minimum rod side clearance

AA Performance · Post by **AA Performance** » Fri Jul 17, 2009 7:48 am

Must agree with Baprace as its only a mathematical formula were the side clearance volume is greater than the bearing clearance volume so there is no restriction in oil flow. However, I'd sure like to be there when a Nascar goes for a test run with around .007" side clearance @ 10,000 rpm

Post by **Baprace** » Fri Jul 17, 2009 7:14 pm

mmmitch588, Nascar engines run virtualy no vicosity oil weight so it pours like water or thinner

I would not be surprised at all to see them run with .007 side clearance, not sure how small a crankpin diameter is allowed.

bobqzzi · Post by **bobqzzi** » Fri Jul 17, 2009 8:07 pm

Baprace wrote:mmmitch588, Nascar engines run virtualy no vicosity oil weight so it pours like water or thinner I would not be surprised at all to see them run with .007 side clearance, not sure how small a crankpin diameter is allowed.

Actually, I think at this point they are all piston guided

AA Performance · Post by **AA Performance** » Sun Jul 19, 2009 6:37 am

bobqzzi wrote:
Baprace wrote:mmmitch588, Nascar engines run virtualy no vicosity oil weight so it pours like water or thinner I would not be surprised at all to see them run with .007 side clearance, not sure how small a crankpin diameter is allowed.
Actually, I think at this point they are all piston guided

So side clearance would be greater than .007" I guess?

CNC BLOCKS · Post by **CNC BLOCKS** » Sun Jul 19, 2009 7:15 am

Baprace wrote:mmmitch588, Nascar engines run virtualy no vicosity oil weight so it pours like water or thinner I would not be surprised at all to see them run with .007 side clearance, not sure how small a crankpin diameter is allowed.

They are running some extremely tight bearing clearances now.

Post by **3V Performance** » Sun Jul 19, 2009 9:50 am

CNC BLOCKS wrote:
Baprace wrote:mmmitch588, Nascar engines run virtualy no vicosity oil weight so it pours like water or thinner I would not be surprised at all to see them run with .007 side clearance, not sure how small a crankpin diameter is allowed.
They are running some extremely tight bearing clearances now.

Nope

Just old std .0012 rods and .0015 mains.

panic · Post by **panic** » Sun Jul 19, 2009 11:09 am

Harley-Davidson V twins (5 piece built-up roller crank) need .020" to .030" side clearance to prevent the crank flex from pinching the rod.
Do automotive cranks wiggle this much?

rmcomprandy · Post by **rmcomprandy** » Sun Jul 19, 2009 11:35 am

SOME ... and not just the weak ones, either.
That sort of condition will require more than minimum side clearance. MINIMUM side clearance is based upon all the parts retaining their dimensional integrity.

I was told that a crank in an IHRA Pro Stock engine gets over .030" shorter when over 6500 RPM.

new engine builder · Post by **new engine builder** » Sun Jul 19, 2009 2:10 pm

rmcomprandy wrote:SOME ... and not just the weak ones, either.
That sort of condition will require more than minimum side clearance. MINIMUM side clearance is based upon all the parts retaining their dimensional integrity.

I was told that a crank in an IHRA Pro Stock engine gets over .030" shorter when over 6500 RPM.

When you machine a crankshaft
do you machine for MINIMUM or do you try and machine for NOMINAL??
Yes,I'm just messing with you.

rmcomprandy · Post by **rmcomprandy** » Sun Jul 19, 2009 8:47 pm

LOL ... that's not such an "off the wall" question in this day and age. If the journals are not absolutely round with no chatter picked-up with an Arnold guage and all journals are not consistant I will return it untill I get a good one.
Crankshaft technicians used to hate me untill I found a good guy who has the same standards I have.
Performance Crankshaft, Inc - Detroit

Len · Post by **Len** » Mon Jul 20, 2009 7:04 pm

Hey Randy you getting kickbacks for advertising?????
Len

rmcomprandy · Post by **rmcomprandy** » Mon Jul 20, 2009 11:44 pm

Hi Len,
I should

but, Adney just does some great work, especially when consistancy is a priority.