Choke is On

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Jan 23, 2001 | 06:03 PM

otto

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From: Racine WI

Choke is On

My 75 F-250 Hi Boy with 390 and edelbrock 650 will only run with the choke on and at about 1500 rpm without choke and high idle it runs real rough till it dies like it has no gas i think there is probably a vacuum leak where it bolts to the manifold am i on the right track here or what ?? also did 75 have duraspark or points ???

Jan 23, 2001 | 06:37 PM

karljay

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From: Northern California

Choke is On

I think 75 was the first transistion year for ele ign. Sounds like a vac leak, try running a vac guage. A stock motor should be 17+ vac. Also spray some B12 carb cleaner at the base of the carb, if the idle changes, you have a leak. Could also be idle mix, or both.

Jan 23, 2001 | 08:26 PM

otto

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From: Racine WI

Choke is On

well it must be a late 74 cuz the title says 75 and it still has points and there are no traces that it ever had duraspark

Jan 23, 2001 | 11:38 PM

390GT

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Choke is On

I picked up a 75 390 that had the electronic style rotor.
so i'm guessing you could get it. unless the dude was wrong and it was a 76

Jan 24, 2001 | 03:44 AM

fe4ever

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Joined: Sep 2000

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Choke is On

75 was the year that Ford changed to the Duraspark. If it's an early build date, it will have points. It's easy to change it, (or any year,) out though!

It sounds like you have a vacume leak at either the carb to manifold mounting surface, or the manifold to heads mounting surface. As already mentioned, use spray carb cleaner on the surounding surfaces, (while running,) and see if some place gives you an increase in idle speed! That's where your vacume leak is.

P.S. Also, check the vacume lines coming off the manifold for leaks.

Jan 24, 2001 | 11:26 AM

mattyk6

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Choke is On

The title for my truck indicates that it is a 1975. The door tag indicates that it was built in late 1974, Oct or Nov. And I have points on the truck. That is why I call it a 74. The only change that I know of between 74 and 75 was the change from points to Duraspark Generation I.

Matt
1974 F-250 4x4 Highboy

Jan 24, 2001 | 08:41 PM

rlehman

Freshman User

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Choke is On

When I picked up my 74 F250 this summer there was a huge vacume leak between the gaskets at the back of the carb. New gaskets fixed that but the carb adjustments were all out of wack. I guess the previous owner was trying to compensate for the vacume leak, any way some tweaking of the carb got things back in order.

Bob L