A66 code 1970 340 Challengers

[Jim W]

I had a good look at the red car. The car was 'old' and fitted the tag. The tag is crisp, but that could be because it doesn't have layers of paint on it. I'm inclined to think the tag is right and the car is late production after A66 was no longer available? And anyway, why fake it?

I've always believed all 340 '70 Challengers are A66, but now I'm not so sure.

[1 Wild R/T]

I had a good look at the red car. The car was 'old' and fitted the tag. The tag is crisp, but that could be because it doesn't have layers of paint on it. I'm inclined to think the tag is right and the car is late production after A66 was no longer available? And anyway, why fake it?

I've always believed all 340 '70 Challengers are A66, but now I'm not so sure.

Added options, color change... Missing tag, guessed at the numbers....     You've got some knowledgable folks weighting in & the consensus is the tag isn't original....

[6bblgt]

ALL 1970 340 Challengers are A66

the red tag is FAKE

[Jim W]

ALL 1970 340 Challengers are A66

the red tag is FAKE

Well it puzzled me. But I am sure you guys are right.

[71383bee]

Was it the FE5 convert parked across from the judged show entrance?  It was for sale and he wanted over 87k for it IIRC...

[Jim W]

Yes that was the one.

[kawahonda]

ALL 1970 340 Challengers are A66

the red tag is FAKE

Hey 6BBL, Do you know how much Burnt Orange 1970 A66 Challengers were made?

A side question. My A66 has J heads that were not original to the car (what gives it away is the "blue" color of the heads). If I wanted to look for date-code correct heads (probably "X" heads) is that a specific date that I should be looking for, or is more of a date range? I believe my build date was sometime in early november of '69, so would that mean any "X" heads before that date are "correct" or is more of a range?

[1 Wild R/T]

ALL 1970 340 Challengers are A66

the red tag is FAKE

Hey 6BBL, Do you know how much Burnt Orange 1970 A66 Challengers were made?

A side question. My A66 has J heads that were not original to the car (what gives it away is the "blue" color of the heads). If I wanted to look for date-code correct heads (probably "X" heads) is that a specific date that I should be looking for, or is more of a date range? I believe my build date was sometime in early november of '69, so would that mean any "X" heads before that date are "correct" or is more of a range?

Your car didn't come with X heads... It came with J heads.... X heads were 68 & 69 model year.....

[kawahonda]

Wild, that would imply that I would need J heads that were casted in 1969. I have yet to see those....

[6bblgt]

ALL 1970 340 Challengers are A66

the red tag is FAKE

Hey 6BBL, Do you know how much Burnt Orange 1970 A66 Challengers were made?

A side question. My A66 has J heads that were not original to the car (what gives it away is the "blue" color of the heads). If I wanted to look for date-code correct heads (probably "X" heads) is that a specific date that I should be looking for, or is more of a date range? I believe my build date was sometime in early november of '69, so would that mean any "X" heads before that date are "correct" or is more of a range?

Your car didn't come with X heads... It came with J heads.... X heads were 68 & 69 model year.....

"X" heads were definitely used in the first third of the 1970 model year - there are a number of threads on the internet looking for "X" heads with a '70 casting date & "J" heads with a '69 casting date - I haven't seen either 

there's no documentable right answer - it's a date range, cast before your engine assembly date (close to the block casting date would seem to make sense) 

[kawahonda]

Thanks. My "J" heads were cast on the 180th day of 1970. So impossible that they would be the original heads...the owner was already driving it at that time!

Essentially, not being exact, but I would need either a "J" or an "X" head that has "9" as the last number. Just like you said, I can find "X" heads that had a "9" cast date, but I have yet to see any "J" heads having a "9" cast date. Here's some "X" heads that have a "9":

https://www.ebay.com/itm/MOPAR-340-X-HEADS-PART-2531894-1968-1970-/232778862060?epid=1430329305&hash=item3632b38dec%3Ag%3AgX8AAOSw9RdbBOu~&LH_ItemCondition=4&nma=true&si=4p69zdvvd5SP5pOm%252Ftlr3jiiRu4%253D&orig_cvip=true&nordt=true&rt=nc&_trksid=p2047675.l2557

Still have yet to see "J" heads that have a "9". Would love to know if someone has ever seen any!

Getting more specific would mean finding out when my engine was assembled, which I don't know where that information would exist. It's an LA car so it doesn't have a build sheet. So then I assume I would need to look at my block casting date. Is that easy to find while the engine is in the car?

The reason I ask is I'm wondering if it's worth the hassle when I pull my heads to re-gasket to find something that's "correct", or simple just repaint my "J" heads (make sure the large intake valves are installed) and slap them right back on. "J" heads are better in some ways anyways. My question is one of those "how important is it"? Do mopar guys come aroudn with flashlights asking you to remove your valve covers to check?

[GY3R/T]

 Guys are not going to look under valve covers to see if your heads are correct for your car.
They don't need to. They'll just look by spark plugs to see if there is an X or J or O,U etc.
Your car came with X heads. I wish people would stop saying X heads are 68-69 only.  Keep your eye
out for a set of X heads to work with your dates.
Curious.... How are J heads better than X or others ?

[kawahonda]

Well, "better" being subjective. "Better" in the fact that if you find J heads that have 1.88 valves for cheap and it's much easier to install 2.02 valves. X heads always have 2.02. If you have worn valves, you are in for much more of an expensive repair if they are recessed. Better also in the fact that some "J" heads came with hardened valve seats. None of the "X" heads did. In some ways, I'm glad I have "J" heads...original owner probably had a hell of a time with the X heads when fuel changed to unleaded and finally had to get them rebuilt...which meant at some point having someone toss on the current "J" heads. It's likely my J heads have the large 2.02 intake valves since they were produced in the "performance years", but possible they don't because they could be "360" heads. They do have "360" written on the casting on the inside....which may mean they are "360 heads", or could mean something else? Then, there's the theory that 1.88 intake valves actually perform just as good, if not outperform, the 2.02 intake valves due to increased velocity...

AFAIK, the flow is pretty much close to the same, and the CCs are pretty much close to the same. I've seen instances of slight increases with the X heads by a few CFMs. Many builders choose J heads due to cheaper cost to obtain and you can still make huge power with them. Resto number's matching people will pick X heads. Chryco will give another option which is to use the 80s head for the "swirl" technology...he's got real world experience with that.

My friend has X heads in storage that he's willing to sell to me for probably a pretty good price. I just need to figure out what date ranges should I be considering for them to be "correct" for my car. I know they've got to be "9" heads for sure. Then I will have other questions: Can I use my rocker assembly on the X heads...is it going to cost an arm and a leg to switch to X heads, etc...

Everything I've written above is not by personal experience in any way. It's after hours and hours of thread browsing from many sites. Take it for what it's worth.

[1 Wild R/T]

If you have the matching numbers engine it will have a cast date & the date it was assembled....

To get the ACTUAL assembly date for the ENGINE, you need to look at the front of the block on the machined face. The numbers for the ENGINE are stamped on the driver side of the block, right under where the head mounts. It'll look something like "FW340 R 3650 1234" where F is the series  W=Windsor assembly plant, 340, P=Premium fuel, 3650=10,000-day calendar date that the engine was BUILT, and 1234=the 1,234th engine built that day.


Hey Look it must be it the tech archives here...

How "Correct" is your car gonna be?   Clearly your not running stock polyglas tires & 14" wheels....   Your choice.... I'd run what you've got.....

[GY3R/T]

 Factory hardened seats (exhaust) are flame induction hardened. The result is a thin layer of hardness in the seat area, and after a valve grind or two the hardening is gone. Doubt anyone is going to find these heads not needing at least a valve job.  Sorry, i just can't buy into the theory 1.88s flow just as well if not better than 2.02 heads. (apples to apples).