I'm on the process of rebuilding my engine and I'd like to be sure of the clearances I should shoot for before start the machining.

I'll use JE Buschur spec 86mm pistons, Oliver rods, stock crank and ACL racing bearings. Considering 0W50 synthetic oil, I have these clearances in mind:

Piston to Wall: 0,004
Ring Gap Clearance: 0,013
Rod to Pin Clearance: 0,013
Rod Bearing Clearance: 0,004
Main Bearing Clearance: 0,001
Thrust Crank Clearance: ?

Sorry if it's been covered before. I couldn't find a topic covering all the clearances at once.

 

i'm not to sure what the rod bearing clearances on our engines are, but on my Honda that I built last year I had it at .0012...... I think, I really wish I could find the build sheet I had to do for class dammit

 

Rule of thumb is .001 for every inch of rod and crank journals but varies builder to builder ptw see what the piston manufacturere says

 

do you mean add .001" to stock specs? would you recomend this for a street build?

 

Rod bearing clearance looks too wide. Will loose allot of oil pressure. .002 to 0025 should be fine

 

first question how much boost? 25+35+ all depends
second what rpm
third what will the motor be used for? drag,RR

 

PWC should be set buy the piston manufacturer. thrust is between 3-5 thousandths. Mains and rods should be around 2 thousandths. This is a rough are to start from, adjust accordingly for your setup and use

 

The car is meant for road racing, with occasional street use.

Turbo wise, I´m deciding between a BBK or a TS GT3076, with 25~30psi. Even with 272 cams and GSC springs, shouldn´t rev beyond 8000RPM.

 

Not to nitpick, but factory build specs allow for up to .0098 on crank thrust. I can't remember what the low limit is. I am speaking original build, not the "what we'll warranty" limit.

 

Agreed that the rod bearing clearance being too loose. I also think the ring gap is too tight. Closer to 0.021"

 

.021 is LOOSE for anything but an all out nitrous application according to the JE ring chart. I'm shooting for around 450 HP with mine, setting me into the middle turbo/ nitrous category. that recommends .005 * bore (inches) for the top ring and .0055 * bore for the second ring.

 

ok, so the clearance sheets that come with the pistons are pretty general, what criteria effect what these clearances should be ,and how do you determine what your final #s are going to be for your application?