3rdCoastPowerSports

iTrader: (5)

street motor that will be sprayed @ stop lights every now and then (of course off road stop lights only). do I need to open up the rod bearing clearances for nitrous. all rod bearings currently set @ .0019". street motor not a race motor.
I originally built the bottom end for N/A but now my buddy wants to spray so im putting in ductile iron rings. just wanted to know if spraying heats up the bearings more

Z28Z06

iTrader: (2)

Never heard of doing this, might be detrimental.

quik95lt1

iTrader: (7)

regardless personally i think .0019 is tight.........i run my street motors out at .0024-.0028 ....my race motor i have at .0030

3rdCoastPowerSports

iTrader: (5)

I try to get my street motors around .002"

.0024-.0028 sounds pretty loose to me for a street motor. .0028" is what i set up my race motors @.

ok so if i wanted to go looser can i just change half a clam shell for a .0003" over sized shell. what is the max over sized clam shell that i can just swap out half the bearing and run?

quik95lt1

iTrader: (7)

i run .001 unders on the caps in my mains and std on the block side to get me out to .0030-.0032 on my mains and theres no issue......upon last inspection with the clearances i run my rods and mains looked like they never even spun and that was after two years of 8000+rpm abuse....

3rdCoastPowerSports

iTrader: (5)

you set up your main bearing clearance's @ .0032". that is loose. If it is a 100% race motor then i can understand but even then those clearances are too loose for my likening. keep in mind this is a street motor not a race motor. the car will sole be driven on the street. my mains are set up @ .0017"-.0019" which is right where i want my main bearing clearances to be. My rods are set up @.0019" which im comfortable with seeing as it is after all a street motor.

KCS

iTrader: (20)

A 200 shot is a bit hefty, I would loosen it up maybe .0005". The worse that can happen is that your oil pressure is slightly lower, which is no big deal.

You know the saying about bearing clearance, "too loose and only you know it. Too tight, and everyone knows it!"

3rdCoastPowerSports

iTrader: (5)

so would i just buy .0005" undersized bearings and then use half of it on the rod cap?

KCS

iTrader: (20)

You would need the .001" undersize, and use half of the shells. That will loosen you up roughly .0005".

TA6spdRDC

iTrader: (2)

I say just spray it.

mark21742

I didn't know you could mix and match bearings like this....never really gave it a thought though lol...you guys taught me something new today, bit hopefully by the time I'm replacing bearings again it will be so many years down the road that I forgot about this info lol.

quik95lt1

iTrader: (7)

later ill post up a pic of my bearings ....... .0017 is very tight IMO

not necessarily true.................common misconception that more clearance lowers oil pressure....to tight will cause low oil pressure also...there is a wedge of oil that forms inisde the clearance area this is what determines the oil pressure of the motor as well as clearance....to little and the wedge cant form....too much and the same issue...

yup i do it all the time no issues.....

KCS

iTrader: (20)

With all else equal, looser bearing clearances will cause lower oil pressure. It's a consequence of giving a certain mass flow rate a large cross section to flow through. What I don't understand is how tight clearances can lower oil pressure. If its so tight that there isn't enough oil flow to form a hydrodynamic wedge, that seems to me to be a blockage which would cause an even higher oil pressure, not to mention, damaging the engine within minutes.

Tony_ONeil

Good information to know