PTV clearance

[ksmrz]

I am swapping on some ported heads. Also some new Johnson lifters since they are off. I shimmed up 2 old lifters, used checker springs and a dial indicator. The new heads were milled .006 to give 68cc chambers. Using an old head gasket I got .056" for the intake and .070" for the exhaust. This is with the night fury cam version 2 on a comp core. Shawn at lethal said it would have .080" on the intake and I was unable to measure accurately when initially installing it because the plunger was collapsing with the checker springs. I'm leary on assembling it and running it. I took his word before that it would be safe and maybe .061 and .076 would be acceptable to some on the stock heads that were unmilled. Seems tight and I'm wondering where to start do I attempt to track down the tools to flycut or go with a smaller cam.? Specs are 233/242 113+1 and .618 .615. any thoughts? Thank you

[ksmrz]

Cam was installed straight up and degreed to be sure. Both intake center line method and actually checking valve events. It was with .5 degree and that's a tough call because it was a 9" degree wheel and the pointer wasn't that sharp or fine.

[CFD]

There can be a lot of variables that have an effect on readings so I always clay the pistons. In the event that fly cutting is necessary the tools are not that expensive and readily available.

[ksmrz]

I spent alot of time to ensure I had zero lash and it was done properly zeroing out the indicator and checking in 2° increments. I trust my numbers but I'm not sure what's a better way to go?

[CFD]

I have trust in my numbers but I always clay. lol. Takes a few minutes and you get a visual so there are no doubts.

[ksmrz]

I think I will give Kip a call at Cam motion and see. Also waiting to hear back from advanced inductions. Seems there are several people that have ran these heads with alot smaller camshaft and still cracked 500 on a dynojet. Pcm of NC does it all the time iirc

[camaro34]

The intake is a little tight but is still ok to run. The exhaust on the other hand is definitely too tight. In a perfect world .080 intake and .100 exhaust is what you want. I have run the intake as tight as .040 on a big block with no issues. The best way to fix this is installing Pistons with deeper valve reliefs, I understand this is not what you want to do. The next best would be to cut the valve faces .020 or so. I hope this helps, good luck

[Bo White]

.006-.007" is 1cc

[CFD]

Originally Posted by Bo White

.006-.007" is 1cc

I'm milled .040 and I'm exactly 64.5cc's with stock gaskets.

[Bo White]

That's pretty close. It's rule of thumb anyway. Some aren't 70cc stock so cc before and after. Also have to mic the cylinder head before and after to see exactly what was taken off. Most don't measure anything.

[CFD]

I measure everything and am quite sure of my numbers. lol. There are other variables some don't consider. I'm running LS3 intakes and Manley exhausts. The head design of the exhaust is different than stock and will be a factor in volume.

[ksmrz]

Originally Posted by Bo White

.006-.007" is 1cc

Advanced inductions says they run 69-70. I told them 68cc and he said that's what it took. I didn't verify with measuring though. Being the cam I knew I couldn't mill much. I knew it'd be close but not this close. I've read that I could gain .015-030 do to deflection. But I dunno if I trust that.

[ksmrz]

Maybe the ramp rates are less aggressive on the new night fury cam but not sure if that's help because they also have 3° of advance ground in. So my guess is it'd be a wash

[Bo White]

I don't question the size of chamber you have CFD. I just post for people to question more than most do currently. Not to just take information at face value. Measure before and after or have the shop do it, will prove them to be a worthy shop. I see too many just copy what others have done and not get the same result and wonder why.