Measuring valve guides... where? how much? etc..
Thread Starter
Race Director
Joined: Apr 2003
Posts: 19,353
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From: Tampa, Florida
Measuring valve guides... where? how much? etc..
I have a set of 133 L98 heads I bought with sole intent of porting. Just something for fun because I've wanted to try it and wouldn't be flushing a lot of money if I screw it up. I know there are much better heads out there.....
When measuring valve stem to guide clearance there's the professional way and the home mechanic way. I measured 2 different ways....
Method 1. With valve seated I measured at the stem tip. This isn't accurate because there's distance from the tip to top of the guide. Geometry is need to correct error.
Method 2. With chamber facing up I lifted the valve and measured at the edge of the face. Again geometry needed to correct error.
So I measure a max movement .009 for a clearance of .00045 From what I've read this is ok for a wiggle type test. Any advice on more accurately re-measuring?
When measuring valve stem to guide clearance there's the professional way and the home mechanic way. I measured 2 different ways....
Method 1. With valve seated I measured at the stem tip. This isn't accurate because there's distance from the tip to top of the guide. Geometry is need to correct error.
Method 2. With chamber facing up I lifted the valve and measured at the edge of the face. Again geometry needed to correct error.
So I measure a max movement .009 for a clearance of .00045 From what I've read this is ok for a wiggle type test. Any advice on more accurately re-measuring?
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
I used a set of these to measure the bore on my valve guides.
https://www.ebay.com/itm/SHARS-4-SMA...sAAOxyakdRET0d
from my experience I can say that if you are measuring .009 deflection at the top of the valve guide that your guides are worn out. New is .002” valve guide to valve.
https://www.ebay.com/itm/SHARS-4-SMA...sAAOxyakdRET0d
from my experience I can say that if you are measuring .009 deflection at the top of the valve guide that your guides are worn out. New is .002” valve guide to valve.
Thread Starter
Race Director
Joined: Apr 2003
Posts: 19,353
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From: Tampa, Florida
.009 was at the valve tip ~1.1" above the guide boss. I'm going to bolt a piece of angle iron directly to the head and remeasure tomorrow. Hole gauges have been ordered!!
Thread Starter
Race Director
Joined: Apr 2003
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From: Tampa, Florida
I took your advice and bought a few measuring tools adding to what I had. After scouring the 'net I found a pic showing a rigid mount for the dial indicator. My previous setup was rigid enough thus my initial .009" measurement. All tools and parts sat out over night so they'd be the same temperature. Feeler gauges and pin gages were used to check outside micrometer accuracy. Valve stems were measured in 3 locations. Bore gauges were adjusted so they'd slide through the guide with just a tick friction
Clearance on both exhaust and intake is .002"
.342 .343 and .344 pin gauges (checked with outside micrometer)
Small hole bore gauge set
Digital outside micrometer accurate to .0001 (checked with feeler gauge)
Section right angle iron
Feeler gauges
Digital micrometer accurate to .001 (checked with feeler gauges
I cut down and mounted the section of angle to the head. Dial indicator mounted
.344 pin gauge doesn't fit... .343 fit but doesn't fall through on its own.
Bore gauge measures .343.
Valve stem measures .341
Clearance on both exhaust and intake is .002"
.342 .343 and .344 pin gauges (checked with outside micrometer)
Small hole bore gauge set
Digital outside micrometer accurate to .0001 (checked with feeler gauge)
Section right angle iron
Feeler gauges
Digital micrometer accurate to .001 (checked with feeler gauges
I cut down and mounted the section of angle to the head. Dial indicator mounted
.344 pin gauge doesn't fit... .343 fit but doesn't fall through on its own.
Bore gauge measures .343.
Valve stem measures .341
Last edited by jim2527; Jul 14, 2018 at 05:09 PM.
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
I took your advice and bought a few measuring tools adding to what I had. After scouring the 'net I found a pic showing a rigid mount for the dial indicator. My previous setup was rigid enough thus my initial .009" measurement. All tools and parts sat out over night so they'd be the same temperature. Feeler gauges and pin gages were used to check outside micrometer accuracy. Valve stems were measured in 3 locations. Bore gauges were adjusted so they'd slide through the guide with just a tick friction
Clearance on both exhaust and intake is .002"
.342 .343 and .344 pin gauges (checked with outside micrometer)
Small hole bore gauge set
Digital outside micrometer accurate to .0001 (checked with feeler gauge)
Section right angle iron
Feeler gauges
Digital micrometer accurate to .001 (checked with feeler gauges
I cut down and mounted the section of angle to the head. Dial indicator mounted
.344 pin gauge doesn't fit... .343 fit but doesn't fall through on its own.
Bore gauge measures .343.
Valve stem measures .341
Clearance on both exhaust and intake is .002"
.342 .343 and .344 pin gauges (checked with outside micrometer)
Small hole bore gauge set
Digital outside micrometer accurate to .0001 (checked with feeler gauge)
Section right angle iron
Feeler gauges
Digital micrometer accurate to .001 (checked with feeler gauges
I cut down and mounted the section of angle to the head. Dial indicator mounted
.344 pin gauge doesn't fit... .343 fit but doesn't fall through on its own.
Bore gauge measures .343.
Valve stem measures .341
valve guides can wear to an hour glass type shape inside. So critical wear is on the top and the bottom of the guide. At least this is where the most wear shows up. Pay particular attention to those two areas.
if they are good then you’re good to go.
