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X7525 MM Spark Plug Torque Specifications [message #256317]

Wed, 23 July 2014 21:10

larry.whisler

Messages: 356
Registered: August 2005

Karma: 8

Senior Member

I am planning to change the spark plugs in the coach in the near
future so I thought that I would look up the torque specification
for the plugs.

To my amazement, the MM lists two different torques for spark plugs,
page 6A-65.

Plugs on the HEI system lists 25 ft lbs of torque and the plugs
using the breaker points ignition system lists 35 ft lbs.

This does not make any sense to me. Perhaps someone with more knowledge
can explain to me.

larry

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Re: [GMCnet] X7525 MM Spark Plug Torque Specifications [message #256355 is a reply to message #256317]

Thu, 24 July 2014 09:27

USAussie

Messages: 15912
Registered: July 2007
Location: Sydney, Australia

Karma: 6

Senior Member

Larry,

I've always torqued the spark plugs "Mit Gefühl" (with feeling). "Feeling" the gasket crush then turning them a bit more. The "bit
more" depended on whether the head was aluminum or cast iron. ;-)

Regards,
Rob M.
The Pedantic Mechanic
USAussie - Downunder
USA '75 Avion - Double Trouble TZE365V100426
AUS '75 Avion - The Blue Streak TZE365V100428

-----Original Message-----
From: larry.whisler

I am planning to change the spark plugs in the coach in the near future so I thought that I would look up the torque specification
for the plugs.

To my amazement, the MM lists two different torques for spark plugs, page 6A-65.

Plugs on the HEI system lists 25 ft lbs of torque and the plugs using the breaker points ignition system lists 35 ft lbs.

This does not make any sense to me. Perhaps someone with more knowledge can explain to me.

larry

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Regards, Rob M. (USAussie) The Pedantic Mechanic Sydney, Australia '75 Avion - AUS - The Blue Streak TZE365V100428 '75 Avion - USA - Double Trouble TZE365V100426

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Re: X7525 MM Spark Plug Torque Specifications [message #256495 is a reply to message #256317]

Fri, 25 July 2014 10:06

larry.whisler

Messages: 356
Registered: August 2005

Karma: 8

Senior Member

I replaced the plugs in the coach yesterday using the AC R46SX plugs.

While I had the plugs out, I checked the compression and was pleased
with the results.

7-170 5-168 3-172 1-170 8-180 6170 4-182 2-180

I found one other problem when I was disconnecting the distributor
for the compression tests. The wire 12V power wire to the clip
broke off. It must have only had a couple of copper strands holding
it.

As I was thinking about how this could affect engine performance,
it occurred to me that this could possibly cause the engine to stumble
when hot and exhibit symptoms similar to vapor lock. I had been
having the 'vapor lock' problems despite installing electric fuel pump.

My thinking is that with just a few strands of electric wire powering the
ignition system, those wires would heat up as the engine compartment heated
up and offer more resistance resulting in lower voltage. And the resistance
would further heat the wire and provide more resistance shutting down the
ignition system. The engine stops and cools some and ignition is restored.

Time will tell if this solves the problems.

larry
at altitude 650 ft

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Re: [GMCnet] X7525 MM Spark Plug Torque Specifications [message #256498 is a reply to message #256495]

Fri, 25 July 2014 10:26

k2gkk

Messages: 4452
Registered: November 2009

Karma: -8

Senior Member

I suggest also replacing spark plug wires with those from MagneCor.

http://www.magnecor.com/

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~ ~ Amateur Radio - K2GKK ~ ~
~ ~ USAF and FAA, Retired ~ ~
~ ~ ~ Oklahoma City, OK ~ ~ ~
~~ ~ ~ "The Money Pit" ~ ~ ~~
~ ~ ~ ~ TZE166V101966 ~ ~ ~ ~
~ ~ ~ '76 ex-Palm Beach ~ ~ ~
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> Date: Fri, 25 Jul 2014 09:06:29 -0600
> To: gmclist@temp.gmcnet.org
> From: larry.whisler@hotmail.com
> Subject: Re: [GMCnet] X7525 MM Spark Plug Torque Specifications
>
> I replaced the plugs in the coach yesterday using the AC R46SX plugs.
>
> While I had the plugs out, I checked the compression and was pleased
> with the results.
>
> 7-170 5-168 3-172 1-170 8-180 6170 4-182 2-180
>
> I found one other problem when I was disconnecting the distributor
> for the compression tests. The wire 12V power wire to the clip
> broke off. It must have only had a couple of copper strands holding
> it.
>
> As I was thinking about how this could affect engine performance,
> it occurred to me that this could possibly cause the engine to stumble
> when hot and exhibit symptoms similar to vapor lock. I had been
> having the 'vapor lock' problems despite installing electric fuel pump.
>
> My thinking is that with just a few strands of electric wire powering the
> ignition system, those wires would heat up as the engine compartment heated
> up and offer more resistance resulting in lower voltage. And the resistance
> would further heat the wire and provide more resistance shutting down the
> ignition system. The engine stops and cools some and ignition is restored.
>
> Time will tell if this solves the problems.
>
> larry
> at altitude 650 ft

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