Greetings,

My name is Nick. I used to be a member of the Slant 6 Club of America until Jack Poehler for some reason stopped responding to me in the mid-late 1990s. Anyone who went to California Slant 6 Club Meets between the S.F. Bay Area and San Diego and between the years 1989 and 1996 may have seen my yellow and white 1981 Dodge B-150 Van, the subject of this post. Really glad to see Doug, Dan, and some other familiar folks here!

To business…

The ’81 B-150 has what may or may not be its original 225 Slant 6. Definitely of the correct period, with hydraulic lifters and all the California smog stuff for that year.

In the process of troubleshooting a crank, no start condition, i pulled off the Holley 1945 and happened to look down the manifold opening to see what appears to be a small hole. Here is an overview picture, for orientation, shot straight down, facing the front of the vehicle (fuel inlet line at the picture top):




Here is a closeup view of that hole:



Now, while i have indeed done a good bit of work on this vehicle, including gathering all the parts and installing factory-correct Speed Control, unlike many or most of you, i do not know my way around the engine innards well at all. I have never gotten into the engine itself, and am not used to looking at the manifolds.

I really cannot tell whether that is a hole that is supposed to be there which is nearly plugged up (and how would it get that way?), or a hole that is NOT supposed to be there (my guess).

Having spent a couple of days going through older posts in this forum, i have read that some/many of the castings from this era were, um, crappy. My handy magnet tells me there is a very slight ferromagnetic attraction to the intake manifold, as opposed to a strong attraction (with the same magnet) to the exhaust manifold and some other nearby parts, so i am guessing the intake manifold may be an aluminum allow (yet i would not know).

My questions:
1) Should that hole be there?

If No:
2) Thoughts on how it got there?
3) What sort of performance issues or other problems can a hole such as this cause?
4) Suggestions for repair or replacement?

And, because i am curious:
5) Any idea why that nice round rimmed circle exists in the manifold casting?

Thanks for your thoughts!

Hoping this first post works correctly the first time,

))Nick((
Call me Nick… call me Sonic… doesn’t matter.

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1981 B-150 short Van, stock 225, California emissions package, Electronic Spark Advance (digital Lean Burn), Non-feedback Holley 1945, AT
Driven for economy, not for speed.

Howdy, there. That hole is where exhaust enters the intake manifold when the EGR valve is open. It looks like yours is pretty well clogged up with carbon. You may want to remove the EGR valve and use a screwdriver to break up the carbon (from the top and the side), then use a Shop-Vac to suck out the chips and chunks. It's a fairly safe bet your EGR valve itself is pretty clogged up by this point. If that's so, then your engine will have a greater tendency to ping, which may have caused you to retard the timing to control the pinging, and that'll spoil performance, driveability, and economy.

More on Jack Poehler here; it was definitely not just you he quit responding to.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Yes, the hole is designed to be there. It is part of the EGR system which lets hot air into the intake for lowering overall emissions. It does this by reducing the combustion temperature. However, most of us don't activate the EGR system or the associated components to get a little more zip out of the engine.
Most after market manifolds don't bother including the hole.

I will defer to Slant Six Dan for more details, however you could clean it out and make the EGR system work. Mine still does and I try it from time to time to see how it affects mileage, like in the dead of winter. I will run a "T" off the flapper door vacuum line on the snorkel down to the EGR valve to get quicker warm ups when it is below freezing or if the Holley carb ices up. It usually makes the mileage worse but it is more driveable when the carb wants to ice up. Sorta like carb heat on a plane with a slight twist by including the exhaust gases too.
Under your dog house it should stay pretty warm especially in your climate.

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

Yikes! That's not what the EGR valve is for, and doing this will really spoil your driveability and mileage. The EGR valve is only supposed to open at part throttle, under load, with the engine at full operating temperature. That's why there are all those widgets and valves and sensors and hockey pucks in between manifold vacuum and the EGR valve.

if your carb is icing up, your thermostatic air cleaner isn't working correctly...

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Nick
Are you or were you a computer programmer?
Your writing style has a programmer flare to it. Very nice.

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

I know it is not really designed to work that way but it does very nicely in the dead of winter. Yes, the flapper works very well and is only on for a short period of time during warm up or when I am tearing down the freeway.
I can jump in the car and go, no long warm ups and it never stumbles.

I have it unhooked now. It only drops about one mile to the gallon.

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

Thanks everyone for your responses, and mighty fast they were!
Dan, you nailed it: I have been experiencing pinging under light (or greater) load recently, and was wondering what to do about it! I’d not started messing with the timing.

Yes, the EGR valve and its ports are crusty with carbon… cleaning them today.
Thanks. Actually, not a computer programmer, though i was a QA tester at Apple a decade ago, and still actively QA a few Macintosh programs, so i guess i still think along those lines.


Followup Questions on Hole Size

Here is what the hole looks like now:


Seems to me that the whole hole should be open, all the way to the edges of the wide rim, yet i am definitely hitting metal at this point. Still, the hole edges look uneven, which strikes me as wrong.

1) Is the hole size precise/critical?
2) Should i leave it like that, or drill/file the hole to be round and reach the outer rim equally in all directions?

No, i didn’t vacuum stuff out yet, in the photo.

Thanks again!

))Nick((
Off to (hopefully) get a can of carburetor soaking cleaner, and start un-gumming that carb!

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1981 B-150 short Van, stock 225, California emissions package, Electronic Spark Advance (digital Lean Burn), Non-feedback Holley 1945, AT
Driven for economy, not for speed.

By "reach the outer rim", i really mean fully reach the inner circumference of that big circular rim in the casting, symmetrically.

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1981 B-150 short Van, stock 225, California emissions package, Electronic Spark Advance (digital Lean Burn), Non-feedback Holley 1945, AT
Driven for economy, not for speed.

I'm going from *old* memories here, but yes I think the hole size is important. Its actually referred to as a "floor jet" and (again, old memory so beware!) I think floor jets came in different sizes for different emissions packages. The size of the jet(s) regulates the maximum amount of exhaust that gets metered into the intake when the EGR valve opens. That memory is based on my 318 v8, so slants might have all used a single jet size.

To me, it almost looks like that jet might have corroded and might be too LARGE, but if you're hitting solid metal with a well-defined edge all the way around, its probably that it was just drilled a little offset from the center of the casting ridge.

As to the benefit of EGR, I've had mixed experiences. On older carbureted engines like my 73 318 where (to borrow Dan's wording) the EGR system is controlled by hockey-pucks and widgets, the whole damn thing seems to work FAR better if you just disable the EGR and tune it like a pre-EGR engine- and its very important to include using a different distributor mechanical advance rate. In contrast, I've had computer-controlled engines (particularly a Caddy HT4100 that belonged to my folks- and no, its not a pleasant memory ) which WOULD NOT FUNCTION without EGR. That engine and control system in particular used EGR specifically to prevent detonation and was known to literally self-destruct if you tried to operate the engine under load without a working EGR system. When Dad's EGR valve failed, it sounded like someone was pounding a piston with a 5-lb sledge, and fortunately he fixed it before it hurt the engine- a lot of people with 4100s didn't and the resulting failures didn't help its reputation any. My wife's Chrysler 3.5L v6 is middle of the road- it won't pound a rod out the side of the block if the EGR quits, but it gets super octane-hungry and will rattle badly even on premium when it is supposed to only need midgrade. I'm certain its more efficient on that engine to keep the EGR working and use the correct fuel, because with it pinging like that the knock sensor is going to back the timing ALL the way down and waste a lot of fuel needlessly.

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It's easy enough to clean the parts of the EGR valve passages that you can actually see, but it's fairly likely you'll need to get a replacement, for the parts you can't see or get access to are probably also clogged.
Looks just fine! No need for continued cleaning, filing, or anything else.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Usually the size of the orifice is built into the EGR valve itself.

Generic replacement EGR comes with pile of washers and a paper. ~~

Cheers, Wizard

On slant-6s, the floor jet was found only on the very first EGR system in '72 in California. This system used no EGR valve, just had the open jet constantly bleeding exhaust into the intake tract. This system killed mileage and driveability, made the cars idle poorly and resist starting. The EGR valve that came in for '73 was a tremendous improvement, because the valve could then be opened (and exhaust emitted into the intake tract) only when EGR would actually help lower emissions, i.e., under part-throttle road-load conditions. The calibrated passage controlling the amount of exhaust flowing through the valve was actually built into the valve. This led to proliferation of differently-calibrated EGR valves; the aftermarket valves usually come with a selection of washers with differently-sized holes in them and a chart showing which washer to use in what application to duplicate the calibration of specific original-equipment valves. In all cases, the calibration hole is much smaller than the hole we're looking at in the floor of Sonic Putty's manifold, which is as it should be and not in need of any further cleaning or enlargement.

Floor jets were used on some Chrysler V8s (in combination with EGR valves) at least through '89.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Hmmm… OK. My plan was to soak the base of the EGR assembly in what i was told today is called "chem dip": the gallon-can solvent with the basket which i recall being called carburetor cleaner (the soaking kind, not the spray-on). The diaphragm assembly would remain high and dry. Is this a bad idea for some reason?

))Nick((
Learning with every post… many ongoing thanks!

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1981 B-150 short Van, stock 225, California emissions package, Electronic Spark Advance (digital Lean Burn), Non-feedback Holley 1945, AT
Driven for economy, not for speed.

That's better from a serviceability viewpoint. The part that clogs is always the orifice that regulates flow. Putting it in the (easily removed/replaced) valve is better than putting it in the bottom of the manifold under the carb!

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Chemdip is a very aggressive brew of very nasty chemicals. Wear complete skin, face, and eye protection and work in a very well ventilated area; this stuff will do you very grave injury very quickly. You can certainly give it a try on your EGR valve, then spray it out with Chemtool (the very good general-purpose carburetor cleaner made by the same Berryman people who make Chemtool). It may or may not get the job done on your valve. You stand better odds of a successful cleanup if you will apply vacuum to the diaphragm and keep it applied during the soak, or at least apply vacuum periodically to move the valve off its seat and allow the cleaner to reach the crevices. Also check to make sure the diaphragm actually holds vacuum.

What do you have in the way of service manuals? You may want to pick up the three books described in this post.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.