Going to start over

[optmaxx]

I figured that it's probably best to start over with my build since I know what went wrong, but I'm having some trouble making up my mind about the piston situation. My machinist suggested to not reuse the pistons because they may be out of round, even though #1 and #2 looked ok. He didn't measure them yet, he just said that it's probably the best thing to do to avoid getting into problems again. I do have a few options:

-The first one is just to buy all new pistons from Bulltear.

-The second option is to possibly use the KB944 that I still have laying around, but something will have to be done so that I don't get any pinging. Will increasing the volume in combustion chamber on the head do that? Also, will a job like that run about the same as new custom pistons?

I guess having those KBs just sitting there is making it tough for me to make up my mind. I'll post pics of the worst sides of the #1 and #2 pistons without cleaning, the scuffs look more like polished marks and their cylinder walls really have no scuffing.

I also have 4.2 rods, I'm not saying that I regret running the 4.0 rods, I just have those 4.2 rods and have not explored what options are available for those.

[jsawduste]

Pistons from Diamond Racing. They make all mine to order with pin height, compression, ring choice, floater vs non floater and more as all options.

[Russ Pottenger]

Can you repost the spec sheet of these pistons.
Where the Pistons above or below the deck and by how much.

[optmaxx]

Here's the spec sheet. They didn't look like they were below, and I'm not sure by how much. Honestly I just figure that they were ready to install, so I didn't measure that. My block wasn't decked either.

[optmaxx]

I can probably put one piston back in and measure it later. I'll need to get a dial indicator.

[Russ Pottenger]

Sorry I can't read your spec sheet on my iPhone.
Just roughly guessing, a 1.390 CD will put you at or just below deck
depending how short the rods got during resizing.

[optmaxx]

Is CD compression distance? My spec sheet says 1.380 in.

[optmaxx]

Thought I should post pics of the 944s with the new design. On the new design there seems to be a good amount of clearance between the con rod and under the piston. On older design, it seemed like there was a small bump under the piston that needed to be shaved off, and clearance issues between the corners of the con rod and piston caused the small end of the pistons corners to need grinding. The new design also has the bottom machined. I actually think that there is more clearance on these compared to my old Bulltears, but that's just from eye balling it.

I did ask the machinist to grind off some material from the small ends of the con rod, but I'm not sure how he did it. I do see the two corners on the small end that are across from each other rounded off, but the other two are still sharp. He says that they did mod the small end, but not too much because there's a good amount of room under there, so I'm not exactly sure what they did to mod the small end, there does seem to be a generous amount of room down there, I just hope i didn't pay for something that wasn't done. If they say they did something then I'll just take it. The walls cleaned up pretty nice cause there no sign of scuffing, and I think they honed it twice because the 944s turned out to be .002 thicker, so now I have about .004 clearance according to them.

[optmaxx]

Thought that I should also post some pics of the old BT piston wear, this is the # 6 piston that showed the most. It looks like there's some scuffing in one of the pin bore, and there's also some scratch marks under the pin bore that I'm not sure where they came from. Could they have been caused when they removed the con rods, cause all the other pistons seem to have similar marks.

[Russ Pottenger]

The scuffing on your piston pin bores isn't in the same direction of Piston pin removal

In my experience there could be most likely three causes.
1st. Inadequate clearance. A min of .0005
2nd. I'm assuming he used a rod heater to initially install the pistons, if for any reason while installing the Pistons the first time your machiniest had a problem and had to press them back off and didn't dust the pin bores with a hone you would have the same problem as in the first example because of the pin board distortion.
3rd. Lack of a good assembly lube under initial installation of pins.

[Russ Pottenger]

.... and now taking a better look at your picture, The lack of rod to piston clearance would cause a load in the pin bore and therefore cause the scuffing.

[optmaxx]

Thanks. I should point out that the #6 piston didn't rock back and forth freely when I pulled it out of the block, it was kind of stiff, and it also made some kind of grinding noise. He did use heat to install them.

I was also wondering about those scratches you see on the first two pics. The scratches that are located where you see the bottom of the piston where it's tan, under the pin bore, and near the manufacturer stamp?

[jsawduste]

Scratches don`t come from nowhere. Two surfaces are trying to share the same spot at the same time. Close examination coupled with a bit of logic will explain most instances.

Another vote for full floating pins is just what we are seeing here. I won`t do a pressed pin.

Grinding the rod for clearance now effects the rod weight and the balance point. So unless you do all the rods as mirror (for lack of a better word) images of each other you have effectively un balanced that cylinder from the rest. How much that matters is open to debate but you cannot argue the fact.

[optmaxx]

Got my stroker running again, and no alarming noises. No knocks, no metal on metal sound and I did the 20 minute break in. I put in a 160 deg thermostat this time only because I wanted the coolant to start flowing sooner. I put a fan in front of the radiator and the engine got up to 210 deg during break in and staid there. I didn't drive it, I just did the break in, I'll drive it in the morning. Sort of sounds like a sewing machine.

Also, I ended up using lucas extreme pressure valve train grease on my MC809 cam.

[jsawduste]