Dropping VM Valves DIY Style & Hardness Testing

[Sdust15]

Well since my last post inquiring about VM heads I've stripped mine down (on the cheap, as pictured below). I came up with a real ad hoc pressure test setup to verify exactly where #1 was leaking to have filled that jug so much. Consists of some angle Alu, A bicycle inner tube and some of the coolant gallery bolts. Filled the head 2/3 full of water and pressurised them to about 35 PSI. Boy did the bastard leak! It came out from the bridge (Insert?) between the valve seats. Toast.

https://imgur.com/a/VlhaJv0

https://imgur.com/a/Ll4tOgn


Took all 4 heads to a local shop and they tested them for hardness. They rang in at:

#1 - 65 HRB
#2 - 67 HRB
#3 - 66 HRB
#4 - 88 HRB

All pretty soft and it shows... The liners have grooved into the heads enough to make a bit of a burr. Guy at the shop was great and said he wouldn't even consider taking my money to test em because they're too soft to be reused anyways. It would just lead me straight into more gasket failures. I've read about quite a few people changing head gaskets on VM's, finding the heads to be "good" and eventually getting terribly short life out of the new gaskets. This could be why?

[5oclock]

Many years ago I watched a machine shop bloke test an aluminium head for hardness by dropping a steel ball bearing down a glass tube resting on the head surface and noting how high it bounced. He had a couple of marks on the tube and if the ball came up to the highest mark it was a good head. Maybe you could cobble something like that up for testing any used heads before you buy them. You would need to "calibrate" the tube ,probably be OK to do it on any surface on a known good Aluminium head. At lest you can put a "stuffed" mark on it. Also I think a stiff clear plastic tube would be ok. Good luck.

[Sdust15]

Making a gauge could be useful! Not just for me but if I calibrate it using a cheap, readily available ball bearing. I could document it for use by other diesel Jeep/Opel/Rover owners.

That was sorta my thinking with this post to begin with. Give some people an indication of my failure mode so that hopefully the next poor bloke isn't flying quite so blindly!

[layback40]

Originally Posted by 5oclock

Many years ago I watched a machine shop bloke test an aluminium head for hardness by dropping a steel ball bearing down a glass tube resting on the head surface and noting how high it bounced. He had a couple of marks on the tube and if the ball came up to the highest mark it was a good head. Maybe you could cobble something like that up for testing any used heads before you buy them. You would need to "calibrate" the tube ,probably be OK to do it on any surface on a known good Aluminium head. At lest you can put a "stuffed" mark on it. Also I think a stiff clear plastic tube would be ok. Good luck.

It easy to just use a pocket knife & try and scratch it on the face some place thats not that important. Once you have tried a good head and a soft one its easy to tell the difference. Also, 180 wet & dry will easy cut the surface of a soft head, it is lucky to even scratch a hard head. Often you can see distortion around the bolt holes on a soft head. If they are bad, they have a habit of stripping the rocler bolt holes.

[amlav]

Had the same on a litle Dayhatsu 2 cylinder head. . It was a bit time consuming to find out where the coolant was leaking inside one of the cylinders . Had to use a magnifying glass but found it. Still not sure why do they crack in between the valve seats.

[layback40]

Originally Posted by amlav

Had the same on a litle Dayhatsu 2 cylinder head. . It was a bit time consuming to find out where the coolant was leaking inside one of the cylinders . Had to use a magnifying glass but found it. Still not sure why do they crack in between the valve seats.

Simple answer.
The inlet port is often the coolest part of the head & the exhaust is the hottest.
This is the region with the greatest heat stress.