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Some basic questions

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Old Mar 24, 2010 | 08:56 AM
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Default Some basic questions

just some random questions here:

How does one check PTV clearance without removing the heads? Is this even possible?

Also, as i read through some of these threads of guys with PTV clearance issues, some have suggested flycutting the pistons. How is this done?

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Old Mar 24, 2010 | 09:18 AM
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I wedged a .100" shim between the rocker tip and valve tip then turned my engine over by hand to check mine.

They make a fly cutting bit that slides up into the valve guide, then hooks to a drill, its not hard, but the heads have to come off
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Old Mar 24, 2010 | 10:08 AM
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The best way is to actually remove the heads.You can use the clay method. It involves putting clay on your piston, bolting your head back up, and cycling your engine a few times by hand. Measure the impression, and you have your clearance. Mark's way will work to give you a minimum, but will not tell you the exact clearance.

Why so afraid to remove the heads? It is just the cost of gaskets and bolts, and if you go with ARP, you only need to buy the head bolts once.
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Old Mar 24, 2010 | 10:18 AM
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haha im not afraid to remove the heads. hell right now i dont even have a car as i just sold my ws6. But im looking for the right LS1 car right jnow and im hoping to do heads/cam asap.
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Old Mar 24, 2010 | 10:18 AM
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Originally Posted by mark21742
I wedged a .100" shim between the rocker tip and valve tip then turned my engine over by hand to check mine.
They make a fly cutting bit that slides up into the valve guide, then hooks to a drill, its not hard, but the heads have to come off
so how does this let you know if you have PTV clearance issues or not?
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Old Mar 24, 2010 | 10:38 AM
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Haha I meant no disrespect, just curious as to why. Using his method, you will know for sure you have at least 0.100" clearance. My recomended minimum is 0.080"
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Old Mar 24, 2010 | 01:09 PM
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Dial indicator with check springs, if you want to leave the heads on.
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Old Mar 24, 2010 | 01:27 PM
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Originally Posted by 99C5Coupe
Dial indicator with check springs, if you want to leave the heads on.
to do what?
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Old Mar 24, 2010 | 01:30 PM
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Originally Posted by 1SLwLS1
to do what?
To check piston to valve clearance.
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Old Mar 24, 2010 | 01:34 PM
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how so?
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Old Mar 24, 2010 | 01:45 PM
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I am at lunch at work right now, so I don't have time to search and write it all down. With light check springs on cyl. no. 1 valves, mount the dial indicator so it contacts the valve spring retainer, and close to parallel to the valve. Check with 15 deg BTDC and 15 deg ATDC, they say check every 2 deg by rotating the rocker until the valve touches the piston and reading the distance on the dial indicator. Crane cams web site has a better description if you have time to search.

http://cranecams.com/pdf/20e.pdf

Last edited by 99C5Coupe; Mar 24, 2010 at 02:58 PM.
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Old Mar 24, 2010 | 02:43 PM
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Thats pretty good stuff right there. I like that, although you would need a degree wheel and quality dial indicator. Thanks for the info!
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Old Mar 24, 2010 | 09:57 PM
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No disrespect taken here lol.
With the shim wedged between the valve stem and rocker the valve opens .100 futher than it would without the shim.

I forgot to add the check springs... I used them so the lifters would not collapes. I think they were around $2 at Lowes.

Best way, no but for a quick check without pulling the heads it works. Also if a .100 shim had clearance I definately had .800
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Old Mar 24, 2010 | 10:43 PM
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I do agree that pulling heads and using clay is a lot better way and more accurate
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Old Mar 25, 2010 | 08:04 AM
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Originally Posted by mark21742
No disrespect taken here lol.
With the shim wedged between the valve stem and rocker the valve opens .100 futher than it would without the shim.

I forgot to add the check springs... I used them so the lifters would not collapes. I think they were around $2 at Lowes.

Best way, no but for a quick check without pulling the heads it works. Also if a .100 shim had clearance I definately had .800
oh okay i get it now. So with the shim between the valve stem and the rocker, you rotated the engine by hand and ensure that no PTV contact occured? Did you have to loosen the rockers at all to get the shim in there or was it able to slide in when both valves were closed?
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Old Mar 25, 2010 | 10:56 AM
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I removed the valve springs on number 1 intake and exhaust and replaced them with "check springs" I got at Lowes hardware store. (They were small soft springs about 3" long and 3/4" across)
With these springs in you can push the all the way open with your finger and slide the shim in with the rockers bolted down
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Old Mar 25, 2010 | 11:46 AM
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you pick up the shims at the hardware store too?
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Old Mar 25, 2010 | 12:11 PM
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I measured an old plastic speader I had laying on the shelf and cut a section out of it to use for the shim
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