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| KB268 Question https://www.slantsix.org/forum/viewtopic.php?t=5249 |
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| Author: | 60Pioneer [ Mon Mar 17, 2003 10:11 am ] |
| Post subject: | KB268 Question |
A question for the brain trust. I didn't put much thought into this when I did it, but then my machinst buddy asked THE question. When using the KB268 piston, do you position the dished section towards manifold or cam side of the engine? Thanks in advance for the help. BTW, I have the dished section on the manifold side. If I have to flip-flop now is the time before we button this sucker up. |
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| Author: | Doc [ Mon Mar 17, 2003 11:02 am ] |
| Post subject: | |
This is a question about piston pin offset. The KB is said to be a "zero offset" piston no pin offset) but I always check this. I find that so called zero offset pistons still have a few thousands of "off centerline" to the pin bore. (production tolerances) The problem is that is can "shift" from side to side at random. I go "majority rules" on this and install the pistons with the offset (larger / heavy side) towards the major trust side. (sparkplug side) Sorry for the "non answer" to your direct question Tom, what does the dish look like, is it a "D" shaped dish or are we talking about some valve notches? For a non-quanch / squash type engine, the flame travel is not really an issue here. DD |
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| Author: | 60Pioneer [ Mon Mar 17, 2003 12:07 pm ] |
| Post subject: | |
The KB268 does have a kinda "D" shaped dish, no valve reliefs. I had checked for pin offset and didn't see anything, so I assumed that there was none. My thought was to place the dish under the valves for clearance, and the "flat" portion of the piston towards the plug for the mass. Your "non-answer" was actually a great answer as it actually goes beyond just the KB268 question. Thanks for the help. |
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| Author: | Doc [ Mon Mar 17, 2003 12:17 pm ] |
| Post subject: | |
Yes, if the piston has no pin offset, then installing it for max valve clearance is a great idea, not that there is any shortage of valve clearance in a -.140 deck SL6. The extra clearance is good "insurance" in case the valves float or something. DD |
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| Author: | 60Pioneer [ Mon Mar 17, 2003 1:18 pm ] |
| Post subject: | |
I did forget and left out one little detail. This is a long rod motor. We trial fitted the pistons and milled the block to ensure a zero deck. I do have about 0.040" worth of head gasket, but that's about it. On a totally unrelated topic, we also cc'd the head and milled it to give us 54cc. We backed-in on the blueprinting on this engine. |
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| Author: | Tom Drake [ Mon Mar 17, 2003 4:37 pm ] |
| Post subject: | |
Gilly, Straight leg of the "D" goes to the intake side of the motor. There is no option on this it is the only way it will fit. If you turn the piston around then the valve relief is at the wrong angle for the valves. Tom |
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| Author: | 60Pioneer [ Mon Mar 17, 2003 8:24 pm ] |
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Thanks, Tom. you saved me some time and potential heartache. We're going to check the valves with clay anyway. Better to do the 'ol flip-flop now. |
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| Author: | Tom Drake [ Tue Mar 18, 2003 6:04 am ] |
| Post subject: | |
No problem. We just had the same question from our engine builder. We took the head down and mount it on the motor just to be safe. Tom |
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