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Old 07-26-2012, 07:54 PM
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Valve clearance

I have a stock SBC 350 bottom end. I am going to be putting some aluminum heads, roller cam, intake etc.

My question is how much valve lift can I get away with before running into valve to piston issues??

Stock flat tops with with 4 eyebrow valve relief, .025 deck heigth, .015 head gasket.

I heard you can run into issues with the eyebrows being to small to accomodate 2.02 valves??

Any input would be great. Thanks in advance.

PS: cam I wont to use has following lift......int .54 / exh .562

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Old 07-26-2012, 08:58 PM
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That cam though not high lift,likely wont fit.depends also on duration and lobe angle.always check clearances
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Old 07-26-2012, 09:16 PM
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There's no way to know and nobody can tell you rather or not your going to have clearance issues you have to check it and there's no way around it.
A cheap method we use is play dough with talcum powder to prevent the valve from sticking.
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Old 07-26-2012, 10:39 PM
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Hmmmm. I was planning on checking clearances but I'm worried about buying a $300 cam and not being able to use it.
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Old 07-27-2012, 12:01 AM
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I'm going to use either AFR 180 street or patriot freedom series 185. I was hoping to use a comp XE288 or XE 294 hydraulic roller. I would attach the link on the cams but I'm posting from my phone so I hope that helps. The only cam I have is a flat tappet magum 270. its 224 at .50
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Old 07-27-2012, 02:29 AM
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safer is better

when i doubt go to a place like howards cams or elgin or something and buy a cheap solid cam with close to the same numbers...may be impossible when comparing to a roller but its worth a try. most solid lifter stuff is 90 bucks from them. Or as an alternative. check with some local dirt track guys and see if they have a comparable one laying around you could use to test. Us dirt guys never get rid of anything.
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Old 07-27-2012, 05:32 AM
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Quote:
Originally Posted by prostcelica View Post
I have a stock SBC 350 bottom end. I am going to be putting some aluminum heads, roller cam, intake etc.

My question is how much valve lift can I get away with before running into valve to piston issues??

Stock flat tops with with 4 eyebrow valve relief, .025 deck heigth, .015 head gasket.

I heard you can run into issues with the eyebrows being to small to accomodate 2.02 valves??

Any input would be great. Thanks in advance.

PS: cam I wont to use has following lift......int .54 / exh .562
Besides the raw lift, the cam timing and additional advance/retard has an effect as well. There are so many variables that it is hard to guarantee anything when it comes to valve to piston clearance. I would definitely mock this up first and check the p to v.

Here is a page on things to check.

Stock piston valve reliefs need to be checked and clearanced if needed w/2.02" intakes. Aftermarket pistons tend to have more generous reliefs.
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Old 07-27-2012, 07:44 AM
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Agreed, can't really tell anything without mocking it up. Too many variables.

However, it's not THAT big a "deal" to have the valve reliefs "fly-cut" (type of cutter used for the operation). Any automotive machine shop that has a "piston vise" and a mill can do it. This is the procedure to be used when cams and pistons not "stock" are used. Common practice.

Jim
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Old 07-27-2012, 09:26 PM
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That seems like a lot of cam for a stock bottom end.
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Old 07-28-2012, 02:40 AM
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Thanks F-bird

Thats great info. That is a good plan. Is it super critical to use a solid lifter for mock up?? I guess I can probaly just buy a couple of solids instead of a hole set. Also what is minimum VTP clearance?
Is there a cam manufacture in particular that sells a "street" solid roller and lifters??
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Old 07-28-2012, 02:54 AM
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Quote:
Originally Posted by prostcelica View Post
Thanks F-bird

Thats great info. That is a good plan. Is it super critical to use a solid lifter for mock up?? I guess I can probaly just buy a couple of solids instead of a hole set. Also what is minimum VTP clearance?
Is there a cam manufacture in particular that sells a "street" solid roller and lifters??
You can buy single lifters. I have used a hydraulic lifter and taken it apart and filled it up w/small washers to make it solid. Either way, just so the lifter cannot collapse. You can reuse it when you check/set the geometry.

0.080" on the intake and 0.100" on the exhaust is considered by many to be a good safe clearance. You will probably find the closest near-miss at the exhaust valve on overlap, when the piston is chasing the exhaust valve back onto its seat.
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