Valve to Piston Clearance

Hi,

I have a set of Skunk2 Tuner 2 series Camshafts for a B18C that I have degreed with no problems. I then went to check the piston to valve clearance using a dial indicator and test springs. I started out at 20* BTDC and ended at 20* ATDC for each cam.

The issue is that at around 15-10* the valve is in the way of the other valve (overlap) and I am unable to reach the piston to determine my clearance with the other valve in the way. This is my first time checking piston to valve clearance so I am sure I am doing something wrong.

Thank You

As you're using test springs, I assume it's a dummy build - if so, can't you just check the intakes with exhaust removed, then reverse the procedure for the exhaust side?

That is what I was going to do, but as it turns out, with these particular cams even though the valve diameters are stock, there is insufficient valve to valve clearance even if installed at 0,0. Upon researching this issue I found that other people with this setup have the same issue. I now have the head removed and I am making a chart of valve-valve clearance X cam degree to make sure I set the cams in the safe zone. Before I put the head back on to check piston to valve clearance I will make sure to remove each valve accordingly so that I wont run the valves into each other when checking piston to valve clearance.

Ah, rather surprised that's a problem with modern engines as I would expect the aftermarket to account for those issues - you may need to talk to the provider/grinder?

There are some engines where 'valve clash' can be a problem with some camshaft profiles as, even when it looks like there's clearance, the valve heads can actually move around a little, especially with oversized valves, and sometimes it can be seen as strange markings on the heads - sometimes as a pile of scrap metal.

Some older folks may recall older Jaguar engines had their standard and "big valve" heads - the latter actually had the cylinder head redesigned with the valve positions and angles altered so they couldn't collide - even the camshafts were moved in the head!

I ended up making a chart of valve to valve clearance x cam degree so that it is always being ran in the safe zone. Retainer to Valve Seal clearance is also something I had to check and ended up with .025" clearance at peak lift. Here is a video of the exact setup I am working with for anyone who runs into this issue: https://www.youtube.com/watch?v=8hJcOrlyWRI&t=154s&ab_channel=MAWFactor