j par
Well-hung Member
I can't run any higher compression without the Piston hitting the head..LOL...
ProComp/Speedmaster aluminum heads
- Thread starter j par
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Heat leaves the aluminum faster than cast which creates lower cylinder pressure which = less power. You'll gain the compression needed with the closed chamber head to maintain cyl pressure
j par
Well-hung Member
You work for Hughes engines or something? LOL where's your proof LOL..
tires in summer vs winter. Cooler temp = less pressure
This is complete bull.
^^to put it nicely.... LOL... So I'm just using general logic. I'm open to more science. Please explain. I can say I know balloons lose pressure in the freezer and they shrink. I can say tire pressure is less in the winter than in the summer. So why wouldn't aluminum heads, which dissipate heat faster not drop the cylinder pressure??
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Impossible to dissipate enough heat between firing cycles to make any difference.
Bull ****! Please provide proof.
Ok. hoping for more science. So air gap intakes don't work either, because the air moves so fast through the intake it won't have time to heat up. So air gap intakes will make no difference anyways??
Making no sense here.
I mean, I'm willing to change my thinking, but somebody is going to have to offer some science. Nobody is arguing tire or balloon deflation with cooler temps = less pressure. Only explanation I'm seeing being offered is the process happens so fast that the drop in temp doesn't lose pressure???? Yet, heat crossovers are blocked and air gaps are used and the air moves MUCH faster through the intake which is feeding 8 cylinders than the air moves through a single cylinder on a 4 stroke.
Prove what’s been proven before—— again?!?!?
yellow rose
Overnight Sensation
I did that. I screwed up and did it in a existing thread and couldn't finish it. Why you ask? Because it always (I don't care the topic, name any topic...politics, religion, sex, money, food, carburation...whatever) takes 50 times more work to refute an error than it is to say it.
For example...you can run 1-1.5 points more compression with aluminum heads then you can with iron.
One short sentence. If I reply the head doesn't know what it's made of, which is no different that the statement you make won't suffice because you don't accept it and say you want "science". Then I ask what "science" do you have to support your presupposition?
I have over 30 years of actual doing it to back me up. I've been running big (big is a relative term) compression on pump gas on iron heads and can tell you, it doesn't matter what the head is made of.
Now, back to the "science" you want. Like I said above, I started doing that but the typing literally made my hands swell up. That's how much it will take for me to explain the "science" to you. I think I had 4, maybe 5 posts in that thread that were at least AJ length posts. So if you think about it...that's a TON of typing. And my RA just doesn't tolerate that much typing.
If you can find that thread over in the small block forum put it at the top and I'll finish it.
But the "science" says head material doesn't matter regarding compression ratio.
Then I can make it simple with these questions. One word answers.
- Does aluminum dissipate heat faster than cast iron?
- Does air being contained (cylinder, balloon, tire) lose pressure in cooler temp?
- Does less cylinder pressure create more or less horsepower?
- So IF aluminum creates less cylinder pressure, does it allow more compression to be run to make up for the loss of cylinder pressure?
He has it all worked out in his head except the actual correct answer.
yellow rose
Overnight Sensation
We have at least 3 threads going on this. Go back to the other thread and I laid it out there. Hughes is wrong. Read what I posted over there.
BTW, I think it was the road kill dude and the long haired Chrysler guy who's name...Dulcich...did a test with the dude form Westech...I'm horrible with names..I can see the faces but can't think of the names...did a test on aluminum verse CI and they found nothing.
Just like I have been doing since 1980.
In my mind, the difference in temperature would be so small regarding it's effect on cylinder pressure, it would likely be immeasurable. When the balloon shrinks in the freezer, there is a 30 degree difference at least (my mind is thinking Celsius here), same for the tire. As far as the air gap intake goes, the plenum never gets as hot, so less heat can get transferred into the air as it rushes through. It is likely a measurable difference in plenum temperature between an air gap intake and any other.
The cooling system in the engine should be designed to maintain a steady temperature of all engine components including the heads that have coolant passing through them. That is why the air gap in the intake is there to separate the plenum from the engine temperature. Aluminum has the ability to better transfer the temperature spikes than Iron but I can't see it really affecting cylinder pressure because the average temperature would be what is having the most effect here.
That's my non scientific view on the subject from a guy who graduated grade 8 and as has been said before, it's worth what I charged you for it?
Cley
The cooling system in the engine should be designed to maintain a steady temperature of all engine components including the heads that have coolant passing through them. That is why the air gap in the intake is there to separate the plenum from the engine temperature. Aluminum has the ability to better transfer the temperature spikes than Iron but I can't see it really affecting cylinder pressure because the average temperature would be what is having the most effect here.
That's my non scientific view on the subject from a guy who graduated grade 8 and as has been said before, it's worth what I charged you for it?
Cley
yellow rose
Overnight Sensation
Exactly. You nailed it. Even if the temp curve under detonation goes straight up (vertical on a graph) there is absolutely no way that temp can get into the coolant and make a difference. And, even if it did, how many BTU's does it take to raise the temp of the coolant even 1 degree in 1 or 2 seconds to make the heat dissipation remotely viable?
You don't need science. You need common sense.
LOL... I replied to your post in the other thread. your coolant remarks I hadn't thought about, which made my points "less factor" although not "non-factor". thanks.
j par
Well-hung Member
My question was more of the head design? Even the question of quench comes in mind...
Phreakish
Well-Known Member
1: no - alum CONDUCTS heat about 2x the speed of iron, but also weighs 1/2 as much, which means two identical parts made from each material has about the same thermal performance (because thermodynamics relationships are based on mass).
2: yes, but it doesn't matter. The amount of energy is dictated by the mass of the air and the mass of the fuel. Being at a higher density and lower pressure will not matter. Once ignited, the temperature and pressure will rise rapidly. An aluminum head will not be able to extract enough heat to have a measurable effect on power - otherwise switching to alum heads would make an engine MORE prone to overheating not less as is often the case.
3: less, but irrelevant, see #2.
4: begging the question.
My understanding, which may not be correct, is that more compression is run with alum heads because alum is a weaker material and deforms under load to a greater extent than iron. This means that the chamber effectively 'stretches' as air is compressed, reducing effective compression ratio. This is why race oriented engines use more headbolts than OEM applications.
Deformation can be overcome with good design. A well designed cylinder head which doesn't deflect as much would reduce the difference between iron and alum. Since mopar heads have shaft rockers, it's incumbent on the designer to ensure a reasonably stiff head to prevent binding or failure of the valvetrain. There's probably plenty of junk heads made in the ancient past for brand X motors that deflected more (especially flathead engines) which were the genesis of this +1.5 myth.
Oh My !
LOL 318hasvalveswillfly vs Jpeghasrubberheads
j par
Well-hung Member
Being jealous of my aluminum heads is not becoming of you...LOL 318hasvalveswillfly vs Jpeghasrubberheads
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