Hi guys,

My engine has been stripped already and is going to send those cylinders to the machine shop tomorrow, so it is kinda urgent... please help with your experiences and knowledge!

I am wondering to find out what's the stock piston/wall clearance like? Is it .003" as normal after market suggested clearance?

The reason why I am asking is that I have a set of forged pistons and they are 0.01" over bored (95.78mm compare to stock's 95.5mm) they also "suggest" to run 0.003" piston/wall clearnace... so how much over bore should I have on my cylinders? Do I need to have AT LEAST 0.01" over bore? or 0.008" is fine too?

Thanks in advance!

cheers,

richie

 

Read the specs that come with your pistons, it will tell you if the clearance is built in to the bore spec or not. Also, your machinist will measure the piston and make sure the bore is right, so don't worry about it. Take him the block, crank, pistons, mains, and main bolts. Then pick it up when it's done.

Lastly - and hopfully this will give you confidence - If you don't think your machinist is capable of making sure this is right, then find another machinist.

Chris

 

chris.... thanks for that! I think I am just over paranoid a bit with what my engine builder said... I didn't realise that I have 0.01" overbore on my pistons and he mentioned that we are going for 0.008" overbore on the cylinders... then when I came back, I was wondering how would the pistons fit into smaller cylinders... but I will double check with my engine builder/tuner (he has built the strongest vq35dett in australia and many other z)...

Thanks for the input!

cheers,

richie

 

the bore is the first step. kinda rough. you can still remove material with honing and that is when they get it exact. i agree though, follow manufacturer specs.

 

He is going to bore them to what ever is needed. He is going to bore them based on actual sizes and desired cylinder to wall clearances. Just because the pistions are a .01 overbore, doesn't mean an exact .01 overbore is what is needed.

What he should be and probably is doing:
1.) make sure your cylinders are round; not oblong
2.) measure the cylinders
3.) measure the pistions
4.) determine the needed bore on the cylinders to achieve the desired clearance

Relax and let you builder do his work

 

Zivman:

Thank you for clearing it up for me... yes... he did say that the cylinders will need to be honed too... Thanks for your help mate! Really appreciate that!

cheers,

richie