Simple chamber mod that can get overlooked

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In-Tech
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Re: Simple chamber mod that can get overlooked

Post by In-Tech »

Hiya,
The super high swirl stuff GM did in the 80's/early 90's was stupid. They realized this and quit. Every GM truck needed a tuned port long runner intake like the corvette/camaro but got the high swirl instead. :cry:

You can't fill a cylinder with high swirl, it's about the mass of the fill and the depth down the cylinder that makes or breaks the deal. Back then(horribly} and today they are still about efficiency at 1200rpm for emissions. Introduce cam event EGR and then worry about how you will deal with NOX stupid so called, emissions you focking dopes. This stuff is really not that hard. 'NUFF said. =D> :mrgreen: :mrgreen: :mrgreen: :mrgreen:
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Re: Simple chamber mod that can get overlooked

Post by Tuner »

In-Tech wrote: Wed Mar 22, 2023 5:08 am Hiya,
The super high swirl stuff GM did in the 80's/early 90's was stupid. They realized this and quit. Every GM truck needed a tuned port long runner intake like the corvette/camaro but got the high swirl instead. :cry:

You can't fill a cylinder with high swirl, it's about the mass of the fill and the depth down the cylinder that makes or breaks the deal. Back then(horribly} and today they are still about efficiency at 1200rpm for emissions. Introduce cam event EGR and then worry about how you will deal with NOX stupid so called, emissions you focking dopes. This stuff is really not that hard. 'NUFF said. =D> :mrgreen: :mrgreen: :mrgreen: :mrgreen:
No doubt you have more experience with high swirl than just about anybody alive today, and you can repeat every negative thing you ever saw on the internet, but you are in the same boat as every other expert who repeats the negative swirl about the Chevy corkscrew head, you obviously have no experience tuning an engine with those heads and a suitable cam for any kind of racing. This is sad because all you do is repeat negative things and you actually know nothing about what you are criticizing.

The summer before covid (and doesn't that seem like a long time ago?) I had the pleasure of using a chassis dyno to tune a 350 with these heads and a suitable cam for a fast banked 3/8 mile dirt track and determined 25 total is all they need for best power. Modifying the HEI for the appropriate advance curve and jetting the carb improved a leaf spring Camaro from struggling and overheating at the back of the C main with 36 degrees to the front of the A main with 25 degrees in a field of cars that the rules allowed any iron head, 4bbl and headers, so you guess what the others were running and you can bet it wasn't screw ports. These heads work a lot better than you naysayers give them credit for, just because they have a funny intake port that flows more than you know and you don't understand anything about.

Lets all don't forget it wasn't so long ago that magazine lore was the HEI would not run above 4500 RPM same as the parrots repeat about the swirl head, so an engine with both swirl heads and an HEI is doomed to never go over 4500+4500=9000, so I guess 7000+ was just a stroke of luck, some kind of divine intervention.

The first time I tuned a TBI motor with a regular carb and distributor was 36 years ago in 1987 when a pal put one out of a wreck in his '73 Chevy PU. Naturally, it pinged like a pig unless it was "retarded way too much" so we thought the balancer slipped or some other silly thing was wrong. Whatever, we tuned it by ear and fixed the HEI to have the right curve for 25 total with 10 initial and learned something. The other major clue is Chevrolet put advice about spark advance for racing the V6 with these heads in the Power Manual, and 25 total was in bold print and italics. Read it and weep.
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Re: Simple chamber mod that can get overlooked

Post by In-Tech »

Haha Tuner,
I've had the luxury of tuning many many(over a 1000) TBI applications with these heads. I thought you knew I used to do a lot of tuning for Whipple. I have the best equipment, next to none on that old crap. Real time emulators to allow programming on the fly, 10 wide band mobile stuff, MAP, RPM, etc etc, whatever I need for data acquisition. I am not sure why you are mad at me for stating how ridiculous those heads are. They have a good place at times and I discovered 24 degrees was pretty good NA and supercharged (10 lbs with stock cam)was limited to about 18 degrees. I developed a camshaft profile that worked well with these heads way back in the early 90's. I have paid my dues, anyway, good times. Do what you want, those heads are junk. :lol:
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Re: Simple chamber mod that can get overlooked

Post by Tuner »

I don't care if you tuned the space shuttle and with your attitude I doubt not many do either. Not everybody has a Whipple budget. If somebody has those heads they don't need to feel they are junk, because they are not. They certainly are not the best, but if they are paid for that makes them better than nothing.

The father/son team had them on their hardscrabble dirt car because they pulled the 350 out of their wrecked PU, put a cam in it and a manifold and carb on it and went racing. They had no idea the heads were left or right hand thread, they only knew they were going racing and had a lot of fun for a summer and it was a lot more fun for them to be competitive in the A main than flop at the back of the C.

My point is the heads are better than the interweb lore and trash talk says they are. You are needlessly bad mouthing when you could have said, "I discovered 24 degrees was pretty good NA and supercharged (10 lbs with stock cam) was limited to about 18 degrees."

What was so hard about that?
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Re: Simple chamber mod that can get overlooked

Post by Mummert »

Everybody has their thing. I've only had 1 personal run in with "corkscrew" vortec heads 20 years ago. My 4.3L v6 in my dunebuggy. I used to work at a shop in 99' or so, we had a deal with UPS to rebuild there engines. Couple years later I thought to myself it would be a decent engine and I knew where there were some good cores. I built the engine pretty mild. 224 comp cam, 9.5:1 hyper pistons, Edelbrock manifold, 600 holley. It was a non countershaft engine with early Vortec heads. Did some portwork, I didn't have a swirl meter at the time. I know I have the flow numbers somewhere, but they werent real impressive. 10% gain or something and they stopped responding to anything. So I asked the owner of the shop about them, he put a bunch of work into a V8 set on his TBI truck and said he couldn't get it pull over 4800 rpm.
That wasn't gonna work for me and with a little digging in 2002 GM was blowing the vertical bolt Vortec heads out. I bought 2 new heads for under 200.00 bucks. Edelbrock had the conversion manifold fresh off the presses and whola! Still have it today.

I almost feel like grabbing one of those old heads just to see what the swirl really is.
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Re: Simple chamber mod that can get overlooked

Post by 1980RS »

Tuner wrote: Tue Mar 21, 2023 11:54 pm
1980RS wrote: Tue Mar 21, 2023 10:09 pm I cut the swirl ramp out of my L-29 heads when I ported them on some good advice from our local head porter I know. Must have worked, that car ran pretty well last fall with those heads, better than expected.
The small block screw port head gets bad press but they run good when the timing is not beyond 25 degrees.

L-29 is a 454 head. What does that have to do with this? I don't know what the L-29 head likes for timing. A pal's Chevy PU that has those heads never advances more than 30 when under load, sometimes less from knock retard I think, at least what you see using OBD scan tool.

How much timing did you use with yours? Did you ever try to find the minimum timing it needed?
It has to do with the swirl port and chamber that my heads had it them prior to porting, I was only able to test at 32° that day but next outing I will test from 28-38°of timing.
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Re: Simple chamber mod that can get overlooked

Post by Tuner »

Copy of post 18 years ago by Fast355 from thirdgen.org and pasted here.

https://www.thirdgen.org/forums/tbi/283 ... 193-s.html

Garage Ported "193"s (Flow #s)
I recently ported a pair of TBI 350 193 swirl ports as an experiment. I went into it knowing that they are swirl ports and can only have so much potential. Thing is when I got done and had a buddy flow bench them, the flow #s suprised the hell out of me. Not bad for 8 hrs with a air grinder.

Valve Lift------Intake Flow---------Exhaust Flow
.050--------------35.6----------------------31.0
.100--------------72.4----------------------60.5
.150-------------105.8---------------------87.3
.200-------------133.4--------------------124.2
.250-------------154.1--------------------147.3
.300-------------180.6--------------------171.5
.350-------------195.5--------------------184.7
.400-------------209.3--------------------196.3
.450-------------217.4--------------------203.7
.500-------------224.3--------------------215.6

All I did was knock the casting flash off the intake, reworked the intake bowl area and swirl ramp (swirl ram is still in place), then reworked the exhaust like you would any small block head. I also unshrouded and opened up the chambers slightly around the intake and exhaust valves. The heads still exhibit very strong swirl. While cleaning them I sprayed water into the intake port and recieved an unexpected shower. The swirl port literally threw water out in about a 6' diameter area. The heads were flow benched at 28 in/h20 just like any other head.

Notice how much better the exhaust flow is than the intake considering the intake is through a 1.94" valve and the exhaust a 1.5"

These heads are going onto a 350 TBI with either a vortec cam or LT1 cam. Probably the vortec since it only has a mild performance spring and considering that over camming won't help performance much.

I wish that someone knew what these things flowed stock??? Should have thought to check one before I reworked it.
Last edited by Fast355; 03-10-2005 at 12:51 AM.
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Re: Simple chamber mod that can get overlooked

Post by Mummert »

Its right at 195-200 cfm. You are right about where I was when I started looking into other heads. Having ported plenty of heads I knew 240-250 was very common for a well ported 1.94".
The later casting was 228cfm out of the box. With some bowl work and attention payed to the head bolt side of the floor leading up to the short turn it went 245cfm with the 1.94". I scored some Fast Burn hollow stem valves 2.0". After machine work and reshaping short turn and bowl they ended up right at 260 cfm. I left the 1.5" exhaust valve alone.
The same shop the that I got the v6 cores from years ago has a V-8 cork screw head. When I get a moment I'm gonna grab it and check the swirl.
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Re: Simple chamber mod that can get overlooked

Post by Tuner »

Mummert wrote: Fri Mar 24, 2023 12:23 am You are right about where I was when I started looking into other heads.

The same shop the that I got the v6 cores from years ago has a V-8 cork screw head. When I get a moment I'm gonna grab it and check the swirl.
That post with the flow numbers is not by me, it is a copy from another forum by user "Fast355"18 years ago.
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Re: Simple chamber mod that can get overlooked

Post by Erland Cox »

The swirl comes from separation on the short side.
The less the short side flows, if you get separation there the swirl goes up and the flow goes down.
It can be seen in the video.

Erland
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