Valve to Piston clearance issue?
05-25-2013, 11:20 PM
#1
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Valve to Piston clearance issue? So my "new" setup:
5.3 Patriot heads stage 2 - bought used no specs
1.8 Terra Yella rockers
stock GM 2002 LS1 head gasket
Cam Specs: 228/232 111 .632/.600
So tonight I put clay on the first piston and bolted down one head onto the block and turned the engine over by hand to see how close I was getting to the piston. The clay was squashed but not broken through. It did look very close though so then I put red grease on the intake and exhaust valves and tried it again with no clay in place. There was no grease left behind by either valve on the piston. The 1.8 rockers are really my concern and I am thinking I would be safe with 1.7s. I am thinking with so much lift from the cam, once the rods stretch and higher rpms come into play, I may have an issue.
I plan to search around on the site some more to find the specs on a stock 5.3 head so I can know for sure if these heads have been shaved or not. Knowing that, HG thickness, cam specs and rocker specs - I should be able to mathematically see where I am and if I have any buffer room.
Thanks guys for any help!
5.3 Patriot heads stage 2 - bought used no specs
1.8 Terra Yella rockers
stock GM 2002 LS1 head gasket
Cam Specs: 228/232 111 .632/.600
So tonight I put clay on the first piston and bolted down one head onto the block and turned the engine over by hand to see how close I was getting to the piston. The clay was squashed but not broken through. It did look very close though so then I put red grease on the intake and exhaust valves and tried it again with no clay in place. There was no grease left behind by either valve on the piston. The 1.8 rockers are really my concern and I am thinking I would be safe with 1.7s. I am thinking with so much lift from the cam, once the rods stretch and higher rpms come into play, I may have an issue.
I plan to search around on the site some more to find the specs on a stock 5.3 head so I can know for sure if these heads have been shaved or not. Knowing that, HG thickness, cam specs and rocker specs - I should be able to mathematically see where I am and if I have any buffer room.
Thanks guys for any help!
05-26-2013, 06:57 AM
#2
Rockers won't make that big a difference IMO since the exhaust valve is near closure an the intake is opening when minimums occur. Rocker ration is likely not the same on the seat as when open, i.e., stock rocker ratio on the seat is 1.54 not 1.7, which occurs later in rotation.
Do you have a head gasket in place of the same thickness when measuring?
Do you have a head gasket in place of the same thickness when measuring?
05-26-2013, 12:40 PM
#5
what PREDATOR Z said.
05-26-2013, 08:01 PM
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Thanks guys, I have a stock head gasket (new) when I did the "clay" check. GM part# 12498544
Brandon I will have to go out and buy a caliper for sure, it was late last night when I started.
Predator and Jimbo - I am thinking on your terms. I think the valve is too close with the 1.8s turning by hand. I think higher in the rpm range I will have some issues.
Thanks so far guys.
Brandon I will have to go out and buy a caliper for sure, it was late last night when I started.
Predator and Jimbo - I am thinking on your terms. I think the valve is too close with the 1.8s turning by hand. I think higher in the rpm range I will have some issues.
Thanks so far guys.
