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Loud engine knock that starts then stops then starts again,
Posted by: red64vair ()
Date: August 18, 2020 01:20PM

A friend has a 64 110 that while running normal suddenly develops a terrible knock. It goes away as suddenly as it started only to start knocking again. This knock is very loud, like hitting the block with a hammer. No noticeable engine miss when this happens. I have only heard this at fast idle. I'm afraid to run engine any faster. It does have a lifter knock when cold but calms down a lot when warmed up. Compression is very low (30) on # 5 cylinder. I thought maybe a dropped valve seat but the knock sounds like it is in the crankcase. I never heard a dropped seat so I don't know what that sounds like. What is your thoughts before I open up the engine.

Larry Blaylock
Saltillo, Mississippi
64 convertible
66 customized Corsa coupe


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Re: Loud engine knock that starts then stops then starts again,
Posted by: thewolfe ()
Date: August 18, 2020 01:28PM

Sounds like a dropped valve seat that gets cocked sideways under the valve and pounded into the head. When that happens it sounds really bad, like a hammer banging on metal. The seat can pop back into place and run normal again. Ask me how I know.

Nate Wolfe
Portland OR
65 Corsa 180

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Re: Loud engine knock that starts then stops then starts again,
Posted by: joelsplace ()
Date: August 18, 2020 02:39PM

Nate's idea is good.
If it is an automatic it could be a cracked flex plate. Those can sound like a broken crank.

Joel
Northlake, TX
5 Ultravans, 114 Corvairs and counting...

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Re: Loud engine knock that starts then stops then starts again,
Posted by: jcorvair ()
Date: August 18, 2020 02:49PM

X2 on Nate's comment. I had the same thing happen on a 110. I made it all the way from Nevada to Canada with it popping in and out occasionally, typically when I stopped for gas.

James
West Kelowna, BC

1965 Corvair, Corsa, Convertible 180/4 - Artesian Turquoise w/ white interior
1966 Corvair Corsa Coupe, 140/4 - Aztec Bronze w/ black interior
2016 Dodge 3500 Crew Cab 4x4 (for hauling cars, trailers, fifth wheels, quads, etc.)
2019 Express Car Hauler (Aluminum, Enclosed)
2015 Polaris 570 EPS
2016 Polaris 570 SP
2019 Toyota Highlander Hybrid Ltd.
2020 Outdoors RV 25RLS
2020 Corvette HTC 3LT,Z51,FE4

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Re: Loud engine knock that starts then stops then starts again,
Posted by: red64vair ()
Date: August 18, 2020 04:29PM

It is a automatic. Is there a way to confirm cracked flex plate without pulling the engine?

Larry Blaylock
Saltillo, Mississippi
64 convertible
66 customized Corsa coupe


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Re: Loud engine knock that starts then stops then starts again,
Posted by: joelsplace ()
Date: August 18, 2020 05:10PM

Not really. Sometimes you have to look at them closely when you have them off the car.

Joel
Northlake, TX
5 Ultravans, 114 Corvairs and counting...

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Re: Loud engine knock that starts then stops then starts again,
Posted by: MattNall ()
Date: August 18, 2020 05:14PM

Unbolt the flexplate from the TQ. Slide TQ back and use a cheap endoscope that works with your phone.

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Re: Loud engine knock that starts then stops then starts again,
Posted by: red64vair ()
Date: August 18, 2020 09:19PM

This is what I found. #5 has blown head gasket and metal fragment stuck to head. All three have the craters and so does the pistons. I assume this is detonation damage.

Larry Blaylock
Saltillo, Mississippi
64 convertible
66 customized Corsa coupe


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Re: Loud engine knock that starts then stops then starts again,
Posted by: joelsplace ()
Date: August 18, 2020 09:23PM

No that is not detonation damage.
That is foreign material in the combustion chamber.

Joel
Northlake, TX
5 Ultravans, 114 Corvairs and counting...

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Re: Loud engine knock that starts then stops then starts again,
Posted by: red64vair ()
Date: August 18, 2020 09:42PM

Would that create the heavy hammering sound? The sound starts and stops.

Larry Blaylock
Saltillo, Mississippi
64 convertible
66 customized Corsa coupe


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Re: Loud engine knock that starts then stops then starts again,
Posted by: REM654DPG ()
Date: August 18, 2020 09:59PM

For what it’s worth that is 102 hp head.

Regan Metcalf
Portland, OR

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Re: Loud engine knock that starts then stops then starts again,
Posted by: JimBrandberg ()
Date: August 19, 2020 07:31AM

Wouldn't a 102 head on a 110 be very high compression ratio?

Jim Brandberg
Isanti, MN
CorvairRepair.com



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Re: Loud engine knock that starts then stops then starts again,
Posted by: red64vair ()
Date: August 19, 2020 08:30AM

Block and heads

Larry Blaylock
Saltillo, Mississippi
64 convertible
66 customized Corsa coupe


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Re: Loud engine knock that starts then stops then starts again,
Posted by: JerryM ()
Date: August 19, 2020 09:12AM

Have you drained the oil or pulled the pan off to look for debris?

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Re: Loud engine knock that starts then stops then starts again,
Posted by: 66vairman ()
Date: August 19, 2020 09:17AM

red64vair Wrote:
-------------------------------------------------------
> This is what I found. #5 has blown head gasket and metal fragment stuck to head. All three have the craters and so does the pistons. I assume this is detonation damage.

Small debris can move from one cylinder to the other damaging each on one side of an engine with common intake/exhaust. Seems unlikely, but it happens.

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Re: Loud engine knock that starts then stops then starts again,
Posted by: steve c goodman ()
Date: August 19, 2020 11:51AM

Larry let's see the tops of the pistons please.

best wishes, Steve
Rear Engine Spec. Inc. Golden, Colo.

1962 spyder 3.0L turbo---1965 Crown V8
1967 monza 110/4---1968 monza 110/4
1971 amante gt 110/4
CORSA/RMC/PPCC/V8 Registry

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Re: Loud engine knock that starts then stops then starts again,
Posted by: American Mel ()
Date: August 19, 2020 12:10PM

steve c goodman Wrote:
-------------------------------------------------------
> Larry let's see the tops of the pistons please.


And the third combustion chamber, too.

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Re: Loud engine knock that starts then stops then starts again,
Date: August 19, 2020 12:22PM

Number on head is 102hp, and ZG on block can be a '61 98hp, '62-'63 102hp, or a '64 110hp

Jeff K
64 Fitch Sprint convt
65 Fitch Sprint coupe
64 Greenbrier
70 Camaro ss 396

Just North of Jacksonville, FL.

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Re: Loud engine knock that starts then stops then starts again,
Posted by: red64vair ()
Date: August 19, 2020 03:20PM

Pistons

Larry Blaylock
Saltillo, Mississippi
64 convertible
66 customized Corsa coupe


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Re: Loud engine knock that starts then stops then starts again,
Posted by: red64vair ()
Date: August 19, 2020 03:22PM

#3 combustion chamber

Larry Blaylock
Saltillo, Mississippi
64 convertible
66 customized Corsa coupe


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