I purchased a 2002 z06 cam, valve springs, and pushrods off of ebay for $250. I didn't plan on raising my stock rev limiter from the stock 6200. Will this cause any major reliability issues? The z06 has lightweight valves I understand. I, however, was looking for somebody who has experience in this matter and has used the cam without better springs or lighter valves. Did you have any troubles? Thanks

-Josh

 

How long are the hardened pushrods you bought?

Ron,

 

Whatever came from a stock z06 <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

 

No reliability issues here. You need either 7.45" or 7.40" length pushrods. I have the '02 springs and cam, with hardened 7.40" pushrods.

 

distortion_69 ...

The stock 7.40" LS6 rods should be fine.

If you have untouched heads, you certainly don't want a set of the shorter 7.35" rods that are readily available.

That 2002 LS6 cam has a [smaller] base circle than his stock LS1 cam. Shorter pushrods than the stock 7.40" length will just make matters worse. He would have NO lifter preload at all with short rods.

In fact, the 2002 LS6 motor uses longer valves in the head just because of the smaller base circle of the 2002 LS6 cam (they don't use a different length pushrod).....

Ron,

 

The stock LS1 cam has a 'base circle' of 1.552" (across the lobe)
That equals .775" (19.7mm) from 'cam centerline' to 'lobe heal'. In fact, GM states that this distance is in fact 19.7mm on the LS1 cam.

GM also states that the 2002 LS6 cam has a 'cam centerline' to 'lobe heal' distance of 19.0mm
That is exactly .748"

The simple math will tell you that the difference in 'cam centerline' to 'lobe heal' distance between the two cams is 0.7mm or .027"

To be exact, the LS6 cam would require a .027" [longer] pushrod than the LS1 cam if you wanted to maintain the exact lifter preload as you had before the cam swap.

However, I am sure you can get by with the stock 7.40" rods with the 2002 LS6 cam .. (as long as the heads have not been milled .. That changes everything).

Ron,

 

The heads have not been touched, no milling.

What are some symptons of lifter preload? Does this cause premature lifter wear?

 

Hydraulic lifters have a shuttle valve (looks like a plunger) in them that basically needs to be positioned in the middle of the lifter bore that this shuttle valve slides in. Engine oil is supplied to both sides of this plunger. I cannot tell you the exact + - plunger travel that is allowed, but it is fairly substantial. As long as the plunger is somewhere near center in the lifter's internal bore, there is no problem. Engineers design the valvetrain geometry (pushrod & valve length) so as to have this plunger positioned fairly centered inside the lifter.

Again, I can't tell you exactly what it is, but it's at least + - .035" from stock spec/centered (thats at least .070" total travel in the lifter), so it really gives you some variance. Having stock spec preload would be ideal, but again, this lifter preload don't have to be exact. Thats one of the things that make hydraulic lifters so forgiving.

If the lifter preload is off a little from the stock spec, don't worry. No damage will be done. In your case, your preload will be slightly less than stock with your setup. Slighty less preload actually will keep the lifters from "pumping up" so fast at high rpm. A good thing...

You should be fine, as long as the lifters still have [some] preload, and they will with your combo.

Now, had you used 7.35" pushrods (thats .050" shorter than stock) and your cam that has a .027" smaller base circle, that would get you .057" less preload than stock spec. I can tell you, I am betting that you would not have any preload at all. You would have a valvetrain that is set up with less than zero valve lash.

1. Lots of noise (loud tapping)
2. Increased wear to the valvetrain (especially to the valve stem ends)
3. Decrease in performance since the valves would not open fully.

BTW, if valve lash is too great (way too long of pushrod), to the point that the lifter plunger is froze in the internal lifter bore, the valves won't completely close causing:

1. Backfireing (partially open valve)
2. May not even run do to loss of compression (partially open valve)
3. Binding of the valve springs
4. Damage to the lifters

Again... You will be just fine!

Ron, <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

 

Ron, you're almost perfect GM has a lifter plunger travel spec of .075"

Jay

 

Thanks Jay....

 

This was a very informative post, I learned alot. Thanks again for your help guys! The cam goes in next weekend.

 

Have fun...

Remember, the dot on the crank gear is very hard to see. Align the dots on both the crank and cam gears up facing each other (crank dot to the top / cam to the bottom) before pulling off the cam gear for your install. May want to put a drop of white paint on the crank gear dot in order to see it again.

After the cam gear is removed from the old cam, don't rotate the crankshaft anymore (leave that crank dot pointing straight up). After that, you can turn the cam all you want because the cam gear will only go back on the new camshaft one way.

The dots will then need to be facing one another after the install. They [CAN'T] be off even 1 tooth, or the valve timing will be way off. <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" />

Ron,