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Old 06-19-2018, 01:13 PM   #31
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Thumbs up She is finally running

I've finally managed to put it all back together and tune it up properly. It wasn't without a hitch - first the machine shop damaged the thread on new rocker arm stud, then I've overtightened one of the push rod valve cover screws and broke it (it was leaking oil at the corner so I kept tightening it up, mistake). I also found after cleaning the cylinders that cylinder #3 where I had the issues with the bent push rods, was hit by a valve - huge nick on the cylinder. But this must've happened before I bought it because when machine shop took out all valves for head cleaning/welding prep, they were all straight. I didn't replace the cylinder, I don't think it should affect anything.

That push rod valve cover is very difficult to put in, I had to remove the whole distributor to do it and seal it properly with liquid gasket. After that, I've adjusted the timing (it was a bit off, not much) and checked the rpm with a tachometer. At 1000 rpm on the dash, it was reading 700 rpm. Then on the plane at 4000 rpm on the dash it was reading 3450 rpm. So my dashboard tachometer is off by about 550-600 rpm which is great to know. Since it was showing 5700 rpm at max speed (loaded) it was actually running at about 5000 rpm. So a prop with higher pitch like 21 should work great as it would lower my rpm by about 600 thus always staying within the recommended range of 4400-4800 max rpm. Added that to my Christmas list

Compression test shows 120-135 psi on all cylinders, so that's good for a used engine. I'm wondering if improperly tightened rocker arms plus the 2 that were different style originally were the main cause of this failure? I would love to test out this theory someday by over tightening the rocker arms to see if the compression goes up?

I've found no water in the engine, all clean.

Took the boat out twice this weekend for good, long drives with the family and she runs like new!

Thank you all for all the insights and help. Appreciate it very much
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Old 06-19-2018, 02:35 PM   #32
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Thanks for the update, and congratulations on tackling this problem.
For your tach, have you tried cleaning the connections on both the back of the tach and the wiring harness?
Do you know if you have the original alternator, or if it has been replaced?
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Old 06-19-2018, 04:04 PM   #33
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Glad to hear she's up and running.

Two comments:

1. The valve hit the piston not the cylinder. The piston travels up and down in the cylinder.

2. Overtightening the valves will decrease compression as this will compress the valve spring and slightly open the valve.
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Old 06-19-2018, 04:50 PM   #34
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Ah, that's great to know Mike about the valves. Originally that cylinder had 205 psi, now after proper alignment it's at 135 psi. Which makes perfect sense, since the rocker arm wasn't hitting the valve stem but the valve spring shield instead. Sorry, still getting used to the terminology, I'm not a mechanic
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Old 06-19-2018, 04:54 PM   #35
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Good questions jrsick. I don't have any receipts for the alternator but it looks original. Distributor looks like it's been replaced though. I'll definitely clean all contacts, most of them has that green/grey precipitate on them. What's the easiest way to clean it? Dip them in CLR?
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Old 06-20-2018, 11:45 AM   #36
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A small wire brush or sandpaper is good way to clean distributor contacts.
The situation I'm thinking of was a distributor that wasn't sealed properly. Distributor cap was either cracked or not seated securely. Moisture built up inside of the cap after an hour or so of running.
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Old 06-20-2018, 09:57 PM   #37
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When I disassembled the distributor cap I've cleaned up the contacts with sandpaper. I'm thinking about the wire connectors, if they are corroded it would increase the resistance thus show incorrect reading. Not sure what else can cause tachometer to be off?

there is a little switch on the back but its setup properly to 4 cyl engine. No other way to tune it up, manual says to replace it if not correct
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Old 06-20-2018, 10:12 PM   #38
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Sometimes the tach will be bouncy and rotating the cylinder select back and forth will correct this.

The tach gets its signal from the negative terminal on the coil which is connect to the sensor in the distributor. The spark plug wires will have no impact.
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