Valve tappet clearances way of. Am I in trouble?

Post by Ties » Sun Feb 04, 2018 1:47 pm
Joined: Tue May 27, 2014 12:17 pm
Posts: 50
Hello,

Today I finally summed op the courage to check and adjust the valve clearances.
I was a bit scared what I would find since the previous owner told me when I bought the van that I could use regular 95 unleaded petrol as long as I filled it up with super98 once a year or so. I very much doubted that especially since there was no record of any headwork being dont to the van and I found a half-used bottle of led substitute somewhere in the back of the van. So i'v always used a led substitute for the 7 or 8 months I'v owned the van now, but presumably the previous owner has run it on regular unleaded 95 for the past year and a half that he had her.

Given this and the fact that the van was quite noisy and down on power, I suspected the exhaust valves may need some adjustment but was quite shocked by how much.

The first valve I checked was the one furthest back into the cab (so an inlet valve) and that was basically perfect, With a bit of pressure I could insert the 0.25mm feeler gauge and move it up and down. Then came the first exhaust valve. Judging from the shape of the screw (it had a flat bit on the side of the valve stem) it was already the first undersized screw, but even with that turned counter-clockwise 2 or 3 turns more that would allow the tappet to go back down, I was only barely able to insert the 0.15mm feeler gauge, and the gap is supposed to be set at 0.45mm according to the manual... :o

So, is there still hope? Can I get a more undersized screw or get shorter valves or something? Or am I going to need a complete new head... :cry: :?
To make matters worse, I also think I saw some water/coolant floating around in the oil under the camshaft housing cover, so my mayonaise problem may actually be a head gasket problem after all...

Re: Valve tappet clearances way of. Am I in trouble?

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Post by Phil Bradshaw » Club admin » Sun Feb 04, 2018 5:47 pm
Joined: Sun Sep 02, 2012 7:15 pm
Posts: 3373
Some mayo in the cam cover and condensate drips into the housing is normal for the Vauxhall OHC engine especially this time of year.

Relatively cheap fix for running out of valve clearance adjustment is to lift the camshaft housing to fit a thicker housing to cylinder head gasket, A59-8 or A59-16 from J&M Gaskets.

Downside is juggling tappet adjuster screws for best fit for all the valves, give or take a bit of grinding and lapping of tapers (about 0.010 inch by the time wear marks are taken out).

This can mean buying 2 gaskets of a thickness, one to use for dry fitting the housing while juggling adjuster screws, the other for final assembly.

This work won't prevent the worst affected exhaust valves from eventually eroding their seats past using the thicker gasket but it will buy time to find a spare cylinder head to have hard seats fitted for a straight swap.
  • What is real is not the external form but the idea, the essence of things. Constantin Brâncuși

Re: Valve tappet clearances way of. Am I in trouble?

Post by Ties » Mon Feb 05, 2018 11:11 am
Joined: Tue May 27, 2014 12:17 pm
Posts: 50
Phil Bradshaw wrote:Relatively cheap fix for running out of valve clearance adjustment is to lift the camshaft housing to fit a thicker housing to cylinder head gasket, A59-8 or A59-16 from J&M Gaskets.

Downside is juggling tappet adjuster screws for best fit for all the valves, give or take a bit of grinding and lapping of tapers (about 0.010 inch by the time wear marks are taken out).
That sounds like a bit of a hassle, but much better then having to source and replace the cylinder head imidiataly! :thumb:

How much extra adjustment would just getting the second undersized adjuster screws get me relative to the first undersize adjusters that (i think) are in the exhaust valves now? Because the inlet seem to still have the original size adjustment screws, so they would probably run out of adjustment in the opposite direction to the exhaust if I use an oversized gasket. What would get me closer on average, oversized gasket or extra undersized screws on the exhaust valves?

Re: Valve tappet clearances way of. Am I in trouble?

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Post by Phil Bradshaw » Club admin » Mon Feb 05, 2018 2:48 pm
Joined: Sun Sep 02, 2012 7:15 pm
Posts: 3373
It depends ...

1/32" thick gasket will increase adjustment overall by approximately 0.015", equivalent to about 5 clicks (full turns) of the adjuster screws.

For the intake valves this shouldn't be a problem if the screws can be turned clockwise 5 or more clicks from correct adjustment now without the blind end of any screw protruding from the wall of its tappet. An extra click is better to allow for intake valve wear (stem tips rather than faces) which tends to increase valve clearances but the wear rate is minimal compared to the exhaust valves which usually are the main problem.

Exhaust valves that already have eroded their seats will need as much adjustment range as possible to offset increasing 'pocketing' of each valve and temperature at its periphery due to increasing obstruction to exhaust gas flow as the head of a valve sinks below the surface of the combustion chamber. The net effect is increasing need to adjust exhaust valve clearances as the seats erode, more so if the valve faces run hot enough to suffer from brinelling.

Grinding and lapping screw tapers to remove wear marking can gain an additional 2-3 clicks for the exhaust valves. Going further is practicable but taking too much off can make things difficult for a rebuild which includes restoring valve stem protrusion above the cylinder head to optimum when seat inserts are fitted. Differences in screw dimensions can be accommodated by machining seats for each screw but setup for each one individually instead of all to the same protrusion can make the job a lot more expensive.

1st and 2nd under-size screws have a limited range of adjustment compared to standard screws, about 10 clicks overall for 2nd under-size compared to about 16 clicks for standard screws. In theory the 2nd under-size range follows on from 1st under-size but in practice the existing valve stem protrusion has a lot to do with what range of adjustment is left.

It may be possible to get away with fitting under-size screws without lifting the camshaft housing but it's not a recommended method because it can be too easy to cross-thread a screw in a tappet. (In the past I've ruined a number of tappets and screws by getting it wrong but in those days there were plenty of spares available for when dodges for beating GM labour times didn't work out.)
  • What is real is not the external form but the idea, the essence of things. Constantin Brâncuși

Re: Valve tappet clearances way of. Am I in trouble?

Post by Ties » Mon Feb 05, 2018 5:18 pm
Joined: Tue May 27, 2014 12:17 pm
Posts: 50
Phil Bradshaw wrote:thicker housing to cylinder head gasket, A59-8 or A59-16 from J&M Gaskets
Noticed that the thicker version only lists compatibility for the 2.3L OHC engines, but since the normal sized gasket lists both the 1.8 and 2.3 I the thicker ones will also fit on my 1.8L right?

Re: Valve tappet clearances way of. Am I in trouble?

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Post by Phil Bradshaw » Club admin » Mon Feb 05, 2018 8:21 pm
Joined: Sun Sep 02, 2012 7:15 pm
Posts: 3373
Camshaft housing to cylinder head gasket shape is the same for all Vauxhall OHC engines.
  • What is real is not the external form but the idea, the essence of things. Constantin Brâncuși

Re: Valve tappet clearances way of. Am I in trouble?

Post by Ties » Tue Feb 06, 2018 8:24 am
Joined: Tue May 27, 2014 12:17 pm
Posts: 50
Phil Bradshaw wrote:Camshaft housing to cylinder head gasket shape is the same for all Vauxhall OHC engines.
Okay, I ordered 2 of both types of oversized gaskets, just in case someone already fitted a thicker one in the past.

Thanks for the help!

Re: Valve tappet clearances way of. Am I in trouble?

Post by Ties » Sun Feb 18, 2018 1:08 pm
Joined: Tue May 27, 2014 12:17 pm
Posts: 50
Phil Bradshaw wrote:Relatively cheap fix for running out of valve clearance adjustment is to lift the camshaft housing to fit a thicker housing to cylinder head gasket, A59-8 or A59-16 from J&M Gaskets.
Well, the gaskets have arrived and I have a week of school, so I decided to try to get it installed today, but I immediately ran in to a problem. :wall:
It's probably something really easy and stupid, and although I have some basic experience working on engines, i'v never done anything like this before. So please forgive my stupidity.

In the Haynes manual in the section on removing the camshaft housing, it says to first slacken the camshaft bolt and then remove the drive belt. (I assume slackening the bolt while the belt is till in place is to prevent the camshaft turning while trying to undoing the bolt.) However, my van is fittet with the plastic cover over the belt, witch is blocking acces to the camshaft bolt. And it seems that in order to remove the cover, the fan pulley and the crankshaft pulley would have to come out first, and that would allow the camshaft to turn freely and I wont be able to get the bolt out, right...?

Is there a workaround? Or am I going to have to remove the pulleys, remove the plastic shroud and refit the whole thing, just to slacken that one bolt and take it all apart again?

Re: Valve tappet clearances way of. Am I in trouble?

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Post by Phil Bradshaw » Club admin » Sun Feb 18, 2018 2:29 pm
Joined: Sun Sep 02, 2012 7:15 pm
Posts: 3373
Remove the fan and pulley and the crankshaft pulley.
A 3/4-inch AF ring spanner walloped with a rubber mallet usually will loosen the crankshaft bolt without the crankshaft moving much.

Remove cambelt cover then refit crankshaft pulley and bolt; rotate crankshaft about 90 degree past the TDC mark on the front of the crankcase.

Timing setup for belt fitting to show TDC mark on crankcase -

Image

Rotating the crankshaft 90 degree past TDC ensures all pistons are well away from contact with valve heads during disassembly (likewise for reassembly).

Slacken camshaft pulley bolt and also the camshaft rear bolt under the rear cover if the camshaft is likely to be disturbed.

Slacken jockey (tensioner) pulley bolts then remove cambelt.

And away you go. :)

Keep the cambelt cover; much as it can be a pain it carries the ignition timing marks. Also prevents the belt from breaking when ploughing through snow drifts but I've only managed that once ...
  • What is real is not the external form but the idea, the essence of things. Constantin Brâncuși

Re: Valve tappet clearances way of. Am I in trouble?

Post by Ties » Sun Feb 18, 2018 3:53 pm
Joined: Tue May 27, 2014 12:17 pm
Posts: 50
Phil Bradshaw wrote:Remove the fan and pulley and the crankshaft pulley.
A 3/4-inch AF ring spanner walloped with a rubber mallet usually will loosen the crankshaft bolt without the crankshaft moving much.

Remove cambelt cover then refit crankshaft pulley and bolt; rotate crankshaft about 90 degree past the TDC mark on the front of the crankcase.

Timing setup for belt fitting to show TDC mark on crankcase -

Rotating the crankshaft 90 degree past TDC ensures all pistons are well away from contact with valve heads during disassembly (likewise for reassembly).

Slacken camshaft pulley bolt and also the camshaft rear bolt under the rear cover if the camshaft is likely to be disturbed.

Slacken jockey (tensioner) pulley bolts then remove cambelt.

And away you go. :)

Keep the cambelt cover; much as it can be a pain it carries the ignition timing marks. Also prevents the belt from breaking when ploughing through snow drifts but I've only managed that once ...
Thanks!! will give it another go tomorrow, hopefully with more succes.
I'll post an update as soon as I have anything to report!

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