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  #46 (permalink)  
Old 09-26-2013, 05:12 PM
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That looks kinda ruff,especially around the large water ports.I definitely don't think I'd try a shim gasket.A good composite gasket will prolly seal up OK,but,IIRC,your pistons are already .045" in the hole,so,thicker ain't gonna be better.I can't believe they didn't @ least give the deck a couple of good cleanup passes.It would have me wonderin what else they did,or,worse,didn't do.Does the surface feel as ruff as it looks in the pics?

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  #47 (permalink)  
Old 09-26-2013, 05:40 PM
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Originally Posted by BaySox1 View Post
Not sure what to do at this point.
I know what I'd do. Disassemble the whole mess, take the block in to get the mains align-honed or align-bored if they didn't check out on the money, then chuck up on the main saddle and cut the block decks for zero deck based on your stack dimension. Then I'd use a composition gasket of 0.039"/0.040" to set the squish.
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  #48 (permalink)  
Old 09-26-2013, 05:55 PM
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Originally Posted by techinspector1 View Post
I know what I'd do. Disassemble the whole mess, take the block in to get the mains align-honed or align-bored if they didn't check out on the money, then chuck up on the main saddle and cut the block decks for zero deck based on your stack dimension. Then I'd use a composition gasket of 0.039"/0.040" to set the squish.
Pistons,IIRC, were the rebuilders type w/ 1.54 pin hgt.,so,even w/ 0 deck I'd opt for a minmum .028 gasket.
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  #49 (permalink)  
Old 09-27-2013, 01:02 PM
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Originally Posted by jokerZ71 View Post
Pistons,IIRC, were the rebuilders type w/ 1.54 pin hgt.,so,even w/ 0 deck I'd opt for a minmum .028 gasket.
I think you need to re-examine what you said here. If you cut the block decks to zero, it doesn't matter what the compression height of the piston is, the piston deck height is still zero and you'd need a ~0.039"/0.040" gasket to set the squish. Now, if you wanted to cut the block decks to 0.010" or 0.020" piston deck height and use the 0.028" gasket, ok.

Last edited by techinspector1; 09-27-2013 at 01:14 PM.
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  #50 (permalink)  
Old 09-27-2013, 05:06 PM
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Originally Posted by techinspector1 View Post
I think you need to re-examine what you said here. If you cut the block decks to zero, it doesn't matter what the compression height of the piston is, the piston deck height is still zero and you'd need a ~0.039"/0.040" gasket to set the squish. Now, if you wanted to cut the block decks to 0.010" or 0.020" piston deck height and use the 0.028" gasket, ok.
I was thinking all wrong.When I hear 0 deck,I just assume cutting approx .025 for a 9" deck hgt which in his case would still leave him .020 in the hole.I don't have a lot of experience with decking.So,you are saying for him to cut .045 from,or,there about?How much can you safely remove?
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Old 09-27-2013, 05:18 PM
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Originally Posted by techinspector1 View Post
I think you need to re-examine what you said here. If you cut the block decks to zero, it doesn't matter what the compression height of the piston is, the piston deck height is still zero and you'd need a ~0.039"/0.040" gasket to set the squish. Now, if you wanted to cut the block decks to 0.010" or 0.020" piston deck height and use the 0.028" gasket, ok.
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Originally Posted by jokerZ71 View Post
I was thinking all wrong.When I hear 0 deck,I just assume cutting approx .025 for a 9" deck hgt which in his case would still leave him .020 in the hole.I don't have a lot of experience with decking.So,you are saying for him to cut .045 from,or,there about?How much can you safely remove?
OK>>now I'm totally lost Should I have them cut the deck AND install different pistons? Or, can I just have them clean up the block deck and go with the pistons that are in there now.

Joker; you are correct. My pistons are .045 down the hole at TDC. I borrowed a depth gauge and checked it today.

Thanks for the help fellas.
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  #52 (permalink)  
Old 09-27-2013, 05:40 PM
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You can go either way.As I said,I wrongly assumed when Tech said 0 deck,that meant cutting .025,which'in your case,would not be 0 deck.You would need to cut .045 for a true 0 deck.Judging from the pics,I doubt,.010,or,.020 would clean those decks.You want a piston to head clearance(quench) of .040 to .045,so,I would cut enuff to get a smooth level deck.Then measure the depth of the 4 corner pistons plus the correct gasket thickness to give you a .040 to .045 quench.You can remove the .045 for a 0 deck & the .039/.040 gasket.I can't believe the shop didn't @ least call to give you the option to clean those up.
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  #53 (permalink)  
Old 09-27-2013, 05:51 PM
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If you deck the block,your current pistons will be fine.Just use the correct gasket thickness for the proper quench.I've never decked a block anymore than to get a clean level surface,but,ppl 0 deck all the time.I have heard that when using the shorter piston combined with 0 decking,will keep the ring Pak cooler by placing it closer to the water jacket @ TDC.
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  #54 (permalink)  
Old 09-27-2013, 06:54 PM
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I'm a fan of using the tallest piston I can find, resulting in the least material off the decks to engineer a good, tight squish, 0.035" to 0.045" with the piston at top dead center and the head gasket in place. I have a fear of cutting too much off the decks, because you begin getting into fitment problems with the intake manifold. The more you take off the decks, the narrower it is between the heads when they are bolted on. One of the most critical things in a build, to my mind, is the sealing up of the ports between the heads and intake manifold. That's why I suggest bolting the motor together, torquing everything down just like you're finished with it, waiting until the next day and removing the intake manifold to inspect the intake gaskets for sealing up all the way around each and every port. If the port is gapped open on the top side, you will probably be able to find a vacuum leak with a combustible spray. If the port is gapped open on the bottom side, you will never find it with a combustible spray and the motor will be pulling in oily vapors every time the intake valve is opened. That's where oily plugs come from many times. If the gasket is pinched all the way around each and every port and you can witness that there is a seal, use another set of the same part number gaskets, bolt it back together, torque and you're done, knowing that the motor is sealed up.
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  #55 (permalink)  
Old 09-27-2013, 07:40 PM
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Have the decks cut to a 9.00 deck height. This will leave you around .020 in the hole. Use a .028 gasket.
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  #56 (permalink)  
Old 09-27-2013, 07:57 PM
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Have the decks cut to a 9.00 deck height. This will leave you around .020 in the hole. Use a .028 gasket.
That would work fine in my opinion.
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Old 09-28-2013, 07:17 AM
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Originally Posted by GMC boogie View Post
Have the decks cut to a 9.00 deck height. This will leave you around .020 in the hole. Use a .028 gasket.
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Originally Posted by techinspector1 View Post
That would work fine in my opinion.
OK>>pardon my ignorance, but a 9.00 deck is measured from what point to what point? So .020 and using a .028 gasket, wouldn't that give me a quench of .048? Or is that .028 the gasket thickness prior to torquing the heads therefore giving making my quench much lower?

So I can better understand, and gain some perspective, can you explain what the effects of for a larger quench, ie. I'm currently .045 down and I go ahead and use an .028 gasket and result in an .073 quench?

Thanks All
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  #58 (permalink)  
Old 09-28-2013, 07:34 AM
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After .050 or so,you lose the benefits of quench.Your engine will be down on power & more prone to detonation.You also won't have an efficient & complete burn of your fuel.The advertised gasket thickness is the actual thickness after torquing head down.That is the actual compressed thickness.Your engine will run as is,but,the effects of a proper quench are well worth the effort.My main concern in your case is gettin a good seal with the condition of your deck.So if your gonna have the deck cleaned up,it won't be any harder to go ahead & set the proper quench distance.You know your .045 deep now,so,have the shop remove .025 from the deck.
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  #59 (permalink)  
Old 09-28-2013, 07:40 AM
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Standard deck hgt on an SBC is 9.025.This is the measurement from the center of the crankline @ BDC to the top of the deck.Removing more than .025 from the deck could start causing fitment/alignment issues with the heads & intake.It can also cause valvetrain geometry issues requiring different pushrods etc.
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  #60 (permalink)  
Old 09-28-2013, 10:38 AM
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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.

Last edited by techinspector1; 09-28-2013 at 10:52 AM.
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