michformulaS
Well-Known Member
I mentioned tonight that I am finally getting my 416 with ported X heads built. Currently I have a 318 with "O" heads in my car....What is an "O" head?
"O" heads
- Thread starter michformulaS
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Same as a X,J,U, etc....A 340/360 head. Valve size of an X is a 2.02-1.60 and sometimes the J as well I'm told though I never seen one stock this way. All others should be a 1.88 intake and 1.60 exhaust though nothing in the MoPar world is in stone.
They all flow about the same reguardless of letter except where the valve is bigger.
They all flow about the same reguardless of letter except where the valve is bigger.
michformulaS
Well-Known Member
Thanks....I figured they weren't anything all that special. I will keep them for a D100 project I want to start next spring
Mark Nixon
Senior Moments Member
They are very unique, from a restoration standpoint.
The 'O' heads are technically correct for 1970 340s only and are 2.02 valved in stock form.
On '70 340s there are 4 other castings that are technically correct, BESIDES the 'X' head. They are O, U, Z and 'J' castings.
Some very late '70 340s got 'J' castings that have a 'U' on the underside, some also were 'J' all around, in very late '70 model year.
The 2 original 1970 360s I have seen had 'Z' heads.
The 360 was actually introduced in May of '70 in certain Dodge 4 door hardtops, it was also the debut for the part-throttle kickdown on automatics.
There is actually a TSB out there advising of the '70 360 and the transmission's part-throttle kickdown, which also specifically gets into car line and manufacture numbers.
Mark.
The 'O' heads are technically correct for 1970 340s only and are 2.02 valved in stock form.
On '70 340s there are 4 other castings that are technically correct, BESIDES the 'X' head. They are O, U, Z and 'J' castings.
Some very late '70 340s got 'J' castings that have a 'U' on the underside, some also were 'J' all around, in very late '70 model year.
The 2 original 1970 360s I have seen had 'Z' heads.
The 360 was actually introduced in May of '70 in certain Dodge 4 door hardtops, it was also the debut for the part-throttle kickdown on automatics.
There is actually a TSB out there advising of the '70 360 and the transmission's part-throttle kickdown, which also specifically gets into car line and manufacture numbers.
Mark.
1968FormulaS340
Well-Known Member
I had to reply to this. It gave me a little laugh...
You say they are not that special (or maybe its how Im reading it).... But....
In reality they are the same head as the x heads you plan on using for your build.
Many people get hung up on that X.
Take that O head, slap some 2.02s in it (if they don't have them now) and it will be exactly like your X head in function. The only difference is your X head will have an X by the plug hole and the O head will have an O by the plug hole.
Mark Nixon
Senior Moments Member
Well, that's part of the difference. lol
The 'O' heads, as with all small block heads beginning with the 3418915 (J, O, U, and Z) casting on, have wider lower head bolt bosses.
Supposedly to help with head gasket sealing.
'O', BTW, some very early '68 "X" heads (2531894) weren't even cast with an 'X', but to alleviate assembly line confusion, Chrysler later had them tooled to be cast with an 'X'.
Mark.
Burntorange70
Well-Known Member
My very late built 70 340 Dart came with a set of 2.02 J heads on it.
1968FormulaS340
Well-Known Member
Thats exactly how mine are. My car is an early 68. X-heads without the X. This can cause problems sometimes People will ask what heads I have... I will tell them they are the original heads. Then they will tell me how wrong I am and how a 68 340 should have X heads......
1969cuda340
Well-Known Member
1969cuda340
Well-Known Member
Pretty old thread. Thanks for the info. Kim
B3422w5
Well-Known Member
i had a 70 340 Duster that had 2.02 J heads.
When i got the car, the heads had never been off of it
Jeff Seighman
aka jeffnmo
My 70' 340 Dart came with 2.02 U heads, now has Indy/RHS X heads and not enough cam!
Topless69
Well-Known Member
Dang it! Got sucked in to the old thread dimension again!
Thanks Kim
Jeff Seighman
aka jeffnmo
Yeah, happens to the best of us!
Maybe so but that was a good post.
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