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Re: [GMCnet] Transmission vacuum modulator leaking? [message #329192 is a reply to message #329189] Thu, 15 February 2018 21:13 Go to previous messageGo to previous message
James Hupy is currently offline  James Hupy   United States
Messages: 6806
Registered: May 2010
Karma:
Senior Member
Don't use 40 year old heat cycled castings. This stuff is ageing out.
Careful inspection and Magnaflux are your friends. Cautious torque
procedure all help. Luck figures in there, too I think.
Jim Hupy
Salem, Or
78 GMC ROYALE 403

On Feb 15, 2018 6:12 PM, "Gordon Gibson" wrote:

> So the verdict is in - hairline crack in the left cylinder head (#3)
> between the intake and exhaust valves. I guess the big question is why?
> Engine
> rebuilt 10,000 km ago (new rings , bearings, timing chain, etc., heads
> done but not magnafluxed) Really sweet running mill, burned less than a 1
> quart of oil over the 10K km. I did experience a stuck thermostat at
> 2,500 KM, but thought I caught it quick enough before the digital temp
> reading
> exceeded 225....and it ran without a hiccup for 7,500 km afterwards,
>
> Matt mentioned short cycles in cold weather, and it was below 0 centigrade
> when I started it up and saw a puff of white smoke for the first time. But
> I'd done a bunch of driving in Northern Alberta at the 5,000 KM mark in
> -10C with no problems - driving another 5,000 problem-free kms after that.
> And surely lots of Toronados got driven to the grocery store in the dead
> of winter....
>
> Frank Borrmann has some J heads. We are going to magnaflux one before
> doing the machining just in case, as well as doing the same for my "good"
> head
> and my manifold before reassembling just to be safe.
>
> If anyone has ideas on what should NOT be done to avoid a repeat, I'd
> love to hear them.
> --
> Gordon Gibson
> 1976 23" Norris Upfit
> Montreal West, Quebec, Canada
>
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