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Old 07-16-2022, 07:46 PM
ta-kid ta-kid is offline
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Default 1974 Log manifold exit size large enough for a 2.5 inch

Got a stock 1974 350 with 1970 #11 heads on it.I an assuming they reused the 74 exhaust manifold logs when the heads were changed which are proably the same as a 70 exhaust manifold.Anyways there is a 2 bolt flange collar sealing a 2.25 stock exhaust down pipe to the manifold and it looks like no donut, just a pipe seal.
I have a pair of mandrel bent 2.5 inch head pipes ,originally for RAm Air manifolds that I would like to install on the log manifolds.I will need new 2.5 inch collars but wondering if these pipes will be too big for the log exits to seal the same way or will I need a 2.25 donut to seal it ?I am assuming again the a 2.25 donut will be a tight fit in a 2.50 pipe.

  #2  
Old 07-17-2022, 07:47 AM
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J GLASGO J GLASGO is offline
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We have taken a 1 inch 2 1/4 piece of flanged pipe and dropped it in the 2.5 pipe

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Old 07-17-2022, 10:20 AM
ta-kid ta-kid is offline
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Yes I thought of that but requires welding , but not a big deal to get done. Was just trying to avoid that and do it myself at home if there was another way but all options still open.

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Old 07-18-2022, 06:48 AM
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No weld necessary

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Old 07-19-2022, 07:43 PM
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Maybe someone else can verify, but I don't think Ram Air downpipes can be used on log manifolds. The Ram Air manifolds exit lower than the logs. The RA pipes won't reach the log outlet.
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Old 07-23-2022, 09:39 AM
SD455DJ SD455DJ is offline
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Pypes make 2.5" mandrel bent headpipes for the exhaust logs that we've used quite a few times. They do neck down at the flange to 2.25" i.d., but that is still larger than the 2.0" and 2.1" log manifold openings. You can grind the openings to 2.20" to 2.25" for a little hp gain, but don't remove all your flange seat. you want to keep at least a solid 1/16" minimum to seal well (no donuts required).

Dennis
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