924Board.org

[Mike924]

Something that's been bothering me:

The Haynes manual says to adjust both valves (inlet and exhaust) with the piston at top dead centre on the compression stroke. Sounds fair enough, but in this position neither cam is right on it's 'heel' (i.e. with the lobe pointing directly away from the valve stem).

I've always been taught to adjust the valves, one at a time, with the lobe directly 180° from the follower (observing the classic 'rule of nine').

Is the Haynes manual the 'official' method, or is it just the author's shortcut, or am I worrying too much...?
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1985 Porsche 924 'Lux', Kalahari Beige (my ex)
1993 Porsche 968 Coupe, Midnight Blue, 6 spd

'There is no substitute for a little grease under your fingernails.' - Chrenan, 924board.org

[FASTdan]

wahey! boy did I have fun with this on tuesday night!! the damn thing would have been on the road by now if this job wasn't so fiddly! Some of mine were set ok, but others were way out - ie NO clearance!

I wondered like you about the TDC thing. I'd go with what you say, cam lobe vertical. whats this rule of 9 thing?

One question i had about this also. I presume you MUST work in full rotations on this type of follower due to its wedge shape grub screw? ie a half turn would actually lift the follower until it had been turned a further 180deg to 'drop' back onto the flat of the wedge. Or have i got this wrong? You can kinda 'feel' this as you turn, it 'clunks' back into place on each rotation.
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1980 924LUX

[Mike924]

Yes, the adjusters must be set one full turn at a time.

In 'older' engines the classic valve layout was E-I-I-E-E-I-I-E (I = inlet, E = exhaust). The rule of nine was you set one valve to be fully open (as shown by the tip of the lobe being right on the follower), say number 3, (counting all the valves 1 - 8 from the 'front') and you adjust valve number six, because 3 + 6 = 9.

However, the 924 valves are laid out E-I-E-I..., so I don't know if it work for this layout...
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1985 Porsche 924 'Lux', Kalahari Beige (my ex)
1993 Porsche 968 Coupe, Midnight Blue, 6 spd

'There is no substitute for a little grease under your fingernails.' - Chrenan, 924board.org

[John Brown]

Just did mine last night. Took about 30 minutes. I just went with the lobes that were within a few degrees of the correct position when I pulled the valve cover. That turned out to be an exhaust in for one cylinder and and intake somewhere else down the line.

I don't worry about the orientation being perfect because the cam profile is pretty even on the off side AND the adjustment should be lose rather than tight anyway.

Each turn of the adjuster is about 2.5 thousand (I don't recall mm now) so with the spec .004 intake and .016 exhaust and knowing that once I get to .006 or .018 if I go more it's too close ... It's just close enough to set them as described above.
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John
80 931 - #931 44Cup
99 Escalade - tows track cars
gone but not forgotten: original 924.org car - 82

[CBass]

This is an easy enough job. You're supposed to do it with a hot engine, which does make a difference.

Replace your plugs at the same time and it's a lot easier. When the plugs are out, the motor has no compression so that it turns over easily by hand.

Get out your set of feeler gauges and pick all of the ones close to what you want, for the intake take your .003, .004, .005, .006 etc and that way you'll be able to tell if it's a little tight or a little loose.

Just turn the engine with a wrench on the crank pulley until the valve is where you want it. It doesn't matter if it's TDC or not, what matters is that the cam follower is in contact with teh base circle of the cam lobe, not teh sides or the tip. Go from front to back, do all the intakes, then all the exhausts, and you're done.
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'81 931 in various states of assembly

[Mike924]

Thanks, John and also CBass.

I feel I am reasonably experienced in adjusting valve clearances, which is why I thought the method in the Haynes manual was a bit strange, but John's reply has made me stop worrying about it.

I have been through the adjustment on the 924 once (using the Haynes method) and it took about 45 minutes (not counting getting the cam cover off). My thinking is that, even if you start with a hot engine, by the time you've got to the last valve, it will have cooled down quite a bit...

I suppose you could adjust it cold and then check it hot, but that means putting the cam cover back on and then taking it iff again if you don't want oil all over the place.
_________________
1985 Porsche 924 'Lux', Kalahari Beige (my ex)
1993 Porsche 968 Coupe, Midnight Blue, 6 spd

'There is no substitute for a little grease under your fingernails.' - Chrenan, 924board.org

[Min]

This is from the installation instuctions that came with my camshaft from integral cams.

[Mike924]

Got it, thanks, Min.

So, it's a quick measurement when the engine's hot, then adjust the valves cold, but for the differences from true when they were warm.
_________________
1985 Porsche 924 'Lux', Kalahari Beige (my ex)
1993 Porsche 968 Coupe, Midnight Blue, 6 spd

'There is no substitute for a little grease under your fingernails.' - Chrenan, 924board.org

[Charlane]

I took off the valve cover gasket and was ready with my feeler gauge and metric allenhead set. So where is the adjustment for the lobe clearances? I have 2 flat lobes so replacing the camshaft is in the near future. I already have the new camshaft.

Please do not tell me to take it to a shop. Not happening here as I have already rebuilt more than a few cars...and a motorcycle.

Thanks,
Charlane
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Electra is Here......

One 1980 924 Turbo
One 1990 KZ1000P (CHPS) Motorcycle
One 1984 244 Turbo Volvo (B21FT) (I installed this engine myself)
One 1977 240D Mercedes Benz
One 1970 Chevy Impala

[Mike924]

The adjustment is inside the tappet bucket itself. Each bucket has a hole in the side which can be accessed from the induction side of the engine. You may have to turn the tappet in its bore to get the hole to point outwards.

You poke a 3 mm Allen key in through this hole and turn it, one whole turn at a time. As you approach one turn it'll snap into place the rest of the way. One turn clockwise reduces the clearance by 0.002" (0.05 mm), one turn anti-(counter) clockwise increases the clearance by that amount.

Note that the inlet and exhaust valve have different clearances. The inlet is smaller. I won't risk quoting the clearances from memory, so look them up in the Haynes book.
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1985 Porsche 924 'Lux', Kalahari Beige (my ex)
1993 Porsche 968 Coupe, Midnight Blue, 6 spd

'There is no substitute for a little grease under your fingernails.' - Chrenan, 924board.org

[dpw928]

Charlane,

Since there is only 7 rotations from center on the adjusters before running out of threads, the max adjustment will be less than .020". If your cam lobes are too flat, adjustment won't help.

Dennis
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81 931 5 sp
78 928 5 sp Silver
78 928 AT Euro Black

[augidog]

Adjust them warm.
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1978 924 95 mile daily driver.
Audi TB/POR174M/High Flow Cat/2.25" exhaust
I knew that positive thinking thing wouldn't work.

[Mike924]

[Tiny]

Did you guys all buy the special tool mentioned in the haynes to adjust the clearances?
Tiny
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*****1981 - 924 - Auto - London, UK******

[Mike924]

Smoothie did, 'cause he's keen!

The rest of us just use a regular 3 mm Allen key.
_________________
1985 Porsche 924 'Lux', Kalahari Beige (my ex)
1993 Porsche 968 Coupe, Midnight Blue, 6 spd

'There is no substitute for a little grease under your fingernails.' - Chrenan, 924board.org