924Board.org

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

ARP has finally responded re: our little lifter adjusting screw project. I have been unsuccessful finding exact specifications on these little buggers. The tech specifications booklet indicates that more notches = thicker screw (which we know), but it doesn't say what the variance is. The other critical dimension that would be really helpful to have is the angle of the flat. I know some of you have actual engineering blueprints of the 924 engine. Any chance somebody has the exact OEM specs for the lifter adjusting screws?????
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erstwhile owner of just about every 924 variant ever made

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

FWIW, the angle should be calculable from the thread pitch and the increase in thickness per turn, which I believe is stated in FSM.
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WeiBe (1987 924S 2.5t) - 931 S3

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

It occurred to me there might be some info in FSM, but I don't have it here at work. Do you recall if FSM says anything about the difference in thickness between the different number of notches?
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erstwhile owner of just about every 924 variant ever made

emoore924 · Joined: 13 Apr 2004 Posts: 2822

its .002 per turn and .005 diff per screw *but they do vary some* even within the same number of notches

I have a bunch of the screws. What do you want me to measure?

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

Need to know the angle of the flat. Anybody know the thread pitch???

It would also be good to verify that the .005 difference between sizes is what you actually see on existing samples. I sent one of each size to ARP, and I've asked them to measure, so it would be good to compare notes. I have some at home too, so I'll see what my calipers say as well.
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erstwhile owner of just about every 924 variant ever made

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

I can get you the pitch tomorrow, if someone hasn't already.
_________________
Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

Min · Posted: Fri May 14, 2010 5:20 am Post subject:

Angle of the slop should be easy to figure out, simple rise over run calculation. I'll see if I can dig out an adjuster screw so I can make that measurement for you.

Min
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Custom means it didn't come from a box.
1980 n/a with EDIS and Megasquirt II Injection. 7 different colors and counting.

Min · Posted: Fri May 14, 2010 5:56 am Post subject:

I'm doing a autocad drawing right now of the screw I've got.

Min
_________________
Custom means it didn't come from a box.
1980 n/a with EDIS and Megasquirt II Injection. 7 different colors and counting.

Min · Posted: Fri May 14, 2010 7:14 am Post subject:

http://www.924board.org/viewtopic.php?p=292203#292203

With a pitch of 0.75 and a slope of 4 degree's, you will have tan 4 degree's times 0.75 = 0.052mm movement for each turn. Which is .00206 of an inch. Sounds right to me.

Min
_________________
Custom means it didn't come from a box.
1980 n/a with EDIS and Megasquirt II Injection. 7 different colors and counting.

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

Min, you rock!

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erstwhile owner of just about every 924 variant ever made

Min · Posted: Fri May 14, 2010 7:21 am Post subject:

heh, thank you, I'll see if I can dig out any other screws in a bit, I was only able to find a 3 tick screw. If someone else wants to give their screws a quick measure to verify that I measured correctly that would be cool too.

The diameter measured at 7.8mm, which is the same as the M8 rod I have laying around. Makes sense M8x0.75 is available, just not that common.

Min
_________________
Custom means it didn't come from a box.
1980 n/a with EDIS and Megasquirt II Injection. 7 different colors and counting.

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

Did you confirm that the pitch is .75?
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erstwhile owner of just about every 924 variant ever made

Min · Posted: Fri May 14, 2010 7:29 am Post subject:

With my thread pitch gauge. Yes.

Min
_________________
Custom means it didn't come from a box.
1980 n/a with EDIS and Megasquirt II Injection. 7 different colors and counting.

Min · Posted: Fri May 14, 2010 7:34 am Post subject:

Also measured it with my vernier micrometers which are accurate to .0001 of a inch.

Min
_________________
Custom means it didn't come from a box.
1980 n/a with EDIS and Megasquirt II Injection. 7 different colors and counting.