Cleaning up head - Valves not sealing properly?

mattyprice4004

mattyprice4004

mattyprice4004

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Hi all,

I'm cleaning up a known good head, and I thought I'd give it a quick test by filling up the inlet and exhaust ports with water to test.

I found that several do leak slightly, which of course isn't conducive to good compression! :p

Upon further inspection and after cleaning up the valve seats, it appears the lifters aren't allowing the valves to close fully. When left for a while, eventually a nearly-perfect seal is made.

Is it normal for lifters to expand slightly, causing the valves not to seal? The head has been sat a few months prior to me cleaning it up.

They're hydraulic lifters, by the way.
It's a Rover L series cylinder head, single overhead cam (8 valve).

Thanks!
 
Don't use water.

Use petrol.

Have you lapped the valves?

If your tappets are causing a gap, you could perhaps have either weakened valve springs OR excessively stiff or nonlubricated plunger in them etc.

Is it all the valves doing this, or just select few?

It shouldn't take a while, the spring strength should almost 'snap' the cam/lobes and valves into place on a revolution/turn.

Shouldn't be a long drawn out affair.
 
Think it could be a lack of lubrication, as it has been sat for a while.

Not tried lapping yet, most of the valves do 'snap' back but the ones that don't leak the worst. Only a few are doing this.

Really would like to avoid disassembling the head, as I need the car back on the road ASAP.

I'm going to try cleaning up the remaining seats and valves later, hopefully this will clear them up a little.
 
none.

Hot gasses pushing past will burn the head/valve out.

Just re grind them. Your always going to be wondering if you don't.

It's a quick job once you start.
 
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mattyprice4004 said:
Think it could be a lack of lubrication, as it has been sat for a while.

Not tried lapping yet, most of the valves do 'snap' back but the ones that don't leak the worst. Only a few are doing this.

Really would like to avoid disassembling the head, as I need the car back on the road ASAP.

I'm going to try cleaning up the remaining seats and valves later, hopefully this will clear them up a little.
Click to expand...

if valves are leaking you will need to reseat them
you cant get away without disassembling the head
and as its already off the engine it would be silly not to reseat them
 
This is my head.

http://www.rimmerbros.co.uk/ImagePopUp.aspx?i=GRID003297

I take it for this job, I'd be needing:

- Valve spring compressor, £35 ish
- Anaerobic sealant for when the cam carrier is replaced, £6
- Grinding paste and rubber sucker device for rotating the valves, £8 for the kit
- New stem seals (the head is 12 years old, so seems sensible for about £12 for the set)
- New camshaft oil seals (again, may as well) £8 for both

Anything I've missed?
 
Filling the ports could give misleading results as you have to consider any leakage up the valve stems. Normally you would fill the combustion chamber with something like paraffin, but of course you won't have one in the L series head.

Hydraulic tappets can pump up if removed, it's very common for some engines to be difficult to start or to misfire for a little while after a head rebuild.
 
The leaking was actually out of the valves, and dribbing down the head face so it's definitely not sealing.

I'll whip the cam out, if it still leaks the whole lot is coming apart.
 
no, that would only give resistance. They tend not to be gummed up or anything, its normally the opposite. Worn guide and stems, worn seal and possibly swarf embedded into those and too much oil leaking through.

wouldn't really stop them seating properly apart from swarf.

OP - pull valves out, the seats are probably coked up etc. The cam won't make much difference unless your lobes are rogered?

check the stems for wear and tapering, the guides would really need to be checked by a machine shop if you are going that far.

if you are going that far, try to get it done ASAP all at once.

otherwise it can turn into a never ending affair.
 
mattyprice4004 said:
This is my head.

http://www.rimmerbros.co.uk/ImagePopUp.aspx?i=GRID003297

I take it for this job, I'd be needing:

- Valve spring compressor, £35 ish
- Anaerobic sealant for when the cam carrier is replaced, £6
- Grinding paste and rubber sucker device for rotating the valves, £8 for the kit
- New stem seals (the head is 12 years old, so seems sensible for about £12 for the set)
- New camshaft oil seals (again, may as well) £8 for both

Anything I've missed?
Click to expand...

Just get a head gasket set, it'll include new seal for distributor etc and will also come with nice new manifold gaskets and also the head gasket.
 
Another quick question: how good does the seal have to be?

If I fill the ports with petrol, even after lapping I'm getting a tiny bit seeping through. It lost about 10ml overnight, so hardly a lot but will this be an issue?

Cheers!
 
Put some grinding paste on the back of the valves, push them into the head, attach a electric drill to the valve stem that is sticking out, and get grinding.
 
Dogbreath said:
Hydraulic tappets can pump up if removed, it's very common for some engines to be difficult to start or to misfire for a little while after a head rebuild.
Click to expand...

Oh dear! - I suddenly feel rather guilty.

Back in 1995, I had some head work done to an S2 Escort Turbo, when i got the car back from Turbosystems, I complained bitterly that they had bodged the job as the car went from a first turn of the key starter to a sometimes non starter!

An apology is in order, if somewhat late! :o
 
stulid said:
Put some grinding paste on the back of the valves, push them into the head, attach a electric drill to the valve stem that is sticking out, and get grinding.
Click to expand...

Don't do this, you can't lap valves in properly with a purely circular motion. All you end up doing is recessing valves and creating ridges in the valve seat.

jigger said:
Sounds like you need to check the shims, trying to reseat the valves could cause more problems.
Click to expand...

Hydraulic followers, no shims.
 
IMG_1260.jpg


Power lapping!
 
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