Hey guys, I just got an NOS slant head that has a small hole by each of the exhaust valves. Is this (as I suspect) part of the EGR system? And should I do anything about them before installing it on the motor for my 63? thanks Mike

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. . . there was good sport at his making.

Where is the hole located? Is it in the chamber or on the manifold flange? I don't remember ever seeing a slant with holes next to the valves. The only setup I've ever seen was one hole aft of the #6 exhaust port and it is real easy to make a block off plate to plug it.

Um, you aren't talking about the spark plug hole are you?

d'oh! I didn't even think of mentioning the spark plug hole.

Well, I'm not trying to insult anyone, I just want to make sure that Michael didin't make the kind of mistake I make all the time- forgetting the obvious. We all do it, no shame in it.

No, its not the spark plug holes. Each of these holes are about 3/16. They are positioned adjacent to the exhaust valve stem inside the chamber.

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. . . there was good sport at his making.

An EGR port will be in the exhaust port, not in the combustion chamber.

Poor something into the hole and see where anything comes out.

If they fill up and nothing leaks out, they're just blind holes and I wouldn't worry about it.


Although I have no idea why there would be blind holes.

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Michael, is there any way you could post a picture? I have never heard of a slant six having anything like this in the head. Where did you find this NOS head? Do you have any casting numbers or other information about it?

Hey Reed, I haven't figured out how to post pics on the site, but I can email one to you. The Head is in a box that says it was made in 1986. It is a late hydraulic vintage unit with the odd-ball valve cover pattern.

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. . . there was good sport at his making.

to post pics you need a website that you can link them too.

There's directions in the section on how to use the forum.


Send me one too.


thanks

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Ok, it's not in the combustion chamber, it's in the exhaust port......


I'd just leave it alone, but block off the EGR port that will be on the other side of the head somewhere..

If you're really anal, you can tap it out and insert a plug.

Or I've heard of guys pouring molten aluminum in the EGR ports on pontiac heads..

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Okay, that sounds like the air injection prt used on late model slant sixes that had an air injection system. Just cap the hole at the back of the block after the #6 exhaust port and you are fine. THose holes don't have anything to do with the EGR valve.

Thanks, sorry that my descriptive abilities fell short of the actual situation. I have seen alot of slant heads, just not that many late generation ones. This one is still covered in the factory goop and reads 9/86 on the box.

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. . . there was good sport at his making.

You're holding a head with provisions for an emission control system known as Secondary Air Injection (commonly "AIR", "smog pump", "air pump").

There'll be the small hole in each exhaust port, all leading to a common longitudinal gallery passage in the head, which terminates at a round, flange-drilled port on the manifold-mounting face of the head, all the way rearward. What's bolted to this flange is a pipe connected to an air pump. There will, in unleaded systems after 1974, also be another line from the air pump to the catalytic converter. In such two-line systems, a control valve determines which line, if either, receives air from the pump depending on engine operating conditions.

In earlier, leaded-fuel systems of the late '60s through early '70s (on slant-6s first in '72 in California, on most '74s nationwide, on virtually all '75s and later), this air injection is a yes/no deal; a control valve looks at intake manifold vacuum and diverts the air to atmosphere under conditions of very high vacuum to prevent exhaust popping on closed-throttle deceleration—and that's the extent of system control.

In unleaded systems, the pump pushes air through the pipeworks and into the "upstream" (cylinder head) port when the engine is cold and/or (with feedback induction) operating in open-loop mode. This extra air allows the exhaust to carry on burning, so excess unburned hydrocarbons are burned off. Once the engine warms up and/or (with feedback induction) enters closed-loop mode, the air injection is switched from the upstream location to the downstream (catalyst) location, to provide extra Oxygen to assist with the oxidation reaction in the catalytic converter. These unleaded systems have two control valve functions; the switching between upstream and downstream, and diverting the air to atmosphere at high vacuum.

Some systems don't use a pump, but instead have a "gulp valve" which admits ambient air into the exhaust system under negative-pressure pulses in the exhaust stream at engine idle. Other than that, the principle is the same.

SO, in a nutshell (at last) what you've got is either:

-The way to comply with local emission laws that by one means or another require you to run secondary air injection in whatever year and model you're building, or

-about 9-15 pounds' additional cylinder head weight and an extra hole in your head to be plugged

depending on your point of view.

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