mark kibort

are you going to do anything to the intake, like extrude hone, or clean up the inlets? how about the spacer? probably isnt that important with your plans for boost.

nice job! looks like jewelry

mk

BC

Yes, high boost. Higher than the normal Stage stuff that Mr. Murphy supplies. It will be a Centrifugal, and possibly up to over 20psi. Thats why I am doing the ethanol, as the 9.4:1 compression may be a bit high for that much boost on regular 91 octane SoCal gas.

The piston coating is a themal coating on the crowns to repel heat before it soaks into the piston on combustion - even little bit will help with the cast pistons, and the skirt coating is to renew a sacrificial layer for the piston. The tin or iron is a sacrificial layer, and wears away. Also, ethanol is not a lubricant, so I need to be careful about oiling and friction where the fuel itself may be.

BC

Well, I don't know then. I just didn't want to make it permanent on such small nuts and studs.

BC

Thanks. I watched a video about how the AMG guys put together thier hand made engines. While they have cooler tools than me, and cranes and prepared assemblies, they still stick stuff together by hand. I was thinking about how the Porsche guys did it by the late eighties - probably with some tools hanging from the ceiling, but they still had to do it by hand. I don't know if any engined can be assembled completly by computer.

I love this part. Its the most fun. I love the clean assembly stage. I haven't had dirt under my fingernails for nearly a year now.

BC

On the intake itself, I have already, or will:

1) debured the bell mouths, cleaning up the entry
2) Match the intake to the gasket and ports
3) Removed the ribs from the inside of the side plates
4) Add a 1/2 inch spacer
5) Had the runners coated with heat barrier.

6.0-928S

Nice work Brendan. You're right, this is the fun part. The nervous part is when you start it up!
Why not open up the combustion chambers a few cc's, maybe remove the quench areas to lower your compression so you can safely run the kind of boost you'll need to reach your power goals? Just thinking out loud.

Regards, Hammer

BC

I have thought about that. The heads are up for disassembly and cleaning (they have already technically been rebuilt), and at that time I may make some changes. Cutting the base circle just a bit for more lift on the S3 cams is a possibility to get more air in at upper revs. I don't know yet.

So the combustion chamber would be an interesting project. Do you have any pictoral ideas as to where to remove material?

6.0-928S

I don't have any pics. It's the same thing Ford did to the Boss 429 heads to go NASCAR racing. Basically you make the chamber a full circle on the head surface & remove the flats on each side of the combustion chambers. They are called the quench areas, for better emissions. I would think it may be difficult to achieve your power goals without high boost with compression as high as you have. You want high boost not high cylinder pressure.

Hammer

BC

Interesting. I thought quench was very important to proper flame propagation? Ethanol burns very slowley, thereby creating more opportunity for timing without any detonation. My power goals were high because I know that detonation won't be a problem. Now total combustion pressure under proper ignition, if you are saying that may be too high, then thats different. Thanks.

6.0-928S

Maybe if you could find an article online about why Ford did the NASCAR mods on the Boss 429 you'd come up with some interesting ideas. I read the Ford papers years ago & remember that they were very interesting & full of power theory & combustion chamber breathing & how the design changes affected each. They did a lot of testing. Sorry, but I don't remember any specifics. It's been 25 years since I read them, but I believe you'd find it very tasty.

Hammer

BC

To be honest, while I can assemble clean parts and do various higher-level thinking about parts and usages, I am not good with that detail work stuff. I am very concerned that I would Fvck something up bad enough to ruin this project. Seriously. If I had some sort of template to cut at the heads with MAYBE I would try it, but I would need specifics. I will look for that info, but did you change your combustion chambers at all?

6.0-928S

No, but I had no reason to. If I was building what you're building I would either have 8.5:1 pistons (minimum) or modify the chambers to lower compression. I would never supercharge an engine with 9:1 compression or higher, but that's my opinion. You can't get maximum benefit from a supercharger with compression that high. And if I was going to supercharge I'd want maximum efficiency.

Hammer

JEC_31

Hammer, would you be thinking of the work of Larry Widmer?

http://www.theoldone.com/articles/

On that page, this article is probably the most pertinent one to this discusion:

http://www.theoldone.com/articles/The_Soft_Head_1999/


As near as I can make out, the quench area's purpose is not to "quench" in the original English definition of "putting out fire", but rather to concentrate the compressed fuel-air mix into the place where it can get lit quickly and well: under the sparkplug(s). Sure the emissions will go down - because all the previously unburned fuel got turned into horsepower instead.

I wonder how this approach will handle ethanol?


And IMO, Brendan doesn't want high boost, he wants high cylinder pressure on the power stroke!

FlyingDog

I have read that if you put a heat rejection coating on the pistons you should also coat the heads. If you don't you will get a lot more heat in the heads.

BC

Well, the way I had it down (and I am being careful to not make factual statements here, as you guys know your ****, and will call me out if I am wrong) is this:

I know these pistons are cast. I know that they provide, with the chamber, a higher CR than is usually allowed when someone talks about high pressures. Combustion pressures create heat, and heat creates a situation with pump gas that allows pre-ignition and detonation, which can create combustion pressures (since the piston is still on the way up) up to 10 times higher than normal. 10 times! Thats what blows up engines.

It is my understanding that this is what destroys engines.

Now, take that away. Take the detonation away, take the pre-ignition away. Put a fuel in there that has a slow burn that also cools the final combustion temps because it starts out cooler. It is about 108 octane, but because of its higher Latent heat of evap, its dynamically higher.

So for these reasons, and for experimentation and some budget/time constraints, I am going to run this block as stock as can be without being stupid about it. I have used coatings, 951 rings, forged (well, as forged as the porshe parts get), girdles,S3 cams, and cometic head gaskets to get the engine as ready for pressure as possible.

Past that, if the thing blows up from sheer HP, then thats fine. But I will not let this thing blow up from Detonation, because thats just a waste. 10 times the normal pressure at its highest peak is possible with detonation and pre-ignition. That means if you have enough pressure in the chamber to make, say 700hp, then if it detonates, you get 7000hp. No engine here will survive that nor are the built to. Control the ignition process, and it stays together it seems.