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#1
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Does anyone know what the absulute min.piston the head clearance i can run on a 360?This engine has forged wiseco flat tops with steel rods and x heads?? I keep hearing different stories what do you think?
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#2
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As a general rule, with steel rods, .040". I am in the process of building a 440, and that is the number I am using. I'm no smallblock expert, but are the X head chambers open style? If so, you have nothing to worry about.
------------------ www.mindspring.com/~dusterdave |
#3
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Dont know myself but I am putting 340xheads on a new chrysler performance 360 shortblock with 10.1 pistons. The pistons are flattops with deep valve recesses and my cam has a 5.09 lift at valve. I contacted Chryslers tech advisors where I purchased the shortblock and they told me I needed a min. of 32 thous. piston to head clearance and not to use a thin head gasket. They advised me to use gasket P-4529454. Now I havent gotten all my valve train done so I havent turned my engine yet to see if they were right. Dont know if this helps, Gene
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#4
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We have always used .035" clearance with the stock type rods and had good success. Use a sandwich type gasket which is .036-.040" thick.
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#5
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I just saw a really kinda cool way to check this clearance..stack a feeler gauge to the tolerance number then place it inbetween the valve tip and the rocker arm then rotate the engine slowly, if it hits..then you know what you have to do..read this method in a hotrod mag. Havent had a chance to do it myself, but it looked good on paper..
Maxwedge |
#6
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MaxWedge that works real good with Piston to Valve clearance but need a different measurement for Piston To Head.
Christian ------------------ 68 'Cuda 383 Formula S recreation Working on adding EFI 69 'Cuda Race Parts Car 76 Duster 273 recent transplant 95 Neon 2.0 SOHC best of 16.96 84 Dodge Ram D50 transplanting 360 |
#7
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Misuderstood..my bad
maxwedge |
#8
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.035 thirtyfive thousandths is the magic number but you better be right on with your figures
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#9
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Just picked my 440 short block up from engine
builder last night,.040 over eagle h-beam rods,10.0 to 1 comp. srp forged pistons ,we measured piston to deck height it was .010" they said not to use thin steel head gaskets use the thicker felpro. |
#10
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Im pushing the envelope at .032 with a 4 spd with no contact at 6800 rpms(steel rods) .035 has always been the rule of thumb...PRO..
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#11
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FYI,
For my 440, the Arias Pistons reccommend 0.040 for steel rods and 0.055 for aluminum rods. 360 should be similar, maybe 0.005 less. One technique if you plan to use compositon head gaskets (0.039-0.042) is too put a head on without the gasket, and slowly rotate the engine. If the head bolts are loose, you need to check for the slightest (dial indiacator?) movement of the head. If tight bolts, be very careful, aluminum dings easily. Confucious says, "Assembly should take 4 times longer than disassembly" ------------------ 440 Jim E-Body Fish [This message has been edited by 440 Jim (edited July 12, 2000).] |
#12
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I assume that your compression ratio is about 10.5:1. This can make a difference. The clearance is most critical when an engine is wound up without a load on it. Like at the end of the quarter or end of the straight away. Typically, the cylinder pressure drops and allows the rod/piston to extend slightly, not to mention the associated thermal loading(expansion) after a full throttle thrash.
Higher compression engines retain more cylinder pressure than low compression engines in this scenario and may offer a little bit of margin. Also the stroke has an effect on the piston speed(momentum) prior to stopping at tdc. My recommendation is to go with .040" and stay a little on the safe side. |
#13
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In line with 340-Kings thoughts about piston speed and momentum is the weight of the piston. i.e. more weight, more rod stretch, hence the need for more piston to head clearance. An alloy rod has more elasticity than a steel rod, that's why they usually recommend more clearance, although GRP says their aluminum rods can go .040 p to h on a low deck 482 I'm building. They are great looking rods and I've heard nothing but good things about GRP but I'm still skittish about running them that tight. Anyway, back to the original question, on a small block short stroke motor .035 is probably safe,especially if Sanborn recommended it. He's forgotten more about small-blocks than I'll ever know and their Mopar dirt car flies. Just remember the longer the stroke the more piston speed per rpm, static piston weight and reciprocating piston weight being two different animals. In other words, the reciprocating piston weight of a 4 inch stroke engine is more than that of a 3.5 stroke with the same static piston weight so the rod is going to stretch more, thus the need for more clearance. Hope I'm making sense. They say your memory is the second thing to go.........I forget what the first is.
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#14
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I am building a 440 with KB quench doam pistons and the magic number is .040 like the other guy's said.
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#15
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Quote:
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