Now I know where the circlip came from

[Jwilli]

Back side of # 1 cylinder. The circlip looks normal. The piece that looks like a washer is part of the piston. The small piece is still unknown. The cylinder wall has 2 grooves starting 2 inches below the top of the block.

[scrapiron]

The dreaded errant wrist pin.

[Tom Wesenberg]

I wonder if a bent rod caused this?

[Jwilli]

Originally Posted by Tom Wesenberg

I wonder if a bent rod caused this?

Tom, I don't know, but I will check that out tomorrow.

[Mark in MT]

We had a close call on a rod of our 29 Tudor, 1/2 the Babbitt came out of the connecting rod, this caused the rod to kick sideways every time the cylinder fired. This hammered the wrist pin against the keeper enough to raise a burr around the outside of the keeper groove. Much longer and it would have blown the keeper out of the groove and scarred the cylinder. We caught it in time, replaced the rod and all is well.

[Mike Crehan]

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All of which is why I use end pads / buttons rather than circlips.

[J Witt]

Jim,

If a rod is bent, look for uneven wear on opposite ends of the piston. That is, the top of the piston vs opposite side skirt.

I'll be over to look as soon as I get the lights working.

John

[George Miller]

It could be a lot of things, but bent or twist in the rod are most likely.
But it could be cylinder not bored 90 degrees from crank shaft, cylinder bored off location, or crank bearings bored out of line from original location.

Also the locks should be put in with the clip ends to the top or bottom, not on the sides. I think most people do not even give that a though.

[Mike Crehan]

When I have put them in other peoples engines at their insistence - always use brand new clips, if you bend or twist it during fitting throw it away and grab another brand new one, once they are both in tap the pin back against the last one fitted to make sure it is seated properly and the pin is not pressing hard against one or the other. But if it is an engine for me then I never use circlips.

[TinCup]

Pretty sure that won't buff out!

[Jwilli]

Tin Cup, I think it would take some serious buffing.

[katy]

Also the locks should be put in with the clip ends to the top or bottom, not on the sides. I think most people do not even give that a thought.

Ditto

[40 Deluxe]

katy, Is the piston speed high enough in an A to pop a clip out if the ends point to the side? Or is this an old wives' tale (like an engine won't run if the ring gaps are all lined up)?

[Chuck Sea/Tac]

Originally Posted by Mike Crehan

When I have put them in other peoples engines at their insistence - always use brand new clips, if you bend or twist it during fitting throw it away and grab another brand new one, once they are both in tap the pin back against the last one fitted to make sure it is seated properly and the pin is not pressing hard against one or the other. But if it is an engine for me then I never use circlips.

Where do you buy new circlips? I was told they only come with new Pistons.

[katy]

Putting the ends of the circlips either up or down is more applicable to high revving engines, but it's a good habit to get into when assembling any engine.
What happens is that if the ends of the circlip are at the side, when the piston stops at either the top or bottom of the stroke, inertia causes the end of the circlip to want to keep going and causes a very small amount of deflection, which eventually leads to metal fatigue and the ring snaps.
With higher speeds there is more inertia, hence more deflection, etc, etc.

[40 Deluxe]

Katy, I was taught that close to 50 years ago. Just don't think it's of concern in the average A. For that matter, I'm not sure a retaining clip has enough weight to overcome its spring tension at any RPM. I wonder if this has ever been documented to have happened or if it's just assumed to be the cause of carnage. Having said that, the last engines I've built with floating pins, I've used Spiro Locks so no gap to worry about.

[George Miller]

Model A is a 4 1/4 stroke engine. So the piston speed is faster per rpm than say 3.48 stroke. At 2000 rpms the piston has to start and stop 4000 times per min.

Along with the flex in the pin. The wrist pin may be trying to push it out.
You need to make sure every thing is done as good as you can get inside a engine.

[40 Deluxe]

some figuring: At 3,000 RPM (around max for most A's, I think) average piston speed is 2125 feet per minute. A 3.48" stroke engine (a 350 Chev.) will easily go 6,000 RPM at which point average piston speed is 3480 ft. per min. I don't have the formulas for peak piston speeds but I think the A would still be lower because of the lower RPM.

[d.j. moordigian]

A few things come to mind when I looked at the photos...

1. The placement of the clip, as it sits in the groove, should be in a North / South position.
2. The pin fit in the rod is a big deal,...should be @ .0005" minimum.
3. The end play of the pin, when assembled, should be "noticeable" when you move the
pin back an forth. Say, about .010" too .012"...

[Mike Crehan]

Originally Posted by Chuck Sea/Tac

Where do you buy new circlips? I was told they only come with new Pistons.

I have not bought any in the USA but a quick search found these http://www.summitracing.com/int/sear...%20clip&page=2

When I need pistons I have always used Ross (well I did use Arias until they made a machining mistake - their solution was to refund my money rather than remake the pistons which was ok but it didn't solve anyone's problem). If we are using clips I always get them to chuck a couple of spares in the box. Unfortunately the tech guy I always dealt with at Ross has left. Their product is still great but they are not so easy to communicate with these days.