[barry425]

You said "9 years older then you". Did you mean "9 years older THAN you"? I'll cut you some slack, seeing as how you are 74. :-)

[thinwhiteduke]

Originally Posted by barry425

You said "9 years older then you". Did you mean "9 years older THAN you"? I'll cut you some slack, seeing as how you are 74. :-)

I'm confused here now, did I miss a post or two here somehow?

Duke

[1Gary]

If you look on the valve cover,the white tag you see is where you would find my name on some of the Cosworth's.



At a 185hp with only 140 c.i. and the first EFI with 12.5 c/r,would outrun any 4 cylinder engine of it's day.Now I'm not saying it wasn't without it's problems,but the factual truth was we fixed that in the later yrs.Had it not been for the car being priced only $600 less than a vett,EPA killing the performance,and a crappy body,the car would have been continued to be produced.These days I'm told the Cosworth's Vega's are a collector's wants.Aside from the dyno tests I ran on them,having driven one,they where far from a turd.At only on the high side only 2,500 lbs,that 185 hp mattered.


Now Barry.Although I am very pleased to see your involvement in Vega's,I got to say .010 is too tight.I'm basing that off all the yrs of building engines,and also building the Cosworth.All I can think of is maybe the measurement is off. That isn't to say you don't know what your doing either.Mistakes are made sometimes by the most experienced engine builders too.

[Landshark928]

Originally Posted by barry425

Landshark928, I'm sorry, but you are just plain wrong about the octane/burn rate. Also, this is a fact that was widely known before the internet was even conceived. Would you mind telling me how old you are? Just curious.

You need to do more research. The facts I mentioned were referenced from the head chemist at Sonoco, Jim Wurth. The guy who blends their fuels and even race gases. I would think he would know a thing or two about Octane ratings and burn rates.

I had 4 years of chemisty in college, I'm a nuclear physics major. First year students learn the difference between flash point and burn rate.

Here are a couple articles you may want to read to inform yourself and dispell the "Octane Myth". It is hydrocarbon content that determines burn rate once ignition takes place, Octane has nothing to do with it anymore.

Sunoco Race Fuels | Beyond Octane

From Sonoco's own site:
"Naturally aspirated race motors with large combustion chambers spinning at high RPMs really like high-octane, fast burning fuels. They need the octane to prevent uncontrolled combustion, and they need a fast-burning fuel so that the flame front can span the large bore of the combustion chamber quickly. If you’re not sure which fuel burns faster than others, one indicator is specific gravity. “Lighter” fuels – fuels with a lower specific gravity – tend to burn faster because fast burning hydrocarbons are themselves light. Look for a specific gravity close to 0.70 and you’ll likely find a fast burning fuel. Of course, consult with the fuel producer to verify your assumptions. You might be surprised to learn that some of the highest octane fuels may also be some of the fastest burning fuels!

You might also be surprised to know that fast burning fuels may not need as much timing as their slower burning counterparts. Many times we get calls from individuals who are dialing in new motors on a fast burning fuel but they’re using timing and jetting numbers from their old motor and fuel combo. “Retard the timing a couple degrees and see what happens” is not the suggestion they expect to hear! With high octane, fast burning fuels, it is easy to dial in too much timing. In such cases, the engine is not detonating, but it is past the point of optimum spark advance, so it’s just heating things up and making less power. A little less timing may really wake up the motor."

And another great read... but a little more technical.

Octane is not how fast a fuel burns

"Octane ratings are ONLY a measure of a gasoline's tendency to resist detonation. It has nothing to do with deflagration. Octane rating tells us NOTHING about the speed at which the flame front travels across the combustion chamber. AGAIN! Octane rating tells us nothing about flame speed. There are hydrocarbon fuels (gasoline is just a mixture of many hundreds of different hydrocarbon fuels) which burn at exactly the same speed yet have wildly different octane ratings. OK, one more time; octane rating does not correlate with burn speed.

Octane rating tells us one very specific thing----> how resistant the gasoline is to the free radical activity that causes detonation. Actually, if all else was equal, a faster burning (deflagrating) fuel would have a HIGHER octane rating than a slower one. Why? Because the faster deflagration takes place, the less time the gasoline mixture around the edges of the combustion chamber has to get "beat up" by the free radicals which cause detonation. There's a race of sorts going on between the advancing flame front and the free radical activity. The goal is to get all the a/f mixture consumed through deflagration before detonation has a chance to occur."


So please come back with empirical evidence that higher Octane fuels burn slower, and not just "It works for me" or "100 internet threads claim it", or "I heard it at the track".

[vinniekq2]

I made the mistake of asking about fuels from Sonoco,they faxed me close to 100 pages

[cobalt327]

Originally Posted by 64nailhead

Cobalt & F-Bird,
Being a novice to engine building, Barry mentioned something that I've never heard of: polishing the head chamber in an effort to get a better/cleaner burn to eliminate detonation. I'm asking how effective this is and if there is a benefit for lower compression, say 9.5 - 10.5 compression when making tuning adjustments for a novice like myself. I ask because I'm going to be changing my head gaskets to get a more desirable quench distance and I could polish the chamber at the same time.

If you have covered all the other bases, and your time is available, sure- go ahead and polish away. Percentage-wise I believe it's a waste of time/effort on a street engine, but there are others who would have you believe it's a "must-do". Beyond knocking down any irregularities that could cause preignition (glowing hot spots), I just do not agree.

If you want to make a difference, do the things that will give a significant, measurable improvement- like keeping the quench tight, maintaining good ring seal by torque plate honing the cylinders, maintaining a good valve stem oil clearance which will also keep the seat concentric, a good valve job and cleaning the bowl up, etc.

Edit- Another avenue you might want to explore is the various coatings applied to the piston crowns and combustion chambers that are said to aid heat retention, etc. Not a cheap process, but there might be something to them that goes beyond polishing the chambers.