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Old 04-30-2024, 10:37 PM
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Odd tidbit about 69 GP exhaust, unlike the GTO which had exhaust selection controlled by a combination of engine determining head pipes (2 1/4” on RA and RA4 engines, 2” on others), mufflers the same on all engines and tailpipes (2 1/4” no resonators on Manual trans and 2” with resonators on automatics) determined by transmission.

The 69 GP exhaust was determined solely by engine. 400-265, 400-350 and 428 370 all had the identical 2” system with resonators but the HO had its own system with 2 1/4 head pipes, the same mufflers and 2 1/4” tailpipes without resonators..

So oddly a 428 HO automatic GP would have big tailpipes and no resonators but a RA4 automatic GTO would have the skinny pipes with resonators, contrary to what you would have expected given the market image of a GP versus a GTO.

Btw, the various tailpipes and resonators interchange between the GP and GTO but mufflers were different as were the headpipes.

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