I have a 496 that im putting new heads on and checked the clearance. With no gasket I have .020 on exhaust and 80 on intake. I have the cam advanced 6 degrees. I have a .040 head gasket and a .080 gasket. With the .040 I have .060 ex and 120 in. I always thought you need at least 100 ex and 80 intake. Do you count valve lash as clearance too? Mine is .025 on both.

If this is a bracket car (and not a Comp car), .090 on the intake and .120 on the exhaust (net totals). Those are conservative but safe numbers, “safe” being the operative word for a bracket engine.

If this is a Comp engine and you are going to constantly check the valve spring pressures and lash settings, with aluminum rods, titanium valves and a reasonably aggressive cam profile plus .904 rollers those numbers can be reduced to .045 on the intake and .090 on the exhaust. There is still some left on the table but it gets scary beyond that, if you do have a lot of money.

Personally, I would go with the safe numbers.

Bob

Pm sent.Let me know if can help.

My cam is 280/290 @ 50, If I change cam to a 268/276 @ 50 would that give me back some exhaust valve clearance? I think both a 110 cl.

More than likely you will gain quite a bit with 14* duration. IM O 280/290 @ .050 is too much cam for rest of combo.

Have you checked with cam straight up,0 advance. Why 6* adavance?

I only advanced it 5 degrees, bullet said 4 . It came out 5 so I left there. All the cam recommendations that I had we're all so different. One would say to 270 / 278 at 50. One would say 276 286 at 50. And one said duration 280 /290@50.

If the cam was ground with 4 degree advance that is where it should be to start. If you can get it with the keyway then you have to use a bushing in the cam gear.
Adding head gasket will just cause compression to drop.
Put the cam where is should be, use real springs and and some used head gaskets, cold lash and check it again. Most cases the pockets do not hit the valve flat so it skews the measurement.
Compromising cam location, head gasket thickness will usually result in an underperforming engine.
And I would use the 276/286 in @106

The cam is a 110 Centerline they suggest to install it at 1:06