Emission restrictions began in 1970. Higher octane fuel disappeared, compression was lowered across the board, & it took mfrs. several years to get things right. Unless I miss my guess, EGR appeared around that time. I had a '73 pickup with a 454, & later. a '74 Suburban. I'm pretty sure both had EGR, though I wouldn't stake my life on it.

N.Y. Bill:

Thank you for your LONG message. That sure answers a few questions. I'll have to look at the engine and see what is where.


Heck if I can remember the deal in 1972 or 73 as I recall my 1973 2002 BMW had smog stuff but I think trucks got a year or so delay... maybe.

I don't recall seeing anything other than a valve in the driverside valve cover than connects to a hose that runs to....shoot I forget.

Well thanks to everyone I'll take a look and ask more questions.

I sure do appreciate your thoughts.

Timothy

...Just a little thread-drift here, but I'm getting an education, so here goes:


A couple years ago, I replaced the manifold-to-pipe donuts. One was cracked through completely and hissed enough to be an annoyance - replaced both just 'cause it made sense at the time.

The broken one (left bank)was the typical hard sintered donut I am familiar with....replacement was straight forward and no leak noise since......

The right bank donut was soft & friable, and kind of peeled off the exhaust pipe - in layers, almost like lead tape....I replaced it with standard hard donut, and have be unable to get a complete seal ever since. Regardless of torque adjustments on the three clamping studs, I still get a little blowby at the joint.

Fast forward to last night: While surfing the web, I came across an International Scout site. It contained a discussion about "crushed foil" donuts being used in place of hard ones for a better seal. I've never heard of this....

SO, does such a thing exist?...And in light of my inability to get a complete seal on the right side with a standard hard donut, is this an option? Further, maybe the "soft" donut I took off originally was that very critter...?

...And if all of the above is N/A, would it help to goop-up the hard donut w/ hi-temp silicone? (pipe flange & clamp do not appear to be distorted) I'd like to know before the Workhorse troops run-up the meter trying to get a good deal at the donut......

UPDATE on my original manifold issue - local Workhorse lead mech says his action plan is to check & clean mating surface of head, resurface the manifold and install w/sealant, new studs/nuts, sans gasket. If I insist on gasketing, any future problems are MY problems......Hope this gets me some time before the big Thorley/Exhaust system project this winter........

"Crushed foil" seals have been around for a long time - thery're pretty much standard (called "Flexitallic") for HP steam, although the mounting is a little different. The general design is a V-shaped strip wrapped into a circle (or several circles) with the open end of the "V" on the inside.

They tend to conform to irregularities better than hard seals, and pressure makes them seal tighter. The disadvantage is they tend not last as long as other seal types.

Actually, it sounds like the one you peeled off was a crushed-foil seal...