IM STUMPED

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Feb 6, 2013 | 02:42 AM

twwtruck

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Joined: Jul 2007

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From: Ohio

IM STUMPED

ok i got a 78 f250 with a stock 460 i found a good deal and put a victor 460 in take and holley 770 vac secondary carb on.now when i get into in park or with a load it falls on its face. i have downsized jets several times and changed the secondary spring. still same thing no vaccum leaks changed power valve nothing. any ideas??? is the intake just to much for all stock motor?

Feb 6, 2013 | 11:53 AM

cbakker

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Joined: Mar 2011

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From: West Central Southern MN

That might be breathing a little hard for a stock motor. Especially if you have stock heads.

Feb 6, 2013 | 11:53 AM

bigdan1979f-250

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Joined: Apr 2006

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From: mid-MO

You might double check and see if your vacuum source to the carb is a regulated ported vac source or manifold vac port. If you are running off of the manifold pressure, any change in rpm would affect it and change your timing advance. The regulated vac port runs off the carb and is less affected by change in rpm. Not saying it is not affected at all, just not to the extent that the manifold vacuum is. Should be a lot smoother too. So my advice is to make sure you are running off a carb regulated vac source. I dealt with the same problem on my 460 and thats what the problem was, however I have an Edelbrock, but the principle is the same.

Feb 6, 2013 | 11:17 PM

85e150

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Joined: Apr 2004

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I looked up the Victor 460. All I can find are single plane manifolds good for 3500 to 8000 rpms. If that is what you have, take it off. You will never be able to make a stock motor run worth a poop with that manifold.

http://www.edelbrock.com/automotive_.../2000/2966.pdf