[Z06] Which exhaust valve to get...
02-21-2013, 02:38 PM
#181
Safety Car
It can happen in modified engines, tuned engines, over exerted engines, but why in the case of none of the above?
02-21-2013, 02:53 PM
#182
In the meantime, it is looking more and more like sloppy machining.
02-21-2013, 03:36 PM
#183
Safety Car
If this is a perfect Guide
||
This is Sloppy machining
\ \ or / / or | |
Incorrect angle, or too loose.
But what we are seeing is
} { or / \ or \ /
Hourglass, top, or bottom wear
02-21-2013, 04:13 PM
#184
A non-concentric seat, a product of sloppy machining, will give you excessive side loading on the stem from the bottom, like this: / \
I can only presume that some type of guide installation error will give you this (seen on a new set of heads): ( )
Excessive side loading on the stem from the top (rocker) as a result of some type of geometry issue can give you this: ) (
I'm sure that we've covered all this territory already. All those examples boil down to sloppy machining, or sloppy machine work if you like.
I can only presume that some type of guide installation error will give you this (seen on a new set of heads): ( )
Excessive side loading on the stem from the top (rocker) as a result of some type of geometry issue can give you this: ) (
I'm sure that we've covered all this territory already. All those examples boil down to sloppy machining, or sloppy machine work if you like.
02-21-2013, 04:42 PM
#185
Team Owner
As we are seeking any and all data, Howie, we'd love to hear. Honestly, I can't logically think that it would matter more than like 5 hp, certainly not likely to be noticeable in that case as a fart from a rabbit near the track could skew it more, but will be nice to hear your input after. I'm more thinking, I know I trap at 133.6-8 in the 1/4 consistently, if I went SS would I be 133.6, 133.5, 131? That's an unknown but less important anyhow. I only touched on it as the "penalty" is unknown. Was simply trying to illustrate that.
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DH
02-21-2013, 04:52 PM
#186
Safety Car
A non-concentric seat, a product of sloppy machining, will give you excessive side loading on the stem from the bottom, like this: / \
I can only presume that some type of guide installation error will give you this (seen on a new set of heads): ( )
Excessive side loading on the stem from the top (rocker) as a result of some type of geometry issue can give you this: ) (
I can only presume that some type of guide installation error will give you this (seen on a new set of heads): ( )
Excessive side loading on the stem from the top (rocker) as a result of some type of geometry issue can give you this: ) (
I don't know if we have seen any seat machining issues, but maybe you have examples.
02-21-2013, 06:00 PM
#187
There have been several reports of seat concentricity, or runout, exceeding spec. Offhand the spec is about .002, and as much as .005 has been reported in used heads although it is also reported that it is a difficult measurement to accurately make with a worn guide.
I haven't seen any exhaust guides at all that are worn more at the top than the bottom, but it's certainly possible I missed it.