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post #1 of (permalink) Old 12-18-2002, 10:46 AM
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351W Intake Problem

I started up my '85 Bronco yesterday to a rather loud noise. It mostly sounded like a cracked exhaust manifold but when I tracked down the problem I noticed a hole/port in the intake manifold was not covered anymore. There is a hole just to the driver side of the carb in the intake manifold about 1" dia. (maybe 20-25mm). It is about 1.5" from the edge of the manifold where there are two bolts. I found the remains of some brittle plastic that looked to be the size and shape of a plug that would fit the hole. What's this hole? How can I fix it? Is this a fire hazard or otherwise bad for the truck if I drive it like this? Thanks for your help.

Chandler, AZ

'85 Bronco
~150,000 miles
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post #2 of (permalink) Old 12-18-2002, 12:17 PM
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Re: 351W Intake Problem

A little more info. The carb is an Edelbrock. I'm getting it figured out here.
I guess with the stock setup you'd have an exhaust crossover assembly at
that hole for the EGR. The Edelbrock carb is a bit wider and the linkage gets
in the way of that assembly. I guess most people just plug the hole with a
freeze plug. I still have a question though. Down in the hole it looks like there
is a "cup" slightly smaller than the hole which will wiggle slightly. I can't tell if
it's rigidly attached or may be part of the former plug. Should there be anything
down in this hole?

post #3 of (permalink) Old 12-18-2002, 07:44 PM
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Re: 351W Intake Problem

Sounds like someone tried to put in a freeze plug and, when they knocked it thru, put in a plastic plug.
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post #4 of (permalink) Old 12-18-2002, 07:46 PM
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Re: 351W Intake Problem

yup auto zone sells them cheap , metal or rubber
post #5 of (permalink) Old 12-18-2002, 08:00 PM
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Re: 351W Intake Problem

That "hole" is part of the carb-heat circuit.
I wouldn't install a rubber plug in there, cause that's an exhaust crossover passage.
You're referring to the noted hole (red arrow) in the following pic?

You could machine a nice cover for it, instead of plugging it.
Just make sure you use a high temp gasket, get longer bolts, and torque them properly, if you go that route.

<font color="blue">Steve</font color>'s correct.
I'm thinking that could be someone's plug gone awry, or.......
it could be a nasty chunk of carbon stuck in there. [img]images/graemlins/shocked.gif[/img]
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