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As engines Near the end of lifespan do you...

As engines Near the end of lifespan do you...

Old 04-08-2012, 10:30 PM
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Default As engines Near the end of lifespan do you...

After you get a certain amount of gallons on an engine and it nears the end, do you go in and pull a shim off to increase compression? Just curious if this is a common procedure?
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Old 04-09-2012, 12:00 AM
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Good question. I usually reduce shimming a little on most of my novas from the start. Usually .70 for p5's and .60 for 7 ports. I rarely take more out. If the compression is going from around the piston then reducing the deck height rarely helps unless it was overshimmed in the first place. I've heard to remove shims after break in but honestly I've tried after and before and it makes the engine easier to know when it's broken in if you do it from the start. Other wise you keep running it because it acts like it's never breakin in with too many shims.

I think it's best to change shimming early on to find the sweet spot then leave it alone and get it resized a bit earlier if the compression goes a little earlier than normal. some engines just plain loose their compression quickly and some keep it right on, and some just seem to last forever.

I say experiment with it. No drastic changes but just .10 shim at a time to see what happens. I think Novas are overshimmed anyway, but going too far makes any engine run irratically. You can always change it back....

Look at what the engine comes with and is recommended and if there is only two thin shims it may be close to perfect from the start, and if there is a stack of shims I say experiment a little.

I hope this helps...
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Old 04-09-2012, 02:08 PM
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Originally Posted by mcion View Post
After you get a certain amount of gallons on an engine and it nears the end, do you go in and pull a shim off to increase compression? Just curious if this is a common procedure?


No, not a normal procedure.I Have heard of people removing shims when the engine gets older and a bit weak. It will raise compression, but it will not correct a worn out piston/sleeve fit.
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