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Discussion Starter #3
Hi Rod,
Very impressive shop.

Have you ever milled the top of a LC4 piston?
I wanted to lower compression for a turbo project
I can't say for sure if we've done an LC4?! We have done several pistons throughout the years. It can be a cost effective alternative to having a "custom" piston made. The biggest thing is knowing how much and where the material is to be removed. If you have some forethought into this aspect it is straightforward. If we need to do the design and testing it gets more involved. While we are capable and willing to do that. It can get expensive quickly when stuff goes to R & D! Let me know if we can be of any help? I'm sure there is good info on this very forum!
 

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Full Throttle
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Thanks for the reply.
Not to side track the product thread for my thoughts,i wonder if i can indulge you in more discussion which includes the head work
Your piston information i understand. R&D is needed .

What about increasing the CC of combustion chambers on these alloy head big singles?

To me it would seem that possibly taking out metal from the chamber and welding new support metal in the valve case section.
Considering its not a moving part.

Would you consider this to be another solution to decreasing compresion or is it problematic.cheers
 

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Discussion Starter #5
Hey Cors,

We regularly rebuild or modify combustion chambers on the CNC. We have digitized numerous head mods through the years. I will have the guys go back through the files and see if we may have something already to go and if it is available. There are many factors which need to be considered when "opening" or increasing the combustion chamber volume. The good news is that it is not VooDoo magic!! On a personal note, I fly cut a 1 1/2" diameter, tapering sphere that was .050" to .0010" in the pistons for my GTO. I wanted to run crappy, ethanol pump gas. Changed my static compression from 10.5:1 to 8.65:1 using the 68cc chambered "correct" heads. This can all be done!!
 

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Discussion Starter #7
Thanks for noticing Cors! We get the chance to work with some of the most fantastic and fastest people in the industry.
 

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Full Throttle
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I noticed some of the older 690 motors have lower compression ratio compared to the newer ones.
2007-2011 11.7:1-11.8:1
2012- 12.5:1-12.7:1

Is there anyway to boost compression on the OHC 690 motors from the head?
I gave up on turbo projects .
 
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