Author Topic: Engine trouble  (Read 383 times)

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Offline Robertw

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Engine trouble
« on: November 11, 2020, 03:55:45 PM »
I have a 1965 DeVille Convertible. It has a 429 motor, one of the plugs keep oiling up and causing it to run rough.
Does the motor require a rebuild?

Offline Bruce Reynolds

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Re: Engine trouble
« Reply #1 on: November 11, 2020, 10:44:40 PM »
G'day Robert,

This is one question that like most things over the Internet, is difficult to diagnose.

How long does it take to oil up?   Have you tried hotter Plugs?   Is the Ignition strong enough to supply a good strong spark?

There are a couple of tests that need to be performed.

(1)   The Compression Test, both Dry, and Wet, and these will give an insight into the condition of the Compression Rings, and the Sealing of the Valve Seats.

(2)   Could be worn out Valve Guides, and or broken Valve Stem Seals.   These can be checked by pulling the Rocker Covers and checking the sideways movement of the valve stems within the Valve Guides, and visually observing the Stem Seals.

(3)   A Leak-down test, which the average mechanic cannot perform.

The above tests need to be performed as a minimum, but without pulling an engine and stripping it down to check the critical measurements, it is hard to say.

With the Cylinder Heads removed, one can feel the tops of the bores to see if there is any ridge, which could indicate broken rings, as the top ring constantly striking the ridge on the upward stroke, don't like hitting ridges.

Bruce.  :devil:

Bruce Reynolds, Lindisfarne, TASMANIA
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
(Past President Modified Chapter)

Offline Robertw

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Re: Engine trouble
« Reply #2 on: November 12, 2020, 03:05:32 PM »
Hello Bruce,
Thank you for that, I will get my mechanic to check these things and go from there.
Regards
Robert

Offline Bruce Reynolds

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Re: Engine trouble
« Reply #3 on: November 12, 2020, 09:29:32 PM »
I forgot to ask, "How many miles could there be on the engine?

There is nothing worse than a motor that has done not many miles, the same as there is not much worse than a motor that has done a zillion miles.

The difference is that the low miles engine will have suffered from poor heating and cooling cycles, as well as poor lubrication from lack of use, and the high mile engine will just be worn out.

The reason Taxis run 1,000,000 Miles is that they never stop, but when they do, the engines are simply a throw-away item.   A low mile engine can suffer greatly from internal sludge deposits.

Bruce. :devil:
Bruce Reynolds, Lindisfarne, TASMANIA
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
(Past President Modified Chapter)

Offline Robertw

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Re: Engine trouble
« Reply #4 on: November 25, 2020, 03:35:15 PM »
Hello Bruce,
The car has done 96,000 miles which is not alot. It was left sitting for a few years when it was converted. This could have caused the problem.
Robert

Offline Bruce Reynolds

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Re: Engine trouble
« Reply #5 on: November 25, 2020, 03:49:26 PM »
Robert,

No engine likes sitting for years, especially the 429.

What has your mechanic done to see what might be the problem?

What was the compression readings, both cold and hot?   Or done a Leak-down test?

Has he checked for broken Valve Stem Seals on the affected cylinder?

How long does it take for a cleaned plug to oil up?

How is the timing?.   Vacuum Advance? Tune-up (running rich or lean)?   Is there slack in the timing chain?

What is the oil Pressure?   You have to insert a mechanical or electric pressure gauge to test that.

As you can see, there are a lot of questions and tests that need doing before a pull-down is required.

I am available any time if you want to give me a ring.   That is unless I am asleep.   My phone number is in the CLC Directory, both here and USA.

Bruce. :devil:
Bruce Reynolds, Lindisfarne, TASMANIA
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
(Past President Modified Chapter)

Offline Robertw

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Re: Engine trouble
« Reply #6 on: December 04, 2020, 08:58:02 PM »
Hello Bruce,
Thank you for all the information. I will get my mechanic to do the the things you recommend and go from there.
I had a 72 Eldorado years ago and sold it to a person in the ACT.
Regards
Robert