Engine over bore Question.

C

cumminsX

Can't make up my mind
Joined
Apr 7, 2008
Messages
447
I am building a motor right now and my goal is 800hp. The pistons will be .020 oversized and I was wondering how many thousandths to allow in the bore for expansion? Also is it best to go all the same on the bore or to allow a little more for #6 ect.. Does anyone have any advice?
 
If you find some .5mm over pistons for a 600 series let me know! I need two.

We always go 1-2 thou over what factory spec is on the bore and that seems to be ok.
 
I can get ahold of some if you need them, my cousin works for cummins and they have them on order to replace the ones that I just bought so they should be in stock soon.
 
youll have to check piston to wall clearance and hone it in to spec. Im not positivewhat the ideal clearance is though. probably somewhere around .003 or so I would think.
 
I see, I guess I'll get the pistons over to him so he can check the clearance.
 
for a hot street motor .006 to .007 piston to bore, with .028 to .030 ring gap.
if you your going to go to a all out engine Like i did with the Nitro Flash truck the .008 to .009 and .035 ring gap.

The fix for # 6 is best addressed by fixing the airflow restriction of the stock intake manifold.
The later CR has directed more water to the back of the block and this is a good patch , but not a fix to the problem .
 
I am looking into milling the intake off and doing an aftermarket intake, right now I am leaning towads the banks big hoss intake because of budget reasons and it looks like a nice unit.
 
I would also say no tighter than .008", Mahle called for .005" on my slugs but I went .008" also. And i agree 100% on the heat from #6 is a direct issue from the non balanced flow back there. I would think the banks twin ram would help conciderable on a Hot street truck...
Ryan
 
Hmm I guess this is why my#6 is off compared to the rest , will b dbl checking my clearances this week ... Greg why the bigger ring gap ??
 
COMP461 said:
for a hot street motor .006 to .007 piston to bore, with .028 to .030 ring gap.
if you your going to go to a all out engine Like i did with the Nitro Flash truck the .008 to .009 and .035 ring gap.

The fix for # 6 is best addressed by fixing the airflow restriction of the stock intake manifold.
The later CR has directed more water to the back of the block and this is a good patch , but not a fix to the problem .
Click to expand...

What about on Total Seal rings with a coated piston and head/valves?
 
Is it any different with coated pistons or am I still good with .006 to .007 clearance?
 
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