 12:27 AM
  #31  
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Originally Posted by 6T2Vette View Post
I found it difficult to respond to your post, as you're stating as fact the results of your favorite commercial TV show. That's fine. We're all entitled to our opinion, based on our set of facts.
Me, I'll stay with tradition and go with what I know. I have a '56 Chevy with a 300hp 327 and dual 2,25" "H" type exhaust. I love the 327 BelAir with the throaty sound and excellent response with a 3sp with OD. I also have a '55 Nomad with a 300hp 350 with a 2.5" "X" type exhaust. It has a very mellow sounding exhaust. It has a 700R4 transmission. That's cool too. No one looks at Nomads as hot rods. they both have the same cam, and the same 14" Dynomax Super turbos. The BelAir has the same Rams horns as the Vette. The Nomad has Sanderson shorty headers.
My C1 is different from these two. It has a high 385# torque at 3700rpm, 330hp 327 engine. I wanna sit in this car and when I turn it on, I wanna be reminded it is not my BelAir or my Nomad. Sound, vibration and response are gonna do it for me, and right now the "H" pattern 2.5" is gonna help me get that feeling.
Different strokes for different folks Sidepipe. That's what makes this hobby so diverse and fantastic.
Thanks for your input, I enjoyed the video.
Bob
The reason it's my Favorite Auto TV show is based on the FACTUAL evidence!!...I believe in Dyno numbers that are Replicated from Exacting parameters ....your mileage may vary!...

I built and fabricated a FULL custom exhaust for my 1991 Ferrari Testarossa.....seen/heard at 2:10 & 2:24 of the video...so I'm Not a neophyte at "Custom Exhaust Systems"....Mark


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Old 02-04-2019, 12:31 AM
  #32  
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Originally Posted by LouieM View Post
The best muffler shop in the Bay Area is, surprisingly, this Meineke shop in Redwood City. Lupe, the owner, is a natural wizard with exhaust systems. I had a hard time believing this at first, because the shop's in a mediocre neighborhood. I couldn't get my Super Turbos to quite fit on my 67 Vette, and neither could other shops, but Lupe got it right. Lupe is a dedicated first-generation Mustang fan but likes all classic cars. He can do anything you want with an exhaust system, he is a perfectionist.

https://www.yelp.com/biz/meineke-car...r-redwood-city

Lou
I second this reccomendation, Lupe has done nice work for me. Reminded me of when I use to live in a small town and shops really cared about the customer and the results.
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Old 02-04-2019, 01:43 AM
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Interesting thread. last year, about 3 of my customers bought my chambered mufflers & ended up returning them to me because they could not find a muffler shop that could custom-bend pipe! I can hardly believe this, but it must be true. All I can say is any muffler shop that does not know how to bend pipe & build a system is a ***** - just parts changers. Scary thought that bending exhaust pipes is becoming a lost art.

Also, muffler shop bends are called compression bends, & honestly I do not believe there is very much loss in HP or performance in these vs. mandrel bends. Another couple things discussed were the differences between 2" flowpath & 2.5" flowpath - comments made that there was not much difference. There is actually quite a big difference in flow between these diameters. From 2" to 2.25" alone is quite significant. Between 2.25" & 2.5" there is not a huge difference. Personally on any V-8 exhaust, I would start at 2.25" diameter & use 2.25" or 2.5" diameter up to 485 HP. Beyond that, stepping up to 3" duals can make sense. On the comment of OE C2 sidepipes & systems in 2.5" diameter, still if you cut an OE chambered system open you'll find a MUCH smaller inner diameter of the core - like 1-5/8". Now THOSE are very restrictive!
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Old 02-04-2019, 02:27 AM
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Originally Posted by 68hemi View Post
H pipes were never intended for additional horsepower but rather to balance out the exhaust from left and right banks to give a quitter more pleasing sound rather than the back down rap it has without it. Any h.p. gain derived no matter how minimal from it was just a bonus.
I agree 100% on your HP summation. I'm not sure about the sound level. You could be right. My question on the crossover was the size necessary. Will it matter on the cam being used?
Bob
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Old 02-04-2019, 03:02 AM
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Originally Posted by sidepipe seeker View Post
The reason it's my Favorite Auto TV show is based on the FACTUAL evidence!!...I believe in Dyno numbers that are Replicated from Exacting parameters ....your mileage may vary!...

I built and fabricated a FULL custom exhaust for my 1991 Ferrari Testarossa.....seen/heard at 2:10 & 2:24 of the video...so I'm Not a neophyte at "Custom Exhaust Systems"....Mark

https://www.youtube.com/watch?v=_UQkr_x-Y9k
I'm posting a photo of the FACTUAL evidence provided by a dyno shop of the average of three tests done on my engine. They used headers for the test. I plan to use the original 2.5" manifolds so I'm looking to Replicate or improve the numbers they got.
You should have used your mileage to provide your opinion rather than a critique of your favorite TV show that spent half their time promoting an oil brand and someone's straight through mufflers.




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Old 02-04-2019, 03:15 AM
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Originally Posted by 6T2Vette View Post
I'm posting a photo of the FACTUAL evidence provided by a dyno shop of the average of three tests done on my engine. They used headers for the test. I plan to use the original 2.5" manifolds so I'm looking to Replicate or improve the numbers they got.
You should have used your mileage to provide your opinion rather than a critique of your favorite TV show that spent half their time promoting an oil brand and someone's straight through mufflers.


I am at a loss to find the correlation of your posting of a dyno printout as it relates to the testing of any gains that the use of an "X" pipe vs an "H" pipe vs No crossover has...
Now "if"....you had a dyno printout showing "Your" engine being dynoed for a possible horsepower gain using an "H" pipe...a "X" pipe ...and No pipe....THEN you would have something to compare!...Mark
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Old 02-04-2019, 08:25 AM
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Originally Posted by 6T2Vette View Post
I'm posting a photo of the FACTUAL evidence provided by a dyno shop of the average of three tests done on my engine. They used headers for the test. I plan to use the original 2.5" manifolds so I'm looking to Replicate or improve the numbers they got.
You won’t have the power you had with long tube headers using the 2.5” exhaust manifolds. When you had the engine on the dyno, it would have been an interesting test do some pulls with the headers, then some with the exhaust manifolds.
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Old 02-04-2019, 12:06 PM
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Originally Posted by Drothgeb View Post


You won’t have the power you had with long tube headers using the 2.5” exhaust manifolds. When you had the engine on the dyno, it would have been an interesting test do some pulls with the headers, then some with the exhaust manifolds.
I agree. When I was having the engine redone, I had the compression dropped to 9.6 - 9.8 using new flat topped pistons. If I remember correctly the machinist told me this might drop my HP to less than 300hp. I told him I wanted my HP at 1hp = CI minimum. We worked on it using the flat topped pistons, hydraulic roller cam with roller tipped rockers and massaged double humped heads. The results with .030 over bore was 330ci with 330 horse. The results they gave me was the average of three tests. I asked him if they had used my manifolds, and he told me they had used their own headers. I should have insisted for a test with my manifolds...dang it. I might go back and have it redone once the 'Vette is on the road, but it's not as important now that I got the results I wanted. I asked the machinist for their opinion on the drop in HP and I'm waiting for answer. You've piqued my interest. Thanks.
Bob
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Old 02-04-2019, 12:16 PM
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Originally Posted by sidepipe seeker View Post
I am at a loss to find the correlation of your posting of a dyno printout as it relates to the testing of any gains that the use of an "X" pipe vs an "H" pipe vs No crossover has...
Now "if"....you had a dyno printout showing "Your" engine being dynoed for a possible horsepower gain using an "H" pipe...a "X" pipe ...and No pipe....THEN you would have something to compare!...Mark
No one on this thread implied any gain with either crossover. You provided the video that disputed any gain. If you did this as an FYI, thank you. I appreciate it.
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Old 02-04-2019, 02:17 PM
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Originally Posted by Drothgeb View Post


You won’t have the power you had with long tube headers using the 2.5” exhaust manifolds. When you had the engine on the dyno, it would have been an interesting test do some pulls with the headers, then some with the exhaust manifolds.

OK, my machinist just told me they used 5/8" long tube headers and the dyno people said I'd lose about 5.0% which would knock down my HP to about 315hp. Their recommendation is to go with 2.5" max, 2.25" min.
Bob

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