Worse combustion chamber design ever? Saveable?
- Thread starter oliver
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yellow rose
Overnight Sensation
I said it earlier but if you make the area around the valve bigger just because it flows more you are killing power. Just because the flow bench says more air flow doesn’t make it better.
@IQ52 I believe has made comments in the past regarding valve shrouding and how it was not "all that" important......although I may be remembering it wrong. I tagged him so he'll come hit me over the head if I'm wrong.
MOPAROFFICIAL
Oogliboogli
In some cases.
Flow benches are just tools. They try to replicate a characteristic of a running motor...but don't accurately simulate a running motor.
Just a thought i have is when you negatively alter the fuel distribution around the valve, or have a biased port... that burn time and efficiency takes a hit.
But be more specific. Is it chamber to bore or chamber to valve. Tossing statements like "just because it flows more air doesn't mean it makes more power" Who should toss their heads in the trash and why..?
And lets talk about flow setup on the bench and the effect of bore center and placement of the shrouded side of the bore lining up. Throw in the importance of an intake manifold straight wall lining up perfect with the port straight wall on power and the reflected flow increase on both the bench and the dyno, volume, discharge etc..
In what example are you using to it's relevancy?
Dissect it more and explain what you are trying to say to these people.
oliver
Well-Known Member
I wouldn't say so. I've dealt with hundreds if not thousands of different cylinder heads and I've never seen a combustion chamber where the intake valve is down into a pocket like that. After some research ford only used this head for one year. It was that big of a failure. Factory rating on this head is down 25hp previous year and next year.
yellow rose
Overnight Sensation
You can talk about it. I’m not typing all that out.
I simply stated you can keep moving the chamber wall out and it will flow more air. You kill pressure recovery when you do that.
The valve job has an influence on pressure recovery (exit loss) too.
Like an exhaust port, using a flow bench, particularly using mass air flow through the flow bench to determine chamber shape is not always the way to do it. Not all air flow is good air flow. The exhaust port is a perfect example of that. Make it as small, fast and quiet as you can and it will flow less and make more power.
MOPAROFFICIAL
Oogliboogli
Ill have to re read your post. I interpreted it as you were aiming at the chamber shape itself being intrusive. You can buy lots of aftermarket iron heads, well...I wouldn't say lots but I quite a few.. where the valves are literally sunk a bit. Many people get their heads reconditioned by old-timer shops that do it...or after many valve jobs the valves are also very sunk. There is more to a good valve job than just the seat.
25 horsepower is right ...because almost every bit of the sub .400 lift is snuffed.
So when you hear a general statements by some folks of how low lift or big low lift is garbage or hurts flow ,a power killer n all these other things... take that with a grain of salt because it takes some unique circumstances to turn a strong low lift against you and you could easily see that in the crystal ball by other issues with the port.. A simple maching process could have remedied it but would have cost them i guess n so they reverted back im guessing.
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My comments are Simple. I think people see things other people talk about and latch onto ONE thing and cherry pick it. It's my opinion that "valve shrouding", while certainly can have an effect, is not a combo killing point, right by itself. That's the point I was trying to make.
oliver
Well-Known Member
Yes, I agree with you. But I cannot see how this design would ever be a good idea. Even if they were directing the intake charge to get more 'swirl', it could have been acomplished just with the shape of the chamber like with so many other heads.
I tell you what, you caint tell the Chevy boys that crap. They'll dang near give a ******* for a heart shaped chamber. lol
MOPAROFFICIAL
Oogliboogli
Where are all the whiners from the 302 head thread. You just made a statement that usually sets their hair on fire.
Because it was. It came when the manufacturers were forced to do something for emissions as per the EPA. Performance was the last thing they were thinking about. They needed efficient combustion. Hell, Ma Mopar started using computers (Lean Burn system) and roller cams in production. They had a lock-up converter transmission with more innovations to come.
Larry Shepard has written in many publications about them finding swirl properties in heads like all of the letter castings, such as X, O, U, J and so on. They were swirl heads before Chrysler even knew about it. It was a complete accident. I've always felt that was one reason why the small block heads were generally better than all the other manufacturers heads of the same era. Even being a smog open chamber, they got the job done.
That's a better chamber than the 302, in my opinion.
A little more shallow and no eyebrow between the valves. 920's are the same. I have a nice pair of those as well.
I have to ask how thick those factory steel shim gaskets are?
Let me look it up.
That's a tough one to answer. .030 - .022 The .030 was the fire ring and the .022 was the very outside corners near the outboard head bolt hole
MopaR&D
Nerd Member
I think it's the wall on the side where the spark plug is that has the most negative effect since it's shrouding the part of the valve where the most flow happens. The air/fuel mixture doesn't flow uniformly around the valve head, most of it flows across it out the side opposite of the intake port. The mixture has momentum and would rather go straight than turn down to go into the cylinder. Big reason raised intake ports are a thing, makes the path into the cylinder more straight.
If you look closely at the pics of the 302 or early closed-chamber 273/318 heads they all have that wall at a much shallower angle and curved away from the valves and the top goes all the way to the edge of the cylinder bore. The more modern chambers (Magnums, aftermarket) have the top of the wall pulled in a bit to make that second small quench area but it's still curved as much as possible so as to not shroud that side of the valves.
I've also heard somewhere before about those one-year-only Ford heads and how they killed power. Not sure what they were thinking it is pretty terrible. Then again IMO Ford has a history of "innovations" that didn't work as intended lol.
If you look closely at the pics of the 302 or early closed-chamber 273/318 heads they all have that wall at a much shallower angle and curved away from the valves and the top goes all the way to the edge of the cylinder bore. The more modern chambers (Magnums, aftermarket) have the top of the wall pulled in a bit to make that second small quench area but it's still curved as much as possible so as to not shroud that side of the valves.
I've also heard somewhere before about those one-year-only Ford heads and how they killed power. Not sure what they were thinking it is pretty terrible. Then again IMO Ford has a history of "innovations" that didn't work as intended lol.
dartfreak75
Restore it, Dont part it!
Those look very similar to my 302 (casting) 318 heads id run them and never give it a 2nd thought !
Okay, thank you! I got to look at a pair of those gaskets tonight but I didn't measure them yet, but they felt like they're around .028-.032 thickness. I was too focused on taking some other measurements. They're from the teardown of a 360 out a totaled out 1973 W300. With 14,714 actual miles on the clock. I been taking notes and pictures, there's a lot of stuff worth sharing on this journey...
MOPAROFFICIAL
Oogliboogli
"Swirl port" is bullshit marketing.
Many years went by before it dawned on me..
The 360 intake port shape, whether on the small side or not...didn't change from the intro of the j head to the "swirl port 308" . Its picking an event and marketing it cause it sounds cool.
Many years went by before it dawned on me..
The 360 intake port shape, whether on the small side or not...didn't change from the intro of the j head to the "swirl port 308" . Its picking an event and marketing it cause it sounds cool.
Puzackly. Just like "Magnum" and Vortec" engines. A snappy name always sells.
yellow rose
Overnight Sensation
I’ll say it this way...the chamber gets filled by a pressure differential. Anything you can do to increase that pressure differential will make power because the cylinder will fill faster, longer and with a better quality air/fuel mixture. The burn will be quicker and cleaner. There will be less residual combustion byproducts in the chamber after blowdown, so less pumping loss.
Anything you do that decreases the pressure differential does the exact opposite. You lose everywhere.
And that happens without an increase in air flow, or a loss of airflow. As someone who is trying to make horsepower, you have to consider everything from the air cleaner to the tail pipe.
Flow isn’t everything.
You have to convince the air to go where you want it to, and that’s into the chamber, in a form that is as easily combustible as possible.
It’s about SHAPE and size. You get those two things correct and the flow will take care of itself.
You want to look at how much HP per CFM of air flow you get. If you have a port that flows 400 and it makes 600 HP you need to see why it’s not making power.
The flow bench is an excellent tool if you use it correctly. It can and will lie to you if you don’t accept it’s limitations. Flow isn’t everything.
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