SB head tech question

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Cheapstreet said:
then
pick a cam that uses the port work/flow chart-map...this will dictate the best cam profile...
for instance if the port is done at 500" you wont need a .530" cam...for example..
cheapst
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I'm of the opinion that you get a cam that is actually larger than the best flow is noted. In the example of the .500 flow peak and a .530 camshaft, that's exactly what I like to do. Actually I'd more likely do something in the .550 range on a SB mopar. The amount of time the valve is hung open at peak lift is so minimal in a hydraulic/solid cam application, it's not really using the flow at peak lift.

Another issue with SB mopars is the crummy compound angles that snag lift at the valve. Your .500 theoretical lift probably isn't at the valve, likely more like .485 if you are lucky.

Home port your heads and ask someone that has done a few what you should and shouldn't touch with a cutter.

Cheapst always has good info.
 
hey crackedback, thank you for the info...that makes sense as well, and seems like a good reason for going with more as opposed to less lift...about asking home porters, theres none that i know of around me that i can ask lol...also, i still trying to figure out the best candidate for which heads i want to port...stick with my x heads? go to 3.08's? (bigger or stock valves?) or use the J heads that i already have (not sure what valves they come withstock- i think they are the smaller ones right?)...interested to know your guys views on which of the iron heads will lend themselves best to porting and work with my piston combo (assuming right now that its the same as stock 340 pistons above the hole)
 
going past the max flow will help hit peak port flow twice...once on the way up and again on the way down...
the problem with these irons...is they get turbulant..so you dont want to open the valve too far past max flow -into a turbulant point/zone.. this will kill efficiency..
your point is well taken ..Crackedback...
 
Ditto as well. But just because you get to peak flow twice doesn't mean your going to get the bennifit you think you are like cheap was saying.

For a street build, if your max flow stalls after .530, stay under it but as close as possible. This way your getting a max effort without any draw back what-so-ever. There really is no sense pushing the limit of going passed peak flow with the cams lift reguardless of what ever/how much you think it is actually lifting at the valve.

Some call me "Playing it safe" or to safe, but I have yet to have a failure this way and the engine isn't over taxing the system in order to achieve what it's doing.

The other big problem is if one person reads/see's/heres that one dude is doing this, going past peak flow in the head with the cam lift, there thought pattern changes and if a little is good, more should be better.

Next thing you know, we got people installing a cam that runs .630 lift in a head that stalls at .550.

It's like beginners corner all over again. A classic mistake from jump IMO.
 
Cheapstreet said:
going past the max flow will help hit peak port flow twice...once on the way up and again on the way down...
the problem with these irons...is they get turbulant..so you dont want to open the valve too far past max flow -into a turbulant point/zone.. this will kill efficiency..
your point is well taken ..Crackedback...
Click to expand...

Depends on how the heads react past peak. If they do get radically turbulent then yes, shorten up the lift beyond peak. Have to find a balance.

Check what the theoretical lift should be at the valve on a 59* sb and what you actually end up with. I've seen them lose anywhere from .015 to .045 depending on cam/valvetrain used. That's another reason to select a cam bigger than max lift flow rates.

Cam lift .500 per cam card for a SB mopar, heads flow max at .500, you're giving up performance from what I've seen.

It's all cool with me. Everybody has an opinion and they aren't always the same.
 
well both of your opinions make sense to me...rumble you are right about not going past the flow, but i agree with crackedback as well for compensating for lost lift..crackedback, if i understand your response correctly your saying that a head that flows max only to .500, that with a cam bigger than 500 lift it actually hurts performance? so theoretically it goes against the balance then and you would stick with something in the say 490 lift range? just trying to make sense of it all guys...once more ill ask though, which iron head candidate is best for my needs, in your opinions lol
 
mshred, yes and no, you have the idea of where we are both coming from. Normaly I recomend a cam lift just shy of where the head flow stalls. Like I said above, people go crazy with lift. I'd rather leave some on the table than go past the sweet spot in lift and cause problems. It's really not a lot of power left behind on the table. It's peanuts really. Nothing. (Spits on floor to demonstate.) Garbage.

Now on my own engine builds, it largely depends on what I'm building and how I want it to react, it's temperment. In example, the Duster project I have going on use's a Crane on a 112 c-line. When it warms up, the idle is very very smooth. So nice, grand-ma drives it twice and smiles.

On the street roughian(SP?) ruff-ian. I've used cams ground on a 106 c-line and moved it down 2*'s. Now we are talking about a idle like a crack head going through withdrawal symptoms while trying to chop some wood 2 feet thick with a butter knife for a free fix if he gets it done in under 2 minutes. Or was that his heart failing? Hummmmm......

If your head stalls after .500, then find a cam (With the duration you want to use/cruise in, will use best for the combo) and go right to .500 directly, don't pass go, don't collect $500.

And extra .010 or less.010 of .500 isn't going to kill or hurt.
 
I understand CB's position and I'm not disagreing with him or think it stupid. It's just not what I would recomend. Would I do it....again? Maaaaaaaybe, maaaaaaaaay be not.

Would I normally do it? Nope. Is he nutz? Well, maybe, but not on this topic. Ha ha hah (JK!)

It's just my position.

Oh, any head on hand will do great.
 
rumblefish360 said:
mshred, yes and no, you have the idea of where we are both coming from. Normaly I recomend a cam lift just shy of where the head flow stalls. Like I said above, people go crazy with lift. I'd rather leave some on the table than go past the sweet spot in lift and cause problems. It's really not a lot of power left behind on the table. It's peanuts really. Nothing. (Spits on floor to demonstate.) Garbage.

Now on my own engine builds, it largely depends on what I'm building and how I want it to react, it's temperment. In example, the Duster project I have going on use's a Crane on a 112 c-line. When it warms up, the idle is very very smooth. So nice, grand-ma drives it twice and smiles.

On the street roughian(SP?) ruff-ian. I've used cams ground on a 106 c-line and moved it down 2*'s. Now we are talking about a idle like a crack head going through withdrawal symptoms while trying to chop some wood 2 feet thick with a butter knife for a free fix if he gets it done in under 2 minutes. Or was that his heart failing? Hummmmm......

If your head stalls after .500, then find a cam (With the duration you want to use/cruise in, will use best for the combo) and go right to .500 directly, don't pass go, don't collect $500.

And extra .010 or less.010 of .500 isn't going to kill or hurt.
Click to expand...

Hey Rumble, your point is well taken...i understand what you mean more clearly now, and it does make sense...i know everyone will have there own opinions on this, and im welcome to all of them to get as many perspectives as i can...and by the way, i love the comparisons...wouldnt want to get into a dissing war with you LOL

as far as which heads to use goes, im thinking of just using the X's since they already have the larger valves (or am i wrong here?)...but depending on condition, they may have to be changed as well...what is it about J's that allow them to flow more than X's with a maximum porting effort (and justin chime in since i know you really wave the J head flag and im interested to know why)
 
Theres really no difference between the X and J head except intake valve size and if it were I doing this build, I'd look at the X head for the track.

I myself wouldn't be useing N02 and if it was a true street car, I'd look at modified 308's w/1.88's. That's just the way I see it for me.

For you, I suggest you use all 3 heads in stock for and see how run the best.

IF anything about me suggests I wave the J head flag more than a X head is due to a resto guy wanting the x head for his resto and you'll get more money for it over a J head which can simply be rolled over back into the J head for porting purpose's.

No sense selling a J head for less $$$ return and putting it into a X head that'll get the same work. Minus maybe a larger vale for the intake.
 
hmm
well after reading most of this and remembering about 1/3 of it I'll ask,
1st
is this turning into a fix my combo thread?

or

2nd
which heads should I use, how do I port them, and is there anything I can do to make power while I'm there[heads off]?

The cam thing is really pertains to flat tappet theory, roller is a different story....
see the idea is that flat taps only stay at max lift for a nano second meanwhile there opening /closing cycles are longer in comparison...so you would naturally want to hold the valve open longer at the cyl heads peak flow/lift.

How far into the saturation do you go?
well If you go too far, the saturation will outweigh the benefits of lengthening the peak flow range and it will fall on it's face and make less power.
It's a grey area.

I say you need flow sheets to determine how far past you can go.
 
Well, it started as number 2 and on the head/lift thought;

Thank you, thank you
 
Well either pull the x heads and cc correct them to get a real 10.5 ratio then port them, open the pinch straight and don't open it to the gasket on that side only the divider side, also grind the vc bolt bosses and get studs for the vc, then grind out the hump [hooked guide boss] on the ceiling and just smooth the short turn a lil along with the bowls venturi. You really need to look at and hold an example ported bowl so you can see the bowl roof and how it's a lil and I mean a lil bigger than the venturi thats located 7/16-1/2 below the 45* [seat] cut.


If no go on the x heads then do the J's, same thing pretty much but now go 11/32 valves and seats on both int/exh to get the valve sticking out of the chamber and flowing, for you don't need to do like some guys and sink the valve to get the short or less tall short side floor, you can port that.

I would get a solid cam around .525-.540 lift 282*-286*
 
Easily QUOTE OF THE YEAR!!!!

"Now we are talking about a idle like a crack head going through withdrawal symptoms while trying to chop some wood 2 feet thick with a butter knife for a free fix if he gets it done in under 2 minutes. "

:D
 
moper said:
Easily QUOTE OF THE YEAR!!!!

"Now we are talking about a idle like a crack head going through withdrawal symptoms while trying to chop some wood 2 feet thick with a butter knife for a free fix if he gets it done in under 2 minutes. "

:D
Click to expand...

i am still trying to visualise this....lol...
cheapst
 
hey guys thanks for the replies...
Justin it started off with question 2...im comfortable with what i have now and want to just drive, but im trying to get ideas for the next step so i have plenty of time to get it ready for when the time comes.

Rumble, what you say about using the J's over the X's for money reasons makes sense, but im not sure if i can sell the x heads (they arent really mine lol)...Id like to be able to run all 3 heads stock and see which works best, but i dont have the 308's...also, nitrous is almost certainly in the picture, so i think it will make sense if i stick with the larger valve head, just have to decide which one

Justin, i appreciate the cam theory...I had no idea about that, and when I am done with my heads i do plan on getting them flowed to ensure that i select a proper cam for my choice...Im still not totally clear on cam style differences (i.e. benefits/ disadvantages over say hydraulic vs solid ,etc.) but there is some good info on that on the comp cams site i think i will give a read...In regards to the instructions about porting, i appreciate them...dont be suprised if you recieve a pm from me to ask you more about it though, since im not familiar with all the terms and such...i know you have photos in your gallery too of this stuff, so ill give that a look as well

and yes im gonna have to agree with moper and cheapstreet, that line was priceless Rumble!
 
moper said:
Easily QUOTE OF THE YEAR!!!!

"Now we are talking about a idle like a crack head going through withdrawal symptoms while trying to chop some wood 2 feet thick with a butter knife for a free fix if he gets it done in under 2 minutes. "

:D
Click to expand...

Cheapstreet said:
i am still trying to visualise this....lol...
cheapst
Click to expand...

mshred said:
and yes im gonna have to agree with moper and cheapstreet, that line was priceless Rumble!
Click to expand...

Thank you thank you one and all!

Msherd, If ya ever heard a cam with alot of overlap and a numerically low centerline with a very fast acting lifter rise, (AKA, a real race cam.) well, that's about it. Sometimes it idles ok, sometimes it seems to drop dead....and then sudenly come back to life chopping staccato. (Cause the crackhead just can't do it any other way.)
 
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