Ken

I can get some awesome flow numbers without the swirl vien..... I know thats not the mian concern when making power.

How many of you with ported heads have a swirl vien on who dosent?

I'm about to decied myself on to keep it or not.

??????

Ken

wizkid

iTrader: (3)

I have them in my CNC ported heads from Total Engine Airflow. I have some excellent flow numbers with them in considering I have my factory valves still in them. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

ERic

BIG PD

you will mess up your velocity if you remove those. i would strongly recommend not touching them, maybe just polish them up a bit. velocity is more or less just as important as air flow numbers.

BlueWheels

I just went through this with a freind of mine who did my heads. He tended to stay conservative and not remove much of the swirl bump. However, I compared his work to a GTP Stage 2 side by side and the GTP (which gets 20 RWHP more on the dyno) had more swirl bump removed along with other slight differences. If you are doing it yourself, be conservative! BTW, my head work cost about $600 compared to the $2400 for the GTPs. $2k was better spent elsewhere for the extra 20 hp in my opinion!!!

rrheads.com

I removed mine mostly and made sure there are no sharp edges. I trap 120mph with a hotcam and stock valves, so it seems to work pretty good.
I make over 400 RWTQ, so velocity is still high.

just my opinion though.

SJH

I removed mine totally on my 98 ls1 castings and took these heads as far as you can take them out in the bowl area without going into the water jackets.I am pulling very good airflow numbers and there is NO loss of response or engine airflow at any rpm range, Only very good gains compared to having it intact with a mild port job.

HOWEVER, this area is very thin once removed and I was able to bust through 1 port with a sharp pick <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" /> .
So I then added a thin layer of epoxy to the area to build the area to a decent thickness.
Be careful in this area of the port if you decide to remove it and check it with a sharp pick to make sure you don't leave it to thin.
Steve

BurnOut

iTrader: (1)

While I am not too terribly familiar with the pecularities of the LS1 ports, I can tell you that on many other heads the device used to induce swirl/tumble is there mainly to combat detonation.

LS1derfull

I go along with swirl helping control detonation, it also helps part throttle by exposing more of mixture to spark kernal in less time, this allows for less timing by computer to burn properly.
I also know this hi swirl condition interferes with max flow, so you would believe if you max flow ported ls1 castings that timing and mixture requirements would change pretty drastically.
Does anybody who went this route know about this and did custom programming bring driveability around?

Loco

Wheres the swirl vein at? Intake ports?

MyLS1Hauls

iTrader: (2)

I was told by several people to leave it in place, just widen it some. Jantzer98SS said he lost high lift flow when he removed it. FWIW, the MTI heads still have it intact, and they are supposed to be one of the best heads available. They also didnt touch the combustion chambers at all. Stock rough casting.

Brad

SJH

My timing requirement did not change at all either N.A. or blown.
If your running forced induction the swirl dam is a big joke in your port.
My plugs showed a centrifuging fuel mix dropping out last year with the dam/vein intact.I had fuel splash markings on every plug when pulled clean after a run.
After removing it( the vein) I have a much nicer plug reading showing much better combustion.
To much swirl can be bad and it will depend on the combo whether you will gain or lose from this area in the port.

All IMO of course
Steve

LS1derfull

SJH, did your speed go up when you removed dam and cleaned up your plug readings? Also if there is water above that dam and you repaired with epoxy, that is pretty Brave IMO.

<small>[ April 13, 2002, 06:06 AM: Message edited by: LS1derfull ]</small>

SJH

I read somebody else checking thickness with a pick and breaking through in this area.
So I tried it with a new sharp pick and did put a pinhole through one port.That bummed me out. From memory I would say it was about .020" thick maybe where I went through??
Another second or so in that area with a fast cut bit and the heads would have been junk.
Not knowing just how thin all the other ports were I just added a thin layer in that area on all the ports for a little insurance.
No problem with the epoxy after 500 miles so far.
I just pulled the intake last night and it looks good in every port.
Probably not going to last forever though.
If a port ever cracks I'll scrap the heads and start fresh and go a little easier in that area next time.Did to much other work to the port at the same time to know just how much gain was a result of the removal of this dam.
But with 5psi boost at only 50% throttle I don't worry much about any low end velocity or swirl motion in my ports <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

LS1derfull

Epoxy doesnt bother me ive used it plenty, its just when theres water pressure behind it that i think its risky. I was asking if your power or mph went up with swirl dam removed?

SJH

Well I did not just remove the swirl dam and call it a day so I honestly can not say just how much it helped all by itself.
I also did more extensive porting in other areas at the same time.
I'm sure we have some porters here who know the actual cfm increases/losses from the is area but they probably won't share the info.
Right now the motor is packing a stock cam and stock manifolds and cats(for emissions testing) with these hogged out heads, yet will still pull 65lbs/min of maf flow.
That's pretty close to my flow numbers from last year with a hotcam and headers using the same blower speed. So I picked up some large airflow gains but it's impossible for me to state it all came from that area of the port.
I don't see any negatives with it gone but this is a blower motor also.
FYI it ran 100+ 1/8th and 125 in the 1/4 last year with only 2.73 gearing at 3650lbs.
I expect those numbers to be exceeded this year while using a stock cam with the better flowing intake ports.
That's my crazy goal anyhow.
Steve

TA2SLOW

I've tested removing the swirl vien, and have seen the following gains

.200 +0cfm
.300 +16cfm
.400 +21cfm
.450 +23cfm
.500 +8cfm
.550 -8cfm
.600 -8cfm

Later Shawn

LS1derfull

Thanks Shawn, what power or speed differences did you gain? And how was throttle response and driving impressions with this done?

TA2SLOW

I wish I would have tested with and without the swirl damn but I didnt.
I ran a comp 212/218 .527/529 cam and the car made great low/mid range TQ with the heads i ported.

http://members.fbody.com/ta2slow/

Jantzer98SS

iTrader: (54)

Well first of all the swirl ramp and vane are two different things. The ramp is what everyone is referring to, the vane is the section off the valveguide that extends down into the port towards the intake entrance.

I wouldn't remove the ramp, but you can pick up some mid-lift flow by pulling it back some. I'm a firm believer in port velocity, especially with the stock 346. So frankly I wouldn't worry too much about flow numbers. If you want to know the truth, I barely touched it on the stage I heads on my car and I'm about to go 10's with the stock shortblock. The rocker boss is still in the port, the ports are barely opened up, and very little work was done on the valveguide itself. If I remember right, the heads on my car only flow around 270cfm! Get a good combo of parts put together and you'll go fast. You don't need a $3000-$5000 set of heads. Don't fall into the trap of thinking you need 2.50" valves, new seats, gold plated valvesprings etc.

I will be shooting for 10.50 with my Stage II's & Custom cam this fall.