Ported top end: Port Match or bolt it on...

[LGAFF]

Some people have asked about port matching the heads to the intake....obvious solution is the taper the IH runner, but if you plan on port matching in the future, you might go ahead and open it up to 36mm from the get go.....

if so this is what a 36+MM IH look like when mated to a stock head...to me its not that bad...not optimal; but I am guessing you are still picking up over a tapered runner:

[LGAFF]

[Schrade]

Don't know much about airflow dynamics, but I do know ALL the good questions ...

With such a difference in bore from IH to head, is it possible that instead of a smooth taper, from IH to head, that you induce vortices in the air column, which would accommodate better flow? Such as with angular FURROWS.

Like the Coriolis Effect - Think of the how the juice and chunky jam goes away through a SMALLER hole, when you pull the trigger in the 'library' every morning.

Or how the water drains in the sink even. It DOES want to spiral out to accommodate the restriction...

( I think GM even tried to mimic this with their VORTEC induction )

Perhaps 'furrowing' at the juncture, that could later be opened for full matching?

Or perhaps 'dimpling' in the juncture (think of a golf ball aerodyne).

If furrowing, would there be the appropriate angle in the column? That would be determined by differences in bore of each player? EDIT: Or determined by bore difference x some linear gradient ( = angle / length of furrows). I think airflow through the juncture AS IS, would have some nasty eddies fighting against the flow...?

Anything that would maintain some semblance of lamination in the flow.

Definitely intriguing. I come up with good stuff huh!

Still thinkin' on this too here...

[Schrade]

Furrowing. (which could be leveled when full porting is done).



In fact, when full head port matching is done, would SOME degree of angular furrowing STILL be in order?

I asked long ago here, if the injector bosses were specifically designed, with flow dynamics in mind - Dunn's or Burmal's mind, that is???

HMMMmmmmmmm..........................

[Paul Workman]

Originally Posted by LGAFF

Some people have asked about port matching the heads to the intake....obvious solution is the taper the IH runner, but if you plan on port matching in the future, you might go ahead and open it up to 36mm from the get go.....

if so this is what a 36+MM IH look like when mated to a stock head...to me its not that bad...not optimal; but I am guessing you are still picking up over a tapered runner:

NOT according to most of my sources RE porting. Air has mass, and therefore inertia. So, leaving a ridge perpendicular to the air flow will direct the flow colliding with that ridge to run perpendicular to the flow direction, resulting in a "standing wave" of pressure at the mouth of the narrower runner. The net result impedance will off-set some or all of the net gain porting the IH afforded, or even (worse) be more of an impedance than if nothing at all was done. AND, to make matters worse, such a lip will result in some pulse reversion - also working against your efforts.

So, some (any transition) tapering is better than none. Multiple sources on the topic of porting seem to focus on 4º (approx 14.3:1) taper (or less) is required to avoid the practical issues of reversion and restriction.

Going from 36mm to 32.5 mm (at the valve guide boss of my 90 heads) at 4º is ≈ 2". However, it is 2.85" from the IH to the valve guide boss (again on my 90). So, I went the whole 2.85" just for a bit more thickness to avoid a coolant/oil incursion problems as I did my (initial plenum/IH only) head port matching with the heads in place.







Wow! I wish I had dyno'ed the result then so I'd have a clearer picture of what the net gain was after I later finished the head porting. But the "ol' seat of the pants" gauge said the lion's share of the net 432 rwhp came from the top end alone.

As you know, the head material is easier to cut than the IH. So, it took under 2 hours per hole to do the initial head runners. (BTW, I pulled the secondaries at that time and applied the same taper to all the head runners while I had the IHs off). And, an added benefit was to reduce the amount of cutting when I later finished porting the heads; eventual full porting was considered too when I initially tapered the head port match.

[Paul Workman]

Originally Posted by Schrade

Furrowing. (which could be leveled when full porting is done).



In fact, when full head port matching is done, would SOME degree of angular furrowing STILL be in order?

I asked long ago here, if the injector bosses were specifically designed, with flow dynamics in mind - Dunn's or Burmal's mind, that is???

HMMMmmmmmmm..........................

As I understand it, the rounded edges of a velocity stack (for example) helps establish a laminar flow of air as it enters the runner. The Webber stacks (pictured) show that "curl" at the mouth of the stacks (that I think you're alluding to). Such a transition would not be required in Lee's case because laminar flow has already been established in the preceding runner length. So after the flow is established, then tapering is how flowing to a smaller cross section is accomplished (also visible in this example).



As for the OE injector bosses, they're massive bastards! Removing them as much as possible (see Lees' pic) is part of the increased flow the stock LT5 craves so much!

[LGAFF]

A 90 I did last year was 36mm, not port matched and it picked up 37hp on the same dyno....so no real ill effects...

And that was without a tune

[Schrade]

Been reading (so more Q's at best)

'Furrowing' is out (except maybe SHORT 45' channels, cut into head inlet, but only instead of NOTHING, such as to prevent the 'standing wave', that PW refers to below).

Furrowing (or channels) would be better serving for solids (bullet rifling, i. e.), or liquids. Gases have plasticity, so dimples WOULD be in order - HIGH order indeed, for variations in bore, and even then, only in absence of taper...

THoughts???

----------------------------------------------------

Originally Posted by Paul Workman

NOT according to most of my sources RE porting. Air has mass, and therefore inertia. So, leaving a ridge perpendicular to the air flow will direct the flow colliding with that ridge to run perpendicular to the flow direction, resulting in a "standing wave"

These are the nasty eddies I was wondering about.
-----------------------------------------

of pressure at the mouth of the narrower runner. The net result impedance will off-set some or all of the net gain porting the IH afforded, or even (worse) be more of an impedance

Which one are you thinking it is? I don't see how it (leaving a ridge) could offset ALL of the gain from porting, but this is interesting here...
------------------------------

than if nothing at all was done. AND, to make matters worse, such a lip will result in some pulse reversion - also working against your efforts.

So, some (any transition) tapering is better than none. Multiple sources on the topic of porting seem to focus on 4º (approx 14.3:1) taper (or less)

That's the 'linear gradient' that I was guessing about.

-------------------------------

is required to avoid the practical issues of reversion and restriction.

Going from 36mm to 32.5 mm (at the valve guide boss of my 90 heads) at 4º is ≈ 2". However, it is 2.85" from the IH to the valve guide boss (again on my 90). So, I went the whole 2.85" just for a bit more thickness to avoid a coolant/oil incursion problems as I did my (initial plenum/IH only) head port matching with the heads in place.

Wow! I wish I had dyno'ed the result then so I'd have a clearer picture of what the net gain was after I later finished the head porting.

Ok, now this is real interesting here PW (actually answers Q's I posted below, before re-reading). Did you do any math on paper for this porting? Or did you just 'open it up', and take what it gave ya'? Is anyone on the boards in water or airflow engineering, that can do math for flow dynamics? Any computer programs available that do it for ya?
------------------------------

But the "ol' seat of the pants" gauge said the lion's share of the net 432 rwhp came from the top end alone.

As you know, the head material is easier to cut than the IH. So, it took under 2 hours per hole to do the initial head runners. (BTW, I pulled the secondaries at that time and applied the same taper to all the head runners while I had the IHs off). And, an added benefit was to reduce the amount of cutting when I later finished porting the heads; eventual full porting was considered too when I initially tapered the head port match.

LeeG; did you do other work on the '90, from which you got additional 37HP??? If you didn't, your result SEEMS to conflict with what I was guessing, and with what Paul was saying...

Just to be sure here tho', you ported IH's, and didn't touch head ports at all? And put it together, like your first snappic above post #1???

Originally Posted by LGAFF

A 90 I did last year was 36mm, not port matched and it picked up 37hp on the same dyno....so no real ill effects...

And that was without a tune

---------------------------------------------------------------

When you port heads too, do you HAVE TO do valvework? Do heads HAVE TO come out, to have tapered portwork done to them???

Has anyone done a partial port of IH's, WITH ONLY A TAPER?

What's the diameter of the plenum ports (once they're channeled to individual ports)?

Where is the bottleneck on the intake on a stock '90? Are dimensions in FSM? Now that I got the OBX's with 2"+ pipes, + 3" PE pipes, and no resonator restriction, where's MY next flowjam???????????????????

[Schrade]

Originally Posted by Paul Workman

As I understand it, the rounded edges of a velocity stack (for example) helps establish a laminar flow of air as it enters the runner. The Webber stacks (pictured) show that "curl" at the mouth of the stacks (that I think you're alluding to). Such a transition would not be required in Lee's case because laminar flow has already been established in the preceding runner (IH???) length. So after the flow is established, then tapering is how flowing to a smaller cross section is accomplished (also visible in this example).



As for the OE injector bosses, they're massive bastards! Removing them as much as possible (see Lees' pic) is part of the increased flow the stock LT5 craves so much!

I'm not following ya' here Paul...

If he DOESN'T taper the head port inlets, then his laminar flow STOPS at the head inlet ridge - doesn't it?

[LGAFF]

The 90 only had ported intake and 63MM TB....I ported the airhorn, etc....doubt that mattered much.

No change in exhaust, or headers