I think it's 0.182 and 0.166 for the EV27.

I'd concur on the Andrews' guy not being very technical and/or not being very interested in Evo cams.

The trick would be working out a workaround without having any special tools like those Trock tools they make ...

Shoot me down John but given the choice of cam, I would not worry too much and would just assemble it all without springs and rods first, drop the valves down to their maxium lift height (.495"), then turn the engine round slowly and gently to see what happened ... watching the valves for the start of any contact or movement, if any. Start at piston TDC and see if it drops down any before going round. Use a little tape on the top of the valve so you don't drop them right down the guide.

Stick a dial guage on them if you must. There's still a chance they won't contact. If they don't contact, then use some clay to see how much they are not contacting.

There are some collars you can buy for countering sinking screw holes for a few dollars that work well enough. 5/16" = 8mm. Not everyone has a fully equiped garage at hand but there's usually a way to workaround. It's not a racing bike and it's squish is 45 thou plus ... I'm guessing it's actually 50 thou plus. He has some slack to play with.

No point worrying about anything until you know really it's time to worry about it.

Like this ... 99c from Hong Kong.

 

Here's someone getting his hands dirty with pics.

 

the problem came along when he said he had the pistons that you cant even buy anymore that have only one valve cut out - the number i referenced for the cam was an example not the actual i did not have those on hand or in my head -

with out machining the cut outs the valves will, not if - HIT the piston tops way before total cam lift is achieved - the 458 he has is a 30 plus year old mistake harley did along with the pistons - we dealt with this issue the winter of 1984, the only cam available was from tom sifton and it was -- Memory - a viper i believe - and the info was in my book but the pages were all torn up after a few years and are long gone - with the instructions said to remove the pistons NOT like that hack with a disc sander on the piston while the motor is assembled Yea thats going to last for the guy --

put them in a bridgeport and angle cut the tops to allow for a bigger cam - at one time i had the info in my head what and how much to remove but its 30 years ago

dont know what to tell the guy his shop he is going to the guy was not in business then and has no idea about what i am referring to

if you install it with out having the top re done you will // not if bend at least one valve and possible i have seen them back in the day brake off the lower section in the port the valve guide

i am done i hope i helped

 

In the guy's defence, he does say, "for minor adjustments" only and mentions doing precision jobs on a machine. I suspect just opening them up to the outside a little.

There's always a right way to do things and ways to get by, which we all have to do sometimes. Here's what you'd be cutting into ... something like below. Plenty of meat.

Just out of interest, if you're not going to use the old OEM pistons, Glide, I'd be interested to see them cut in two to know what's there. Failing that, you could always get creative (or below again) with them.

 

I need to clear up a few things I guess... I did not measure piston top to deck as you stated, I just disassembled the engine, don't know that spec.
John, my stock pistons don't have one cut, they have NO valve relief at all,flat as can be.
I see two options, buy new stock pistons like I seen in J&P CYCLE or buy used cam/pistons from Bob "HOTROD" .Not sure yet....

 

Neo-con,cool pic, however I don't think I have the heart to destroy my Oem pistons but I am capable of measuring how thick they are and post for you.
Sorry if I misled anyone with all the numbers I've been spitting out...

 

 

It's the only pic I have of pistons..

 

It's worth doing regardless of where you take all this. Do you know how, or have you searched/googled for a howto?

You're a kick in the *** off a really good engine for no real additional expense, and without going all out for a perfectly optimized one. It's a good cam, and you should be able to cut or source some pistons to suit for very little to nothing. I don't think you'll need to cut that deep.

I raised the issue of knowing the deck height because it will mean your squish/clearance is much more than 45 thou. It could be 60 or even more. In fact, a 30 thou head gasket is a more common pick up for these engines. I'll guess you have a 15 thou base gasket too?

Clean those pistons tops and start by measuring it all. Do as they told you and see how far down your valves come, e.g. do it with the heads off, and a straight edge across the face.

Knowledge is power.

 

See, here's a good example comparison of actual protrusion versus existing cut out in a piston.

I suspect you won't need to cut out as much as a stock piston comes with (and if you are going to buy new pistons, calculate the whole price and then compare it to the extra required going for higher compression pistons would cost. The cam likes a little more pressure).