tbirdscwd

Because I have checked with a compressed lash adjuster and the tightest I am seeing is .045" @ 108. I am not going to call that the clearance until I get in there with an adjustable one so I can set it to zero lash and see exactly where we are.

tbirdscwd

Official ptv clearance is .025" installed at 107.75 degrees ICL. That was measured at 5 degrees atdc.....everywhere else I had more clearance. I'm not going to even try to get a quarter of a degree to get them in at 108 LOL. If it was a quarter of a degree retarded, I'd probly go over it again and shoot for 108 exactly.

mrtstang

Wow that really amazes me! I mean i only got .030"-.035" with mine at a 110 ICL. Hey if you can get away with more advance like that, i'd keep it that way too.

tbirdscwd

I honestly thought it would be closer than it was. .010" was going to be my "no-go" and would have retarded them accordingly. I had them in at a few different centerlines to see how they did. The clearance was only a couple thousandths more at 109ICL........and really it just changed where (meaning position of the crank) the closest spot was. IIRC, having them at around 110 ICL made the clearance smallest around 15* ATDC and advancing them just made the the clearance smallest closer to TDC. At 110 ICL I was getting in the upper 40 thousandths.........

mrtstang

It's weird because we both have the same intake duration as well. With that in mind you would think the measurements would be very similar at the same ICL. Yet you were getting well over .040" to my .030"-.035" at a 110 ICL.

According to Nick you'll loose like .020"-.030" by advancing the ICL 2 degrees. Like going from a 110 to a 108 for example.

Regardless, it seems to work for your application. I'm anxious to see how it all turns out.

tbirdscwd

I think bottom line is that every motor is going to be a little different when it comes down to thousandths of an inch. I'm willing to bet that both of our readings are within the average range for these motors.

Anther thing to remember is that when it comes down to thousandths of an inch, everything comes into play including piston manufacturer, head gasket thickness, exact tolerances on machine work and block, etc......all of which can vary slightly. Even some of the components were completely different throughout the years.

mrtstang

That's a good point and makes sense. It explains why some people may hit the valves while others don't.

tbirdscwd

One thing that I noticed that few might even think about is that you need to compress the oil out of the lash adjusters when installing cams on these motors. My valves definitely were making contact when I installed a stock lifter that had expanded. They are hydraulic and will settle down after starting up and running, but not before making contact with the valves on initial startup. When you release the pressure on the lash adjusters to remove the cams, they expand which sucks in whatever oil is still in the passages. Once they do this, they are essentially full length solid lifters for the initial startup, which will definitely cause ptv with an even semi aggressive cam profile. I had ptv all the way back to 115* ICL with an un-bled stock lash adjuster. This is because the valve was hanging open father than it was supposed to due to the lash adjusters being all the way extended. Even when on the base circle, the valve was hanging open like 1/10" which is way more than the clearance these cams are supposed to have.

I think this is why people note hearing a chattering or valve noise on initial start up and then it goes away. Unfortunately, by the time the adjusters settle back down to provide a true zero lash, the damage to the valves and the marks on the pistons are already present regardless of whether or not the cams actually did clear with the right amount of valve lash.