Flathead oil gallery warning

[Lynn Eades]

A month or two back, I was talking to another Kiwi forum member about a little trap we have heard about in the V8 motor.
So Andrew, here it is:

When you decide to find another block to build up, or pick up a complete motor to fit into your vehicle,the motor may have laying inside it a problem that may give you a bad day.
As these motors shift around from truck to carrier to car, they can have their oiling systems slightly altered enough to cause a bearing failure.
In a standard car the oil path is as Henry designed it, All internal.
However if the motor has been fitted in a carrier it will have an extra drilling above the existing oil gallery tappings at the back of the block.
If your new motor has this extra hole, then there are a couple of options as to how it is set up.
On the standard "gallery boss" at the rear of the motor are two holes. One is normally (externally) plugged, and the oil pressure sender unit is installed in the other.
If you remove the horizontal plug, there may be, further in, another plug.
It is critical that this plug, is in there, or not in there, depending on how you intend to have this engine set up.
In the case of the Carriers the oil flow comes along the main gallery and out to a (full flow) oil cooler(there is also a bypass valve, should the cooler become blocked) The oil returns through the 3rd (extra) plug. and goes on to lube the main and big end bearings.
To make the oil flow out to the cooler, there is a plug in the gallery.

I am not sure about the detail between the carriers I THINK?? the riveted carriers don't have a plug because, I think the long return fitting does the job of the plug. I need feed back on this.
I understand that the Australian carrier is fitted with a plug. This plug could be a solid plug, or have a hole drilled through it and act as a restricter. I don't have the details. (a restricter makes no sense to me)
I have been on another forum where a chap kindly posted this picture. It shows the use of a "full flow" filter system, which can only be used if the third plug has been added.
If you don't have an external circuit, and there is a plug installed, then NO oil gets to the crankshaft.
I would like to see the details of these set ups from an Australian, and from a Canadian carrier, preferably from what appears original.
Looking forward to some definitive replies.
Note: the "plug" I am talking about is identified in the picture as a "grub screw"

Ron, What details are identified in that good parts book of yours?

[Bob Moseley (RIP)]

Hi Lynn - I was alerted to this years ago. In the early days hot-rodders used to grab Carrier motors for their vehicles. And lo and behold they very quickly cooked their motors due to this oil gallery plug that ran the oil through the oil cooler. My understanding is that it is a grub screw setup but never having to remove one I am not 100% sure.

Bob

[Andrew Rowe]

Good explanation Lynn.
Having removed many of these plugs on our production line, they all have holes in them, just off the top of my head the diameter is about 5mm, but can check.
It sits in the middle of the horizontal gallery when it bottoms out on the thread, between the two vertical galleries.
I think the reason that it had the hole was that if the cooler did get blocked there was at least some oil returning through the bearings.
One motor I checked recently was not running a cooler and it had a vibration when revved up, upon checking this engine it still had the plug with the hole in it.
( so was only getting small amount of oil to the bearings )
The vibration went away when the plug was removed, this carrier does not run a cooler but if it were fitted the plug would then be reinstated.
You could run cooler without this plug , but I presume it would not be that efficient as the cooler would only act as a bypass and the oil would not be forced through it to cool. Cheers

[eddy8men]

thanks for posting up the info fella's, that would be a costly lesson to learn especially for me as I've just spent a ton of money getting a 24 stud rebuilt for the carrier. I will be checking the oil gallery. cheers

rick

[rob love]

Yes, a very good point. After 70 years, engines may have been through a number of different vehicles and applications, from military vehicles to hot rods. A very good idea to check what was done and not done on a new to you engine.

[ajmac]

Agreed, 70 years of tinkering can lead to anything! Always check the details. Lynn, my 24 stud 3.6 litre flathead has a British mod, possibly the one you mention as 'on riveted carriers'. There is a waisted fitting that slips down the vertical bell housing oil pump outlet port this directs all oil flow (except the rear main and associated feed parts) to a cooler or filter etc and back to the horizontal bell housing fitting, as the vertical fitting is waisted oil can flow around it and into the main oil gallery. There is no internal plug or third threaded hole in the bell housing, i.e. standard truck service v8.