So, I got my '68 Dart when I was 17. I didn't care too much about the car's history at the time, just that it was only five bills and it ran. For years I just told the people at the parts counter "'68 Dart" whenever I needed a part, and didn't usually have a problem. Then I moved on to my Volvo and this car sat in my parents driveway for several years.

It's become a project car for me and my dad, now. I had, somewhere along the way, figured out that this wasn't the original engine, and gauged it to be mid-seventies (based on what - I can't remember). Then, a little while back I was going through some old paperwork that had come with the car when I bought it, I found a bill of sale for a '74 Duster and thought, "Ta da! The donor car!" So I've been going around saying '74 Duster/Valiant for a little while now whenever I was ordering engine parts, thinking everything was golden.

But then I started thinking.... what if it's not? I take my mechanics more seriously these days, and I need to nail this down if I'm going to be making informed decisions on spark plugs, timing, etc. Lo and behold, I'm not sure what the hell I've got anymore. I'll say right now, I've scoured My Mopar to little avail (read on). The situation is this:

1. There is no number stamped in the typical location. From what I understand, it may have been machined off at some point.

2. When I had the engine on a stand years ago, the only numbers I could find on the block were "330-4", "2929" (in two spots), and "AAWJ".

3. On the head, I found the numbers "3698447-7" and, again, "AAWJ". Now, minus that last "7", there is some documentation that says it may be a 75-80 head. But, the entire 8-digit sequence turns up very little online.

Every time another person brings up this issue their thread dies, or it comes to no real conclusion (example 1, example 2, example 3, example 4 from another forum).

Is there just not enough information to nail down a precise date? The head is likely somewhere between 75-80 - should/can I assume the block is too?

_________________
J.R.
Tucson, AZ
'68 Dart 270 with a '76-'80 engine

Probably a later engine's been swapped in. Check the side of the block below the rearmost spark plug.

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

I know where you're going with this - there's a flattened-out tab-like thing there. It's blank, though. The first time I saw it I thought it must be the spot for the serial number. Here's a poor picture of it. Is that tab on earlier blocks, or did it make an appearance later?

_________________
J.R.
Tucson, AZ
'68 Dart 270 with a '76-'80 engine

I'm curious as to why the year of the engine is so important to you? Aside from the obvious use of different spark plugs on the post 75ish heads, the crank hub size change in 67, the cast crank change over in 76, and the different valve cover and hydraulic cam starting in 81, nearly all slant six parts are interchangeable within displacement sizes.

The best way to determine your base timing on an unknown slant is to find out what governor is in the distributor. Multiply the number stamped on the governor by two and subtract that number from 32 to get your base timing.

All post 71 factory mechanical lifter slant six cams are the same.

From your pictures, you have a post-75 "peanut plug" head. Use the plugs for the later head.

What numbers are cast in the block near the freeze plugs?

_________________
Casually looking for a Clifford hyperpak intake for cheap.

A later cast crank, "peanut plug" engine.
The next question... figure-out if it's a hydraulic lifter engine. (does it have a wide valve cover?)
DD

Or, if you don't have an older valve cover to compare it to, check if the rocker arms have adjusting nuts on top of the pushrods. Adjusters = mechanical lifters, no adjusters = hydraulic lifters.

_________________
Casually looking for a Clifford hyperpak intake for cheap.

Well, Reed, you pretty much summed up why I want to know. Is that all I need to be concerned about, then? It was the spark plug issue that really spurred this - I recently put in some ZFR5Ns based on the false supposition I had a '74. (Is the head what determines spark plug, then? Could a '75 and up head even be put on a pre-'75 block?)

Yes, it has mechanical lifters and a normal size valve cover. So between that fact and numbers cast on the block, we can deduce it's between '76 and '80.

Okay, this has me feeling better. I wasn't aware of that process regarding timing. I will look in to that. Nor was I familiar with the term "peanut plug." So I need different spark plugs then. I understand the NGK UR5s are the way go. Are the CH-410 cap and MO-3000 rotor still appropriate for this engine (with electronic ignition)? Those, at least, I haven't installed yet.

Thanks so much, guys. I'm sorry I can't contribute as much knowledge to the board as I draw from it. Let me know if any of you ever need to crash on my couch!

_________________
J.R.
Tucson, AZ
'68 Dart 270 with a '76-'80 engine

You're going to need to get 'em out of there in a big hurry. You can screw ZFR5Ns (which are gasket-seat plugs) into a '75-up head but they will not seat, seal, or cool correctly. You must use taper-seat plugs in that '75-up head.
Yes and yes.
That's a fine choice.
Yes.

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

Well, I'm satisfied. Thanks. By the way, NGK 2771 is the [current] part number for the UR5 plugs I got today. I'm sure you guys knew that, but I couldn't find that in my searches of this forum. Now it's documented.

_________________
J.R.
Tucson, AZ
'68 Dart 270 with a '76-'80 engine