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Old 10-16-2010, 07:58 PM   #21
cw
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Default Re: #4 Piston Engine Mystery - Help Please

It's been a while.
The engine is back and running fine.
The diagnosis was to little piston/head clearance.
Another 40/1000 off the pistons and we will update you in 400 miles.
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Old 06-10-2011, 03:38 PM   #22
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Default Re: #4 Piston Engine Mystery - Help Please - Saga continues

First car show of the year, beautiful day, everything running great (oil pressure & water temp fine) and driving 45-55 mph, got 75 miles away from home and catastrophic failure.

Babbit hammered off of rod #4. - Same as before

Since the last post, we installed a stock model b head, added electronic ignition to the mallory distributor and replaced the demon with a stromberg 97 carb. So we reduced the compression, eliminated timing variations and reduced fuel volume.

The only things that are the same are the cam, crank and the driver. And the driver is becoming a crank ;-)

I suspect the crankshaft.

Could it be in the drive line some where? If so where should I look?
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Old 06-10-2011, 05:42 PM   #23
James Rogers
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Default Re: #4 Piston Engine Mystery - Help Please

I would chuck that motor and buy one outright that has been run for a while on a stand or in a car. That way you will know if it is Driver or, Drive train or, You have a black cloud over your head.
So many people have suggested the crank, I believe that is where I would go next if you decide to stay with thin engine.
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Old 06-10-2011, 06:53 PM   #24
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Default Re: #4 Piston Engine Mystery - Help Please

Crank is all it could be. Was the engine balanced? Crank-rods-flywheel-clutch should have been balanced together and if it was done, should have shown an out-of-round or bent situation. James Rogers hit it on the head also, except 'stay with this engine.' Only thing left of 'this engine' is the crank and it's getting like Uncle Dan''s ax -- it's had three new handles and a new head! Same ax, though...
Fearless
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Old 06-10-2011, 07:23 PM   #25
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Default Re: #4 Piston Engine Mystery - Help Please

Every time I've ever seen repeat piston failure of the same hole the root cause has been igntition at the wrong time either detonation or spark.Because it's always #4 I'm thinking spark.Maybe the distributor cap or rotor has a carbon trace or crack allowing a path for a stray spark ?
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Old 06-10-2011, 07:37 PM   #26
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Default Re: #4 Piston Engine Mystery - Help Please

thanks. Along the way we replaced the distributor cap, rotor button, spark plug wires and spark plugs. We have a modern timing light and timing gauge, builder marked the pulley with TDC for reference.
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Old 06-10-2011, 08:56 PM   #27
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Default Re: #4 Piston Engine Mystery - Help Please

Rig up a degree wheel on the front pulley or at least a pointer and some marks to indicate where each cylinder should fire, making sure the distributor cam is not ground wrong. This could cause #4 to fire early as was mentioned before. Just make sure thats not it.
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Old 06-10-2011, 09:27 PM   #28
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Default Re: #4 Piston Engine Mystery - Help Please

As long as you have a degree wheel set up, check tdc for each piston as well. That should tell you if you have a twisted crank.
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Old 06-10-2011, 10:31 PM   #29
Kurt in NJ
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Default Re: #4 Piston Engine Mystery - Help Please

Degree wheel

Long travel dial indicator ( for measuring stroke and index)

normal dial indicator (for valve events)

piston stop--heavy bridge across cyl with bolt

plot out all timing events, piston stroke, piston to deck --then you can know if crank is off, cam is off ---you can compare #4 to #1, #2-#3

A distributor machine can be used to check you 1-4 timing ---just because it is electronic doesn't mean it is correct. ---and it can verify your advance curve.

Have you tried sourcing rods from a different place?

Both #4, and #1 should show the same when using a timing light

A 4cyl crank can also be checked with V blocks , a height gauge on a surface plate -set it up, flip it over, check again.

Is the same rod being rebabbitted again and again, or is a different rod core being used?
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Old 06-11-2011, 01:05 AM   #30
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Default Re: #4 Piston Engine Mystery - Help Please

I have not seen anything to indicate whether you have verified the accuracy of the distributor lobes, or even tried a different distributor. There should be an obvious difference in damage between melting the babbitt due to oil starvation and pounding the babbitt out due to detonation in #4. Tell us if the distributor has been positively eliminated as a possible cause.
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Old 06-11-2011, 08:35 AM   #31
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Default Re: #4 Piston Engine Mystery - Help Please

It sure seems like you have a crank problem.. You don't appear to be getting any damage to the piston top so it doesn't seem to me that you're having an ignition problem.. What does the babbitt or journal look like??
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Old 06-18-2011, 03:32 PM   #32
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Default Re: #4 Piston Engine Mystery - Help Please

Thanks for all of the help and advice.On ignition, we have a new distributor (mallory), cap, rotor and electronics. The flywheel is a newer lightened version with v8 clutch.

I have asked the builder to replace the crank.

We'll update when we get it back on the road.

Oh buy the way - here is the mystery machine... (and my son ;-)
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