2.25" intake with a .14 cc dome clearance help - Hot Rod Forum : Hotrodders Bulletin Board
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Old 06-25-2012, 04:58 PM
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2.25" intake with a .14 cc dome clearance help

Been a bit since I've ben on here. My build going slow due to $$ suree we
all know how that goes. Any have BBC 468 with .14cc SRP forged alum pistons and just recently rebuilt 291 rect port heads with 2.25", 1.88's
my cam is the 396284/294 Isky. Lift is 578 in, 608 ex. The 454 block doesn't
have too big of a cut on the intake side (you know that little fly cut on the cylinders at the top for the valve) I am wonder about any V/P issues. with the 2.25" intakes. She is basically a LS6, 454 with more cam and I think the LS6 only had 2.19's (could be wrong) Any help on this please? These valves look pretty darn big to be able to open more than a 1/2"
Help or experinece(s) is as always appreciates

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Old 06-25-2012, 05:40 PM
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v/p clearance

With my LS-5 and 2.19 valves I had to delay the cam 2 degrees for clearance.Better check before you balance the engine.I used a z-55 cam,from what I remember its close to what you are using
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Old 06-25-2012, 05:52 PM
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No one on here can tell you what your P/V clearance will be or is. You need to check it yourself.
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Old 06-25-2012, 06:07 PM
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You are reffering to the chamfered area at the top of the cylinders bore. It is primarily to help "unshroud" the valve so it can breath in better when it open.
Advancing the cam has nothing to do with the clearance at that area.
But you do need to check to be sure it is adequate if you had oversize valves installed.It may clear just fine , but with the oversized valves, the cylinder wall side of the valve may now be closer to the cylinder wall, wich can actually hinder flow. You may or may not have any room to open up the chamfered area depending on the amount of deck area between the cylinders. AND it is a tedious task to say the least.
Set the head on the block (with bolts and a gasket, lightly tightened) and open an intake valve to the max lift of your cam and look inside the cylinder from the bottom of the engine ( I am assuming your engine is not assembled and is on a stand) so you can see what kind of clearance you have.
If the short block is built allready, you can use clay to make an impression. Just put some in the cylinder, with the piston down in the hole a few hundred thousanths more than the max amount of lift of the cam you are using, set a head on, using a dial indicator on the retainer to measure, open the valve to max lift, leaving an impression in the clay. wipe some petroleum jelly on the valve head area so it releases from the clay and the clay will stay on top of the piston. That should paint a good picture for you. Bada Bing.
Fact is stranger than Fiction
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