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#1
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When setting valves with aluminum heads on a cold engine,is it true you should set them tighter?I've heard as much as .006 tighter than you are planning on running,because the aluminum when it gets hot will loosen the adjusment,any truth to that?I have'nt had much experience with alum. heads I'm sure there is someone who knows for sure.THANKS,REX JR
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#2
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I have never heard that you should set valve lash tighter with alum heads. When alum gets hot just like steel it will expand. It does so at a different rate. You should follow the cam mfg specs. If you want more low end set with more lash, less lash for more top end. We are talking hundreths of a second. Stock/Super Stock racer do this. I have raced and have crewed with racers with alum heads, they never had me adjust lash different because of the head materal. Maybe someone is trying to sell you a bridge.
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#3
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Rex..The B-1s I had on my car loosened up .012 when they got hot. For .024 hot I set them at .012 cold. Set them about .006-.008 tight, fire it and see where they go.
Monte |
#4
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This is what Crane Cams says to do w/ a cold engine:
With iron block and iron heads, add .002 lash With iron block and aluminum heads, subtract .006 lash With both aluminum block and heads, subtract .012 l |
#5
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I stand corrected on valve adjustment. I called someone I know in Indiana who builds somes engines, Steve Schmidt. I posed the question to him. He said that some alum heads do not expand any more than steel, it depends on the material used in the casting, and some expand a ton. He said it is best to adj valves hot. If you prefer to do them cold, first adjust hot, then let the engine cool, then check lash. That will give you a value on how much they change from hot to cold, then you will have that for reference. He also said that they try defferent lash settings on the dyno and often end up setting lash different than the cam mfg spec.
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#6
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GTXMONTE thanks for the info. What rocker arms are you running.
I have the 451 "B" block stroker with B-1 B/S Heads and the 1.6:1 aluminum roller rockers. I set the lash just a bit tighter than spec, but when the engine gets warm I can hear the valve train tick pretty good so I probbly need to set them tighter. This would be a bonus for me also, since the loose lash is making my small cam (only 251 duration @ 0.050", 0.620" lift) seem even smaller and I could use more top end power. |
#7
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451...I had the B1-MC heads and ran a 1.8 Jesel set-up. The cam had over .900 lift so valve setting was a very regular thing. We set valves and inspected springs every couple passes and checked spring pressure every race.
Monte Smith |
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