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 Post subject: Egr
PostPosted: Thu Dec 03, 2009 7:01 am 
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4 BBL ''Hyper-Pak''

Joined: Fri Nov 06, 2009 6:52 am
Posts: 30
My plan for my 1987 pickup is to build a stock spec 1976 short block and use the 1987 head, intake and carb. I'll use the pushrods and rocker assembly from the solid lifter engine.

The truck had a functioning EGR system on it. Is there any reason to keep it, or should I leave it off and plug the port in the head? It looks like it would be blocking access to the valve cover.

The '76 head doesn't have the EGR ports , but it would need quite a bit of work to re-use it.


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 Post subject:
PostPosted: Thu Dec 03, 2009 7:10 am 
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TBI Slant 6
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Location: Nashville
Will you be keeping the rest of the lean burn system? If so keep the egr.

Your best bet for better performance AND mileage is to convert the whole ignition system and carburetor to the older style.

If you HAVE to keep the feedback carb and everything was working as well as it could, keep the egr.

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 Post subject:
PostPosted: Thu Dec 03, 2009 7:37 am 
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Supercharged
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Location: SW Washington
EGR passages are in the intake manifold. The passages in the head leading to the exhaust ports are for air injection.

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 Post subject:
PostPosted: Thu Dec 03, 2009 7:39 am 
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The port(s) in the head aren't related to the EGR system, they're for air injection. If you won't be using air injection at the cylinder head (even if you will be injecting air at the catalytic converter, if any), you can block off the system with the factory blockoff plate, part number 3751 249 with gasket 4275 834.

The EGR passages are in the intake manifold — that's where the EGR valve is bolted on. If you won't be running EGR, you can simply leave the valve in place but disconnected, or you can install the blockoff plate 3671 447 with an ordinary EGR valve gasket.

The decision of whether to run or omit EGR depends on what kind of carburetion and ignition setup you'll be running and what kind of emission tests you have to pass with the truck.

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 Post subject:
PostPosted: Thu Dec 03, 2009 8:44 am 
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Turbo EFI

Joined: Sat Feb 19, 2005 9:57 am
Posts: 2090
can also just flip egr and it will block off/not work


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 Post subject:
PostPosted: Thu Dec 03, 2009 10:46 am 
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4 BBL ''Hyper-Pak''

Joined: Fri Nov 06, 2009 6:52 am
Posts: 30
Sorry.
I picked up a hayes manual this morning.
The part i was referring to is apparently a Canadian only piece called an "air aspirator". I had thought it was part of the EGR system.

It says that it is simply a one way valve that lets the exhaust ports suck fresh air during the negative pressure pulses in the exhaust flow.

How would I tell if I have a feedback carburetor? the '87 and '76 units look pretty close sitting beside each other on the bench.

I'm in Canada, and through most of the '80s emission controls wern't really required on light trucks. I had an '86 f-150 with a 300-6 that came from the factory without a catalytic converter and had a large fuel filler that could accept leaded gas nozzles. ( but it was phased out long before then..)


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 Post subject:
PostPosted: Thu Dec 03, 2009 10:56 am 
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twissty wrote:
Sorry.
I picked up a hayes manual this morning.


Haynes manuals are notoriously incomplete and inaccurate; you'll want to get the real (factory) service manual as soon as you can.

Quote:
How would I tell if I have a feedback carburetor?


If there's an oxygen sensor installed in the rear wall of the centre collector of the exhaust manifold, your truck was originally equipped with a feedback carburetor. Yours being a Canadian model, it probably was not.

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 Post subject:
PostPosted: Thu Dec 03, 2009 11:47 am 
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Supercharged
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Joined: Sun Nov 03, 2002 9:20 pm
Posts: 13230
Location: Fircrest, WA
The Canadiar "air aspirator" serves the same function as the AIR injection pump on US models. It injected air into the cylinder head but used the pules from the exhaust to do it.

Same advice applies- if you aren't going to use it, just block off the hole in the head.


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