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Valve Clearance

 
Old 03-06-2019, 07:47 PM
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I have an LY6 with a stock bottom end and I put 823 heads and an ls3 intake on it too. Iím about to put a btr ls3 3-bolt stage 4 Cam into it but Iím worried about my compression ratio. Currently Iíve read itís supposed to be at 9.5-9.6, which is garbage because Iím NA for now. I wanted to know if anyone who did a simular build, how much could I mill the heads so I can gain compression at least to 10.5 or more.
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Old 03-06-2019, 08:35 PM
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The only way to know for sure is to measure PTV clearance with the cam you intend to use before milling. It's easy to shave the heads....much harder to put it back on if you guess and get it wrong.

PS The LY6 came from the factory with LS3 style heads, 821,823, If you know your heads haven't been milled before you got them then you might be able to find out what other LY6 owners have found clearance wise. If they have been milled then you'd just be guessing on how much further you can mill them.
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Old 03-06-2019, 08:40 PM
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Originally Posted by LLLosingit View Post
The only way to know for sure is to measure PTV clearance with the cam you intend to use before milling. It's easy to shave the heads....much harder to put it back on if you guess and get it wrong.
yeah I know but before I go through the time because Im porting the heads and gotta measure for the pushrod length and once I mill the pushrods might be too small and all that stuff.
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Old 03-06-2019, 08:43 PM
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Do you have the heads, cam and a adjustable pushrod checker?
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Old 03-06-2019, 08:46 PM
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If you donít have pushrods yet just buy 1 or 2 loose 7.400 pushrods or bum some old ones from a buddy so you can measure PTV clearance now. Then you can mill the heads accordingly. Then once final assembly is almost done, use a checker pushrod to measure preload and buy a full set of correct length pushrods.
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Old 03-06-2019, 08:47 PM
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Originally Posted by Maxwnn1234 View Post

yeah I know but before I go through the time because Im porting the heads and gotta measure for the pushrod length and once I mill the pushrods might be too small and all that stuff.
If it's not worth doing right then why bother? How much time and money do you think you'll waste if you get it wrong? You could get install the cam and trying using the stock pushrods to check PTV clearance. If that doesn't work get a pair of the correct length pushrods or even buy a second adjustable pushrod (you should already have one right?)
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Old 03-06-2019, 09:50 PM
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Originally Posted by LLLosingit View Post
If it's not worth doing right then why bother? How much time and money do you think you'll waste if you get it wrong? You could get install the cam and trying using the stock pushrods to check PTV clearance. If that doesn't work get a pair of the correct length pushrods or even buy a second adjustable pushrod (you should already have one right?)
no I donít have an adjustable pushrod checker, I was gonna either try the clay trick or borrow my buddies.
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Old 03-06-2019, 09:51 PM
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Originally Posted by 98CayenneT/A View Post
Do you have the heads, cam and a adjustable pushrod checker?
I have everything but the pushrod checker.
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Old 03-06-2019, 09:53 PM
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Originally Posted by Maxwnn1234 View Post

I have everything but the pushrod checker.
https://ls1tech.com/forums/generatio...ve-method.html
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Old 03-06-2019, 09:56 PM
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Originally Posted by 98CayenneT/A View Post
thatís an amazing write up and I will have to try this, did you just use any pushrod lying around or did you measure before hand?
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Old 03-06-2019, 10:12 PM
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Originally Posted by Maxwnn1234 View Post

that’s an amazing write up and I will have to try this, did you just use any pushrod lying around or did you measure before hand?
I used my adjustable push rod checker, set it to the correct length. You need to know your pushrod length for checking ptv

I already knew what pushrods I needed but had not ordered them yet. I had my heads/cam/ head gasket and it was just a matter of if I needed to cut valve reliefs or not.

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Old 03-07-2019, 06:54 AM
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Originally Posted by Maxwnn1234 View Post

no I donít have an adjustable pushrod checker, I was gonna either try the clay trick or borrow my buddies.
You're going to need a pushrod length checker to get the pushrod length set at some point so why not get a couple now, You could always sell one or both when you're done with them.
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Old 03-07-2019, 07:18 AM
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Originally Posted by LLLosingit View Post
You're going to need a pushrod length checker to get the pushrod length set at some point so why not get a couple now, You could always sell one or both when you're done with them.
to see if my buddy has one and if not Iíll probably just have to rent it from the local auto parts store
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Old 03-07-2019, 10:51 AM
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LY6 should have had 823 "type" rectangle port heads on it to begin with (maybe 5364's, or....). Also LY6 is a VVT motor, so I'm guessing you should have (intake) valve reliefs already cut into the stock pistons? I'm only speaking from my L92 experience, but same engine family. Does the cam you want specify 10.5:1 target compression ratio? There should be a ton of info available for compression points gained per amount of milling. You can tweak head gasket thickness as well, but keep quench in mind if you want the best out of it.

For me, I'd put the cam in you want, assemble one head side with a light valve spring for checking, and spin the engine over with a dial indicator on the valve, and hand push the valve open further each few degrees to check and measure clearance. Then you would know your allowances. Maybe a dinosaur method, but should work. Also ask the cam maker, they should have knowledge and experience of guidance level advice, but it always ends up as final check on your end.
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Old 03-07-2019, 12:42 PM
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Originally Posted by FormulaBoat View Post
LY6 should have had 823 "type" rectangle port heads on it to begin with (maybe 5364's, or....). Also LY6 is a VVT motor, so I'm guessing you should have (intake) valve reliefs already cut into the stock pistons? I'm only speaking from my L92 experience, but same engine family. Does the cam you want specify 10.5:1 target compression ratio? There should be a ton of info available for compression points gained per amount of milling. You can tweak head gasket thickness as well, but keep quench in mind if you want the best out of it.

For me, I'd put the cam in you want, assemble one head side with a light valve spring for checking, and spin the engine over with a dial indicator on the valve, and hand push the valve open further each few degrees to check and measure clearance. Then you would know your allowances. Maybe a dinosaur method, but should work. Also ask the cam maker, they should have knowledge and experience of guidance level advice, but it always ends up as final check on your end.
BTR says not to mill the heads but they said that referring to the LS3, and I called them and they told me to check the PTV clearance. The pistons have the valve release in then already but I donít think itís enough, we are using a stock gasket so it will
be thin.
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Old 03-09-2019, 04:37 PM
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Originally Posted by Maxwnn1234 View Post
I have an LY6 with a stock bottom end and I put 823 heads and an ls3 intake on it too. Iím about to put a btr ls3 3-bolt stage 4 Cam into it but Iím worried about my compression ratio. Currently Iíve read itís supposed to be at 9.5-9.6, which is garbage because Iím NA for now. I wanted to know if anyone who did a simular build, how much could I mill the heads so I can gain compression at least to 10.5 or more.
Stock bottom end with a zero deck and 0.045 compressed thickness gasket you would need to mill the heads to a 63cc combustion chamber in order to reach 10.5:1.
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