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Old 02-19-2005, 06:14 PM
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To zero deck or not to zero deck?

Im going to have a 383 built and i want to get my quench right and such so i can use pump gas. Ive read stuff about zero decking and seems like the best way to get your quench distance right. But by doing this, it seems to me like the piston and head are almost too close together to compensate for expansion and stretch after warm up and high rpms. My engine builder doesnt recommend a zero deck at all for the fact that if something goes wrong or if you have alot of stretch, something is liable to come together....He builds his race motors with pistons .010 in the hole. But wouldn't this put your assembled quench distance at .050 with a .040 compressed gasket. Will warm up expansion compensate for this and give the desired quench? He said he would rather not zero deck the block at all, but he would if thats what i really desired...Hes the builder and knows his stuff, im just the crazy guy who wants a hot motor. What are everyones opinions on zero decking compared to .010 in the hole. Im wanting to run at least 10.1 compression with aluminum heads with 64cc cnc combustion chambers and forged, slightly dished, JE/SRP pistons without detonation problems on 91-93 octane pump gas. Thanks for all opinions and suggestions.

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Old 02-19-2005, 06:21 PM
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Here is a link that explains quench.

http://www.speedomotive.com/Building%20Tips.htm

You will be fine if your gasket puts you at around .040" to .045" and you use cast iron or steel rods.
I wouldn't go .050".

My pistons are down .005". I wish I had zero decked. My gasket is at .039" so I ended up at .044"

At 10:1 you will be fine anyway. If you have at least 220o I wouldn't worry about pump gas. You should be able to use the cheap stuff, 87 octane.
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Old 02-19-2005, 07:23 PM
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Ive read that link before, thats why i really dont want a .050 quench. I plan on using a eagle 4340 H-beam rod and a 240 at .050 cam. I would like to be between 10.0.1 and 10.5.1 compression and still be safe. I guess i could run a thinner gasket. Are there any good thinner gaskets out there that i wont have sealant problems with? I really want to get my quench as tight as i can and still be without other problems, i dont want anything hitting together or blowing out on me. If i had a .030 gasket with .010 deck i would have a .040 quench distance, but i definitely dont want sealing problems. Thanks for any more help. Im trying to ward off any detonation...
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Old 02-19-2005, 07:31 PM
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Parallel decking

Paying for parallel decking is fine if you are putting in good parts. Decking to zero is a bad idea. You may have to deck again in the future and there is nothing below zero.
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Old 02-19-2005, 07:40 PM
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Especially on a seasoned block it is always a good idea to machine and square the deck surface, we also do the pan rail surface as well, just good common sense machining. You will always benefit with running a zero deck and keeping the quench at .040 or less. It will be much more efficient. I run .35 and the hard core racers run less, around .030 with forged rods making 900 HP with no problems.

There is NO reason to worry about a .040 deck as it's been done thousands of times. Your correct and the builder is a touch behind the times. Quench is very important for detonation resistance.

Corteco, Fel Pro and Cometic all have gaskets that should work out for you.
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Old 02-19-2005, 07:54 PM
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I plan on using the best parts i can for what i need. I told my Builder that i wanted it to handle 500+ horsepower and 7000 rpm, even though it wont be pushing either. What exactly do you mean by parallel decking? having all pistons the same in the hole? would it be safe to still have the pistons .010 in the hole, and just run a thinner gasket? or if i could get him to put it at .005 in the hole, would that give me the right quench? that way i can still have room to build again and deck it again if need be. I know he he takes a lot of time machining and clearancing and honing and boring and stuff from other people ive talked to. De doesnt bore or hone until he has the pistons and hones each cylinder according to the piston that will go in it. Im just really concerned about detonation and quench. any help and suggestions is greatly appreciated, i need ideas of what to discuss with him before he gets started.
THanks again
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Old 02-19-2005, 08:03 PM
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Parallel decking is is making sure the deck surface is square and parallel with the crankshaft centerline. Deck height is the distance from the crankshaft centerline the deck surface. Factory blocks are fairly crooked, it's almost always a good idea.

Your builder's probably concerned about a wiped rod bearing causing contact with the head and creating even more damage. Tell him that it's what you want, it's your money, and to please do as you ask.

Here's a pretty good article on block machining for performance.

http://www.circletrack.com/howto/4661/

Larry

Last edited by coldknock; 02-19-2005 at 08:35 PM.
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Old 02-19-2005, 08:43 PM
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haha good point larry, ill probly just have to tell him that. Im determined to get my quench where i want it. Yeah he is real concerned about stuff coming together if something does fail. But honestly, in my opinion, if something fails, it doesnt matter if its .030 or .070, thats still really close, so its still gonna affect something, but then again, i really dont know what im talking about, but i know where i want my quench at. back to that one question i had, would it be safe to run a piston .010 in the hole and use say a .031 compressed gasket, giving a quench of .041? or should i run .005 in the hole with that gasket? let me put it this way, can i get a proper quench without zero decking, and if so, how? thanks again for as many suggestions as i can get.

Last edited by Lthompson; 02-19-2005 at 08:52 PM.
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Old 02-19-2005, 09:08 PM
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It's possible, yes. I'd rather have a slightly thicker gasket for peace of mind. Sealing issues around water jacket openings with thin gaskets can crop up, even with two freshly machined surfaces. This is usually only an issue with steel or copper "shim" type gaskets.

You can have deck height at whatever makes you comfortable as long as the gasket leaves 0.040"-0.045" quench distance. 0.010" in the hole with an MLS or composition gasket such as Cortecos or Mr.Gaskets would be fine and leave material for correcting deck surface imperfections in future rebuilds.

Larry
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Old 02-19-2005, 09:13 PM
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0 decking

i am running a 302 ford with 289 rods and pistons cut for 0deck has 4 years on it no problems run mid grad fuel. its in a 32 2drsdn.goes well and i drive the crap out of it
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Old 02-20-2005, 06:44 AM
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if you're worried about using low or mid grade pump gas and i don't know who wouldn't be these days,i wouldn't get too cazy about decking if it isn't neccessary,you're only talking about few thousanths that can be made up in the head gasket.the important thing is simply to make sure the deck is square.when you deck you have to worry about pushrod length especially when chaging rocker ratio's and shaving your heads to true them up and that just starts being a pain in the butt when h.p. is just too easy to make.i have a 406 i'm putting together now that the piston sits .017" in the hole and the other 406 was decked .009" and the piston still sat .017" in the hole and they both make right at 450 h.p..its only money but rember all the decking and shaving when its time to put the valve train together cause it only gets harder to remember everything that has to be allowed for.
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Old 02-20-2005, 07:32 AM
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Most factory small blocks have a deck height of 9.025" give or take a little.

Most milling machines will parallel deck the block as most of them bolt to the main bearing bores to begin with. I've usually would deck about .015" off of a block if it was just to true up the deck surface.

There is absolutely nothing wrong with zero decking the block. Blocks can have a negative deck if you so choose. You are the assembler and the builder, so it' is your baby if a piston kisses the head.
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Old 02-20-2005, 10:20 AM
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Take off the minimum necessary to square the block, there is way to much emphasis on "decking and squaring" in the literature printed these days, as if 0.010" will make or break your motor and the factory machine work was so poor that its required.

Just remember the deck is where you get your head seal from, thinner is never better from a durability point of view. As a matter of fact if some of these engine builders would check the surfaces with a straight edge and a set of micrometers and see how straight it is in the first place they would realize most of the machine work done these days is completely unnecessary. When was the last time anyone has seen a mains out of square with the deck? The factory machine work was done on very accurate machinery (broaching machine for decks) and is likely more accurate and flat than any rotary tool can approximate. Heads are where all the warpage takes place, not the block.

I once stuck a very worn unrebuilt 302 Ford engine on a CMM machine just for practice in using the machine and found the surfaces within 0.0001" of perfect on almost all the machined surfaces (the cam cover plate surface was out 0.001" over 10 inches but that surface is non-critical). The only place I could find inaccuracy was around the bolt holes where the cast iron had pulled up the material from the bolt torque. Then again, these machine shops wouldn't make a dime on you if they didn't machine everything in sight would they. 99% of the time the only thing that gets accomplished is your pocket book gets lighter.

Good rule of thumb is too always remove the minimum and then only if there is a problem with that surface, just because every engine buildup you have seen in a magazine had multiple pictures of the block machining procedure doesn't mean it was necessary or required. I call it the shiny object syndrome because everybody likes to see shiny fresh machined faces don't they...even if it is less accurate than the original factory work.

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Old 02-20-2005, 10:27 AM
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I had my block decked .010, and I`ll be using a .028 GM head gasket so Quench will come in around .043, This is the only block I ever had decked, and the only reason why was because I wanted to get the quench right so I could run a little higher compression. Most times I just clean the deck and make sure it`s not too far out of whack, if it`s not then I don`t bother unless I`m shooting for a certain quench, and I agree with chucky, no reason to deck it no more than needed, the thinner the deck the more problems can surface.
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Old 02-20-2005, 10:56 AM
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I had my 400 decked .014". There was a scallop type gouge on the deck surface on one side. This is how far they had to go to eliminate it. I ended up with the pistons down .005". Close enough.
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