inline 6 overheating

[itstim]

gm inline 6 (1974) overheating above 2000 rpm. Impeller new and working. Water pump good, Therm good. Intake water passages clear. I'm suspecting the big long Osco manifold is partial blocked and not draining the higher volume of coolant water at the higher rpms. It is not leaking anywhere (yet) and there is not steam coming out but it is rusty on the outside and I would imagine the inside is too. Not removed yet. Does it sound like I'm on the right track?

 

[itstim]

Re: inline 6 overheating

anybody there?

 

[akriverrat]

Re: inline 6 overheating

yes. yes. where is my island? p. bethel.

 

[itstim]

Re: inline 6 overheating

That's Sacramento Delta Bethel Island in Calif.

 

[Boomyal]

Re: inline 6 overheating

How hot does the manifold get? Should be able to hold your hand on it. If it is restricting water flow, it ought to be plenty hot.

 

[itstim]

Re: inline 6 overheating

It's plenty hot! Engine too...and the out drive when you touch the top. It's fine below 2000 rpm but go above that for just a short time and its blazen. Gotta shut it down right away. Outdrive lube level correct.

 

[yoced]

Re: inline 6 overheating

Which Osco manifold? How old?<br />Which riser? How old?<br /><br />How plumbed?<br /><br />If you keep running that manifold hot I can promise a wicked set of cracks internally if it ever gets a shot of cold water into the system...