A strange head porting question....

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Moparmal

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Ive been reading a forum recently where the discussion was "How much can you get out of a set of J heads"...

Thats NOT my question - but it raised a question in my mind -

Is there a point where so much porting is done - it doesnt matter what type of cast factory head was selected to start with?

IOW - Does a J head still have better chracteristics than a smogger if they are both ported to flow 270 cfm - or has the original profile been lost?:read2:
 
I'm no expert but I'll give my two cents.

Water jackets limit porting for most. They vary from head to head and year to year. Most like the J or X for the bigger valves(less money) and they flow good in stock form but they have bad exh. ports. The closed chamber 302 have small valves but you can put 2.02 in them but you can't open them up all the way or you will find water. Bottom line most great porters make the port exactly what form they want. They will use epoxy, weld whatever it takes to get the port like they want it. Basically all smallblock LA heads have the same valve spacing, port window, port height, valve angle......so just make the port look like you want it to.
 
Thanks SD-

So if you are really hogging a cast head out - it doesnt matter what head you start with??
 
If you don't mind playing with putty then nope. All critical dimensions are basically the same.
 
IMOH,
Thats where your wrong.
They may be the same looking but they are very different..............to a porter.

SD I've never seen any #'s of flows from you, do you port? And if so how long?

Just asking, as I'm always willing to learn.

From what I've done every head is different, and to each engine for power curve or Tq. curve.

I'm here ready to learn, don't get me wrong I want to know so I can be a better builder.
 
Moparmal said:
Thanks SD-

So if you are really hogging a cast head out - it doesnt matter what head you start with??
Click to expand...

It does matter which head you start with. You can't just open up any head to the port shape you want. Valve to head angles differ, port heights, water jackets etc. There are some basic proven things you can do to any port to improve flow (pocket port, 3 angle valve job) but to really understand what is going on you absolutely need a flow bench.

A good book to read (even though it deals with chevys) is by david vizard. I think it is called "modifying small block chevrolet cylinder heads". There is a lot of basic port theory in there.
 
Yes I port. I don't go for maxxed out porting. As I stated before I'm no expert. I flow test every head I port but posting numbers IMO really don't do much because every bench is different along with what you use around the intake port, weather(actually seen 10cfm difference on same bench with the shop doors closed then open) bore size and even holding your hand close to the port window. I'm currently doing some 516 BB heads which have horrible short turns that I put some putty on then reshaped them.

I agree it is better to find a head that flows good then just rework small things to get even better. He asked for max porting; I think yes you can get great flow out of any LA head but you better be prepared to weld or putty....some heads more then others.
 
OK - so the message Im getting is that if if we were going for 270 cfm from a factory cast head, we'd be better off with a J than a "smogger" - thanks for the replies...

...I asked this because I wanted to make sure that if you were buying some used cast heads to really go wild with, it would still make sense get the best factory design possible to start with -
 
Moparmal said:
OK - so the message Im getting is that if if we were going for 270 cfm from a factory cast head, we'd be better off with a J than a "smogger" - thanks for the replies...

...I asked this because I wanted to make sure that if you were buying some used cast heads to really go wild with, it would still make sense get the best factory design possible to start with -
Click to expand...

If you are talking about 340/360 heads the ports are all the same from the X heads of the late 60's to the smog heads of the late 70's and early 80's. The smog heads are only different in that they have an air injection port and the slight bump in the exhaust port has almost no impact in stock form and is easily removed during porting. The late 80's early 90's 308 heads and the late model magnum heads are the only ones significantly different. 302 heads are a small port head intended for use on a 318.

I don't know if you saw the small block dyno competition in Mopar Muscle but this years competition was small blocks up to 410 cid. They all had to run on the same 93 octane fuel and as with previous competitions there was a points penalty for after market parts meaning the after market parts had to make more power than they gave up in penalty points to be worth while. The folks looking to win the competition all used factory heads.

Now the competitors could use any factory head and do any porting they wanted but could not use epoxy to build up areas and could not use off set rockers. Everyone used magnum heads; no X, J, O, U, 308 or any other factory head. These guys all made 500+ HP with these heads on 93 octane. I would say that pretty much tells you which sb factory head has the most potential.
 
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