Its a risky proposition. First off the valves are not flat on the bottom, so they wont cut flat. Secondly, it potentially leaves 0 side clearance between the valve and the relief.

Now to look at it while the piston is still partially down the bore (where p to v is usually closest). vecause of the 15* valve angle, the side clearance will increase, however now it presents a new problem. Since the valve is not flat, its tuliped, its gonna leave a bump in the relief. As the valve has moved over laterally (the piston is slightly down bore), the edge of the valve is not on top of the bump left from the tulip shape.

See if you can order a couple larger valves, like a 2.120 and a 1.675 valve, then fill in the bottoom tulips with JB weld, file flat, then use the adhesive backed sandpaper. You really need to cut bigger than your valves.

 

I was thinking that too. Maybe you could put a piece of circular metal at the base of the valve to make it the right size and to also have a true flat surface. My valves have a concave shape and are too small in diameter. You need slightly bigger than what you'll be running I believe. Anyone know size diameter ur supposed to run w/ a 2.02 and 1.57 valve?

 

Chances are that if you add a metal disk to the bottom, it wont fit under the stock head with the picton all the way up. Go with anything thats just a bit bigger than the largest valves you see yourself ever running.

 

Once you get a head that can be used (I think one head would be enough) What do you use to cut the size of the seat for the fly cutting tool?
And how precise does it the open have to be?

 

Just pry out the seats, thats usually enough. I actually took an angle grinder and sliced through all the seats so that they were easier to pry out. all the preceision is in the valve guide, not the seat area.

 

Thanks,

I'm going to be using oversized valves 2.04", how do I get that to seat flush with concave area where the seat? that's what I'm talking about. Do you open that area up?

 

If youre talking about installing larger valves on a head you will be using, a machin shop has to install larger valve seats, or at the least cut the existing ones a bit bigger.

 

How much would a shop normally charge to flycut pistons? I'd like to run the TREX cam with a set of aftermarket heads but will not be doing the install myself. I am not sure if the guy installing the parts would flycut them so I might need to take it somewhere, anyone know how much I should expect to pay?

 

So you use a cutter that's just a little bit bigger than your valves??

 

Correct. Id go atleast .050 bigger, giving you atleast .025 lateral clearance in case theres some play or flex between the valve and the guide when the engine is running.

 

So for my 2.08,1.60 valves

Which cutters should i get? 2 1/4, right?


Lol, I have no idea what I'm doing...I really hope my PV is okay.

 

Bueellller?

 

2 1/8 should be fine for the intake. For the exhaust, 1 5/8 is a little tight. Might have to move up to 1 3/4.

 

Listen to Guitsboy on this one. His idea of a homemade setup works like a charm. I think using the hardened steel cutters might be a little more precise because of the way the sanding disks wear out faster on the edges like JRracing said, but it works. And if you are doing this job with the engine in the car, be prepared for the last 2 cylinders on the passenger side to kick your ***. They kicked mine. Get yourself a high quality, smallest you can find 90* angle for the drill to fit back there.

BTW Guitsboy, I got everything together and it runs like a champ with the bigger cam. Will be doing some tuning and have it dynoed again soon. Thanks for all your advice!

 

I WANT VIDEO!!!! (if youve got the means) Glad to hear shes up and running. Now how long until youre ripping it apart again for a bigger cam again!??

 

What about cleaning up the metal shavings? Any precautions to prevent getting that down in the motor? Its my only hesitation. Shouldnt you tape the entite block deck each piston?

At what height is the piston actually cut at since the interference doesnt occur at TDC....please let me know in piston distance from the deck since degrees wont help me without a wheel or experience.

Thanks

 

It would be hard to say the exact height, as it differs for every setup. Duration makes the key difference. Best way to measure actual clearance would be to mock it up with solid lifters, test springs and a degree wheel. Then start from about 45* BTDC and measure the distance of the valve from the piston with a dial indicator (push the valve down until it contacts, noting the difference on the indicator). Going in steps of 2-3 degrees should let you home in on where it is the closest. Sounds tedious, but if you set it up, and read the numbers aloud to someone recording them, it shouldn't take long.

Continue turning the motor over in small increments until ATDC, looking for the clearance to start getting wider. Once you find the positions where the valve is closest, turn it back to that point (or those points) that were closest, using the degrees indicated. If you make more than one cut, you'll want to smooth the remaining material between the cuts so that you don't end up with a hot spot, leading to detonation.

Keep in mind that even advancing or retarding the same cam will change your clearance and where it contacts. Also, if you change cams later, less lift doesn't mean you are safe if you add duration. You'll need to check it all over again.

Hope this helps!

 

Since releifs in forged pistons are universal, there must be a universal position you can flycut. Is it that you need to make them bigger using a bigger cutter?