Aluminum is different than cast iron. I assume you're talking about the 4.7
heads. For us cast iron heads heat expands but the expansion happens to
both the head and the plug. As the heads and plugs cool down they contract.
The plugs cool down faster because they're smaller and they have the ceramic
parts. SO if you let everything cool down a couple hours the plugs (in
theory) are smaller than the holes in your head [ ;-P ], therefore, easier
to take out.
Ron
00 PB SLT QC 4X2 5.9 46RE 3.92 LSD
For modifications see my DML Profile (URL follows)
http://www.twistedbits.net/WWWProfile/dakota/Kw9pV1EkFeOYY
-----Original Message-----
From: owner-dakota-truck@buffnet.net
[mailto:owner-dakota-truck@buffnet.net]On Behalf Of Marty Galyean
Sent: Tuesday, March 20, 2001 6:32 PM
To: dakota-truck@buffnet.net
Subject: Re: DML: How hot is too hot?
Ok, not disagreeing, but the MAIN reason to change plugs cold is to prevent
stripping the softer (hotter) threads; especially in aluminum heads.
Contrary to what one might think, a hole in metal gets bigger as the metal
is heated. Of course the plug is getting bigger too. I think its a wash,
not sure.
Marty
frank golembieski wrote:
>
> The reason you change your plugs cold is metal expands
> when it is hot . If it is hot when you change plugs
> they might lock in the cylinders .. I would wait till
> at least the valve covers are down to just warm before
> you change the plugs
>
> =====
> Frank G
> http://members.onecenter.com/autoworld/dakota/index.html
> Mopar or no truck
>
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