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adjustable vernier gear 

 

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 Post subject: adjustable vernier gear
Posted: Tue Jan 16, 2007 8:02 am 
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hey guys i just bought a billet crow cam so do i need one of these? if so who makes them and how much are they? its for a ed 4L
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Posted: Tue Jan 16, 2007 8:25 am 
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Crow Cams make them, depends which cam you bought weatehr you need one.
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Posted: Tue Jan 16, 2007 11:55 am 
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IMO no you don't *NEED* one.

The vernier cam gear allows you to advance or retard your static cam timing relative to the position of the crank.

By retarding the cam you can move the effective range of the cam UP in the rev range.

Similarly by advancing the cam to kick in earlier you move the power range DOWN.

IIRC 2 degrees (measured at the crank) can mean a shift of up to 500rpm.

One of the main reasons you would want to use a vernier gear is to correct any machining problem with a mis-aligned keyway resulting in a less than true TDC mark. Most people fit their aftermarket cams in the stock position (for typical street cars) anyway.

 

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Posted: Tue Jan 16, 2007 12:14 pm 
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aaron_hogan wrote:
IMO no you don't *NEED* one.

The vernier cam gear allows you to advance or retard your static cam timing relative to the position of the crank.

By retarding the cam you can move the effective range of the cam UP in the rev range.

Similarly by advancing the cam to kick in earlier you move the power range DOWN.

IIRC 2 degrees (measured at the crank) can mean a shift of up to 500rpm.

One of the main reasons you would want to use a vernier gear is to correct any machining problem with a mis-aligned keyway resulting in a less than true TDC mark. Most people fit their aftermarket cams in the stock position (for typical street cars) anyway.


Thats the best description yet of what they are and how they work.
Damn your good. :D

 

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Posted: Tue Jan 16, 2007 1:04 pm 
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For around $110 they are a cheap tuning tool.
But I agree with aaron and twr7cx, you don't need one.
Just make sure if you get one and put it in yourself, that you tighten the bolts on it!

 

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Posted: Tue Jan 16, 2007 1:09 pm 
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yeh but it sounds hell good when your rattling off modifications to the car

 

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Posted: Tue Jan 16, 2007 1:40 pm 
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ok yer a mechanic described it exactly the same way. he rekons crow cams are machined perfectly anyway so you wont need one unless you want it to kick in earlier- and its just another thing that can go wrong. thanks guys
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Posted: Tue Jan 16, 2007 1:45 pm 
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In future, the best people to speak to to begin with would of been Crow Cams themselves, as they'd know the cam more thoroughly than anyone else. Also looking on there catalogue on there website you might be able to read what they recomend for there cams - e.g. in the case of my Valiant there was a note saying needed to replace oil pump drive gear aswell.
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Posted: Tue Jan 16, 2007 1:50 pm 
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GRN-WGN wrote:
ok yer a mechanic described it exactly the same way. he rekons crow cams are machined perfectly anyway so you wont need one unless you want it to kick in earlier- and its just another thing that can go wrong. thanks guys


Its not just the cam grinding that determines the angle. If the head has been machined, if different gaskets have been fitted, if the timing chain has a few k's on it, etc, etc the cam timing can move.

I agree with those above though, it might well be $100 you dont need to spend. Its not hard to put in so you can put the cam in and see how it clocks up, then buy a gear if its out.

 

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Posted: Tue Jan 16, 2007 1:55 pm 
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is there any instructions or guides anywhere on how to put my cam in? i know how to undo all the rocker gear etc its just setting the cam timing i dont know how to do?
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Posted: Tue Jan 16, 2007 2:26 pm 
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GRN-WGN wrote:
is there any instructions or guides anywhere on how to put my cam in? i know how to undo all the rocker gear etc its just setting the cam timing i dont know how to do?


get a workshop/repair manual for your vehicle.
also have a look in the technical documents on this site.
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Posted: Wed Jan 17, 2007 12:12 pm 
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install the cam, and check the cam cam timing with the stock gear.
If it out a few degrees get the new gear an time the cam properly.
if it's within a 1 degree leave it
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