Main bearing clearance

[kidrabbit84]

Since I am twiddling my thumbs for the next few weeks waiting for new rods from Manley, I think I am going to start second guessing some things.

I got a set of Sealed Power Federal Mogul mains for the 98 GST block I am building for my 97 GSX. I plasti-gauged the original mains, got a healthy .0015" reading, and the journals were very clean. Hence I didn't have the machinist turn the crank.

I plasti-guaged the new mains and get a healthy .002" reading. The manual states .0008-.0016 is nominal with a limit of .004". What clearances are you guys runnin? .002" ok? I am thinking so, but I am all ears. I could probably tune this a bit with some Class 3 Mitsu bearings, but $35 each.

Adam
98 GST Engine
Balance Shaft removal
.020 Over Wiseco 9:1 Pistons
New valves, guides, 3 angle on intake, shave
PTE 50 Trim (SCM-5031E)

 

[perley03]

With the higher oil pressure you will be seeing due to the removal of the balance shafts, I would say run it. The main purpose of running clearances on main and rod bearings is the oil is providing a cushion from the reciprocating forces and stress on the crank. Without this cushion, your motor will fall apart within minutes of initial startup. Today's engines run a smaller clearance, thiner oil, and high pressure/low volume oil pumps to reduce weight, and free up horsepower. Stick with 10W-30 or even 15W-30 oil and you should have a reliable bottom end. If you second guess yourself, call either Slowboy or Magnus and ask them about the clearance. THey will probally say the same thing.