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  1. #1
    rc423423r's Avatar
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    Valve clearance deebs build.

    Sorry if this has been covered before, but I will be assembling an engine this weekend, and wanted to know if it would be necessary to clay the pistons or if I'm in the safe zone for valve clearance. More information can be found in my build thread.

    I have 3rd gen rods, .110" shaved engine pistons. (The top ringland was .220" before shaving). And a .005" head shave. I calculated it out that I will have about .020" piston protrusion. Running - American Custom Cams Stage 1: (IN .370 x 270/EX .340 x 260)

    For the more experienced engine builders out there do you think valve clearance will be an issue? Should I clay the pistons or is it a waste of time?

    Sent from my XT1096 using Tapatalk

  2. #2
    siris's Avatar
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    If you have the time and means, I would. Especially if you have changed the cam timing. It won't hurt anything.
    72 Charger: pissed me off, on jackstands.
    95 SW1m: Dohc swap. DD. I can haz boost?

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  4. #3
    Approved Vendor ZombieSatty's Avatar
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    Interested in responses and or results.
    It's not my fault, blame the radiation.

  5. #4
    rc423423r's Avatar
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    Would I be able to reuse the head gasket if I clayed it?

    Sent from my XT1096 using Tapatalk

  6. #5

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    no. But you could ask one of us hoarders to send you a used one.

  7. #6
    rc423423r's Avatar
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    Hmm okay we probably have a used one lying around.

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  8. #7
    siris's Avatar
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    Clay it without the HG. Cut the clay and measure the thin spots. If it clears without the HG you are more than good.
    72 Charger: pissed me off, on jackstands.
    95 SW1m: Dohc swap. DD. I can haz boost?

  9. #8
    rc423423r's Avatar
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    Ok that sounds like a plan...I'm thinking it should be okay, because I've heard of guys cutting like .040" off the head with much more aggressive cams. Also stock protrusion is like .0118 with a .0149 service limit. According to this I guess I'm worried because I didn't get valve reliefs cut into these pistons because I wanted to keep compression high.

    It's looking like I'll have to clay the pistons after all unless anyone else chimes in with Indisputable evidence lol

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  10. #9
    6S Moderator S.Bretz's Avatar
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    I wouldnt even bother...you will be okay as long as the cams are time properly.

    To be honest i dont know why they put valve releifs in. The valves are nowhere near close if the cams are timed properly.
    -6S Resident Mechanical Forensics member #001.
    1995 SC2 Turbo 3.6L DOHC, 6sp manual, Ford 8.8 rearend running on MS3x.
    1998 F-250 5.4L triton...stock.

  11. #10
    rc423423r's Avatar
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    Okay thanks man, I'm pretty sure I've heard of much more extreme builds on here without issue. I'll keep you guys posted in my build thread. In case things go boom

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  12. #11
    saturnspeed_12's Avatar
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    What year vehicle are the pistons intended for you bought? Reason I ask is because your pistons are completely smooth, whereas mine have a very slight indentation still in the middle. I took off the minimal amount I could. I have 01 rods and 92 pistons with flat faced valves. I slapped mine together and have put at least 40k on it. I also am running twin intake cams. I wish I could remember my protrusion, but I thought it was something ridiculous like .040-.045". I also had my head resurfaced recently as it was warped .004".

    The only issue I have been having is timing, not mechanical. I am pretty sure the pcm keeps pulling time, whether just noise to the knock or if I'm actually getting ping/detonation. But I am also a bit on edge for fuel knowing I'm still stock running 93. Even tuned, I still think I need slightly higher octane.

    16487630_1443406159005893_525437075963078708_o.jpg


    That is mine just a week ago. I had low compression in two cylinders from my head being warped, so I had to tear it apart.
    Last edited by saturnspeed_12; 02-09-2017 at 03:41 PM.
    Ian---The Fat Ass

    1995 SL2-High compression engine w/boost and MS2 (in progress)
    2006 Nissan Xterra- long hauler
    2010 Chevy Cobalt SS- tuned with plenty of goodness

  13. #12
    rc423423r's Avatar
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    They are 2nd gen pistons. When you say indentation are you talking about the valve reliefs? Because mine are still there but barely visible. What compression ratio are you running with that much protrusion? Because I calculated I should be around 11:1

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    Last edited by rc423423r; 02-09-2017 at 04:43 PM.

  14. #13
    rc423423r's Avatar
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    http://sixthsphere.com/archive/index.php/t-59197.html

    This is the link I was basing my calculations off of

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  15. #14
    saturnspeed_12's Avatar
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    Okay, that is what I was thinking. Mine are the earlier ones, which had larger upper ring land. But if you see my pistons have an indentation in the center of it. That was due to the flat faced valves used in early heads. When the concaved valves were used, that indentation was removed. It was for compression ratio.

    There was another article on this same thing that I used when building my engine. I took the information and didn't calculate mine. I just can only make a guess, and with the numbers I was using from the article I used (before building), it looked to be like 12:1 or more. The one thing I know, but still wish I actually wrote down, was the protrusion since I just measured it last week. I had to use two feelers to find the gap, so I know it is at least .035". I just made the mistake of taking the information, using minimal clearance, and went wild with the build. Had it all balanced to 8k, and was amped to get it together. So my true compression ratio isn't fully known. My cylinder pressures are 250psi on a very cold engine, that I truly know. lol
    Ian---The Fat Ass

    1995 SL2-High compression engine w/boost and MS2 (in progress)
    2006 Nissan Xterra- long hauler
    2010 Chevy Cobalt SS- tuned with plenty of goodness

  16. #15

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    You need some long tube headers. I was looking to do an high comp build and I looked to Mazda for inspiration and tech ideas as to how they mitigate detonation on their new skyactive motors. These motors run 14:1 and higher comps on some models. On the fuel side they are using 2 injectors per cyl. one on the intake runner to cool the charge and then another spritz via direct inj. to cool the charge on compression. On the exhaust side they play with valve timing and speeds with the cams, which unless your running an older head with custom ground cam and adjustable gear, we're limited. The exhaust manifolds are another area they prevent ping by running long tube headers that have more room per runner than exhaust gas expelled. This and the fact they prevent a pulse pushing ex gas back into another cylinder keeps chamber temps down. That also helps keep away from the ping. We've also discovered through rigorous googling and math that Mazda bp pistons on 1st gen rods will work in our motors for high comp builds. you just have to replace the bushing in the small end of the rods to accept the pin from those pistons, which any engine shop should do for about 40 bucks. They are a stronger piston and better designed than ours, especially since you've had to get rid of so much of the top land with the machining. I think that bill gude offers it a package for 400. but you can get away with doing it in house for much less. His math also puts the comp at I think 13.5:1 but he machines some off the top to bring it to 12:1. Also they have valve relief in them so then you just have to worry about slap, also why he takes some off the top and land I think.

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