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Author Topic: Brodak 40 head clearance  (Read 1452 times)

Offline Rob Duckering

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Brodak 40 head clearance
« on: August 11, 2007, 08:56:17 AM »
Hi there, I just aquired a new Brodak 40 and checked the head clearance. I got .017" without the supplied .007" shim and of course, .024" with the shim installed as it came out of the box. I'm just wondering what the guys with the good running Brodak 40's are running for head clearance?

Cheers...... H^^
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Duck

Offline Jim Oliver

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Re: Brodak 40 head clearance
« Reply #1 on: August 11, 2007, 03:45:26 PM »
Dumb me---I'm running it it was when I bought it.  Whatever that is---never checked.

As stated in an earlier post: Powermaster 10/22,  Zinger Pro 11x5, launch at 8900-9000. 

Bill Little suggested the APC 10.5x4.5 but I haven't tried it yet.

Jim
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Offline Ralph Wenzel (d)

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Re: Brodak 40 head clearance
« Reply #2 on: August 11, 2007, 06:18:39 PM »

Bill Little suggested the APC 10.5x4.5 but I haven't tried it yet.

Jim
[/quote]

Do try that APC, Jim. I've been running a Rev-Up 12-5 cut to 10½", with a little undercamber sanded in, and it pulls a CardinalARC around with excellent line tension, even overhead. I need now to get another cardinal ready so I can try some of RSM's new props! They may be even better.
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Offline tom hampshire

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Re: Brodak 40 head clearance
« Reply #3 on: August 12, 2007, 05:51:24 PM »
Rob - It depends on the weight and wing area of the airplane.  The single gasket should work well up to about 44-45 oz, 575 sq. in.  Any heavier/larger than that, and you'll want to go up in compression, but only after it is fully broken in.  Tom Hampshire
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Offline Bradley Walker

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Re: Brodak 40 head clearance
« Reply #4 on: August 21, 2007, 10:42:11 AM »
Quote from: tom hampshire on August 12, 2007, 05:51:24 PM
Rob - It depends on the weight and wing area of the airplane.  The single gasket should work well up to about 44-45 oz, 575 sq. in.  Any heavier/larger than that, and you'll want to go up in compression, but only after it is fully broken in.  Tom Hampshire

Hi Tom,

First of all, I LOVE the Brodak 40.  I think this engine is misunderstood and under appreciated.

My question here is how do you raise the compression?  Take out the single gasket?
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"The reasonable man adapts himself to his environment. The unreasonable man adapts his environment to himself, therefore all progress is made by unreasonable men."
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Offline tom hampshire

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Re: Brodak 40 head clearance
« Reply #5 on: August 22, 2007, 07:19:18 AM »
Brad - Right, remove the head gasket.  If the engine is scratched up, lap the head to the sleeve with rottenstone or toothpaste until it comes up dull gray through the entire area where the sleeve top meets the head face.  Try to keep the lapping compound out of the side of the head, where it contacts the cylinder bore.  This should always be a very slight press fit.  If it is loose at all, RPM goes down.  Tom H.
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Offline Bradley Walker

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Re: Brodak 40 head clearance
« Reply #6 on: August 23, 2007, 10:38:35 AM »
Quote from: tom hampshire on August 22, 2007, 07:19:18 AM
Brad - Right, remove the head gasket.  If the engine is scratched up, lap the head to the sleeve with rottenstone or toothpaste until it comes up dull gray through the entire area where the sleeve top meets the head face.  Try to keep the lapping compound out of the side of the head, where it contacts the cylinder bore.  This should always be a very slight press fit.  If it is loose at all, RPM goes down.  Tom H.

Hey, Tom,

On the next batch, can we have .007" taken off the bottom lip of the head, and then ship the engine with two .007" gaskets?  That way we can use the higher compression setting once the engine is broken in without lapping the head?

Also, a question:

As the Brodak 40 has been developed, the timing has been lowered on subsequent versions, right?  Has the head clearance ever been changed?
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"The reasonable man adapts himself to his environment. The unreasonable man adapts his environment to himself, therefore all progress is made by unreasonable men."
-George Bernard Shaw

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