Thought I'd have a go at the porous/cracked head modification!

[joff-turbo-nova]

Hi all,

Having recently rebuilt a 2.0 16v C20XE engine I was having a few water/oil problems which I narrowed to a head gasket issue.

Turned out to be a couple of head bolts that had pulled the thread due to a previous helicoil bodge I was unaware of.

Anyway I have sorted this out by replacing the head bolts with studs as supplied by Steveboyslim (cheers!) without further need for helicoils.

I sent the head off for a light skim just to make sure and to do a belt and braces job I wanted to sort the head mod for the porous/cracked issues mainly associated with the GM heads.

Had a read up on the various sites (including on here) and decided to give it a go as it looked quite straightforward.

First job - get one GM head :-



Next take out the grub screw from the exhaust side :-



And do the same on the inlet side :-



Then it was time to clean out the oilway which was full of oil / emulisfied oil and general cr@p . I used degreaser and carb cleaner to clear out the oilway and used some small bits of rag and a rod to push through from one side :-



..... to the other :-



Once all cleaned and dried out (used about 15 bits of small rag!) I measured up the necessary sleeve that would be required - turned out that an 8mm pipe would be just the job - quite tight but not so tight that it would bend on tapping in.



The 8mm tube came from B&Q and was a couple of quid. The tube was about 87mm long and was measured to fit the oilway but not come out of either side and foul the bolt hole. I have enough left to do about 7 other heads !!!

I then coated the outside of the 8mm sleeve with some special threadlock used for inserting bearings - supplied by a mate in a engineering workshop (cheers Chris). This stuff is designed to keep the item in place permanently - not recommended for disassembly - ideal for this use!



Tapped the sleeve in far enough to clear both bolt holes - cleaned out all excess threadlock and replaced both grub screws using normal threadlock. The bit that is sleeved is shown in the pic below :-



Just need to fit the head to the Vectra at the weekend to ensure its all tickety boo.

Hope this helps anyone thinking of doing this. Should be doable with the head in situ - just a little more difficult for access and cleaning out the oilway.

Cheers

Joff

[Tom Williams]

does the sleeve need to be right from one bolt to the other? or does it need to be shorter to allow liquid to enter/exit

[Benn]

Is that all thats done? you just slide a bit of pipe in it? Surly if its blocked at both ends to start with why are you putting the pipe in there?

[Tathan]

iirc there are two channels at 90deg to the sleeved run about an inch or two in heading down, so these will need to be open.

[Benn]

ah so its a U like shape?

[Tathan]

upside down u, aye. IIRC, as always.


edit: or 'n' shape as they're also known.

[Tom Williams]

Is that all thats done? you just slide a bit of pipe in it? Surly if its blocked at both ends to start with why are you putting the pipe in there?

its blocked at both ends so that it does not leak.

oil flows through it but you cannot cut a pipe in the head with a bend in it

therfore oil flows into that gallery to go elsewhere

Tom

[Benn]

Think i get it.

[Jack]

upside down u, aye. IIRC, as always.

edit: or 'n' shape as they're also known.

lmao lmao lmao lmao

[joff-turbo-nova]

I've sleeved this bit here :-



More info here :-

http://www.orsas.com/CarStuff/cav/sleeving.php

Joff

[Tom Williams]

Oh right I see, sorry i was not being picky but i had never seen what actually happens but i knew that fluid had to get in there somehow

[Benn]

I've sleeved this bit here :-



More info here :-

http://www.orsas.com/CarStuff/cav/sleeving.php

Joff

Ah i see how it works, thank you for the pic.

[Frisco]

The oil flows up the head bolt hole. The bolt itself is not tight to the side walls.

[cavvyturb]

I've sleeved this bit here :-



More info here :-

http://www.orsas.com/CarStuff/cav/sleeving.php

Joff

where`s the other grub screw?

[essexrsturbo]

that look clever mate!

[joff-turbo-nova]

where`s the other grub screw?

The oil gallery is slightly off centre of the head - the head in the pic was cut down the middle , hence the grub a one end not showing as its in the other half of the head.

Joff

[cavvyturb]

ahh i see now, its to the right of the core plug in this pic
I will be keen to see if your method works as i have been saving a load of pourous heads to weigh in might repair them instead

[Frisco]

It does work, ive had mine done and running for well over a year now.

Mine was done with solid bar to blank the oilway fully. Then the oil gallerys are joined externally by a braided hose between the grub screws on the dizzy end.

[Bean]

cool guide i've got a std porous head in the cupboard, think i'll give it a try

[Adam]

why did he use a hollow bar and u use a solid one then? lmao aghh

[Frisco]

The hollow one still lets the oil pass through it so you dont have to bypass it on the dizzy end.
I thought the solid one had a better chance of sealing and that there was no chance of the ends closing in from tapping it into the head . I used the exact same loctite stuff (borrowed from work).
Its never coming out

[steveboyslim]

It is also worth renforcing the oil gallery before the head cracks.
Not all GM/KS heads have an oil gallery plug on the inlet side, so a suitalbe hole may need to be drilled tapped and cleaned.

Steve

[CortraGTE]

Nice!

How did you get it to stop in the right place? Once it was inside the head what did you use to tap it in further? A stick?

[cambridge]

It is also worth renforcing the oil gallery before the head cracks.
Not all GM/KS heads have an oil gallery plug on the inlet side, so a suitalbe hole may need to be drilled tapped and cleaned.

Steve

agreed, If I ever got a 20Xe engine'd car the first thing I'd do is that fix!!! saves faffing about when you may not be wanting to do it.

[Frisco]

Nice!

How did you get it to stop in the right place? Once it was inside the head what did you use to tap it in further? A stick?

If you look at the sectioned head pic, the two virticle(sp?) channels at either end of the highlighted bit are the head bolt holes.
You can look down them when the head is off and see when to stop.

A pin punch is made for hitting things into holes