Whats the difference please.

[JMB711]

Picked up a 73 340 and looking for the correct intake manifold which I see is 3671918A but, now I see a 3671918Z. Is there a difference to be concerned about?
Thank you

 

[pschlosser]

The casting numbers (the part numbers found cast into a part) and the dealer parts book part number are not often the same number. Often, the first 4-digits are the same.

The number you cite, #3671 918 seems like a 1972 part number, not a 1973. Sometimes, there is a revision number after the casting number, and it refers to the revision of the casting. Happens when they have to tweak it or make a change to make the castings better, minimize machining, and so forth. In every case I can think of, that is a hyphenated number after the casting number.

So I'm thinking the "A" and the "Z" are not relevant and if you like the manifold you found, be it an A or a Z I think either one will be fine.

That is among the ThermoQuad intakes for the 340, and it's highly regarded.

 

[Chryco Psycho]

68-70 used the square bore 4150/4160 mounting , these are a great intake
72-73 used the Thermoquad spread bore mount also a very good intake .

 

[JMB711]

Yes am very aware that even a tiny change can mean a new #.

But here we have the same# but A or Z. Maybe its one size fits all A to Z. LOL

 

[Vaanth]

Picked up a 73 340 and looking for the correct intake manifold which I see is 3671918A but, now I see a 3671918Z. Is there a difference to be concerned about?
Thank you

Intake manifold casting number 3671918, part number 3698656, is the original intake manifold used on 1973 340 engines. The suffix of "A" or "Z" on the casting number is a foundry reference and does not affect the function or application of the manifold.

The "Z" suffix is on the earlier manifolds and may or may not have the boss for the temperature operated vacuum by-pass valve drilled and threaded. This boss/port is used for this valve if so equipped or plugged if not equipped. The following image shows this valve installed:

1973 introduced a new design choke well and electric assist choke thermostat. The following images show the 1973 well compared to the different 1972 well design which contained a cup installed in the well.

1973, and continued in use through 1984:

1972, also used in 1971:

 

[Xcudame]

My Mopar brothers have answered this pretty good, but I wanted to throw in my two cents. There will be a casting date on the intake manifold and it should be a few days to a couple months before the production date your car was built!

For a unique example of on time delivery, my 64 Imperial's 413 was built one day prior the the build date of the Imperial! Pretty impressive in April of 1964!

 

[JMB711]

Wouldent the Z intake be into the mid/late 70's 80's temp vaccum control?
Once had a 68 396 with date codes block heads and intake all within a few days of each other.
Pretty cool stuff...

 

[Vaanth]

Wouldent the Z intake be into the mid/late 70's 80's temp vaccum control?

The temperature operated vacuum by-pass valve, or thermostatic ignition control valve (TIC), was released for some 1973 engines, including the 340, typically based on region or accessories. The valve is used to reduce the possibility of engine over-heating under very high heat conditions. With the valve, if coolant temperature reaches 225 degrees Fahrenheit, the valve opens allowing full manifold vacuum to the distributor vacuum advance unit, bypassing the orifice spark advance control system (also introduced in 1973). Engine idle speed is increased, thus providing additional cooling until the engine coolant temperature drops and the valve closes, releasing the OSAC bypass.

Intake manifold casting number 3671918, part number 3698656,was only used for the 1973 340. With the replacement of the 340 with the 360 high performance in 1974, the intake manifold changed (part number 3698435) with the changes for exhaust gas recirculation (EGR). Subsequent minor changes in the 360 four barrel manifold occurred in 1975 and 1977 until the major revision with the thermostat size change and relocation for the new C-171 air conditioning compressor for 1979 and later.

The image of the example valve in my earlier post is on a 3671918A manifold, cast on March 7, 1973.

The following image is a 3671918Z manifold, cast on June 27, 1972 with the valve boss/port not drilled/threaded:

 

[JMB711]

Ahhh yes, California specifications. I think that explains the Z rating. They led the emissions charge a few years early. My 73 Z-28 has the remains of the spark control system on it as well.
I see what to look for now...