PTV clearence recomendation cam gurus

[dumpycapri85]

I am in the middle of a build and have found a strange clearence issue . The notches in my pistons have plenty of depth thru the rotation to clear the valves but I noticed the arch of the notch is very close to the arch of the valve buy looking at the clay . What is the recomended clearence for the radious of the notch ? It is the same for the intake and exhaust .

[85whtgt]

Whole lotta crickets in here...

[dumpycapri85]

Yea right .

[JETFAST]

how much clearance do you have on the intake and exhaust? If you have at least .100 on the exhaust is a good place, a little less on the intake is tolerable.

[Grape]

i think he's talking about side clearance between the edge of the valve and the edge of the pocket, which is a good question. i've never heard of any rules on such a thing

[85whtgt]

i think he's talking about side clearance between the edge of the valve and the edge of the pocket, which is a good question

Correct, clearance between the outer edge of the valve and the edge of the valve relief is what's in question.

[dumpycapri85]

i think he's talking about side clearance between the edge of the valve and the edge of the pocket, which is a good question. i've never heard of any rules on such a thing

This is exacty what I mean . There was still clay on the wall of the pocket but it was so thin it was almost tranlucent . Jet , I have well over .100 on both but was a little supprised by the edge . The heads are inline valve but they have some exstensive milling and port work . I will clay every hole to check but have never heard of an issue with this . I don't want to grind on the pistons if I don't have to with the assembly already being balanced . I thought I might be able to take some meat off the edge of the valve depending on where the seat angles start but I'm not sure if thats cool . They are Ferrera's if that matters .

[Magnimike1]

Srp recommended I didnt cut mine any closer. My valves are 2.08 and their pistons are cut with a 2.10 cutter on my particular application. ??? Maybe that helps..

[dumpycapri85]

They fit the notch Mike but like I said the valve was like a shear with the clay . I think if they all clear I will put it together and run it .

[80coupe]

They fit the notch Mike but like I said the valve was like a shear with the clay . I think if they all clear I will put it together and run it .

do it! i think it looked ok!

[dumpycapri85]

You get that rear in yet ?

[80coupe]

You get that rear in yet ?

hell no! iv got a story for ya PM your way in a couple mins!

going to do it tomorrow!

[turbos66coupe]

I would say the .100 rule still applies. The exhaust will really need it if its that close. That rule is there to take into acount many things but heat exspansion being one major one.

[JETFAST]

Radial Valve Clearance never gets talked about cause most never check.

You must take into consideration the piston has to rock over in the bore at tdc as it changes directions of travel. thermal expansion, high rpm, a little valve float, connecting rods stretch, will surely knock those valves of the seat.

Total deck height + .010, is the minimum IPTV clearance i would set it up for.

Minimum EPTV on exhaust is intake clearance x2.

You need the deck clearance around .050 with a steel rod, so .050 + .010 = .060 This is the minimum IPTV clearance I would run. Double that value for .120 EPTV clearance.

Radial Valve Clearance should be no less the total deck height plus .010 on the intake and exhaust valves. You want to check this clearance at 10* ATDC, as this is the highest pressure point of the power stroke.

The valve relief pockets should be cut on the same angle as the valves, with .060 radial clearance in the brow area of the valve relief.

[dumpycapri85]

Thanks Jet , thats the pearl of wisdom I was in search of . These heads are also milled so far that the edge of the valve actualy sits lower then the deck surface of the head . I think I may have to clearance the pockets on the brow just to be safe .