IROC-Z_85

Say you lined up your dots on your gears. What is a ONE tooth movement either direction worth? 4 degrees? more or less?


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1985 IROC-Z, nuff said :P

jcb999

I think about .010" offset of the cam is like 2 degrees.

Look at the crank gear (if it has multiple keyways). Compare the keyway location with the alignup dots. The dot for 4degrees advance is only a little offset for the one that has 4degree retard (about a half a tooth I think). So, 8 crank degrees is about 1 tooth (maybe)

[This message has been edited by jcb999 (edited July 12, 2001).]

ColinOpseth

your car shouldn't run if it skipped a link on the timing chain..

my Dad's '76 Olds 98 with a 455 rocket skipped ONE tooth and wouldn't run..

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Webmaster: www.IROC-Z.org

IROC-Z_85

Pardon my ignorance, but then how are you supposed to advance/retard your cam?

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1985 IROC-Z, nuff said :P

jcb999

three (or 4) ways.

Use an offset bushing in the cam gear. It involves drilling the top gear out for both the mounting bolts and the cam pin. You can then use a bushing (mrgasket) to orient the cam advanced or retard.

Use an offset keyway for the crank gear in the timing set. Has some draw backs because the key is actually weaker.

Use one of the multiple keyways on the crank gear (if so equipped). Look at this pic, see all the keyways cut in the bottom gear?

http://abacus.sj.ipixmedia.com/abc/M...b44a34/i-1.JPG

Each keyway has its own dot to line up the top gear with. One with be Zero, and the others will be from 1 to 6 degrees advanced and from 1 to 6 degrees retard.

or a chain designed to do exactly that
See this
http://cgi.ebay.com/ebaymotors/aw-cg...item=593222150



[This message has been edited by jcb999 (edited July 12, 2001).]

RB83L69

It's not the same for all timing sets.

How many teeth does your cam gear have? If you slip it by ine of those teeth, then you change the cam timing by 720°/the number of teeth. A typical cam gear might have, say, 48 teeth; so one tooth would be 15°. One crank gear tooth would be twicw as much since there are half as many of them.

The 3rd method jcb referred to is the most common and usually most satisfactory. A more typical timing set like that has three keyways, cut at -4°, 0°, and +4°. Of course if you are having a cam custom ground, you can tell them where you want the intake centerline set up at, which has the same effect, since exhaust centerline is usually referenced to intake (lobe separation).

So what are you really asking?

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"So many Mustangs, so little time..."
ICON Motorsports

IROC-Z_85

I was "really asking" how its done

I've never had a reason to advance/retard a cam so i didn't know how it was done

My cam/chain/sproket has no noticable way other than moving it over a tooth which i never considered.


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1985 IROC-Z, nuff said :P

RB83L69

A "regular" stock replacement type timing set doesn't have the multiple keyways; but most of the true hi-perf ones do. The bushing thing isn't as popular as it used to be before the multiple-keyway type became common; it's real labor-intensive and involves risk of destroying the parts; I always hated to have to deal with it, and would get people's cams custom-ground instead of that if possible in motors I built for people. The offset crank key has always been considered something of a {insert favorite minority here}-rig, suitable only for emergencies or people who didn't care very much about the quality of their finished product.

I was curious if you were afraid you had accidentally done it, or were going to try it, or were having some kind of trouble and wondering for that reason, any of which could be a possibility as well as pure intellectual curiosity, and might lead to some further info being needed.

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"So many Mustangs, so little time..."
ICON Motorsports

IROC-Z_85

Nothing but pure curriosity

If you want to see another one of my "curious" questions head over to the exhaust forum and head down the page a little way, i have a "technical" exhaust question there that they stopped answering :P

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1985 IROC-Z, nuff said :P