...specifically where they concern an '02+ LS6 motor.

cam base circle
LS1 - 19.7mm
01 LS6 - 19.3mm
02 LS6 - 19mm

Now - the valve LENGTH in the 01 LS6 remained the same as in the LS1. In the 02 LS6 the valves were lengthened by 0.6mm to accomodate the reduction in base circle on the cam.

What implications, if any, would placing a cam designed for an LS1 or 01 LS6 motor into a 02 LS6 motor, could arise?

I would imagine that given stock heads, not milled, not much would happen. Possibly some higher than advertised lift numbers would actually be seen?

Once the heads are milled, what options would there be? Custom length pushrods? Flycutting the pistons for valve relief?

Some of you bastards are really damn smart - please, discuss amongst yourselves... <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

 

It seems to me that with the conditions described the valve would not be able to close, so a low or no compression condition may arise, though .7 mm might not make enough difference to matter.

 

By the way, do you have a power adder?

 

The measurements above are actual measurments of the '02 LS6 cam and valves...this isn't a hypothetical question, I'm curious about the actual results of putting in a different cam which is off of a "LS1" base circle, and thus a diameter 0.7mm larger...

No power adder here - 100% NA. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

 

Any other thoughts - insight?

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by TAMUz06:
<strong>...specifically where they concern an '02+ LS6 motor.

cam base circle
LS1 - 19.7mm
01 LS6 - 19.3mm
02 LS6 - 19mm

Now - the valve LENGTH in the 01 LS6 remained the same as in the LS1. In the 02 LS6 the valves were lengthened by 0.6mm to accomodate the reduction in base circle on the cam.

What implications, if any, would placing a cam designed for an LS1 or 01 LS6 motor into a 02 LS6 motor, could arise?

I would imagine that given stock heads, not milled, not much would happen. Possibly some higher than advertised lift numbers would actually be seen?

Once the heads are milled, what options would there be? Custom length pushrods? Flycutting the pistons for valve relief?

Some of you bastards are really damn smart - please, discuss amongst yourselves... <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" /> </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Interesting topic, although I am sure its been covered before. GM engineers reduced the base circle of the cam by .7mm, which in turn brings the lifter and pushrod further down .35 mm (base circle reduction / 2). The rocker translates this displacement by a factor of 1.7 for the valve tip, which is .595 mm (.35 mm X 1.7). This is only .8% off from the valve change in length of .6mm, so this makes sense.

Now for an LS1 base circle cam in a 02 LS6 motor:
This will result in .6 mm of additional lift if something else in the valvetrain is not adjusted (shortened pushrods would be the easiest solution).

.6 mm (1 cm / 10 mm) (1 in / 2.54 cm) = .0236 in. of extra lift

I think something in the valvetrain would take up the slack (hydraulic lifters?) so I doubt this is an issue, but I could be way off base <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

 

Weren't the 02 LS6 valves lengthened in order to keep the rocker arm contact area on the valve tip closer to center with increased valve lift? That, and more room for longer springs, is often what determines valve and pushrod lengths.

However, wasn't the base circle size reduced in order to grind in more lobe lift? That's necessary because the lobes can't stick out farther than the bearing journals or the cam won't fit in the engine.

Using your base circle numbers, .7 mm is only about .028 inches. The best aftermarket pushrods come in .050 inch length increments, so you probably wouldn't need to change pushrods with this small base circle change.

So, IMO, putting an LS1 base circle cam in a 02 LS6 shouldn't be a problem, except you are limited in lift with the LS1 base circle. Why would you be putting in a lower lift cam than the 02 LS6? Hmmm.

I suspect that aftermarket cams with more lift than stock LS1 or even LS6 have smaller base circles than stock LS1, even if they are ground on "LS1" cores.

I would be most concerned with getting the rocker/valve stem contact patch correct, especially with higher lift and more spring pressure.

How about asking the cam supplier what actual base circle dimensions are with a specific grind. Get both intake and exhaust dimensions. The best grinders will grind the lobe with the biggest base circle which allows the lobe to fit thru the bearings. Some might not. It depends.

There should be enough adjustment in the system to accommodate the increased lift/reduced base circle dimensions. Again, ask the cam supplier. If they won't help with the info, maybe they aren't the supplier you should choose.

My $.02

<small>[ October 04, 2002, 11:38 AM: Message edited by: Old SStroker ]</small>

 

There should be enough adjustability in the valvetrain to account for the base circle difference, but the position of the plunger with the hydraulic lifter would be less than optimal from what I read here: http://ls1info.com/article.php?sid=148

 

Fenris Ulf, that is some good info.

 

Interesting thread guys, I wondered all of this too, I think Tamu had a thread like this 3-4 months ago.