How much swirl is too much swirl

[bill jones]

---this is a note I wrote to myself about a set of corkscrew heads on my own 400 SBC

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

-I'm not an expert on fast burn heads but I experimented with a set of the early 1987 vortec heads that had the corkscrew intake ports.
---------------------------------------------------
-Those heads had a LOT of swirl and the engine would not tolerate any more than about 28 total timing yet still wanted about 16 at idle (at 4500 elevation) when used on a 9.77:1 cr 400 sbc.
-When you would expect the engine to start to ping it didn't ping like normal----it hammered loud and hard.
-Then if you backed the timing down just one degree like from 29 down to 28 you could eliminate that hammering 100%.
-----------------------------------------------------
-The chamber didn't look to be significantly different than a 1000 other stock chevy heads---but the intake port was very obvious.

-Doing some simple wet flowtesting outside my shop just using a siphon spraying solvent thru the port with the valve open at .400" lift:

A-a stock style intake port showed the most fluid and air coming around about 65% of the valve----with lots of slobber droplets near the shroud.

B-the vortec head spray pattern looked more like the wrinkle wall pattern on a drag tire except this pattern was virtually 100% of the valve circumference----showing a very obvious pattern difference between the conventional port.

[hoffman900]

---this is a note I wrote to myself about a set of corkscrew heads on my own 400 SBC

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

-I'm not an expert on fast burn heads but I experimented with a set of the early 1987 vortec heads that had the corkscrew intake ports.
---------------------------------------------------
-Those heads had a LOT of swirl and the engine would not tolerate any more than about 28 total timing yet still wanted about 16 at idle (at 4500 elevation) when used on a 9.77:1 cr 400 sbc.
-When you would expect the engine to start to ping it didn't ping like normal----it hammered loud and hard.
-Then if you backed the timing down just one degree like from 29 down to 28 you could eliminate that hammering 100%.
-----------------------------------------------------
-The chamber didn't look to be significantly different than a 1000 other stock chevy heads---but the intake port was very obvious.

-Doing some simple wet flowtesting outside my shop just using a siphon spraying solvent thru the port with the valve open at .400" lift:

A-a stock style intake port showed the most fluid and air coming around about 65% of the valve----with lots of slobber droplets near the shroud.

B-the vortec head spray pattern looked more like the wrinkle wall pattern on a drag tire except this pattern was virtually 100% of the valve circumference----showing a very obvious pattern difference between the conventional port.

Good to see you still around here, Bill. You should post more!

Mike should make your username gold or something for being an OG member here

[bill jones]

INITIAL SWIRL TESTING RESULTS:
---to establish what to look for and how to get the swirl meter adjusted in
---and to get a baseline developed for future use
---this set of tests are ALL smallblock Chevys---INTAKE FLOW ONLY
---a left and a right hand port were on a variety of SBC heads that were readily available
---details are listed below the flow/swirl data
---swirl (and rotational direction) is noted right next to the CFM/ and the cylinder number
---an example is: 242 cfm and 52 units of swirl are listed as 242/52 and cylinder #4 has a clockwise direction noted as 4cw
---Cfm is “cubic feet of air per minute” measured at 25” H20 test pressure suction
---a radius inlet was used on all of the port entrances
---units of swirl relates only to Bill Jones's handmade swirl meter
---none of these heads require special intake manifolds—they also all have stock pushrod location
----------------------------------------------------------------------------------------------------------------
-------------------------------INTAKE CFM/swirl --------------------------------------------
VALVE----cyl--993's--cyl-------cyl--492's--cyl------cyl-VORTEC-cyl--------cyl-Brodix 8-cyl-----cyl--461's--cyl
--LIFT----2ccw/swrl-4cw-----5cw/swrl-7ccw-----4cw/swrl-2ccw--------8cw/swrl-6ccw-----1cw/swrl-3ccw
.100”----59/18----59/20-----59/20----56/22------58/36---64/0*---------65/14----65/10------60/20---62/17
.200”---119/32--115/30----115/52--116/40-----110/79--121/6--------129/15--126/26-----121/8--119/34
.300”---163/42--164/40----160/60--160/46-----137/80--174/38-------177/35--178/28-----163/28--162/36
.400”---185/74--189/75*---190/52*-171/38*----147/81--209/61-------215/53--216/57-----201/14--196/45*
.500”---187/75--190/81----192/78--197/72-----151/82--229/87-------242/52--247/57-----222/26--198/70
.600”---192/76--193/32----196/80--199/78-----153/82--245/78-------260/61--261/73-----217/78--207/78
.700”----------------------------------------------------------------------------271/68--275/75------217/78--211/82
993's---stock ports of open chamber 993 heads---intake valves were 1.94” but had been swirl polished *NOTE---there was a fluctuation here from 70 to 80
---They had 153 CC intake runners and had been milled to 71.3 cc's in the chambers

492's---stock ports of a closed chamber
*NOTE---at .400” lift both ports fluctuated up 2 and down 2 more numbers

VORTEC---a GM V/8 (and 4.3 V/6's) Vortec swirl port used on 1986 and later 350 fuel injected pickup truck engines---has spiral vanes in the intake ports
---Cylinder #4 is absolutely stock (180cc's) and #2 was ported “to the nuts” (216cc)
*NOTE---the swirl meter would not start at .100” lift---but sticking a finger in the port would “kick start” the swirl and jump the meter up to 26---the swirl was not affected by giving it the finger at any other lift point---apparently the flow was falling straight into the center of the port at .100” lift

BRODIX 8---this s straight forward Brodix 8 head with 2.050” valves---It had been ported pretty decent and is considered a good normal race head---Intake runners CC'd at 224 and chambers at 66cc's

461---this is an old “fueler” head casting #461---results shown are of a typical cheap porting job---a couple hundred bucks worth with Manley 2.02” “street flow” valves
--basically stock chambers opened up a little to 67CC's
*NOTE---cyl #3 had a 40-50 fluctuation at .400” lift

[Art Smith]

any names come to mind if I'm looking to talk with someone with "swirl improvement" experience in a Heron head setting? squish is already at the mechanical limit; ie: 0.039"/1mm (the thickness of the required head gasket)

Art
artesmith@earthlink.net

[SchmidtMotorWorks]

One experiment worth doing regarding swirl on 2 valve heads is, make a mold of your port, then use that to make a port that is on the center of the bore, no chamber.

I have tested that on a few heads that were supposedly designed for swirl, they had no significant swirl, it was all in the chamber.

[Art Smith]

One experiment worth doing regarding swirl on 2 valve heads is, make a mold of your port, then use that to make a port that is on the center of the bore, no chamber.

I have tested that on a few heads that were supposedly designed for swirl, they had no significant swirl, it was all in the chamber.

Heron heads (ie: Kent Fords) have NO combustion chamber in the head which is flat, they have a combustion bowl in the top of the pistons making them heavier than most. the pistons have a squish band around their circumference. the rules I play by are very restrictive regarding any changes to the piston and head beyond the ports & valve seats; NO changes are permitted to the valves.............. three key questions in my mind are:
1. will swirl increase with increasing flow? intake valve maximum lift is 0.356" !!
2. how large of a "fin" upstream of the valve is required to materially increase swirl? the rules preclude "adding" material to the head so a SBC turbo port is out of the question!
3. how large is the tax on flow for a "fin" upstream of the valve large enough to materially increase swirl?

IMG_0520.jpg

Art
artesmith@earthlink.net

[RW TECH]

The often maligned reverse-swirl "Elkins fin"

You mean Butch?

[Erland Cox]

From what I understand swirl takes energy and will always lower the flow.

Erland

[Walter R. Malik]

I thought tumble was a 4 valve only thing? Am I in correct on that?

Four valve heads will be no NET swirl unless inlet steering or staggered valve size/timing induce swirl.
Hemi heads will be no NET swirl unless the intake trajectory or pushrod tube staggering induce some swirl.

There can be small pockets of localized swirl, even though net swirl is zero.

I remember that Oldsmobile added some swirl to their Quad 4 road race, Achieva engines by grinding staggered valve timing on the intake camshaft between the 2 intake valves. They shared the same valve lift but, one was 242 degrees duration and the other was 248; (@1mm lift).

The weird part was that the "smaller" lobe was advanced from the other so, the opening was only a degree different but the valve closing was 5 degrees different.

[HQM383]

From what I understand swirl takes energy and will always lower the flow.

Erland

Do the benefits outweigh the cost with the ICE though?

[Bryan Maloney]

The often maligned reverse-swirl "Elkins fin"

You mean Butch?

Yes, a Dodge engineer told me that Butch Elkins was the one who deserved credit for the reverse swirl fin.

[Bryan Maloney]

From what I understand swirl takes energy and will always lower the flow.

Erland

Do the benefits outweigh the cost with the ICE though?

That's the $64,000 question. The answer will vary depending on your priorities. Are you an OEM concerned about CAFE standards and paying a gas guzzler tax?
Are you a race team that has to consider winning or losing a race on fuel strategy?
Are we fortunate (or cursed?) that cylinder head design has progressed far enough that we must ponder mixture motion as opposed to just "big flowz"; as it was in the old days?

[SchmidtMotorWorks]

One experiment worth doing regarding swirl on 2 valve heads is, make a mold of your port, then use that to make a port that is on the center of the bore, no chamber.

I have tested that on a few heads that were supposedly designed for swirl, they had no significant swirl, it was all in the chamber.

Heron heads (ie: Kent Fords) have NO combustion chamber in the head which is flat, they have a combustion bowl in the top of the pistons making them heavier than most. the pistons have a squish band around their circumference. the rules I play by are very restrictive regarding any changes to the piston and head beyond the ports & valve seats; NO changes are permitted to the valves.............. three key questions in my mind are:
1. will swirl increase with increasing flow? intake valve maximum lift is 0.356" !!
2. how large of a "fin" upstream of the valve is required to materially increase swirl? the rules preclude "adding" material to the head so a SBC turbo port is out of the question!
3. how large is the tax on flow for a "fin" upstream of the valve large enough to materially increase swirl?

To answer your questions, make a research model where the axis of the valve and the cylinder are colinear.
I'm not saying that it is impossible to get swirl from a port, but I have tested many that claimed to produce swirl with the valve guide positioned as described above, none of them had significant swirl.
If you can't get swirl from the port, any modification made to the port that supposedly trades swirl for flow is only losing flow.

[hoffman900]

From what I understand swirl takes energy and will always lower the flow.

Erland

Do the benefits outweigh the cost with the ICE though?

That's the $64,000 question. The answer will vary depending on your priorities. Are you an OEM concerned about CAFE standards and paying a gas guzzler tax?
Are you a race team that has to consider winning or losing a race on fuel strategy?
Are we fortunate (or cursed?) that cylinder head design has progressed far enough that we must ponder mixture motion as opposed to just "big flowz"; as it was in the old days?

Bryan,

Would love to hear more about what you guys found / how to introduce more tumble in a 2 valve application.

I don’t expect it to be like a 4 valve, but it seems to be the direction to head in.

[Erland Cox]

I thought tumble was a 4 valve only thing? Am I in correct on that?

Four valve heads will be no NET swirl unless inlet steering or staggered valve size/timing induce swirl.
Hemi heads will be no NET swirl unless the intake trajectory or pushrod tube staggering induce some swirl.

There can be small pockets of localized swirl, even though net swirl is zero.

I remember that Oldsmobile added some swirl to their Quad 4 road race, Achieva engines by grinding staggered valve timing on the intake camshaft between the 2 intake valves. They shared the same valve lift but, one was 242 degrees duration and the other was 248; (@1mm lift).

The weird part was that the "smaller" lobe was advanced from the other so, the opening was only a degree different but the valve closing was 5 degrees different.

The earliest SAAB 16 valve engines (4 cyl) had 2 different lobes. A later model had different ports and the same lobes. This was in the mid 80:s.

Erland