I have asked about this a little in the past, but let's say you're having a carbureted parallel valve 540 built custom, what options do go for?

Compression ratio? 7.3:1 or 8.5:1? I'd be comfortable burning 92 mogas in either, especially with 100LL constantly being mixed in.

Ignition? Currently planning on traditional magneto and one electronic unit (Electroair, etc). What about harnesses and plugs?

Carburetor? Precision Airmotive MS clone?

Alternator? This was discussed in another thread. I ended up with a new Plane Power 50A in a trade with a Halestorm.

Starter? What's the cat's meow for starter adapter/motor these days?

Oil filtration and cooling? Is there an aftermarket cooler and filter adapter that is better? The 540 adapter seems pretty good if you can set your cowling up for easy access to unthread the filter. The Van's cooler good enough? There's actually a lot of 540 goodies on the Van's website.

Fuel primer system? After my experience with breaking the copper oil pressure line a while back, is there an alternative to copper for the primer line? PTFE lined stainless braided? I kinda like the idea of this electric primer kit that would avoid me bringing fuel through the firewall to a primer pump in the panel.

What else is there to specify that I'm not thinking of? This is pretty exciting but a little scary.

Z,

Why not use a PMag instead of a regular mag? Has a built in alternator to keep if firing if you loose electrics, you get the advantage of electronic ignition, can use automotive iridiums at $9 each instead of aviation iridiums at $90 each. If your main battery is dead you can use a 9 volt for the PMag so you can hand prop the engine.

Propeller governor?

http://www.mt-propeller.com/en/entw/pro_gov.htm

I would go injected instead of carb - eliminates any carb ice, and just as simple as a carb. My two cents.

Greg

For an oil cooler take a look at these:

http://www.aircraftspruce.com/catalog/eppages/xseriesOilCooler.php

Barnstormer wrote:Z,

Why not use a PMag instead of a regular mag? Has a built in alternator to keep if firing if you loose electrics, you get the advantage of electronic ignition, can use automotive iridiums at $9 each instead of aviation iridiums at $90 each. If your main battery is dead you can use a 9 volt for the PMag so you can hand prop the engine.

Thus far the PMag for 6 cylinders has been vaporware

Zzz wrote:...Thus far the PMag for 6 cylinders has been vaporware

Duh! Stupid me. Sorry.

Barnstormer wrote:

Zzz wrote:...Thus far the PMag for 6 cylinders has been vaporware

Duh! Stupid me. Sorry.

Not stupid. I have been planning on it for a long time until I started reading. It's been "nearly available" for years. Such a cool product for the 4-cyls, I wonder why such trouble getting it out for the sixers?

Twin turbo's and NOS

How about a propeller gear reduction box and run her at 6000 RPMs? That will get the power curve right.

GO-540 baby.

I second the fuel injection comment. If there was one thing I'd change in my Maule, it would be to go FI instead of the carb......

I change my mind daily on the fuel delivery. I'd rather not focus on that here. For the other component/accessories of an engine, let's hear it. If you've never paid attention to this stuff, well lurk and learn with me.

Re compression ratio and mogas: what mogas options do you have locally? Planning to use 92 octane is great, unless it is or becomes unavailable. What do you gain going from 7.3 to 8.5? Is it worth it in terms of losing fuel flexibility? If you can set yourself up to use E0,E10, or 100LL, that'd give you unlimited options.

I agree with Eric on compression ratio. The increase in hp from higher CR isn't worth the loss of fuel flexibility. I may reduce the compression in my engine when I overhaul it to gain that flexibility.

On fuel primer: a primer pump in the panel is a must in my opinion. Hand proping even a carb engine without a manual primer would be tough if possible at all.

Is it proven that 8.5:1 causes detonation with 91 or 92 auto gas? What is the threshold? I read different things.

The power increase is about 25 hp at 2575 RPM vs 235hp with the 7.3:1.

I would third the lower compression. Then even 85/87 becomes no big deal - less $$ and is widely available. 235hp is plenty adequate for a Bearhawk.

Our O-320-B2B 160hp with high compression can be STC'd by Peterson for 91 octane Mogas, FWIW.

Zzz wrote:Is it proven that 8.5:1 causes detonation with 91 or 92 auto gas? What is the threshold? I read different things.

No. Todd Peterson proved that 87 was enough for 8.6:1 TCM engines but the FAA wanted a larger detonation margin so required the STC to only allow 91 or higher. If I remember correctly it was the same deal on the 8.5:1 Lycomings.

There is no real threshold because the are so many variables. You hear guys claiming 10.5:1 pistons in there engines and running 91 but what have they done with timing and are they instrumented so the know they aren't experiencing some detonation? After all the digging I've done I've determined that running 91 in my 8.5:1 engine will be fine but I want the ability to run 85 in a pinch. To make that possible I feel like I need to drop down to 7.5:1. I think it was Light Speed Engineering that offers electronic ignition that can be retarded on the fly in case a low grade fuel in required...that might be a cool option.

whee wrote:On fuel primer: a primer pump in the panel is a must in my opinion. Hand proping even a carb engine without a manual primer would be tough if possible at all.

I beg to differ. I prop planes multiply times a week. All of which are carb'd and lack the need of a primer. Now it may be a good idea for the bigger 6 cyl's for easier starting, but that would be the same regardless of hand prop or using an electric starter. Just saying, I disagree of your assessment of a primer being required.

whee wrote:can be retarded on the fly

This might be my new tagline.