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#1
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3.5” or 3” slip on collector
Hello everybody I have a question if anyone wants to answer. I have a 69 gto. It has a 428 with 270+cfm 722 heads. It has a old faithful cam with Crower solid rollers. Has a sd performance real ram air IV cnc style ported intake. Max a lite connecting rods with je pistons. 10.5 compression. 4 speed M22w with 3.73 gears. The headers are 1 7/8” Indian adventures headers with 3.5” slip on collectors and a 3” exhaust with x pipe and dynomax ultra flow mufflers. Just wondering if changing to a 3” slip on collector would pick me up some torque? My thinking is first of all the exhaust slows down a bit in the large 3” collector them reduces abruptly to the 3” exhaust. Wouldn’t the stranger flow from the 3” collector to 3” pipes work better? Idk. The car works great but you know how it goes. Can never leave these cars alone.
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#2
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I would bet not much difference. With the exhaust/intake ratio of RAIV heads (85%) and the fact the exhaust side flow as good backwards as out anything that reduces velocity will hurt you. My RAIV 400 picked up going to 1 3/4' headers vs the 2" Hookers and resolved the mild reversion issue I had and being only barely responsive the jet changes. I had 3' front system into 3' mufflers and 2/5 exhaust pipes.
Added a 'reverse split cam and picked up even more! But most folks here disagree that should have worked. 242/236 @ 0.050
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Skip Fix 1978 Trans Am original owner 10.99 @ 124 pump gas 455 E heads, NO Bird ever! 1981 Black SE Trans Am stockish 6X 400ci, turbo 301 on a stand 1965 GTO 4 barrel 3 speed project 2004 GTO Pulse Red stock motor computer tune 13.43@103.4 1964 Impala SS 409/470ci 600 HP stroker project 1979 Camaro IAII Edelbrock head 500" 695 HP 10.33@132 3595lbs |
#3
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There is two ways to gain torque.
1) if you want more off idle torque, then you need headers with longer primary tubes then what you have now. 2) The best way to get a gain in torque from the mid range on up along with a good hp gain will be by converting your headers with what’s called a Merge collector of the diameter that your using now. Merge type collectors due to the higher level of vacuum that they make produce a higher level of VE across a wider rpm range then any standard type collector ever could regardless of size.
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I do stuff for reasons. |
#4
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Quote:
You can do it one of 2 ways. What you have described, removing the slip on 3 1/2" collector and switching to a 3" to match the exhaust diameter. Assuming your engine likes a 3" collector... Or.....leave the 3 1/2" collector, change the X to a Dr. Gas setup with 3 1/2" inlets and 3" outlets. That way the exhaust piping is the same as the collector and it's not reduced until the "X". Doing it this way shows gains over just simply installing a cheap reducer to mate up to the exhaust system. Of course more money and work redoing the exhaust in front of the X crossover. If the 3" slip on collectors aren't overly expensive it's a rather simple change and probably the route I would try since you have that option. 3 1/2" collectors that are not slip on, I use the other method mentioned. |
#5
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I like what you have now I wouldn’t mess with it much.
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#6
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if your timing curve and low speed carb mixture isnt optimum your low end torque output will suffer
your build level is at the point where these things should be looked at and tweeked to find power vrs assuming over the counter or 1969 carburation or timing curves will suffice if you havnt worked them already Last edited by Formulas; 09-07-2022 at 02:07 PM. |
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