Mk3: Engine boils some time AFTER stopping the engine

[Philip Lochner]

I have converted my '73 to EFI (http://www.joc.org.uk/phpBB2/viewtopic.php?f=20&t=15116). This allows me to read the engine temp very accurately with my PC (or my Android phone) connected to the Megasquirt ECU via Bluetooth.

Since doing the EFI conversion and sorting out the radiator, overheating has been the least of my worries. I can drive in stop-start traffic in mid summer (30 - 38ºC), the two ORIGINAL fans will cycle calmly on and off, I don't lose coolant but....

I drive calmly home. Engine Temperature is 86ºC as I stop in the garage. Fans are off (and they do work!) and I shut the engine down. After a minute or two, the engine starts to boil and this carries on for a while till it stops.

My theory has been that there is a hot spot in the engine, most likely due to the head gaskets that restrict coolant flow through the heads to run them hotter with emissions in mind.

Well, yesterday I pulled the heads off and what should I find? Yep, the head gasket has those narrow slots that limit coolant flow through the head and some coolant ports are completely blocked off!

[taximan]

Do your fans come back on when it's boiling?
Shaun.

[Philip Lochner]

Do your fans come back on when it's boiling?
Shaun.

Can't be 100% sure but I do not recall them coming on when its boiling. I've got the car wired that they could come on (with ignition off) though if the temp switch were to close.

[Chris_R]

Where do you read the engine temperature from?

[Philip Lochner]

Where do you read the engine temperature from?

From "the same" location as where the sensor for the dash gauge is. IIRC there was an extra plug there which I simply removed and installed the GM sensor.

[DaveAK]

I don't think the ports in the heads are lining up with the ports in the block. I'd say that the orange circles indicate where the head ports are and they look to be closer to the inner two cylinders, whereas the picture of the block shows the ports closer to the outer two cylinders.

Unless I'm reading the picture all wrong.

[Philip Lochner]

I don't think the ports in the heads are lining up with the ports in the block. I'd say that the orange circles indicate where the head ports are and they look to be closer to the inner two cylinders, whereas the picture of the block shows the ports closer to the outer two cylinders.

Unless I'm reading the picture all wrong.

I've also noticed that but have not specifically checked it - yet. What is definite is that two ports on the outside of the block are completely blanked off by the head gasket.

We will have to careful though, otherwise we could end up "short circuiting" the cooling in the block by creating a shortcut for coolant towards the front of the block/heads. (This is a situation that was identified on the Jag V12)

[DaveAK]

I have a 400 and a 383 block and they both have oval ports where yours has a single hole. I don't know if all 440s are like yours but that looks like the problem to me. I took a picture on my phone that I'll upload tomorrow.

Edit: OK. I think all your photos show the gasket on the block so the port underneath the gasket might be oval too. But I still reckon that the ports in the head don't line up looking at the discoloration on the gasket.

[RAP72]

I've read about electric water pumps that when wired in with the fans, continue to run after the engine is switched off, and using the fans, allow the engine to cool down. Has anyone tried one?

http://www.mawsolutions.com/html/electr ... pumps.html" onclick="window.open(this.href);return false;

[taximan]

Ports have never lined up, has been discussed many times, the gaskets restrict flow to make the heads run hotter, if you open up the slots it allows extra flow, whether it stops your car boiling is another matter, descale your water system thoroughly and backflush.

http://www.joc.org.uk/phpBB2/viewtopic. ... asket+slot" onclick="window.open(this.href);return false;

Shaun.

[AH1951]

Tony Wilde in Oz has fitted an electric water pump to his 541R.
It's mentioned in his posts.

[Philip Lochner]

Ports have never lined up,

Was this by design or some mysterious manufactring flaw?

Has the question been asked if one can drill the heads in the appropriate places? If possible, I would put small holes towards the front going progressively larger towards the rear in order to limit the amount of "short circuited" coolant that would pass through the front holes.

[taximan]

Assume deliberate so they could meter the flow through the heads, have your read the monday club page on the subject?
Shaun.

[Steve Payne]

There are some blocks with figure 8 holes so the holes in the head will line up, these are still restricted with the head gasket so I presume this is done by design.

deck2.jpg (19.54 KiB) Viewed 5541 times

Open up the holes in the head gasket and use the Felpro head gasket so you will get maximum flow without modifying the engine. The pre emission head gaskets had the slit almost the same width as the holes so the narrow slit was only done as a cheap way of getting the engines to pass emission regs by raising the head temp,

On the subject of boiling, if you don't allow the engine to get that hot in the first place it wont boil.

Steve

[DaveAK]

There are some blocks with figure 8 holes so the holes in the head will line up, these are still restricted with the head gasket so I presume this is done by design.

deck2.jpg

Open up the holes in the head gasket and use the Felpro head gasket so you will get maximum flow without modifying the engine. The pre emission head gaskets had the slit almost the same width as the holes so the narrow slit was only done as a cheap way of getting the engines to pass emission regs by raising the head temp,

On the subject of boiling, if you don't allow the engine to get that hot in the first place it wont boil.

Steve

Both my 400 and 383 block are like this. And I think the 440 I built and sold was like this too. I've read about the gasket hole being turned in to a slit to increase head temperature for emission control, but the head ports and block ports not lining up seems crazy to me.

I've just taken a look at a picture of an Edlebrock head and it has the ports in the same location as the discoloration on your gasket. Does your third picture show the block with or without the gasket? My eyes aren't good enough to tell.