best heads to work with

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cowest432

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was big block now small and need some help and info,heard about x-j hands now o heads,i have j heads now and don't know if there big valves or not[to cold to find out],how about a little on o heads,and what work would i gain the most for my buck,besides gasket match and runner cleaned up
 
they are the same.
if you were to fiddle the letter J on the casting you'd see how it can come out as a J,O,U...

the 'j' is half of the 'U' and the 'O' is a 'U' made into an 'O'

know what I mean vern?
 
You will see a benefit by going to a roller setup (cam, lifters, and rockers) and by using stainless steel valves.
 
cowest432 said:
was big block now small and need some help and info,heard about x-j hands now o heads,i have j heads now and don't know if there big valves or not[to cold to find out],how about a little on o heads,and what work would i gain the most for my buck,besides gasket match and runner cleaned up
Click to expand...

skip gasket matching, thats worth 2 squirts compared to some bowl work.

The port window is not the issue, it's the bulging where the push rod passes through that needs to be opened up.:burnout:
 
At the same time factory heads can only do so much. The best heads on the market for sb is w series heads, not even about cheap but when your the best very rarely you are the cheapest
 
ok i get it about o heads,the seller claims these are factory big valve heads,were my j heads might not be,any truth to this
 
yes some were 2.02 and some were 1.88, but all had 1.60 ex valves.
early 340 versions had 2.02, '70-'71

You can add 2.02 for the price of the valves and valve job.
 
They are all pretty much the same but X and O are earlier and I don't know of any of these castings that had the smaller intake valve. The J, U, and "915" heads were for the most part 1.88s, but I've seen some early Js ('71s) that had 2.02s in them. Have a valve job done and put 2.02s in any of them and you're there.
 
If you have 1.88 the cost to have them pushed up to 2.02 (if you can do the work yourself) you'll be right about the cost edelbrock rpm head which are alum and a better way to go. But again the best on the market are the w series heads from Mopar.
 
The Mopar 340/360 heads are all fairly similar. Nice thing about the 1.88" versions is that you can open them up to 2.02 (if needed) and have a nice high intake seat that flows better than a head that has had several valve jobs and/oor had the seats beat up from long term use. Finding decent X heads that came with 2.02 is getting hard. Some of the 915 heads did have 2.02's also. I like to refer to the heads by the last 3 numbers rather than the letters. 894 are the 2.02" X heads, then 915, 587, 974, 308, etc. Light pocket porting/blending and smoothing out any casting imperfections are a safe, easy way to get some better flow.

Most stainless valves have a nail head intake design that will help flow, They will also help compression a tiny bit because they don't have a deep "dish" on the chamber side like OEM valves.

If you want a good aftermarket replacement head, the closed chamber RHS heads are a good buy, plus Summit had the 15% discount code. Comp Cams/RHS also has OEM length and +.100" valves to go with it. My engine builder said that the factory valve job on the bare heads is pretty good! You can get the heads for the shaft rockers or Magnum style. They are identical otherwise.
 
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