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  #106 (permalink)  
Old 12-19-2012, 05:28 PM
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Quote:
Originally Posted by 0trbo4myCHEVUICK View Post
So if you can see where the 1/16th mark would be I am one notch above that mark.
The finest scale resolution is 1/64". So are you saying 5/64"? That would be 1/16" (4/64) plus 1/64 = 5/64". I hope it's not that, it would be a quench measurement of a whopping 0.078". Not good.

In any event, using a ruler like that is not accurate enough IMHO.

Edit I see you're getting feelers tomorrow. Good deal.

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  #107 (permalink)  
Old 12-19-2012, 05:32 PM
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Quote:
Originally Posted by cobalt327 View Post
The finest scale resolution is 1/64". So are you saying 5/64"? That would be 1/16" (4/64) plus 1/64 = 5/64". I hope it's not that, it would be a quench measurement of a whopping 0.078". Not good.

In any event, using a ruler like that is not accurate enough IMHO.

Edit I see you're getting feelers tomorrow. Good deal.

:/ By the looks of the thing and other pictures I have seen on the net. It doesent look like my pistons are very far down in the hole at all. now im nervous as heck.
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  #108 (permalink)  
Old 12-19-2012, 05:38 PM
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Quote:
Originally Posted by 0trbo4myCHEVUICK View Post
:/ By the looks of the thing and other pictures I have seen on the net. It doesent look like my pistons are very far down in the hole at all. now im nervous as heck.
That would be a good thing- if they were even with the block it would be even better. I'm going to guess they're 0.045" down the hole.
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  #109 (permalink)  
Old 12-19-2012, 09:49 PM
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Originally Posted by cobalt327 View Post
That would be a good thing- if they were even with the block it would be even better. I'm going to guess they're 0.045" down the hole.

Nah if they are even with the deck my compression will be too high i think.
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  #110 (permalink)  
Old 12-19-2012, 11:19 PM
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Technically the chamber volume includes the space between the deck the top of the top ring.In cases where you where right at the rag-get edge of a limit then that would be important. Some piston companies move the top ring down because of the application and heat issues.
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  #111 (permalink)  
Old 12-20-2012, 08:26 AM
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Quote:
Originally Posted by 0trbo4myCHEVUICK View Post
Nah if they are even with the deck my compression will be too high i think.
That would depend on the chamber volume of the head and the dish volume of the piston, now wouldn't it. You did read the page on quench, right?

The "ideal" quench measurement is right at 0.040". About the most common composite head gasket thickness is 0.041". So a zero deck (piston even w/the block) and a 0.041" head gasket will put the quench measurement right where it needs to be.

You do not want to adjust the compression ratio by making the quench distance wider. So using a thicker head gasket or a piston deeper in the hole are both bad plans as compared to a zero deck and a 0.040" range head gasket- or any other combination of HG thickness/piston deck height (piston in the hole) that equals about 0.040".
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  #112 (permalink)  
Old 12-20-2012, 03:54 PM
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Okay, measured with the feeler gauges. Placed the steel ruler in the 3-9 position if looking at the side of the block and measured from the squish band. Got .038..

was only able to measure the #1 piston at the moment.
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  #113 (permalink)  
Old 12-20-2012, 06:17 PM
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Quote:
Originally Posted by 0trbo4myCHEVUICK View Post
Okay, measured with the feeler gauges. Placed the steel ruler in the 3-9 position if looking at the side of the block and measured from the squish band. Got .038..

was only able to measure the #1 piston at the moment.
And you jiggled the crank a little clockwise and counter-clockwise to make certain that the piston is at TDC, right? And no air gap under the rule at the block deck, right?

OK, now it'll be interesting to see what the other 3 corners look like.

This is one of the cornerstones of having a good build and not having a good build. The more information you can put together about various pieces in the motor, the better your choices will be for parts that contribute to the combination.
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  #114 (permalink)  
Old 12-20-2012, 06:40 PM
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might catch hell for even mentioning this, but IMO you can figure deck height fairly accurately with a dial caliper. when i originally assembled my engine(350 sbc) i borrowed a friends deck bridge and indicator to check mine. They were found to be .010-.011 in the hole.. the other day just for curiousity i had a degree wheel on and rotated it to bdc. Using the leg on my caliper i measured from the deck surface to the piston edge inline with the wrist pin. 3.491"... - 3.48" stroke = .011" ...thats close enough for gasket selection purposes. Beware if you tried this method at TDC the chamfers would ruin any hope for accuracy..
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  #115 (permalink)  
Old 12-20-2012, 07:41 PM
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Quote:
Originally Posted by cr480r View Post
Beware if you tried this method at TDC the chamfers would ruin any hope for accuracy..
As I say often, this stuff ain't rocket surgery
All you would need to get a very accurate measurement at TDC is a small framing square. Maybe I'm saying it wrong, but it's the flat measuring rule that is shaped like an L. Sit one side of the square down on the deck and butt the side of the dial caliper up against the other side of the square and measure with the slider on the caliper. There's room at the tip of the caliper to make contact with the deck and also to reach the crown of the piston with the slider part of the caliper.
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  #116 (permalink)  
Old 12-20-2012, 08:34 PM
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After rocking the crank/piston to establish that you're at TDC, tap the top of the piston to seat the bearing against the crank journal. It won't make much difference (not more than ~ 0.002"), but it helps w/accuracy if you're measuring the all four corners to get a rough estimate of what the decks look like for being square.
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  #117 (permalink)  
Old 12-20-2012, 09:10 PM
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Okay I will. What if we assumed all were within the. 037 -. 038 range? Just until I get it
to a position to measure all four..
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  #118 (permalink)  
Old 12-20-2012, 09:43 PM
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Well, it wouldn't be good news, that's for sure. Getting a decent quench w/that much piston deck height isn't going to happen, not as things currently stand.

You have the option of one or more:

• shaving the decks
• using a taller compression height piston. If you have rebuilder pistons w/a 1.54 CH, that can gain you 0.020" (piston closer to deck)
• thinner head gaskets. The thinnest are 0.015" steel shims, they need a flat surface on both sides to seal to. The finish is important, too. That usually means a clean-up skim off the decks and heads for best results.
• You also could build it w/a less-than-perfect quench. Using a thin composite gasket (0.026-0.028") and your pistons you'd end up with about 0.065" quench. Definitely not ideal but I've seen worse. Not saying to do this, just saying.
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  #119 (permalink)  
Old 12-20-2012, 09:52 PM
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Quote:
Originally Posted by 1Gary View Post
Technically the chamber volume includes the space between the deck the top of the top ring.In cases where you where right at the rag-get edge of a limit then that would be important. Some piston companies move the top ring down because of the application and heat issues.
The OEM's have been moving the top ring up closer and closer to the crown just because of what you have addressed. The mixture that sits there between the piston and the bore never gets lit, so when the cylinder is evacuated, the unburned mixture contributes to dirty emissions.
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  #120 (permalink)  
Old 12-20-2012, 11:37 PM
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wonderful
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