I'm assembling the bottom end of my 350 4 bolts main and here are the result of my mains oil clearance,

#1, 0,0025
#2, 0,0035
#3, 0,0035
#4, 0,0035
#5, 0,0040

The specs for the 1996 block are around 0,001 thighter than the ones I have. I'm building for 400 hp with a regular oil pump. Would it be ok?

Stephan


[Modified by American Boy, 9:50 AM 3/3/2003]

 

you could get a set of .001 under inserts if you have a std size crank and use the top half if the inserts in the 3 journals that are .0035and use the full pair in the rear. the clearance you now have will not cause any problems but the tighter you get the mains the more oil you get to the rods. if this is a street engine i would let it where it is now but if you use it at higher RPMs like drag racing i would go for the tighter specs. JMHO :chevy


[Modified by clem zahrobsky, 11:18 AM 3/3/2003]

 

First off, are those micrometer measurements or Plastigauge? It's pretty tough to figure those .0005 numbers without real mic's.

The engine will run Ok there, but those are pretty loose for a street deal to me. The general rule of thumb is .001 per inch of journal clearance, so that's back to .0024-.0025 or so. Another .0005 for nice loose race running puts you out to .003.

I think a stock pump is going to have a hard time keeping up with those clearances with hot oil and at street speeds.

The old rule of 10 psi per 1000 rpm is very conservative, but it makes you feel good to know you have it. I've seen lots of race motors living in the 50 psi range at 8000-9000 rpm, but that is on stuff regularly torn down and inspected, not street stuff.

You got two choices, turn crank to .010 under and get proper bearings. Or use the .001 bearings discussed above. They work fine, but cost about double+ over regular bearings. The price difference almost pays for machine work. You can mix and match up to .0005, but then you have to buy TWO full sets of bearings, one stock and one double priced .001 set.

I'd double check clearances with mic's, and then decide. A little looser on rear main is normal and acceptable.


JIM

 

Thanks,

Clem Zahrobsky:
That engine will have max hp at around 5500 rpm. It's for street use with occasionnal drag racing.

Hot rod 427:
The crank is already turned 0.010 on main and rod. The mesurement are made with green plastiguage 0.002 to 0.006. A friend of mine got different result with the red plastiguage. The clearance were about 0,0005 smaller with the red. I'll get some red one and I'll recheck them.

The specs for my engine are:

#1, 0.0007-0.0021
#2,#3,#4, 0.0009-0.0024
#5, 0,001-0,003

Looks like I'll have to find a way to minimize the clearance.

Stephan


[Modified by American Boy, 11:29 PM 3/3/2003]

 

Here's what I always suggest. Put the bearings in the block, torque to specs with no crank. Load it all up and haul it to someone with mic's. They will be able to measure crank and bearing ID and determine clearances in about 5 minutes with real tools. Considering the cost of doing it again, it's worth the trouble!

Do the same with at least one rod and check them too. Better to do all 8 though of course.

JIM