$ per mile: high compression/high test vs. low compression/regular

Just changing from flat top pistons to domed pistons increases compression ratio. Did that. Eventually, I could no longer readily find the high octane fuel for it.

Yes, I understand that from new car design now. Where were you 30 years ago when I needed that information?

I get more and more confused as to what you understand and do not understand about spark ignition internal combustion engines.

The "conventional domestic cyl heads" of today are actually pretty darn good.

And what do you mean by "try to keep shallow spots to a minimum." to "allows a higher compression ratio to be used successfully with lower octane fuels." ?

High quench fast burn cyl designs rely on VERY CLOSE piston to cyl spaces. Less than 0.065" is REQUIRED to get good power from high compression and low octane. The ideal is to have as little static clearance between the piston and head as you can get away with without having the piston kiss the head at speed. On a 450 HP Chevy small block 350, you can go as low as about 0.025". At 0.024 on a well built engine you are good to about 7000 RPM before the pistons touch the head..

The "quench" serves 2 purposes. (at least). It increases the surface to colume ratio, absorbing more heat from the "end gasses", delaying detonation, and it causes a lot of "swirl" in the remainder of the combustion chamber, causing faster burn.

In FACT it is actually the opposite - in a lot of cases. If you reduce the quench clearance from 0.070" to 0.030" you REDUCE the tendancy to detonate.

To reduce the quench clearance you generally also reduce the combustion chamber volume, which, all else remaining the same, increases the CR.

This is a quote: "Chamber cavities between the piston and the cylinder head between about .060-inch - .0120-inch appear most likely to be the site of detonation. Speeding up combustion mixture motion/agitation is vital. This means maximizing the quench action. On a small-block Chevy with a stock block height, a stock compression height piston is typically .025-inch down the bore. With a .040-inch gasket this makes the static quench clearance .065-inch, which is way too wide. By cutting the quench clearance the burn rate and quality improve to the point where the motor gains compression and is less likely to detonate even at the higher ratio involved."

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And how did they do it????? They use high quench fast burn combustion chambers that use the same principals.

Have you read Sir Harry Ricardo????Or even know who he was?

Are you one of them? The phds, that is?

it's

It DOES happen. Not often, but I've seen and replaced several.. More common in the sixties and seventies - the newer hoses are designed better - with better materials so the liner does not de-laminate from the cord and collapse into the passage of the hose. Another thing that happens is the steel brackets that hold the flex lines away from moving pard will rust and swell, pinching the hose - the pressure of the master cyl will still force fluid past the restriction to apply the brake - but the restriction causes the cyl or caliper to remain partly applied because there is not enough return force to push the fluid back to the master. Breaking the rusty bracket off releases the hanging brake. I've seen quite a few of those as well.

One lead into the antifreeze and one to ground WILL give you an indication of electrogalvanic potential which is an indication of the antifreeze PH being out of spec and potential galvanic corrosion problems.

What are your credentials to make the assertions you are making about automotive engine design and theory????

Believe me, there was NO carbon buildup in the combustion chambers of that Valiant when I removed the head. Carbon restricts inlet and exhaust and increases compression ratio, and causes hot-spots that cause pre-ignition. Not good for sure - but removing the carbon does not increase performance beyond factory stock.

Those numbers are of coarse not absolutely accurate - but the difference of 2.8 octane is VERY close. I'll tell you - the car NEEDED premium to run properly.

How much do you allow for rod stretch?

In the case of the quoted 350SBC, 0.024" for rod stretch and big-end and pin bearing clearances combined at 7000 RPM.

In FACT it is actually the opposite - in a lot of cases. If you reduce the quench clearance from 0.070" to 0.030" you REDUCE the tendancy to detonate.

To reduce the quench clearance you generally also reduce the combustion chamber volume, which, all else remaining the same, increases the CR.

This is a quote: "Chamber cavities between the piston and the cylinder head between about .060-inch - .0120-inch appear most likely to be the site of detonation. Speeding up combustion mixture motion/agitation is vital. This means maximizing the quench action. On a small-block Chevy with a stock block height, a stock compression height piston is typically .025-inch down the bore. With a .040-inch gasket this makes the static quench clearance .065-inch, which is way too wide. By cutting the quench clearance the burn rate and quality improve to the point where the motor gains compression and is less likely to detonate even at the higher ratio involved."

Read more:

Yes I've seen it too. It is pretty easy to discover the cause of the problem when you find a brake caliper that is dragging. If you open the bleeder, and the brake instantly releases and the wheel turns free. When you see that you know something is blocking the flow from the wheel cylinder back to the MC. When you step on the brake the wheel is locked again. This time you release the hose fitting on the MC side - nothing happens. Then you release the hose fitting on the wheel side and instantly the brakes release. Now you know the blockage is inside the hose.

-jim

i don't think you read what i actually said - the designs are very different.

i already told you that.

i never said it would improve it over stock, but it /does/ improve it compared to when it was carboned up - with is an increase in compression ratio.

yes indeed, because of poor combustion chamber design, not because of compression ratio. the honda s2000 has an 11:1 compression ratio and that will run on regular 87.

and with a properly designed motor, you can go to 9500rpm, stock, outputting 120hp/liter, with no clearance issues that cause dead spots or emissions.

you're replaced constricted hose, but you've never replaced one with a "flap" in it.

that whole "flap" thing is just the most spectacular made-up bullshit urban legend imaginable. i have no clue how people could invent such nonsense, let alone regurgitate it as "truth". all you're getting is circumferential constriction due to polymer degradation. end of story, not a "flap" in sight.

absolutely not. you obviously don't know about electrode potentials and how they're generated, so this is not a criticism of you, but when you dip a metal electrode into an electrolyte, you get a voltage. any metal electrode, any electrolyte and that includes meter test leads. so what you're "measuring" is the potential difference between the actual test probe metal and the grounding electrode, nothing more, nothing less.

if you have corrosion in your cooling system it's because you're not changing your coolant on schedule and using tapwater as dilutant. in future, stick to schedule and use distilled - you'll have no more corrosion.

purported "credentials" on usenet are utterly ridiculous - anybody can pretend to be anything they want. all that matters is the accuracy of what they say. regurgitating nonsense other people make up on shade-tree gossip sites, however much it may have seemed plausible absent the real facts, simply doesn't qualify.

Due to very fancy variable valve timing, more than head design

Of course. But someone just asked ME how much was allowed for rod stretch ON THE EXAMPLE I HAD GIVEN.

Enough. Goodbye.

Bullshit. I've cut the hose open - the liner has come loose from the cord and "flapped" down.

It is because the Ph is out of range. Period- for whatever reason. And if the PH is off you will get a higher reading on the voltmeter. It is not PROOF of anything, but an INDICATION. No voltage - no problem. voltage, possible problem - check further.

So you have no reason or excuse for anyone to trust what you say to be anything but the above. Goodbye.

sorry, that's bullshit back at you. of course, you could always post a pic of your spectacular new invention, but you won't.

in the mean time, here's a "but the earth's not flat" concept that i think you'll have problems with - brakes don't work on "flow", they work on hydrostatic pressure transfer. since there's no "flow", there's no mechanism by which any "flap" can possibly be created.

whoever failed to teach you basic chemistry at high school really did you wrong.

no, it's not pH, it's electro-chemical electrode potential - you're dangling a metal probe into an electrolyte and measuring the potential difference for that metal relative to the [dissimilar] ground electrode.

this is usenet. "trusting" someone that tells you they have credentials rather than bothering to check facts and educate yourself is absolutely insane.