x vs j

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Do they both have 2.02's?

Then nothing, no difference. Perhaps in the casting itself, core shift issues, theres a difference.
Look under the intake valve and see if the X head has more area removed vs. the J head.
 
When you start porting them any open chamber 340/360 head has the same potential, the X head has no advantage over a late 70's smog head.

The only head that had any advantage when porting were the TA heads and that was because the pushrod holes were offset (with offset rockers) allowing you to grind out more of the pushrod pinch in the intake ports.
 
A-BOMB360 said:
stock for stock its about equal. when you start to port them thats when the
X head shines.
Click to expand...

im not claiming anything here, but i always thought from reading on here that with a 2.02 int valve on a J head up against an x head, that full ported the J has more potential???
 
On the X vs J thing...I'd rather start with a 1.88 head if I was porting & just cut the 2.02 in.

If there's a diff at all it would be the x head's exhaust floor seems wider at the slant coming off the wall, but that could just be cast tic's or the ones I have.

I have both.
 
From what I have been understanding for a while now on the heads are there the same minus the valve (intake) that was installed as OE.

Now, what is under the valve, as cast and then installed on a engine may be a different story. That is why I ask/mention that.

From what head porters have told me, the smog year heads flow a little less due to port reshapeing. But potentail is there for some super smokin numbers if need be.

More work than a letter head? IDK. I'm not a porter, I have no flow bench.
Talk to a porter.
 
mshred said:
im not claiming anything here, but i always thought from reading on here that with a 2.02 int valve on a J head up against an x head, that full ported the J has more potential???
Click to expand...
well #'s mean nothing. except to the guy pocketing the $$$,
and some people here who think HP & flow #'s are gospel.
At the track however, you'll see what the X head can do thats been ported by somebody who knows WHAT TO LOOK FOR IN X-HEADS.
cheers.
 
A-BOMB360 said:
well #'s mean nothing. except to the guy pocketing the $$$,
and some people here who think HP & flow #'s are gospel.
At the track however, you'll see what the X head can do thats been ported by somebody who knows WHAT TO LOOK FOR IN X-HEADS.
cheers.
Click to expand...

Can you elaborate on what to look for? I ask because I've owned and ported both (but I'm an amateur porter) and didn't see any difference at all in design other than the X heads had bigger valves. It looked like when you cut the J's for 2.02 valves and blended the bowls they'd be the same. Your right #'s aren't everything but at the same time I don't consider them to be "nothing". If they were nothing there'd be no need for a flow bench, would there? I personally feel flow velocity is more important than big numbers. JMO

BTW: There's a fellow that races locally at Gateway that runs high 9's with a 360 and J heads. Apparently he knows the magic tricks with J heads. Wish I did. LOL
 
A-BOMB360 said:
well #'s mean nothing. except to the guy pocketing the $$$,
and some people here who think HP & flow #'s are gospel.
At the track however, you'll see what the X head can do thats been ported by somebody who knows WHAT TO LOOK FOR IN X-HEADS.
cheers.
Click to expand...
What ? are you some rank amatuer high school kid? Have you read to many issues of hot Rod :read2: written by Chevy guys? Yes indulge us with your superior knowledge on what makes a X head shine. :bootysha:
 
We have been over this many times. X and J heads are the same thing other than valve size. Once 2.02s are installed in J heads the only difference is one has a J and one has an X.
 
hi, Mr. betts , of super flow , stated, port velocity and port shape are everything. don't get hung up on the big numbers(flow). velocity fills the cylinder faster in a given time frame(duration). the comparison was made in reference to opening a door slow or fast. cam lobe shape plays a part in getting flow started faster and sooner. just food for thought.
 
71Demon360 said:
What ? are you some rank amatuer high school kid? Have you read to many issues of hot Rod :read2: written by Chevy guys? Yes indulge us with your superior knowledge on what makes a X head shine. :bootysha:
Click to expand...
yup. took all my knowledge from Chevy's little "302" hemi killer.
or was that the new "hemi" being a mercedes designed engine..
anyways, go ask Bob Mullen his opinion of the X-head. I'm sure
he's been quoted many times in HotRod magazine.
 
A-BOMB360 is all spin and no info. He should go into politics.

You will not get a useful reply from him so stop allowing yourself to be trolled.
 
well i got my answer about x-heads and j's so im happy....the rest after that like knowing what to look for in x heads is all opinion in my eyes..unless there is solid back to back proof, there is no point in pulling statements from the air and claiming they are valid
 
mshred said:
well i got my answer about x-heads and j's so im happy....the rest after that like knowing what to look for in x heads is all opinion in my eyes..unless there is solid back to back proof, there is no point in pulling statements from the air and claiming they are valid
Click to expand...
You got that right.. Dont listen to that A-bomb fool with his Bob Mullins (who has probably died of old age) 1970s articles X head jargon.
 
Got 915 "j" heads on mine with 2.02 int 1.60 ex. milled .020 I'm running a 1 5/8 hooker comp. header in which I believe I need to go bigger 1 7/8 or even 2".
 
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