[Z06] Basic causes of valve guide wear
01-28-2015, 12:23 PM
#61
Originally Posted by Undy
I would think that your geometry would remain the same as with your regular pushrod. The only 'possible' problem I can see would be deflection of the pushrod checker under load.
In real world you would 'fix' your plunger travel at the planned preload depth for an accurate contact patch.
Last edited by Mark2009; 01-28-2015 at 12:26 PM.
01-28-2015, 12:27 PM
#62
Safety Car
Member Since: Dec 1999
Location: Virginia Beach, VA & Port Charlotte, FL (snowbird)
Posts: 4,407
Received 1,095 Likes
on
578 Posts
No it shouldn't, due to the fact that you're adding the plunger travel to the length of the (adjustable) pushrod. The total length from the cam lobe to the rocker will remain the same, thus your geometry will remain constant.
01-28-2015, 05:51 PM
#63
O.K., back to the LS7 heads I'm playing with. So went back and looked all them again. All intakes in spec at 48k. All exhausts out. I measured again on the chamber side about 1/2" down into guide. All were about 0.020" when measured along the long axis of the head and about 0.017 - 018" when measured along the short axis indicating that side load is playing a (minor) part at least in these heads.
If the rocker pedestals were mislocated it was only the exhausts.
If the rocker pedestals were mislocated it was only the exhausts.
01-28-2015, 06:58 PM
#64
01-28-2015, 07:04 PM
#65
Safety Car
Member Since: Dec 1999
Location: Virginia Beach, VA & Port Charlotte, FL (snowbird)
Posts: 4,407
Received 1,095 Likes
on
578 Posts
I'll let everyone know once I try it, unless someone does it first.
It might take me a while to get another 9K miles on the car before my next wiggle test. I'm down to driving the car 5-6 months a year as it's up at my northern home.
It might take me a while to get another 9K miles on the car before my next wiggle test. I'm down to driving the car 5-6 months a year as it's up at my northern home.
01-28-2015, 07:16 PM
#66
Melting Slicks
O.K., back to the LS7 heads I'm playing with. So went back and looked all them again. All intakes in spec at 48k. All exhausts out. I measured again on the chamber side about 1/2" down into guide. All were about 0.020" when measured along the long axis of the head and about 0.017 - 018" when measured along the short axis indicating that side load is playing a (minor) part at least in these heads.
If the rocker pedestals were mislocated it was only the exhausts.
If the rocker pedestals were mislocated it was only the exhausts.
01-28-2015, 08:44 PM
#67
Safety Car
Thread Starter
O.K., back to the LS7 heads I'm playing with. So went back and looked all them again. All intakes in spec at 48k. All exhausts out. I measured again on the chamber side about 1/2" down into guide. All were about 0.020" when measured along the long axis of the head and about 0.017 - 018" when measured along the short axis indicating that side load is playing a (minor) part at least in these heads.
If the rocker pedestals were mislocated it was only the exhausts.
If the rocker pedestals were mislocated it was only the exhausts.
01-28-2015, 09:00 PM
#68
I'm not following your measurements.... you mean all the clearances you note are at the combustion chamber side of the guide? That would indicated an excessive seat concentricity issue, provided the clearance is considerably less on the rocker side of the head. And was there much carbon build up on the valve stem where it would rub the bottom of the guide?
08-31-2015, 02:42 PM
#71
Safety Car
Thread Starter
Bumping this thread. Looks as if there are some new members who are looking for a silver bullet.
Stick to the basics. There is always a reason for a failed component. You just need to know what to look for.
Stick to the basics. There is always a reason for a failed component. You just need to know what to look for.
09-01-2016, 06:47 PM
#72
Race Director
Thanks. And thanks to everyone else for the nice comments.
I may add pictures later.
I had also thought to put something together that would discuss guide type/alloys/manufacturing/ect in the second post. Brain storming that idea now, as I want to keep my personal opinions out of the discussion.
The hour glass wear pattern is created by where the binding occurs; the tip of the stem, or the valve head. If the rocker pushes the stem, then you will see more wear on the top of the guide. If the valve head lands on a seat that is not concentric to the guide, the valve head will be pushed directionally, causing the stem to rub/bind at the bottom of the guide.
I may add pictures later.
I had also thought to put something together that would discuss guide type/alloys/manufacturing/ect in the second post. Brain storming that idea now, as I want to keep my personal opinions out of the discussion.
The hour glass wear pattern is created by where the binding occurs; the tip of the stem, or the valve head. If the rocker pushes the stem, then you will see more wear on the top of the guide. If the valve head lands on a seat that is not concentric to the guide, the valve head will be pushed directionally, causing the stem to rub/bind at the bottom of the guide.
My 09 LS7 with 46K miles including HPDEs and other performance events.
All exhaust valve guides out of spec, hourglass worn most on the bottom --> seat not concentric.
Six of 8 intake valve guides out of spec, hourglass worn most more on the top --> rocker side loading.
A year or two ago I did a quick check of the rocker wipe pattern and the cylinders I checked had good hourglass wipe pattern on the rocker pad on all valves checked.
Last edited by AzDave47; 09-01-2016 at 06:48 PM.
08-14-2017, 12:34 AM
#73
Le Mans Master
Googling Corvette stuff mostly gets me right back here!
Old thread referenced in another thread today, my WCCH measurement data assessment.
My 09 LS7 with 46K miles including HPDEs and other performance events.
All exhaust valve guides out of spec, hourglass worn most on the bottom --> seat not concentric.
Six of 8 intake valve guides out of spec, hourglass worn most more on the top --> rocker side loading.
A year or two ago I did a quick check of the rocker wipe pattern and the cylinders I checked had good hourglass wipe pattern on the rocker pad on all valves checked.
My 09 LS7 with 46K miles including HPDEs and other performance events.
All exhaust valve guides out of spec, hourglass worn most on the bottom --> seat not concentric.
Six of 8 intake valve guides out of spec, hourglass worn most more on the top --> rocker side loading.
A year or two ago I did a quick check of the rocker wipe pattern and the cylinders I checked had good hourglass wipe pattern on the rocker pad on all valves checked.
Last edited by johnglenntwo; 08-14-2017 at 12:35 AM.