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Old 01-04-2019, 01:22 PM   #1
Dibdob62
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Which Manifold and Carb

Just got this 77 GMC C15 and it was running like a bag of ****, The carb had an allen key stuck through the choke linkage and it didn't look like it was the right manifold to go with it so I pulled the lot off.


The holes that are circled are blocked with something, not sure what ?


Any wasy ive been given another manifold and carb (the clean one off a 1969 C10) but they are slightly different but I think it will fit.

Could someone advise me as to which manifold would be best ? Also the carb ive been given doesn't have the pipe coming out the back for the brake servo, How can I get around this ?
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Old 01-04-2019, 02:46 PM   #2
truckster
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Re: Which Manifold and Carb

That big fitting right in front of the distributor is for the brake vacuum.
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Old 01-04-2019, 04:04 PM   #3
Dead Parrot
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Re: Which Manifold and Carb

Looks like a PO got a intake gasket set that did an EGR delete by blocking those passages. The EGR is that smashed round thing on the #6 intake port. Assuming you don't have to worry about emission compliance, the clean intake will work.

As already mentioned, you can use the manifold vacuum port between the distributor and carb mount for your brake vacuum source. Some plumbing modifications required. Depending on the carb you have, you might be able to get a spacer that includes a factory type port for your brake.

Many aftermarket gasket sets will encourage you to block off the exhaust crossover ports, 'for performance'. If you are building this as a normal daily driver type street setup, you probably want some crossover flow. Also research the THERMAC system. Both help with carb icing, something that happens in cool damp air. Could be one of the reasons your truck was running like a *********.

That older manifold will need either a oil fill tube or plug for the front hole in front of the t-stat port. Think it is a press in fit. The newer ones moved the oil fill to the valve covers. Personally liked the older style better, a lot easier to add oil.
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Old 01-04-2019, 08:43 PM   #4
kwmech
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Re: Which Manifold and Carb

What other modifications are you doing to this?
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Old 01-05-2019, 05:16 AM   #5
Dibdob62
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Re: Which Manifold and Carb

Quote:
Originally Posted by kwmech View Post
What other modifications are you doing to this?
Just trying to get her running right and sort all the stuff that need sorting so I can get it registered over here in the UK then I will look at lowering it
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