| replacing driver's side head on a 455 [message #362723] |
Mon, 08 March 2021 14:46  |
rgogan
Messages: 82
Registered: February 2004
Location: Milwaukee, WI
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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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