How to properly measure valve diameter

[siuauto]

Ok, its been a while since I have had to do this so I want to make sure I am doing it correctly. I recently bought a set of Edelbrock knock off heads from a buddy for my SBM. These heads have been heavily modified with porting and such. When I put a micrometer across the valve margin I am getting 2.18". That is a big block valve size to me so I must not be doing it correctly. Do I measure at the margin or do I measure the valve face? Thanks in advance...

 

[Demonracer]

Pictures of the heads would be helpful.

 

[toolmanmike]

...

 

[siuauto]

Pictures of the heads would be helpful.

 

[PRH]

If the valve is out of the head, and you’re measuring across the head with like a dial caliper........ and coming up with 2.180...... it’s 2.180.

If you’re using a “micrometer”, don’t take this the wrong way....... but I’d suspect the valve is likely 2.080”, and maybe you’re reading the mic wrong.

I can’t imagine being able to make good use of a 2.180” valve in that type of head.

 

[siuauto]

I may have goofed up on reading my mic. It looks like a 2.08" Intake and a 1.60" exhaust. I think this makes more sense but that 2.08" still seems pretty big.

 

[yellow rose]

If the valve is out of the head, and you’re measuring across the head with like a dial caliper........ and coming up with 2.180...... it’s 2.180.

If you’re using a “micrometer”, don’t take this the wrong way....... but I’d suspect the valve is likely 2.080”, and maybe you’re reading the mic wrong.

I can’t imagine being able to make good use of a 2.180” valve in that type of head.

You MIGHT be able to squeeze a 2.150 valve in there if you use a 1.500 exhaust. Of course, you’d need to be able to get a valve job on the exhaust and I don’t think you ca go that small on the exhaust valve even with a 55 degree seat.

 

[siuauto]

If the valve is out of the head, and you’re measuring across the head with like a dial caliper........ and coming up with 2.180...... it’s 2.180.

If you’re using a “micrometer”, don’t take this the wrong way....... but I’d suspect the valve is likely 2.080”, and maybe you’re reading the mic wrong.

I can’t imagine being able to make good use of a 2.180” valve in that type of head.

I think your correct

 

[Demonracer]

The 2.08 & 1.60 sounds better, 2.18 would be a stretch in a SBM head without severe modification. LOL The 2.02, 2.05 & 2.08 valves really help with the breathing at high RPMs.