Forum » General Engine Building Discussion » Now I've got my v2p clearances and they are shocking. Can this be right / am I this lucky?

Now I've got my v2p clearances and they are shocking. Can this be right / am I this lucky?

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First I feel I need to apologize, I feel like the drama queen of this form. It's always something. I'm trying really hard to get this stuff right and I really hope I'm not aggravating people along the way. Many many thanks for those of you that chime in to help. You are always helpful, and know I'm working hard to keep my questions shorter and more concise wherever possible.

This is a separate question but related to my last question in this topic. Worth checking the other question as it has the measurements of where my timing is at in relation to the cam manufacturer's recommendations and my measurements of the cams' peak lift which I found to be quite a bit higher than the advertised values (assuming I've measured correctly).

Moving on, I measured my v2p clearances. I used the check spring method and the results are shocking given I have been driving this car around with these cams at (0,0) for quite a while. These are stage 1 smog legal cams from Skunk2 and they are their mildest cams they sell so I am struggling to believe the results and hoping someone can suggest somewhere I may have gone wrong. These cams have been advertised as drop in cams! I have them in my b18c1 (USDM GSR) with stock pistons and stock valves. There are tons of people using Skunk2's far more aggressive cams on much higher compression pistons than me and with bigger valves than me so I just have a hard time believing my measurements could possibly be correct but I've done it over and over and it's consistent.

Here they are (I'll list the exhaust cam only as that's the trouble maker):

I found the minimum clearance seemed to always be between 6 and 7 degrees BTDC.

Cam Gear Setting / Min v2p Clearance

-4 / .026

-2 / .036

0 / .043 ---> I have been running the car for nearly 2 months and 1k miles at this setting.

+2 / .052

+6 / .071

If the minimum safe exhaust clearance is .100 then I have been operating quite far from that for quite a while! And extrapolating from my results I'd have to advance the exhaust cam somewhere around +13 in order to get to that safe .100 clearance. Mind you if you've read my last post as it sits with my exhaust cam at 0 on the cam gear I would have to retard the cam 6 more degrees in order to match the manufacturer recommended settings. This would put my exhaust clearance somewhere around .020 if I've been doing this correctly.

Is it possible that I've done this correctly given these are Skunk2's mildest cams even approved for use on California streets! Maybe the grind on them is really off as I measured in my other post which has the exhaust peak lift almost .01" more than advertised.

Is it possible I've really been driving around with .043 exhaust clearance and not wrecked the engine? I've driven it quite hard and it drives quite well.

What are some reasons why my measurements could be skewed? Is it possible I bent an exhaust valve putting in the check-springs and maybe a bent valve causing it to not seat correctly and affect these clearances? The process of whacking the retainer with a socket was a bit unsettling for me, some of them took more of a whacking than I felt comfortable about, lighter whackings just would not release the retainers. I did do a leakdown test after I was done with that process of installing the check springs and there was no leak to the intake or exhaust. A bent valve is the only idea I have as a possible excuse for these measured clearances.

My head and block have been milled but the machine shop said it was only to clean them up and it was minor (though the exact amount at this point is a bit of a mystery). Given that with the degree wheel I can see that I'm retarded 2 degrees when the cam gears are in the TDC position this indicates the milling can't have been that much.

These measurements were taken at 0.000 lash. Normal lash for exhaust is 0.08

All good. Nothing to see here. Move on. You've got plenty of clearance. Add 0.08 to any of those numbers and it's greater than 0.100.

I have run race engines with 0.040" clearance, you have that even with zero lash.

Best reply ever!

The Skunk2 cams I have had some doubtful clearances as well. For Instance the Skunk2 Tuner 2 cams installed in a stock B18C GSR set 0,0 will provide insufficient valve to valve clearance. To get it to atleast .035" I had to install the cams at +6 exhaust and 0 intake. Very odd to me how this goes un-noticed by them.