So finally fixed my noisy 445!

[mbrunson427]

Pin offset is your friend on the street    It doesn't cost much HP and it gives you more arrows in your quiver to set up a happy engine.

Explain this for me. Offset the pin in which direction to cause what result?

[C6AE]

I always selected for an offset pin if I had the option. All my cars were/are street cars, with mufflers...

more here, with an interesting graphic;
http://www.kfz-tech.de/Engl/Biblio/Kurbeltrieb/Desachsierung.htm

[Dumpling]

Reply #4 to this thread, 20 days ago...

[wowens]

Pin offset is your friend on the street    It doesn't cost much HP and it gives you more arrows in your quiver to set up a happy engine.

Explain this for me. Offset the pin in which direction to cause what result?

Not being a engineer I hope you can make me understand also.

[Heo]

Oil controll and stops the piston from rocking in
the cylinder. Gives less fricktion with centered
pin they say. Ford flatheads have the whole crank
off center. An oldtimer trick was to put the piston
backwards suposed to give less friktion but more
rattle more oil consumption

[Katz427]

Yes Ford flathead engine used the Desaxe principle. The practice of offsetting the whole crankshaft centerline. Originally developed in steam engines.  I believe I read that VW uses the Desaxe principle in their V type engines.

[TorinoBP88]

What you can not see in a piston picture is inside a stock piston casting is often a bar of steel to help reduce piston expansion when hot.

Offset pins are usually standard option especially on overbore sizes, and I prefer them if I have a choice.

[WConley]

http://blog.jepistons.com/piston-orientation-rights-lefts-tops-and-bottoms

To stabilize and quiet the pistons on street engines, the manufacturers typically offset the wrist pin towards the major thrust side by about 1 mm - 1.5 mm.  The pin offset shifts the piston over to the thrust side earlier as it reaches TDC, usually with much less "rocking" motion.  The rocking of the piston creates most of the slap noise you hear when cold.

There is a small increase in friction, which will cost a race engine a few HP at high rpm.  The good thing pin offset gives us on the street is more even cylinder wear and better oil control.  For me it's a no-brainer if I'm not chasing a hundredth in the quarter mile.

[wowens]

http://blog.jepistons.com/piston-orientation-rights-lefts-tops-and-bottoms

To stabilize and quiet the pistons on street engines, the manufacturers typically offset the wrist pin towards the major thrust side by about 1 mm - 1.5 mm.  The pin offset shifts the piston over to the thrust side earlier as it reaches TDC, usually with much less "rocking" motion.  The rocking of the piston creates most of the slap noise you hear when cold.

There is a small increase in friction, which will cost a race engine a few HP at high rpm.  The good thing pin offset gives us on the street is more even cylinder wear and better oil control.  For me it's a no-brainer if I'm not chasing a hundredth in the quarter mile.

Best explanation yet. I have all ways known of pin offset and need to install pistons in correct orientation but never really understood the engineering need for offset. I think I get it. This old dog learned a new trick!

[My427stang]

I am toying with the offset idea if it is an option, I haven't used Racetec, but Brent mentioned they have a lot of options, when I am ready to put this one back together I may consider it if affordable.

[My427stang]

Well, two lessons learned here. 
1 - When you don't verify something, you can get bit
2 - When you go cheap, you increase the chances of it going wrong

Brent recommended seeing where I was with the heads bolted up, measuring from the bottom, I trust him like a brother and didn't have a smoking gun, so I did it, but really didn't expect it to pan out, I was wrong!  Sent Barry the pics too, he saw the odd marks and the numbers below and agrees that it would be noisy.  I appreciate both of their advice.

Despite me wanting to hate the pistons, looks like it likely is the block, and likely my "reblock" would have worked if I did my normal block prep (sonic check, square deck, torque plate hone).  I guess the good thing is that the Probe pistons have been checked 8 ways to Sunday and a cause was found, so they are good pistons, just won't work in my block.

When I replaced the block knowing it was .0075 clearance, I used a block that was already finished for a buddy's 390, it measured at .0045 clearance (no torque plate) and looked nicely done.  In the end, I have one of two issues, or both, need to figure it out.   But, knowing the shop by buddy uses doesn't have an FE torque plate. it's either just crooked when things are bolted up, or the cylinders are thin and moving around.

1 - Mocked up cylinder to see how far the piston skirt  hung out.  Did not hang out very much, .250 max and checking point on skirt never exited bore

2 - Pulled crank, installed heads, torqued caps and heads with head gasket

3 - Checked 6 points on each cylinder from bottom, 3 pin direction and 3 thrust direction, checked bore gauge vs piston after each bore

Summary
- Pin direction - 7  cylinders the same behavior at .0045 to .0055, growing toward bottom of bore, most measurements between .0045 and .005 (one oddball at .005-.006)

- Thrust direction - All 8 cylinders were bigger than pin direction, but  2 cylinders grew bigger as approaching bottom of stroke, 6 cylinders got smaller at the bottom

When I look at cylinder #7 in multiple pics, it is certainly the weirdest, but it's hard for me to show you, but it does correlate with the numbers.  Numbers in bold are outside of Probe's limits, and all of #7 is bold because it is likely the noisiest, but the inconsistency is the odd thing.  I put away my tools and went to lick my wounds, but I do intend to pull the heads and crank and do this again, just to see how far off the numbers are without the heads.  When I originally asked the question, I took a lot of measurements, but not as many as I did here, and not in as regimented locations.  My hunch is that numbers will get closer, but when I map it out there will still be something to see

In the end, if the cylinders are thick enough, my intention is to torque plate hone at a minimum oversize and put a set of 4032s to fit maybe shifting compression height up to 1.335 for a zero deck, but that is likely overkill

Cylinder Clearances
Top/Middle/Bottom - Thrust direction----------Top/Middle/Bottom - Pin direction

#1
.0065/.0070/.0070----------.0045/.0045/.0045

#2
.0070/.0065/.0060----------.0050/.0050/.0050

#3
.0075/.0070/.0065----------.0045/.0050/.0050

#4
.0070/.0070/.0065----------.0045/.0045/.0045

#5
.0060/.0065/.0065----------.0045/.0050/.0055

#6
.0075/.0070/.0065----------.0045/.0050/.0055

#7
.0080/.0080/.0065----------.0050/.0060/.0060

#8
.0055/.0070/.0070----------.0045/.0050/.0050

One thing I need to point out is, before yesterday, without the heads on, I had absolutely no numbers in the .007 or greater range.  I have not been a torque plate nazi, although I like to when I can, if this block checks good for thickness, you won't see me prep one without a plate again.

[plovett]

If you end up needing a new block are you considering using your Probe pistons and fitting the block to them?  Just wondering.  I'm glad you definitively found the issue.

paulie

[machoneman]

Good find Ross. I'm a tad amazed at the large variances from bore-to-bore but that's the cause of all the noise I'm sure. Interesting too if this was a pure race engine w/o any exhaust system you'd have never heard the noise!

[jayb]

Great detective work Ross, sounds like you found the problem.  Have you thought about just getting a new block and getting it machined to fit the pistons you have?

[mbrunson427]

I have a standard bore 390 block If you need it, never been re-worked, still has the factory head gasket pattern in the top of the deck. I was going to post it on Craigslist this week.

If that sounds interesting, you have my email.