Water/coolant blocked

[John Mann]

Hi everyone,

I've begun to disassemble the engine, and I noticed that there were plates on the aft of the block covering the holes that I would normally think would be open to allow coolant flow. Is there only coolant flow on the front part of the engine?Is this normal? Any reason for these to be blocked?

[Funky61]

Hello John,

My 61 is the same so I'm guessing that's normal. It be interesting to find out why it was done that way. Henry

[David R Leifheit]

If you look closely at the heads, they are ... the same.
There isn't a right and left.
It is more economical and efficient for the company to make one head casting and use it for both sides.

Unless you intend to put another thermostat housing and radiator hose at the back of the engine, those passages are not needed. Another way to look at it is that if those were connected at the back, you would probably have a real messed up water flow through the engine.

Thus the block off plates.

[John Mann]

Well now, that is indeed interesting. I was wondering how best to mark the heads left and right. Guess I won't be doing that.

Thanks for the insight, David.

[WE7X]

That is actually rather common..to have the heads identical... for manufacturing reasons.
The Ford Ranger V-6 (~1999-2004? vintage) has a somewhat common problem with cracked cylinder heads, causing a slow water loss. It shows up in the front cylinder of the head casting on the driver side bank, and in the rear cylinder on the other bank, due to a design flaw in the casting.

Rod Johnson
Issaquah
1970 RM-5700

[TJ's GMC]

My 305 v6 is the same. Has those plates in the back. Also yes, both heads are the same. Doesn't make no difference. :thumbsup: