[68BirdOrlando]

I'm attempting to break in a fresh rebuild on a 455, I've now ran the motor twice for a total of 7 min (@ 2100 rpm). Had to shut it down the first time for a water leak between timing cover to intake. The second time I shut it off because it pushed about 3/4 gallon of water out of the system (I don't have a recovery tank).

The first time it ran I don't think the thermostat ever opened so I expected to have to add water when it opened on the second run so was really worried about letting it continue. Also noticed the #2 and #5 cylinders running hot (both header pipes were glowing red). I've got intial time set at 12 deg. I don't have the vacuum advance hooked up.

Should I hook up the vacuum advance? (Could lack of advance be the reason for hot cylinders?) Should I be using a recovery tank? I thought I could leave the rad cap off and add water as needed but when it began to overflow from expantion I capped it and it blew water out the overflow shortly thereafter.

I am using an electrial fan, which ironically came on after I shut it off....

[74Grandville]

I would hook up the vacum advance, but I don't think that will resolve all your issues. it should bring the heat down a little. did you check the thermostat to verify it would open up as expected? I always check mine in a pot of water on the stove.

[limejudge69]

Another trick to help prevent airlock in a cooling system is to drill a small hole (or holes) in the flat part of the outer ring of the thermostat.

[pont3]

Relax, that's normal. It won't harm anything as long as nothing combustible is close by.

[pont3]

Just so you know, vacuum advance only steps in when the engine rpm doesn't produce mechanical advance. Has zero to do with break-in. Break-in should occur around 2100 RPM and at that point, the mechanical advance is fully engaged, unless the springs in your distributor are really stiff.

Merry Christmas!!!

[Brent Flynn]

richen your carb up...sounds like running lean at part throttle... maybe richen the primaries a couple steps....

Originally Posted by 68BirdOrlando

I'm attempting to break in a fresh rebuild on a 455, I've now ran the motor twice for a total of 7 min (@ 2100 rpm). Had to shut it down the first time for a water leak between timing cover to intake. The second time I shut it off because it pushed about 3/4 gallon of water out of the system (I don't have a recovery tank).

The first time it ran I don't think the thermostat ever opened so I expected to have to add water when it opened on the second run so was really worried about letting it continue. Also noticed the #2 and #5 cylinders running hot (both header pipes were glowing red). I've got intial time set at 12 deg. I don't have the vacuum advance hooked up.

Should I hook up the vacuum advance? (Could lack of advance be the reason for hot cylinders?) Should I be using a recovery tank? I thought I could leave the rad cap off and add water as needed but when it began to overflow from expantion I capped it and it blew water out the overflow shortly thereafter.

I am using an electrial fan, which ironically came on after I shut it off....

[Stuckinda60s]

Originally Posted by pont3

Just so you know, vacuum advance only steps in when the engine rpm doesn't produce mechanical advance. Has zero to do with break-in. Break-in should occur around 2100 RPM and at that point, the mechanical advance is fully engaged, unless the springs in your distributor are really stiff.

What???? No part of those statements is correct.

I would install a mechanical fan for the break-in, run manifold vacuum advance, maybe bump the initial to 15-18 for the break-in, as well. If you can get a good-sized fan to place in front of the radiator, you should. Late timing will cause the headers to get hot.

The engine will make more heat as it breaks-in, and timing can be more critical for several reasons. As stated, the carb may also be a little lean. That would cause the headers to get hot, also.