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-   -   Piston Problem (http://squarebirds.org/vbulletin/showthread.php?t=18981)

partsetal 06-06-2015 05:58 PM

Piston Problem
3 Attachment(s)
I've pulled apart a 430 that was rebuilt years ago by others, in search of the cause of a knock. After removing one head I discovered that the step on the pistons was at the bottom, not the top as I've done on 430 rebuilds. Since this motor has right and left pistons, I pulled the other head and the story was the same, all pistons had their steps at the bottom. Not sure why, so I looked a little closer and could see that the .030 pistons all had 'Front' and an arrow pointing to the front, so the rebuilder installed them that way. It appears to me that these pistons were marked wrong by the manufacturer and should be rotated. This motor has had about 45 min of run time and I think that I could easily do this without replacing any parts. Of course I'm still searching for the rod/piston knock in #2 cylinder. Has anyone else come across a similar situation or have any advice?

simplyconnected 06-06-2015 08:01 PM

Carl, I'm not surprised you found that. Most engine builders never laid eyes on a 430 and they have no clue.

To make matters worse, correct pistons are made of unobtanium and must be specially made. All the 'engine rebuild kit' houses sell flat top pistons for the 430 with no regard for compression loss or the 9-degree bevel in the block.

Check your clearances. Piston to bore should be around .0015" Wrist pins should be 'slip fit' and bearings should be ~.0015". On my last FE build, I had new wrist pin bushings installed in the con rods.

Another problem is that the crank end of the con rods get egg-shaped over time. My machine shop shaves a small amount off the cap's mating surface then assembles it and hones the rod round again. My machine shop uses an air-gauge so they can rotate the rod while measuring. Try and find a shop around you that also has an air-gauge. - Dave

tbird430 07-29-2015 05:42 PM

Pistons must have been installed on the wrong side connecting rods?

By simply moving the pistons with connecting rods from one cylinder bank to the other will move that "step" back to the proper TOP location- And the arrows will still be pointing forward. Correct??

-Jon in TX.

partsetal 07-29-2015 09:43 PM

4 Attachment(s)
Yes, I thought of that. Problem is the rods that run on the same crankpin have faces that work in contact with each other. By rotating these rods, which I would have to do to switch to the other side, the chamfer in the rod end would be facing the chamfer in the other rod, not the smooth face to smooth face that it should be. It gets worse; I sent the rods and pistons to a machine shop to have them remove the pistons and just turn them 180 degrees. They called soon after I sent them and asked for 7 more rods. When they went to press the pins out, the pins just about fell out the piston and the rod. It caused me to check the block and I found that the pins had cut nice grooves in 4 of the 8 cylinder walls, rendering this block too expensive to repair. It became apparent that whoever assembled this block or did the machine work on it had no idea what he was doing.

simplyconnected 07-29-2015 11:45 PM

Holy COW!!! Carl, I'm looking at galling caused by wrist pins that floated out. Not good.

Let's back up and set things in proper perspective...
Your connecting rods have a 'squirt hole'. Every time the crank rotates, this hole sends a squirt of oil to the opposite piston (on the opposing bank). So, these con rod holes on each bank need to face each other (toward the cam).

Your con rods should be a press-fit. Other Ford engines use this method quite successfully including Mustang engines. We do NOT press them in place but rather, we heat the top of the con rod to 600 degrees F, right when the color goes from straw (400) to blue (600). If you get to cherry red, that's too hot. Engine machine shops have a 'special' oven that is set for 600 degrees. They simply throw all the con rod small ends in and wait for the heat to soak in. When up to temp, the wrist pin slides in with no interference for about 10 seconds, which is plenty of time to adjust the pin, left-to-right. Then, the con rod shrinks and holds the wrist pin solid. Real solid.

Since there is no wear between the wrist pin and the con rod (they are solid), the dimensions should always be the same unless someone honed your rods.

FE rods are free-floating. The piston has end-circlips, the wrist pin freely floats in both piston bearings and in the rod bushing. Your rods do not have a rod bushing and your pistons have no circlips.

If this were my 430, I would get new rods (or good used rods). The numbers stamped on the rods and caps should be readable with the engine upside down. In other words, the numbers face down.

You have already discussed piston orientation. They are a set of four RH and four LH and the arrows should face forward. If the Shop Manual isn't clear, this is what they are trying to illustrate.

So, set aside the rods and their caps for one bank along with their pistons. Heat the rods and push the wrist pins in, using no tools. Stuff the assemblies in their cylinders. Now do the other bank. - Dave

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