Author Topic: ALMA's trusty Atomic 4 out for first overhaul  (Read 1251 times)

T_schlueter

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Re: ALMA's trusty Atomic 4 out for first overhaul
« Reply #15 on: December 21, 2020, 04:49:16 PM »
Block is out for machining. What type of hose is suitable for cooling water? Will heater hose suffice?
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Alma

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Re: ALMA's trusty Atomic 4 out for first overhaul
« Reply #16 on: December 21, 2020, 05:22:55 PM »
Good news!

You can use QUALITY automotive hose everywhere the water is under pressure (from the pump on).

The suction half from the raw water inlet on the hull and to any strainer and from the strainer to the pump needs to be QUALITY (expensive) marine hose with a spiral stiffener so it doesn't collapse if you get up against plastic debris at the hull inlet.

ALMA came with no onboard strainer. I think it is just another set of several fault points that can suck air, cause an impeller burn-out and create havoc. Anything that gave me a clog in 25 years was at the inlet over the side before a strainer could help.

I once got a clog in my engine inlet so I substituted the raw water through-hull that goes to the saltwater pump in the galley sink. It was good enough to get us to the yard where ALMA was getting pulled for Winter.

You may want to use an inlet hose that is longer than necessary so you can reach a substitute inlet in an emergency.

« Last Edit: December 21, 2020, 05:35:02 PM by Alma »

T_schlueter

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Re: ALMA's trusty Atomic 4 out for first overhaul
« Reply #17 on: January 16, 2021, 10:32:30 AM »
Engine is remounted in engine compartment.  I should have taken the mounts out.  Instead I chose to lift the engine off the mounts and dropped it back in over the the mounting bolts.  That was silly and a real pain.  I left the mounts in as I was afraid of messing up alignment.  Compression ranges between 75-80 which is a great improvement but not what I was hoping for.  I had the valves and seats reground.  Head surface ground slightly.  Cylinders honed.  Kept pistons and replaced rings.  I installed Indigo PCV and raw water cooling systems.  Also placed a timing pointer on the auxiliary pulley to enable easier timing with a gun.  Pics are attached.  Bench tested.  Runs great! 
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m_boone

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Re: ALMA's trusty Atomic 4 out for first overhaul
« Reply #18 on: January 17, 2021, 04:08:55 PM »
Beauty! Nice test set up too.

Alma

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Re: ALMA's trusty Atomic 4 out for first overhaul
« Reply #19 on: January 18, 2021, 04:43:53 PM »
WoW nice job!

You might see those compression numbers rise after a careful break-in. Be sure to run the first couple hours at all different speeds and loads. Don't worry about ignition timing yet. You'll be able to get the optimum timing running at cruise speed and slightly turning the distributer for best performance. The same goes for carb mixture. Did you get or already have an adjustable main jet on the carb? The idle and cruise mixture can be set while running just like the timing. Built in dynamometer! I never ran a compression test. These flat head engines don't have a lot of compression and don't need a lot to perform well. If all cylinders are similar you're all set.

I'll be looking forward to seeing how that Indigo thermostat works. I've had several different setups through Moyer and all of them rely on expensive and hard to find thermostats. The Indigo thermostat checks several boxes for maximum engine life.

Where did you get that nice exhaust mixer? It is similar to the one I had when we got ALMA. It was green and was ONAN brand for their generator. I'd like one like yours.

Well done!

T_schlueter

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Re: ALMA's trusty Atomic 4 out for first overhaul
« Reply #20 on: January 19, 2021, 09:50:23 AM »
Exhaust elbow: It was with the boat when I bought her.  I simply cleaned it up.  It is Onan P2833.

Timing: Yes, I'll recheck/adjust timing when I launch in the spring.  I really like using a timing light to take out some of the guesswork.  I've attached a pic of rather crude timing indicator installed next to the auxiliary pulley.  I punched and painted a notch in the pulley that references TDC of piston #1.

Adjustable main jet:  No, I don't have one.  I'll revisit that.

Indigo thermostat:  I'll let you know.  I bench tested without temperature gage and could definitely tell when it opened.  The bypass loop is quite sensitive to air pockets so I have to be careful to purge air otherwise exhaust gas doesn't get cooled when the engine is cold.  I melted my makeshift exhaust hose.  It was sump pump hose so it didn't take much heat.

Indigo PCV:  My engine has a history of "exhaust fumes" escaping out of the engine compartment.  Turns out the shifter cable was pinching off the rubber breather tube which allowed crankcase fumes to escape out both oil fill tubes.  I didn't catch this until I removed the breather tube in my garage.  It was actually torn.  I had ordered the PCV kit by then so I just went with it.  Added bonus of the PCV kit are fuel hose and fittings to replace the copper loop connecting the mechanical fuel pump and carburetor.
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Alma

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Re: ALMA's trusty Atomic 4 out for first overhaul
« Reply #21 on: January 20, 2021, 07:18:22 PM »
I have Tom Steven's original PCV and when my engine was worn I had a lot of oil consumption. The Indigo PCV kept the interior salon blow-by free. I was using 1 quart in 3.5 hours running! Still the engine ran well, idled smooth and spark plugs were satisfactory. That oil consumption is equal to a two-stroke yet there was no smoke. The engine was down on power- but I never knew better.

I haven't been able to measure any oil consumption with the new engine.

Some experts state that PCV isn't a good idea for constant speed engines like boats and aircraft...

I don't see a problem and I kept mine on the overhaul.

PS HA!

I had also filed a small mark on the auxiliary pulley for TDC also!

Great minds think alike!




« Last Edit: January 20, 2021, 07:22:17 PM by Alma »