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Re: [6pack] Cam Indexing

To: John Cyganowski <janah@att.net>
Subject: Re: [6pack] Cam Indexing
From: Robert Lang <lang@isis.mit.edu>
Date: Tue, 13 Nov 2007 08:03:00 -0500 (EST)
On Sat, 10 Nov 2007, John Cyganowski wrote:

> I was wondering how cam indexing was done on the TR6?  On some cars, I have 
> heard that offset keys were used on the cam or crankshaft. I have seen the 
> vernier cam sprokets, but they seem very expensive.

Cam indexing on a TR6 is done with the cam gear. There SHOULD be two sets 
of holes on the cam gear, one lining up with the center or the teeth, the 
other lining up with the valley of the teeth. This you get 1/2 tooth worth 
of indexing. 360/42=8.5 (more or less) so you should be able to get +- 
around 2 degrees (8.5/2=4.25, 4.25/2=2.125)

If you need more exact than that, you have choices, some good, some not so 
good. You could open up the holes on the cam gear, but without indexing 
bushings like the V8 guys, you'd be playing with the possibility of the 
cam gear slipping (and thus loosing your advantage indexing the cam in the 
first place.) The cam verniers are expensive, but they give you a lot of 
latitude (somthing like 15 degrees) and you don't have to pull the gear 
off to adjust. If you're tuning on a dyno, being able to make small 
adjustments will pay for itself in saved dyno time.

For the street, the cam vernier is overkill, +- 2 seems to work just fine.

> Regards,
> John Cyg

regards,
rml
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