Is decking worth the money

[PackardV8]

My point is if the deck is good enough to seal and the builder sets the height via gaskets there will not be a measureable performance gain from decking. He is having this one decked so it's a moot point now. The .040 minimum quench is constantly quoted here. I just redid a 2006 5.4 Ford engine with .120 quench.

Engines with OBDII and better computer controlled EFI and ignition behave very differently than carb/distributor builds. Supercharged/turbocharged/diesel engines go deeper in the hole as the boost goes up. Some TF engines have/had the piston .500" in the hole.

Bottom line - without full details of the build and the intended use, squish is just a number.

jack vines

[Schurkey]

My understanding--and I may be wrong--is that the "squish" danger zone is from about .050 to about .090. Once you get beyond about .090, there's no squish action at all, but there's enough room to not inhibit flame travel. Acts like an open combustion chamber. Tighter than .050 to the point where the piston just kisses the head, acts like a closed chamber but with lots of mixture motion. From .050 to .090 or so, the quench isn't tight enough to provide mixture motion, but it's too tight to permit flame travel. Worst of both worlds.

Am I wrong?

[Crepitus]

Great thread Lots of good stuff here, my .002$; This reminds me a lot of a conversation I participated in about balancing cross weight. A couple of the guys wanted to know how much they would gain, how many tenths would it take off a lap. An impossible question to answer unless you know the environment and how far off the spec in question is to start with. IE if a SBC is assumed to have a 9.025 deck. the stroke / rod / piston is speced at 9 chamber is speced at 56cc. if one end of one bank is .007 tall. the stroke/rod/piston is .008 short, the head is surfaced reducing 1.5cc and one end of the head is 1cc small. that hole happens to be a nice warm one in the back. tolerances stack up giving 1 hole that has poor quench, high heat, and high compression, hell throw in a lean port and a loose valve adjustment. On paper the dynamic comp number looks fine but the thing detonates like a hand grenade. Is decking worth the money? How far off is it? How easy will it be to replace it. If you have 3 more in the shop slap it together and run it. If breaking it will leave you out of business you better make sure its right the first time.

[340king]

To add to this, typically when a boat breaks down it is a bad thing. Just witness the recent cruise ship ordeal. Those folks would really have liked the added reliability. I think that is a missing part of this discussion to some extent thus far and you nailed it.

Boats typically don't have any easy cruising time. Even at steady state, they work much harder than their highway brethren. So getting good equal combustion conditions in all eight cylinders is important in my eyes, even if no measurable HP is gained.

[wyrmrider]

1989transam
still lurking
you are the top of the list
viewtopic.php?f=1&t=34764

[janus]

My point is if the deck is good enough to seal and the builder sets the height via gaskets there will not be a measureable performance gain from decking. He is having this one decked so it's a moot point now. The .040 minimum quench is constantly quoted here.

Would it be reasonable to take this one step further by tolerance-matching deck height with crank stroke, rods and pistons. I mean, as in using the rods and pistons with the tolerances at the higher side in the cylinders that measured the higher numbers for piston-in-the-hole, in an attempt to equalize deck clearance among the cylinders?

And I strongly recommend using a fine-cut triangle file to smooth both the heads and the decks of the block.
Just work slowly/easy going from bolt-hole to bolt-hole while watching the file clean/cut the surfaces smooth.
NOW, this is a feelie/touchy deal so go easy. Use WD-40 as a cleaning solvent while doing this.
I've done this for years everytime that I rebuilt a hopped up stock engine.
Now if you have the $Bucks to resurface the heads and decks, then by all means do it, but I never seemed to have the extra cash.
pdq67

Anyone else using this approach?? I guess you could only take out variations on the surface but not a shifted or tipped deck, so it's more for creating a good seal?

[twl]

If the deck is already perfectly square to the line-bored crank centerline, and it achieves my desired height with the parts I'm running, and it seals right, then I don't deck it.
If it doesn't achieve these goals, then I do deck it.

[MadBill]

Well of course those criteria are the sum total of everything one hopes to achieve in the decking procedure, so it makes sense not to repeat the process. What it usually comes down to though is "What is perfect?" , i.e. how close to zero thous tolerance in every measurable do you accept before breaking out the heavy equipment?

For example, the Dart block for our current 380" SBF project has a beautiful finish out of the crate and is square side to side and end to end within 0.003", averaging 0.001" over the spec. height, BUT if rods, crank and pistons are all right on spec., the latter will be 0.022" down the holes at TDC. What to do? If the calculated piston to deck numbers check out, we will embark on a search for suitable 0.015" to 0.025" gaskets. If it doesn't or if we come up empty-handed, we'll cut it to zero deck and use a pair of the many available 0.040" gaskets.

[cpmotors]

My point is if the deck is good enough to seal and the builder sets the height via gaskets there will not be a measureable performance gain from decking. He is having this one decked so it's a moot point now. The .040 minimum quench is constantly quoted here.

Would it be reasonable to take this one step further by tolerance-matching deck height with crank stroke, rods and pistons. I mean, as in using the rods and pistons with the tolerances at the higher side in the cylinders that measured the higher numbers for piston-in-the-hole, in an attempt to equalize deck clearance among the cylinders?

And I strongly recommend using a fine-cut triangle file to smooth both the heads and the decks of the block.
Just work slowly/easy going from bolt-hole to bolt-hole while watching the file clean/cut the surfaces smooth.
NOW, this is a feelie/touchy deal so go easy. Use WD-40 as a cleaning solvent while doing this.
I've done this for years everytime that I rebuilt a hopped up stock engine.
Now if you have the $Bucks to resurface the heads and decks, then by all means do it, but I never seemed to have the extra cash.
pdq67

Anyone else using this approach?? I guess you could only take out variations on the surface but not a shifted or tipped deck, so it's more for creating a good seal?

The ONLY time a long fine cut file is used on decks in my shop is if its a #'s matching block that can't be decked, and its only to lightly hit the high spots around head bolt holes and any other minor variations. Its not a good way for anybody that doesnt know how to properly use a file to try and get decks flat with.

[pdq67]

Right Pete,

"and its only to lightly hit the high spots around head bolt holes and any other minor variations.", as well as to gently clean the crap off all the decks.

You notice I did say that this is a "feelie" deal so take your time, be easy and watch the deck's turn to shiney metal, 1st around the pulled bolt holes going from a pair of them on the block and then around the headbolt holes doing the same thing. Along with a can or two of WD-40 to wash eveything down as you go..

Last time I did this, I used a fine cut, single cut, trianglar shaped file that was about 8" long or so. it was a Nickelson file..

pdq67

[kirkwoodken]

If you lay those "flat" files on a surface plate, you may find they sometimes look flat, buy contain a twist or a bow. And sometimes a bow is an advantage. They may also be flat on one side and not on the other.

[wyrmrider]

Here is a block vendor that mentions detailing their blocks
http://www.allpontiac.com/buildingnotes.htm

[cpmotors]

Right Pete,

"and its only to lightly hit the high spots around head bolt holes and any other minor variations.", as well as to gently clean the crap off all the decks.

You notice I did say that this is a "feelie" deal so take your time, be easy and watch the deck's turn to shiney metal, 1st around the pulled bolt holes going from a pair of them on the block and then around the headbolt holes doing the same thing. Along with a can or two of WD-40 to wash eveything down as you go..

Last time I did this, I used a fine cut, single cut, trianglar shaped file that was about 8" long or so. it was a Nickelson file..

pdq67

I did notice that and your right, it is not as simple as it may sound. However, a triangle shape file IMO is not the right choice, too narrow. I prefer a larger/wide 1"+ fine single cut file. And as Kirk points out, they may not be as flat as one may believe.
i.e.