| Re: [GMCnet] replacing driver's side head on a 455 [message #362725 is a reply to message #362723] |
Mon, 08 March 2021 14:55   |
stu@97381.com, Emery
Messages: 232
Registered: June 2020
Karma:
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Senior Member |
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I had an overheating problem about 2 years ago on a fairly recently rebuilt 455 engine.
It turned out when the engine overheated two of the center pistons swelled and rubbed on the cylinder walls generating a lot of heat which ruined the engine.
I haven’t made a trip with the latest engine yet due to Covid. Hopefully this summer or fall we’ll take a trip.
Emery Stora
77 Kingsley
Frederick CO
> On Mar 8, 2021, at 1:48 PM, Robert J. Gogan via Gmclist wrote:
>
> Blew out a water pump last summer and overheated the engine trying to pull over. New water pump installed, but engine is running hot despite a tested
> good thermostat and good radiator especially on long uphill grades. Pressurized coolant system and found a leak down without any external antifreeze
> leaks.
>
> Did cylinder compression tests:
>
> All cylinders 150-160 psi on my rebuilt 455 engine with 55,000 miles on it EXCEPT cylinder #5 which is reading 55-60 psi.
>
> Figure I've got one or more of the following:
> 1) overheated cracked head at cyl #5,
> 2) overheated warped head and blown head gasket at cyl #5
> 3) burned valves or seats at cyl #5 or
> 4) piston ring failure at cyl #5.
> Don't think it's a cracked block. Had that before and oil and antifreeze leaking out was pretty evident.
>
> Starting the disassembly process to replace the J head on the driver's side:
>
> After removing the driver's side exhaust header (just installed two years ago) found that the nice thick gasket that Jim K sold me was broken up in
> the web area between the exhaust ports. No external leaks yet.
>
> Same thing happened on the passenger side last year, but the outside of the gasket broke down it that area and it leaked.
>
> The original heads were designed for manifolds and it was not necessary for the dividing web in the central exhaust to press against the gasket web
> onto the exhaust header. Talked to my head rebuilder about this and he was willing to put a bead of weld onto the head web to build it up to engage
> the web portion of the gasket. However, he suggested that I just cut the web out of the gasket to prevent the exhaust pressure from tearing it up and
> ripping out the more important peripheral gasket.
>
> This is, for sure, the first of many questions that I will have during this rebuild process:
>
> Should I build up the exhaust port web with a weld and machine it to engage the web portion of the gasket or should I just cut out the web part of the
> gasket so it doesn't tear out the important peripheral sealing portion of the gasket?
>
>
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