[Z06] More bad guides *video inside*
#241
Pro
Aftermarket cam, stock rocker arms, last ~4k had the comp trunnion upgrade. In fact, the rockers are probably one of the few non-aftermarket things in the engine bay. Block, pistons, rods, crank, valve covers, alternator, headers, blower, etc is all aftermarket.
Coils, front cover, rocker bodies, and sensors are all OEM. Everything else has been changed.
Coils, front cover, rocker bodies, and sensors are all OEM. Everything else has been changed.
Thanks for taking the time to answer my questions.
It's just goes to show one never can tell for sure.
There was a post a while back about PRC heads not being "the fix".
I think half the battle so to speak is setting things up correctly. i.e. pre-load, cam profile, valve train geometry, wipe pattern, correct valve spring install height, coil bind, tuning and maintenance.
Just my 2 cents.
#242
Burning Brakes
About that video...
I got my sectioned LS7 head off the shelf and took some rough measurements (ie: eyeball and ruler) of the part I have that's a sectioned exhaust port, half a chamber cut right down the CL of the exhaust guide.
Eyeballing the position of the dial indicator as shown in the video, then measuring half the guide (about an inch) plus the apprioximate distance from the guide down to the head of the valve, as shown in the video–say 3.75-in.–then, using trig, working out the difference between the observed clearance (.020) and what it would be if the measurement was taken in the proper place–it looks like the difference is a factor of about 3.8. That's huge.
So, to put it another way–if, measured the way it was done in that video, you saw .020" clearance, the actual stem-to-guide would be about .0053, which is well outside the Service max. tolerance of .0037
Nevertheless, I think I'd be careful with any conclusions you make if you measure stem-to-guide the way the video does. For example, let's say you saw .010 on the indicator, measuring the way it was done in the video. You might think OMG! But...the actual stem-to-guide would be .0026, well inside the Service tolerance and just a tenth outside the Production tolerance of .001-.0024.
I got my sectioned LS7 head off the shelf and took some rough measurements (ie: eyeball and ruler) of the part I have that's a sectioned exhaust port, half a chamber cut right down the CL of the exhaust guide.
Eyeballing the position of the dial indicator as shown in the video, then measuring half the guide (about an inch) plus the apprioximate distance from the guide down to the head of the valve, as shown in the video–say 3.75-in.–then, using trig, working out the difference between the observed clearance (.020) and what it would be if the measurement was taken in the proper place–it looks like the difference is a factor of about 3.8. That's huge.
So, to put it another way–if, measured the way it was done in that video, you saw .020" clearance, the actual stem-to-guide would be about .0053, which is well outside the Service max. tolerance of .0037
Nevertheless, I think I'd be careful with any conclusions you make if you measure stem-to-guide the way the video does. For example, let's say you saw .010 on the indicator, measuring the way it was done in the video. You might think OMG! But...the actual stem-to-guide would be .0026, well inside the Service tolerance and just a tenth outside the Production tolerance of .001-.0024.
#243
Pro Mechanic
Pro Mechanic
For example, let's say you measure .0035". Your actual stem-to-guide would be .0028 or just outside production specs and well inside service specs.
Also, click here for the web-based triangle solver I've been using.
Last edited by Hib Halverson; 12-16-2013 at 09:53 PM. Reason: added content