Oil gallery plug mystery / welch plug fitment procedure

[2cams70]

Hi Guys,

Whilst checking my 681F "L" block I noticed that one of the press fit gallery plugs is missing in the rear of the block whereas a 1500 Cortina 2731E block that I also have has this plug fitted. All the blocks I've seen pictured on this forum also seem to have this plug fitted. What is the purpose of this plug and should the Twin Cam have one fitted? Looking at the parts manual it seems only the pushrod engines had the plug fitted but would like to confirm exactly. See pictures and parts manual extract attached.

On another issue - what is the correct method of installing welch plugs? I've read that you are supposed to press it in on the inside diameter using a socket or suchlike. You are not supposed to press on the outer ring. Is this a load of baloney? I've always installed welch plugs by using a 25mm thick flat round piece of aluminium of larger diameter than the outer ring of the welch plug and hammering it in via force applied through the outer ring. Never had a problem with leakage.

I've never seen a factory installed welch plug with witness marks on the inner diameter that would indicate it had been installed this way.

[rgh0]

Yes you need the plug in a twin cam. it is a cross drilling between the pushrod holes, i presume for oil drainage and oil will come out the end into the bell housing if not plugged.

cheers
Rohan

[StressCraxx]

The later 711 "tall blocks" had a bearing ball peened into the oil galley in the back of the block. The two choices for removal were grinding it out or arc welding a piece of weld rod on it and using a slide hammer... I wish I could have a conversation with the engineer in Dagenham who came up with that idea.

[2cams70]

Yes i see now. There's a straight pathway to the number 8 tappet bore. Why did Ford use a ball bearing on the later blocks? Weird.

I don't recall ever removing the plug from my block so unless it was removed by the reconditioners it does help explain at least some of the oil leaks - and this wasn't the worst of the bodges discovered on disassembly !

Presume this is the one.

http://www.burtonpower.com/oil-gallery- ... fp507.html