deck height ?

[rob w]

I am still confused about this deck height measurement. Is the importance of this a)to assure proper clearance between the dome of the piston & head? b)To adjust compression ratio? c) to adjust proper port timing? or d) all of the above? I am planning on following the instructions in the piston kit (wiesco) I think it was .068-.072. The owners manual says .051 (probably because they were using a Mahle). If I am smaller than the given dimension will it really only boost the compression to beyond what is safe? Thanks, Bob.

Edited by - rob w on 08/03/2002  1:54:44 PM

[rob w]

I have a small assortment of base gaskets to adjust the deck height.(this is a 400) If it still does'nt work out exactly to the right height (suggested in piston kit), how far under is it safe to go? Or should I be safe and go slightly over(higher)? What happens if the dimension is small? What happens when the dimension is larger? Maybe I'm making too much out of this, can someone please explain, so I can sleep tonight. Thanks Bob.

 

[john durrill]

Bob,
 deck height sets the clearance between your piston crown and the squish area on your head. to little and the compression goes up and the piston can (in some cases ) touch the head. too much and the compression goes down and power can drop off. I don't know what the setting is for your engine but follow the instructions in the manual and err on the high or to great a distance side. we don't have the high Oct. gas available any more at the pumps . so  a little more is usually a good thing . like .010 of an inch more .
what does the book call for and are there measurements for more than one type of piston?
 the 175 motor has at least 4 types and the deck height is set different for one type over the other three. the piston crown is a different shape on that one.
we have a copy of a 77 manual that has the 400 in it . we can look for you if you don't have one and give you the measurement in it.
John

 

[rob w]

Hi, thanks John. I was guessing that's what it's all about, usually when I do things for the first time, I like to clear up any doubts I have. I've never tried to understand as much about the motors than I have since I started into these vintage bikes. I'll go with what is recommended in the piston kit. Hey John, it's been fun hearing the updates and progress of your 175 project. Thanks, Bob.