4 replies to this topic

[nballard76]

Hi All,  I am having the block on my '99 cleaned up before I put a brand new head on it.  I'm hoping this can just be a simple hone and clean up and some new piston rings, crank bearings, and rod bearings.  

 

The machinist is asking what the piston/bore clearance should be.  The 1999 Engine Shop Manual says:

 

Stk. piston clearance 0.0013 - 0.0023 in.
stk. piston clearance max. 0.006 in.

 

Is there an ideal number we should be shooting for?  Thanks!

[Steve Scheifler]

It depends slightly on your preferences. Your machinist should be able to explain the compromises involved between looser and tighter but since you are starting with a used block and sticking with stock bore, it will probably amount to putting a good hone on the “worst” one and measuring where that leaves you. It will surely be looser than factory minimum so if it isn’t too loose then shoot for that on the rest. The pro builders each have their own preferences that they swear by on clearances, hone, ring gap etc but most are likely to just say follow the book. Unless you expect to be playing at the pointy end of HST races it’s very low on the list of things to sweat, and even than it’s minimal at best but that’s part of what you are buying from them.

[nballard76]

Thanks Steve,  Very helpful.  I understand that these are the closely guarded secrets of the pro builders.  

 

On this one it sounds like we are going to end up with a .003 gap which is slightly looser than the loose end of the stock numbers but well within the max.  We'll try that for now.  

[chris haldeman]

.003 will work. That said there is a lot more to the bore than just diameter.

[nballard76]

Thanks Chris,  I understand...I'm at the top (actually over) of my budget on a new 1999 build so I put the money into the head and am going to run this motor with the stock bore for a couple of seasons before I get a rebuilt pro motor...just wanted to get the bottom half cleaned up and sealed as well as possible...There's a lot more than this keeping me from the pointy end!

 

Thanks again for the help!