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396/402 Engine Vacuum Reading

2258 Views 5 Replies 5 Participants Last post by  Jerry70
Hey guys...I recently got a 72 SS 396/402 and my father-in-law and I have been working on the engine. It's a numbers matching car, but someone did a poor tune-up on it sometime before we got it. The question I have for you is---

Does anyone know what kind of vacuum reading we should get on the car in park at idle (700rpm)? It's an air injector reactor engine, if that makes any difference.

I know this is kind of a specific question, and my knowledge of engines is layman at best, but my father-in-law is very good, and he's having a tough time getting this thing tuned...

Any feedback would help immensely, and if I need to provide more info than I did here, let me know...

Thanks again everyone for all of your help...It means a lot to a newbie owner..:)

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I'm bumping this up John, as I truly have no idea what a stock 402 would idle at, other than well north of 10-12" Hg. Check your timing to see if its set at the stock spec, and then change it to 12-15 BTDC, while checking your total advance with the engine at 4000 rpm to ensure it doesn't go much over 40. ( Disconnect the vaccum advance).

I'm guessing the idle vaccum should be 14-17" Hg, but that wont happen unless you have enough timing, and then you can tackle carb tune issues.
Yes, steady or fluctuating reading makes a difference.
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