7MGE camshaft question

[ira11y]

Ok i pulled the front of the 7M on the cressi apart yesterday to fix a leak from the front cam seals, and when i pulled off the cam wheels i noticed that both the cams and the cam wheels have 3 locating positions for the dowel pin. Can any of you 7M nutters out there enlighten me as to why there are so many location points?

Oh and the dowels seem to slip in and out nicely too, and on my particular engine both cams were located on the centre dowel point. Id take a wild guess and say that the retarded dowel point might be for the turbo engine if this is a stock setup. but any info from Norbie, Draven, Ed or any of the other boys out there would be usefull.

[-==L=a=N=c=E==-]

The 3 cam positions is fairly common accross the toyota range. The 3S series of motor has them as well.

In a nut shell, it is to fine tune the alignment of the cams. As they don't always line up because of a few factors (like the belt being slightly off etc..)

The pins can also be used to retard/advance the cams if you so wish.

http://ugbox.net/~lance/GT4/Technica...ing%20belt.pdf <--- this document is specific to the 3sgte, but is the same idea. On page 12, at the top, it talks about lining up the cam wheel and then inserting the pin in th eappropriate hole.

[ira11y]

I dunno about fine tune?

The steps would be around 10 or more degrees on the camshaft, seems like a big adjustment to me for a factory realignment?

[ViPeR_NiPPleX]

u have to realign the cam gear to the belt..

im guessing the adjustment is 1-2 degs ret/adv?

whereas if you just jumped a tooth you could go 10degs either way

[gianttomato]

Yep - for "fine" tune of the cam shafts. The old M single cammers had 3 different positions which would vary the cam by a total of 9 degrees. This was to compensate for any chain stretch or head surfacing (presumably after a BHG ). The same thinking applies here.

[ViPeR_NiPPleX]

as soon as a read "old M single cammers"

somehow i knew it would be you GT

[ira11y]

hmm okies.. but this is a twin cam.. no chain stretch.. its belt driven.. seems weird is all but thats the way it is i suppose.

[gianttomato]

Still allows servicability after head machining so that cam timing is minimally altered....

[Alchemist]

Is a BHG common on the 7M

[Joshstix]

The idea is that you can move the pin from the centre hole in the pulley and shaft to either the left or right hole in both the pulley and shaft. This should give quite a small adjustment to the cam alignment. You can move the gear in relation to the shaft and belt then mark a new top mark on the pulley and use eg the centre hole on the pulley and left hole on the shaft for more extreme adjustements.

[ira11y]

hmm thanks josh, now you explain it that way i can see how you could get smaller increments.