porting

[DTanklage]

ps - did ya ever measure the pockets?

just stick your calipers in there and see how wide they are

(side to side)

curious

thanks

[DTanklage]

ppppppps - david, how much boost did your truck make with the stock head?

and are you doing any other mods to it other than porting the head?

[BC847]

Don,

I've got a manual boost controller set to 38psig. Without it, I'm pretty sure it'd go higher. Especially with W/M.

100% cold air box > BHAF > PDR HX35 Hybrid > 3.5" CA plumbing > Banks 1st gen intercooler > Banks TwinRam >

100% stock/OEM head >

14cm (wg) exhaust housing > 4" f/turbo to past r/axle w/big muffler.


Additional mods? Who me? Nah! (other than 12mm studs and the funky little rear block freeze plug plumbing thingy).


The long range plan (pocket pending) is to up-size the turbo and EDMs. But then twins present with a much lower drive pressure to the HG don't they . . ...



Pockets . . . . The throat of the port immediately after the seat? In further .25", .5" ? Side to side looking on axis down the port? (I'm funny that way).

Crap! I need my durn inside protractor! I've got precision bore guages from 1.500" on up to well over 8.000". With such, I can only measure the height of the port.

I've got killer precision dial calipers, but like you the inside side only reaches a half inch or so.

[DTanklage]

can you measure the pocket vertically (with the head on its side like it is in the pic)? (that would be side to side when its on the motor, right?)

with the calipers, the 6" ones will work just fine

don

ps - curious how much boost decreases for both of us

[seeker1056]

Port flow 101

when fluid meaning air runs in a tube of varyin shapes ( a port) it doesnt want to bend and makes eddy currents that reverse flow, when it is forced to go around corners

In an attempt to prevent that, a Dr of engineering over in England ( i forget his name and the book is packed away) who pioneered most of todays porting technigues ( a rich european version of Smokey Unik) and came up with all kinds of neat little things to straighten an ease flow thru a port and was doin this stuff way back in the forties n fifties.

the number one thing he came up with was a "ratchet" which a first he used in the port itself just behind the valve seat, and then realized that one could do almost as good job preventing stall and reversion by making the same "backcut" or "ratchet" in the back of the valve head. There is a complete science to depth and angle of this cut and its placement on the back of the valve head.

This Dr was also the pioneer of the multiple angle valve and seats

Yes many machinists today mistakenly call multiple angles that lay back the edge of the valve "backcutting"

Multiple angles work best on an intake valve as it helps stops turbulence

Multiple angle on an exhaust valve tend to burn away too quick, and should be reserved for race only motors where they are touched up regularly

In any event most performance valves today are made with the "backcut" already incorporated in the back of the valve head - just as in the pic of the valve on the right side in this post. (This particular machinist was quite correct in what he called it)

Why - its a cheap increase in flow in any motor - it had nuthin to do with weight savings - thats what reduced stems were done for

[DTanklage]

what do you charge to port a head and do a valve job, doctor?

[seeker1056]

I no longer do either for hire - hands wont take it - i never learned about vibration nerve damage issues till it was too late

Now n then i may do one for a friend if they dont mind waitin so i can take my time between bein numb

[TWorline]

[quote="seeker1056"]I no longer do either for hire - hands wont take it - i never learned about vibration nerve damage issues till it was too late/quote]

I worked at a GM Foundry for 25 years, poured iron for most of it but spent some time in the finishing dept. I learned about the nerve damage there. I have some friends who worked most of the time in finishing running air hammers and 6 inch grinders who cannot do much of anything today even after having the surgeries and poping pills all of the time.

[DTanklage]

the problem with porting is more the emphysema

the old man that ported my '64 stg III Max Wedge heads died from it right after he finished em

[GLHS]

BC; If those flow numbers are correct that's 34% increase on the intake and 44% on the exhaust!
I think those stock flow numbers are for a 2nd gen 12 valve head.
A 1st gen head flows about 5 cfm less if I remember right.
I see PDR has removed the flow numbers for the stage 3 ported head.

[TWorline]

the problem with porting is more the emphysema

the old man that ported my '64 stg III Max Wedge heads died from it right after he finished em

emphysema of the hands

[DTanklage]

emphysema of the hands

no, its a breathing thing

[DTanklage]

BC; If those flow numbers are correct that's 34% increase on the intake and 44% on the exhaust!
I think those stock flow numbers are for a 2nd gen 12 valve head.
A 1st gen head flows about 5 cfm less if I remember right.
I see PDR has removed the flow numbers for the stage 3 ported head.

why would a first gen head flow any diff than a 2nd gen head?

if a intake runner flows twice the air at 10" of vacuum when compared to one from another head, how much more will it flow when there is 3 bar in the port?

if a ex port flows twice the air at 10" what will it flow when there is 50 psi back pressure in it?

if you have 3 ex ports all capable of flowing 3000 cfm ea, what do they flow when you run em all together and the exit at the flange is only 1x2"?

lol

[BC847]

can you measure the pocket vertically (with the head on its side like it is in the pic)? (that would be side to side when its on the motor, right?)

with the calipers, the 6" ones will work just fine

don

Sorry about the delay.

As you may know measurements are approximate. The intake is about 1/4" in there @ 1.52".





The exhaust is about 5/16" in there @ 1.38".

BC; If those flow numbers are correct that's 34% increase on the intake and 44% on the exhaust!
I think those stock flow numbers are for a 2nd gen 12 valve head.
A 1st gen head flows about 5 cfm less if I remember right.
I see PDR has removed the flow numbers for the stage 3 ported head.

Yeah I'm pretty stoked with the flow numbers.

I don't know what's up with the website, growing I guess. I asked if my head was an example of things to come and they said no, just luck of the draw in my case. I wonder . . ..

[DTanklage]

Speaking of valves, be sure to keep the swirl on the backside if you whittle there ~

you had asked about back cutting and how to tell if they were back cut. this is what mine look like now:



the ex face is 45° so it is back cut with a 30

the intake face is 30° so it is back cut with a 15

tank