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  #61 (permalink)  
Old 09-30-2013, 12:21 PM
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Originally Posted by techinspector1 View Post
Most everyone, including David Vizard, agrees that the tighter the squish, the more power the motor will make. Mr. Vizard tested a tighter and tighter squish on a small block Chevy and didn't encounter a piston to head collision until......I believe 0.027". That's why you will see a range of 0.035" to 0.045". That range allows for the piston growing taller from the heat of combustion, the connecting rod stretching a little and the crankshaft bowing a little at speed. I agree with Jay that over 0.050", you begin to lose the squish effect. Your example of 0.073" squish might better be termed a "lack of squish".

Tighter than 0.035" could get you into a piston/head collision situation and looser than 0.045" will not be as effective as a tighter squish. The idea is to blow the mixture across the chamber by squeezing it out from between the crown of the piston and the flat area of the cylinder head opposite the chamber, homogenizing the mixture and eliminating any rich or lean pockets of mixture so that they will burn completely. I generally try to spec a piston that has a generous amount of flat area on the crown to accomplish this squishing. If you get the squish right, you can generally use a lesser grade of fuel without suffering detonation.

Here is an example of a flat-top piston that would work well.....
http://www.summitracing.com/parts/su...0-30/overview/
Here's a D-Cup piston with a generous flat area on the crown to mate up with the underside of the head....
http://www.summitracing.com/parts/ue...make/chevrolet
I don't use pistons that have a thin ring of crown material all the way around the perimeter and a shallow dish. Not enough flat area to effect a good squish. I couldn't find a photo of that type of piston right away.

I have little experience with blower motors, but I'm told that they will not benefit so much from a tighter squish as a naturally-aspirated motor will. The mixture is homogenized by the blower on the way in.
Tech, thanks so much for the education. It would have been EXTREMELY useful today when I took the engine back to the machine shop. I was, however, armed with the squish, quench rate, knowledge which was a great help in my argument.

They, Bob at the machine shop, really didn't want to take the block back apart and deck it because I had not specifically asked that it be done. My first argument was, "well at the very least, I should have received a phone call" Bob just shrugged his shoulders and stuck with "the gasket will seal that".

So I posed the quench rate argument for about 2 minutes. I got a blank stare and he said, "bring it back in and I'll disassemble and deck the block for $100. I felt, particularly with my dearth of knowledge, further argument would only hurt me so I agreed. I don't think I'll be dealing with them anymore.

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  #62 (permalink)  
Old 09-30-2013, 12:34 PM
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Originally Posted by BaySox1 View Post
Tech, thanks so much for the education. It would have been EXTREMELY useful today when I took the engine back to the machine shop. I was, however, armed with the squish, quench rate, knowledge which was a great help in my argument.

They, Bob at the machine shop, really didn't want to take the block back apart and deck it because I had not specifically asked that it be done. My first argument was, "well at the very least, I should have received a phone call" Bob just shrugged his shoulders and stuck with "the gasket will seal that".

So I posed the quench rate argument for about 2 minutes. I got a blank stare and he said, "bring it back in and I'll disassemble and deck the block for $100. I felt, particularly with my dearth of knowledge, further argument would only hurt me so I agreed. I don't think I'll be dealing with them anymore.
Which is when you should have replied<"I didn't request it becuz I didn't know you were gonna use El Cheapo Pistons ". Good deal tho>Glad you are getting it took care of.
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  #63 (permalink)  
Old 09-30-2013, 12:39 PM
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when the engine performs well,go back and praise him for a good engine.He will be happy for good news.He might learn something for future customers???Not every machine shop does high performance engines,and stock engines will run fine as long as the fitment is all "close enough".
Your next engine you will be better equipped to do a better more powerful engine. Next time you will take the same care custom fitting piston to wall clearances and ring gaps for even more power
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  #64 (permalink)  
Old 09-30-2013, 01:11 PM
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$100. to deck the block is very fair.Make sure you bring a bottle of whiskey/bourbon or w/e to smooth things over.well worth the few extra bucks
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  #65 (permalink)  
Old 09-30-2013, 01:15 PM
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Originally Posted by vinniekq2 View Post
$100. to deck the block is very fair.Make sure you bring a bottle of whiskey/bourbon or w/e to smooth things over.well worth the few extra bucks
I agree. Make sure he checked the mains for being round and parallel.
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  #66 (permalink)  
Old 10-08-2013, 05:37 PM
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Originally Posted by techinspector1 View Post
I agree. Make sure he checked the mains for being round and parallel.
OK--I asked Bill, machinist, to check the mains to insure that they are round and parallel. Not sure if that was correct because he looks sort of confused The other guy that is there, looks like perhaps the owner as he is always in the office, responded, "no problem".

So>>>>I picked up the engine today and it looks pretty good. The pistons are now .035 in the hole. I think I mentioned that I'm having the stock heads worked by a local guy that does work for the racing crowd. As I explained everything that I've learned here about the heads he nodded and said no problem.

So>>He is cutting the heads, installing 2.02/1.60 valves, guides, porting the heads and intake, springs and retainers. Estimate was about $750.00. I need recommendations on assembling the engine, (gasket type and thickness etc) what cam and are my stock injectors going to be OK?

The guy doing to heads said he would give me some recommendations re: cam etc, but I've come to realize that some of what I hear "in the street" is BS. The information I get from you guys puts me in a better position to make the best decision for my motor.

Thanks so much
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  #67 (permalink)  
Old 10-08-2013, 09:57 PM
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after decking the pistons are down the hole .035?
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