LET'S TALK ABOUT 472's

If you look at a direct injected gasoline piston, it has the swirl enhancing ramps in it to continue what the injection can't quite do prior to combustion.
Cad heads have a swirl built into the port already, like many others.
Sometimes a flat piston continues swirl enhancement with the piston headed up top as well as other shapes.
4 valve heads have more tumble and shear off the short turn that continue it's direction the same way.
Sbc TBI swirl port as the precursor to BBC vortec heads show huge potential, seen previously in some experimental years of Nascar and reportedly...incorporated into Honda combustion design strategies.

There's available tests and research info from MIT and other sources in college textbooks focusing the continued education towards emissions in engine design. Much effort published from the 80's as fuel injection progressed.
Because of confidentiality agreements, it's doubtful that you'll find much directly from the OEM's, but in my opinion what you can do is fairly limited anyways, and if you put the engine outside it's original rpm range for that characteristic's intended effect...you negate what you are doing by finding a point of diminishing returns having a negative effect somewhere else or missing the effect altogether.
Tests can show the over-acceleration of the swirl effect to toss fuel right back out of suspension, or the odd protrusion or casting feature (wall) contributing to the weirdness.
Fancy way of stating that if you change much from stock, you have to re-think that part.
 
8ad-f85 said:
If you look at a direct injected gasoline piston, it has the swirl enhancing ramps in it to continue what the injection can't quite do prior to combustion.
Cad heads have a swirl built into the port already, like many others.
Sometimes a flat piston continues swirl enhancement with the piston headed up top as well as other shapes.
4 valve heads have more tumble and shear off the short turn that continue it's direction the same way.
Sbc TBI swirl port as the precursor to BBC vortec heads show huge potential, seen previously in some experimental years of Nascar and reportedly...incorporated into Honda combustion design strategies.

There's available tests and research info from MIT and other sources in college textbooks focusing the continued education towards emissions in engine design. Much effort published from the 80's as fuel injection progressed.
Because of confidentiality agreements, it's doubtful that you'll find much directly from the OEM's, but in my opinion what you can do is fairly limited anyways, and if you put the engine outside it's original rpm range for that characteristic's intended effect...you negate what you are doing by finding a point of diminishing returns having a negative effect somewhere else or missing the effect altogether.
Tests can show the over-acceleration of the swirl effect to toss fuel right back out of suspension, or the odd protrusion or casting feature (wall) contributing to the weirdness.
Fancy way of stating that if you change much from stock, you have to re-think that part.
Click to expand...

Interesting thought.

Thanks,

d
 
Heat and rpm accomplish the same things to some extent, or rather you need more mixture motion energy at low speeds or with less heat.
It's splitting hairs at our level trying to make more power but the various methods of pre-combustion energy help fill the low spots in the curve, raise output at lighter throttle settings and use less fuel at WOT.
 
I've read several articles stating that a flat top or dished piston helps the initial flame kernel stay in oval form promoting a more robust burning in the combustion chamber. I'm going to look at the heads more closely to see what they look like. I'm curious as to the effect the design would have when nitrous in introduced into the equation. With the compression ratio being low as Dave stated I would think it would possibly assist in producing more power because it is not inhibiting the flame travel through the combustion chamber.
 
One aspect of the running engine and the combustion cycle is that it lets you know if a faster and more energetic burn is taking place as seen by the new timing requirement.
 
One thing I can say about this adventure with Cadillac engine is that it has shown me a lot about tuning engines. I've never been more in tune with an engine. I've drag raced Chevy engines for 40 yrs and not seen the results I have with Caddy. Ground strap reading, fuel mixture reading has never been so easy. I love it. And I'm looking forward to more progress.
 
Howdy,

I agree on the Big Block Caddy tuning experience. Could you please explain more about ground strap reading???

Thanks,
Roy
 
Welcome to the family Roy. The ground strap reading tells the amount of timing the engine requires. There are several things to look at. First is the burn mark on the strap. You want the burn mark in the bend or just below it. As you advance the timing the mark will move down the strap towards the threads. Retard the timing it moves away and towards the tip of the strap. The next thing to look at is the color of the strap. This will be an indication of the heat in the cylinder. Gray is the correct color. If it's dark, plug's cold. If it's a rainbow colored it's too hot. Contrary to what people believe the plugs should look like they came out the box after usage. You might wind up with all different jets in each hole. CJay
 
Very nice. I have lots of jets, and will try to read the ground strap.

I say 472 with Forged Flat Top Pistons is the way to go. Seems like a nice way to make it hook up harder off the line. Then work on the last inch of each port under the valves, get a bigger cam, spray it on the top end, and make huge power with a 472.

The crank is stronger, so you can spray a bit more Nitrous Oxide with a 472, and it should rev quicker. Also, e85 or Race fuel can let you run high compression, so think about the advantages of a Street-Screamer-472 on e-85 !!!

Thanks,
Roy
 
ccjohn2 said:
Welcome to the family Roy. The ground strap reading tells the amount of timing the engine requires. There are several things to look at. First is the burn mark on the strap. You want the burn mark in the bend or just below it. As you advance the timing the mark will move down the strap towards the threads. Retard the timing it moves away and towards the tip of the strap. The next thing to look at is the color of the strap. This will be an indication of the heat in the cylinder. Gray is the correct color. If it's dark, plug's cold. If it's a rainbow colored it's too hot. Contrary to what people believe the plugs should look like they came out the box after usage. You might wind up with all different jets in each hole. CJay
Click to expand...


CJay,

You were right, and I now have a different sized jet in every hole of the 850 Double-Pumper Holley.

Next up is a wide-band O2 for each header collector.

Anyone know of a way to probe the temp of each header tube about 1 inch from the cylinder head ?

Thanks,
Heisenberg
 
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