924Board.org

[peterld]

I'm putting together a new (to me) head to replace a rather dodgy version currently in use, using up the last of my squirreled away spares.

The head is just still in spec, has been surfaced, new guides and new SS valves.
I have new springs, lifters and rebuilt cam......so pretty much everything new.
And I have fair selection of the lifter screws.

I have read (I think Haynes) that new parts require 0 (no marks) adjuster screws. On measuring my adjuster screws, none are exactly the same (within each marked group). It's such a palaver to have to lift the cam to replace the adjusting screws, so I'd obviously like to get it right first time. Added to that is the fact that no matter how well the machinist fitted the guides/valves, there will be some differences in valve recession between cylinders.

My question is this: surely there must be a way to measure/assess the valve adjustment gap prior to assembly to obviate the need to pull the cam later in the process.
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80/81 932/8 ROW

[924RACR]

We did this once, set the clearances using a surface plate instead of the cam. Was pretty sweet and fast, just sliding the indicator around to get the right values once we got one pair of lifters right.

Assuming your head isn't wedged, is actually parallel...
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[peterld]

Thanks Vaughan.

But how did you use a surface plate......I'm not quite understanding.
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80/81 932/8 ROW

[924RACR]

Simply set the head directly on the surface plate... well, actually, had to set it on surface blocks too, since the valves stick out. Then a dial indicator on a sliding base. So done at a machine shop.
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[peterld]

Yes, now I've got it. Thanks.
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80/81 932/8 ROW

[peterld]

So I spent a rainy day sitting at my workbench measuring up the adjusting screws for the valve lifters..........somewhat of a revelation.
Now remembering I have a rebuilt head with new guides, new SS valves, new lifters, new springs and rebuilt cam to standard specs. Old valve springs were ultimately retained as the new springs (bought in a group buy years ago) were actually softer!
Measured each adjusting screw at it's thinnest and thickest end and split the difference to establish a nominal centre measurement; and then measured the middle just to confirm......spot on 99% of the time.
Established I needed a figure around 6.5mm at the centre for all eight valves.
Group 0 = 10 screws with an average of 5.85, with one outlier at 6.60
Group 1 = 21 screws with an average of 6.07
Group 2 = 16 screws with an average of 6.22
Group 3 = 16 screws with an average of 6.26 with one outlier at 6.55
Group 4 = 7 screws with an average of 6.39 with one outlier of 6.05

Needless to say I used 6 of the Group 4, and the extra sized Group 0 and Group 3 to just squeek-in. Ideally I would prefer not to use two of the Group 4 which only measured in at 6.35mm.

So what does all this prove? You absolutely have to carefully measure each adjusting screw before application. The numbers on the end mean nothing.
The ramp angle can vary dramatically between srrews, even though the mid point measurement may be the same.

I have been collecting these screws for nigh on 30 years, even buying buggered lifters to just get the screws. Though some display witness marks of the valve stem, all pass the fingernail test. I have seen some shockers over the years, including several which some 'tuner' had machined on the side to form a new surface!!
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80/81 932/8 ROW

[Rasta Monsta]

Strongly suggest ditching that insane setup for shims. If you're committed to the car long term, is worth it.
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Toofah King Bad

• WeiBe (1987 924S 2.5t) - 931 S3