J Heads on a 1970 Challenger 340? Who can solve a mystery?

[kawahonda]

My 340 has J heads. As I understand, J heads can come with both 1.88 and 2.02 intake valves. Also as I understand, 1970 340 Challengers came with J Heads. My Challenger was produced in November of '69.

Marking on my heads are 3418915.

So you can probably assume that I have the 2.02 valves, right?

Here's the mystery: they are blue. They've either been replaced in the past, or simply rebuilt-repainted with whatever the mechanic had in his garage.

Who is the head expert here? Is there a way to know what valves these heads have without pulling them?

[kawahonda]

One possible way is to check the casting date numbers. If they are produced in 1969, then is it reasonable to assume that they for sure will be 2.02 intake? What if they were produced in 1970?

Another possible way, do the valve stem diameters differ between 1.88 and 2.02?

[RUNCHARGER]

Casting date #'s are what count.

[kawahonda]

Hey Run: are these located on the bottom of the intake runner? That basically means pulling the head.

I wish there were some other way to tell. I just removed the driver's valve cover. Found the casting # plus some other 4-digit code, but cannot see not much else meaningful.

Here's the 4-digit code that's on a tag: 1890

[Cuda Cody]

The dates would be under the value covers.  You'll find a photo here:

https://www.e-bodies.org/resources/mopar-chrysler-10000-day-calendar-date-code/julian-perpetual-chart-decoder/

[kawahonda]

Thanks Cody! What an awesome decoder that we have. I kept banging my head on what these codes mean!

So this would mean that these heads (or at least the one I verified) was built on the 189th date of 1970. That would be July 8th.

I think that would mean that these have 2.02 valves.

The car was assembled in November in 1969. So that would mean that these heads are not original to the car...?

Some good history there that's unsolved. Wonder why they were changed out. Maybe they came with "X" heads and he was tired of the valve jobs with unleaded gas.

[6bblgt]

by July of '70 they would've been casting heads for the '71 360 (blue painted engines) as well

it's been asked, has anyone seen a "J" head cast in 1969? 

[kawahonda]

So the date code doesn't solve this, as you've eludded to 6bblgt. Well, I think it solves most of it, though. ALL 360s have 1.88 intake valves if I remember correctly.

It would be really nice if Chrysler had any other markings that could help here.

For my engine upgrade plans, I have a chance to buy "X" heads from a friend. That may be more original than what I have now. I will check the casting date #s from him. If they were casted in 69, then it's a "bingo" for originality I would think...

There is still a chance that these have 2.02" intake valves, but I think at this point, the chance would seem slim. The blue color being very highly suspect, as well as the July 1970 casting date puts these really at risk.

It seems like the only fighting chance that these are large valve heads is if they were late 71 340 heads, which have been stated to be painted blue from the factory or as CudaCody suggests, they had a 2.02 valve job.

Does this mean my compression ratio should still be 10.5:1?

Seems like most likely these are 360 heads and I should expect to find 1.88" intake valves upon removal. Either way, we DO know at this point that it did not come with the car...

Runs great and all, but may want to take a step back before taking these current heads down to get them cleaned up, checked, etc when there's a set of what could appear more date-code correct. What year heads would Dodge have used for a November built A66 340 Challenger? 1969 only?

[6bblgt]

So the date code doesn't solve this, as you've eludded to 6bblgt. ALL 360s have 1.88 intake valves if I remember correctly.

I believe so, 360s are all 2bbl until '74

[Cuda Cody]

If the heads have been rebuilt they could have been worked to any size.  So "assuming" they are stock is only half the battle.  It does not appear they are stock and that's means they could have been rebuilt to any specs.  If it runs good i wouldn't worry much about it.

[Chryco Psycho]

The only way I can think to check is to slide in a boroscope through the spark plug hole & take a look with a camera check the clearance between the 2 valves .
Nothing else is going to determine the difference , likely being produced in the performance years I would guess it will have 2.02 valves ut as Cody says it will not make a huge difference anyway

[kawahonda]

@Chryco Psycho
@1 Wild R/T
@6bblgt
@GY3R/T

My friend finally had the chance to go up in his attic to take pictures of his X heads. Good news, they were casted in 1969. One was casted on March 23, 1969 and the other was casted March 11, 1969. My current J heads have "360" stamped on them. These clearly have an "X" and a "340" stamped on them.

My engine was casted on Friday, September 12, 1969. So these X heads were casted 6 months prior. I'm assuming that these would be "close enough" to consider buying.

That's where I could use your guys' help because I don't know a lot of engine/head work.

When I eventually rebuild the engine, I plan to obviously rebuild/mill the heads. My J-heads may/may not have the larger ex valves. I would certainly plan to install those if I keep the J heads.

The X heads obviously have no valves.

Basically, is there going to be a cost difference rebuilding these X heads vs J heads, or are they going to be roughly the same price? It's worth spending more on the X heads, but I don't know "how much" more I'd be spending. Just would like to know up front.

Nice thing about obtaining the X heads is that they are more correct for my car, but maybe it gives me a chance to start working on them while still driving what I have now...

Now the famous question....what are these X heads worth in my case?

[Cuda Cody]

IMO, they are paper weights until they are magged. 

[kawahonda]

He would allow me to get them magged before buying...

[6bblgt]

they are expensive to have rebuilt, that's one reason why aluminum heads are so popular today - but correct is correct, even if you are the only one who will know

&
07099 = Wednesday 7/9/69
08269 = Tuesday 8/26/69