440 Source Rods - How tight?

[EngineerDoug]

Hello all,

I have started mocking up my stroker kit from 440 Source. Got a question.

The pins slide right into the pistons very easily, but the fit in the rod is tight.

The rod includes a bushing (bronze?) - I put some light oil on the pin and bushing before sliding the pin through the rod end. I am wondering if the fit is too tight. It is tight enough that I can persuade the pin through the rod with fingers, but just barely. Once in the rod the pin does not want to rotate in the rod. Using just my hands it is of course not a press fit, but you have to finagle it through the rod.

Should the rod ends be honed out a teeny bit? Or should they be a tight fit as described?

Thanks.

 

[zyzzyx]

If you can insert the pin in the rod by hand but can't rotate it with your oily fingers, I would
say it is too tight! I would call 440 Source and check with them before doing anything myself.
We're talking one or two tenth's of a thousandth of an inch! Maybe the pins are "Heavy" stock-wise?
Call & check.

 

[beanhead]

It's finicky to get them started sometimes until they line up perfectly straight....but that said, once they're in they should slide right through. The pin fit on my 512 kit was perfect, I could hold the rod sideways and the pin would start to slide out(even with no oil besides what was on them out of the box). You'll have to have them honed a touch if they're too tight to move, you wouldn't be the first..

 

[68 HEMI GTS]

They will need pin fit by a machine shop. Have the rods and pistons opened up to 0.0008-.0010. All their kits need this, I’ve used several.

 

[tomlin]

Hello all,

I have started mocking up my stroker kit from 440 Source. Got a question.

The pins slide right into the pistons very easily, but the fit in the rod is tight.

The rod includes a bushing (bronze?) - I put some light oil on the pin and bushing before sliding the pin through the rod end. I am wondering if the fit is too tight. It is tight enough that I can persuade the pin through the rod with fingers, but just barely. Once in the rod the pin does not want to rotate in the rod. Using just my hands it is of course not a press fit, but you have to finagle it through the rod.

Should the rod ends be honed out a teeny bit? Or should they be a tight fit as described?

Thanks.

As said earlier, take the pistons, rods and pins to a machine shop and have them fitted. A couple years ago I was helping a friend of a friend start a fresh 235 Chevy. Got everything dialed in and engine running smooth. Started breaking in the cam and the RPM began to drop till she stopped. Yep, she locked up tight. Everyone, including myself was shocked. A well known builder built the engine. We proceeded to pull it out and pull the pan. Checked bearings and bore, everything looked great. Started to pull #1 rod and piston. Rod would not pivot. Finally got it out. The pin had seized. Machine shop said it was the third time in a month he had seen that happen. All different manufacturers, all had pin clearance issues. Guess it is fairly common now days.

 

[33 IMP]

There was a instruction sheet/warning that came with my source rods that said they are intentionally left tight in the pin fit because of piston manufacture variations, and they MUST be pin-fit to the pins you have. It actually said that the customer could do this with a wheel cylinder hone, but since the tolerance is measured in tenths of thousandth of an inch, I recommend someone who knows what they are doing.
68 Hemi gts mentions a tolerance of .0002 . That's about the same as trying to slice a human hair into 15 pieces.
Doug (DVW) says if you motor is too loose, you will know, if it's too tight, everyone will know.

 

[EngineerDoug]

I talked to 440 Source about this. He confirmed that the pin fit can be too snug, but indicated that the rod end should be burnished with some scotchbrite. This should be done until the pin fit in the rod is as "loose" as the pin fit in the piston. And yes, we are talking about something a good deal less than one thousandth.

A wheel cylinder hone sounds like trying to kill a fly on a glass table with a hammer...