Captainkirk
Old School Mopar Warrior
Is there a difference in flow between 340 X heads and the later 2.02 J heads? If not, what are the differences between the two?
X vs J- flow differences?
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Same head as far as I know. The different valve sizes will make a difference.
Keith Mopar
Mopar Nut
I think if both those heads have the same size valves there would not be a lot of flow difference as they are basically the same casting.
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Two X heads will flow differently just from casting to casting. I'd say leave the X head to the restorer and let him pay the money, and grab a cheapo 360 head and move on.
As cast X heads flow better than as cast 2.02 J heads. Not enough to change heads, but if you had both...
Captainkirk
Old School Mopar Warrior
I do.
MOPAROFFICIAL
Oogliboogli
Iirr Stock 2.02 j heads I have peak 228cfm on the best port. My x heads were 219-224 peak. They are hand picked 1970 j's though, stock class stuff.
The numbers in between could be the deciding factor and all heads vary some.
The numbers in between could be the deciding factor and all heads vary some.
PRH
Well-Known Member
On my current bench, and my previous bench...... in equal condition...... X heads outflow J heads.
And with equal amounts of porting, the
X heads still outflow the J heads.
The X heads have a superior intake floor and SSR.
They are not “the same” heads.
Taking one of each in ootb form, by running my finger down over the intake SSR from the bowl side, I could easily tell which was which....... while blindfolded.
And with equal amounts of porting, the
X heads still outflow the J heads.
The X heads have a superior intake floor and SSR.
They are not “the same” heads.
Taking one of each in ootb form, by running my finger down over the intake SSR from the bowl side, I could easily tell which was which....... while blindfolded.
It would be interesting to find out what the engineers at Mopar did to create the casting differences. Next time I see Radar (Roger Luctenberg) I will ask him if he did any porting for the OEM. I know he was on the B1 team and when he worked at Gary Ostrich's shop they did experimental work for Chrysler Corp.
PRH
Well-Known Member
There is no mystery why the J head floor was cast the way it is.
The X head only ever came with 2.02 intake valves, and the final approach of the floor into the bowl was shaped to meet up with a bowl sized for that 2.02 valve.
The J head comes with both 2.02 valves and 1.88 valves.
The floor of the X head doesn’t extend into the bowl area enough to have a proper transition into a bowl sized for a 1.88 valve.
The J head has material added to the floor to facilitate the use of a 1.88 valve.
The bowl is just machined larger when they use the head with the 2.02 valve, but by adding the material to the floor to work with the 1.88 sized bowl, and then machining it out to the 2.02 size results in a sharper, more abrupt change at the SSR where the casting meets the machined bowl.
The X head only ever came with 2.02 intake valves, and the final approach of the floor into the bowl was shaped to meet up with a bowl sized for that 2.02 valve.
The J head comes with both 2.02 valves and 1.88 valves.
The floor of the X head doesn’t extend into the bowl area enough to have a proper transition into a bowl sized for a 1.88 valve.
The J head has material added to the floor to facilitate the use of a 1.88 valve.
The bowl is just machined larger when they use the head with the 2.02 valve, but by adding the material to the floor to work with the 1.88 sized bowl, and then machining it out to the 2.02 size results in a sharper, more abrupt change at the SSR where the casting meets the machined bowl.
K.O. SWINGER
Meeting in the alley since 1976
If valve size and valve jobs and Port work is equal the heads are pretty much a wash. There was always a little more mystique with the x head due to it was the original high compression340 202 giant killer head
MOPAROFFICIAL
Oogliboogli
I've said it for years. I just stated the port floor differences in another thread yesterday or so.
X head has a flatter ssr peak. You can about wipe the turn flat before you hit water too in an x head. But the real deal is if you know how to port a j head...it flows better than an x head .100-.450 the turn doesn't need to be laid down as much. To each his own.
I can only speak from my experience.
K.O. SWINGER
Meeting in the alley since 1976
I have no reason to believe this statement is not totally accurate. And goes along with what I've read over the years. But stock to stock I don't think you could tell the difference by the seat of your pants
MOPAROFFICIAL
Oogliboogli
Pretty much.
autoxcuda
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I have ~’73 to ‘79 Small block development correspondence between Tom Hoover and paid consultants’ “experimental work”.
For small block heads, it’s mostly X head, street T/A, race T/A, W-2/2.5/3. There is a “360 production” head in the notebooks from 75 or ‘76. IIRC, the casting # wasn’t listed.
I believe the effort/development was focused on whatever classes Chrysler (Hoover) wanted to focus on.
Below is a 894 X-head BTW. Note tested by Mullen in early 1970. Attached to the 1973 document for reference.
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K.O. SWINGER
Meeting in the alley since 1976
So cool!
Yes, that is some cool stuff!
autoxcuda
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that doesn’t even scratch the surface !
I have all Bob Tarozzi’s notes from start to finish developing 1968 Super Stock A-bodies. Also notebooks on 66 trans am, Keith Black hemi and block development, early 70’s nascar, can am, etc, etc.
Carlton, SVI, Mullen, KB, Tarozzi, and some others were all contract Chrysler race development.
Wow treasures for sure!
autoxcuda
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learning there are some castings “within” the casting numbers...
seen references to “Petty castings” and notes like “... give these “good” castings to select drag racers”
.....hmmm ;)
autoxcuda
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notice they are talking about W-2’s in May of 1973.
I see W-2’s for sale in the 1976 DC catalog but not the 1975 DC catalog.
Funny you mention that. I thought 73 was awfully early for W2's.
autoxcuda
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In 1975 they are already working with W-3’s. May be just a huge 2.19” intake valve in a regular W-2 ???? :dunno:
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