Inliners International Forums General Discussion Blown and Injected Zero deck

Hey fellow inliners,

Was reading about zero decking and was wondering if this was always needed i am building a 292, stock rods, fordged pistons and turboed of course i know you want to keep the c/r decently low unless you are using some kind of methenol injection. I guess i'm just wondering how important is this and what are the benefits and if i do go about it whats the proper way? Premeasure then deck then bore woth a torque playe?

Much appreciated
Josh

The main goal of getting the piston up closer to the deck surface is to try to obtain a better quench clearance. A distance of .040" to .060" between the head and piston is considered ideal, it not only helps you gain a slight bit of compression, especially if the pistons are far down in the cylinders as a 292 is, but helps obtain a better burning of gas by really squeezing the air/fuel mixture into a tighter space and helps reduce the tendency of detonation if you were to have too much quench.

Checking the piston deck is more involved than just taking a wild guess at how much to cut the block surface, it requires you to physically insert each piston and rod assembly into their respective cylinders and not only make a measurement of how far down in the cylinder it falls, but you have to check the pistons at the side where the spark plug is as well as the quench side, never at the center of the cylinder. You will then rock the piston from side to side and measure how far up and how far down each side of the piston moves, and from this you can calculate the deck height of that side of the piston, and how to compensate. You need to simulate exactly how the engine will be run as far as making sure all the machine work is completed, such as crank reground, rods reconditioned, cylinders finish honed, block rough decked, etc....Trying to do this before the machine work is completed will introduce error to your readings at every step and compound the inaccuracy of your measurements significantly. You will find that often, to obtain your desired deck height, not only will the block need to be final decked by some amount, but most if not all of the pistons will need to be cut on one or either side as well to equalize them for zero or whatever you determine to be your objective.

It does require some specialized tools like a dial indicator with a stand to span across the deck surface, and this would also be a good time to degree your cam, so a degree wheel would also be a good investment if you don't already have one in your tool box.

great had to read that a couple time to absorb it like a pretty looking gal ha!

what to you mean or how do you "rock the pistons"

and I'm not finished with all the machining have the block bare and down at the shop getting dipped and magnafluxed along with its counter parts the crank and connecting rods being inspected

have rebuilt a few engine but nothing performance/ turboed which i know changes the whole game

and where can one acquire a stand that will span the block or is this a machine shop specific job?

No, this is something that is well within the abilities of the DIY'er. Companies like Powerhouse and most cam companies have these items for sale at a reasonable cost. Rocking the piston is just as it sounds, you physically use your fingertips to push the piston away from you and take your reading, and then pull the piston toward you with your fingertips and take that reading, the average of the 2 readings is your deck height for that side of the piston. You will need to do this to both the spark plug side and quench side of each piston.

So by doing this when you get an average will the piston always be flush or have a just in just out of the block as it rocks?

Does that make sense?

Thi is all much appreciated i'll looki into those brackets for the dial indicator

I'll make a simple example to help show what you could encounter when checking the deck on your engine. Let's say you are checking the spark plug side of your piston on the #1 cylinder, you first need to establish it is at TDC, and then push or rock the piston toward the intake/exhaust side of the block. Lets say this gives you a reading of -.020(below the deck), and then rocking it in the other direction gives you a reading of -.005(below the deck). Since the #'s are both negative and represent a value that is below the deck surface, you add them together and divide by 2(-.02 + -.005 = -.025, -.025/2 = -.0125 deck on the spark plug side). Now check the other side of the piston, the quench side using the same method as above, you might find that that side is -.015 in the hole. It gets tricky when you rock it one direction and get a positive #(above the deck) and the other number is negative(below the deck), but its not uncommon. Once you check both sides of the pistons on all 6 of them, you not only see a variation from front to back, but also from side to side. It would be the determination of the machinist at that time how much to cut the block, and whether any pistons needed to be cut to equalize the deck to zero or -.005, or whatever is determined to be the target number for your deck height.

Frequent reason why the block's deck height is progressively worse from end to end: it was milled once, but not accurately. Same thing with chambers - size different as you go down the casting.
Quench pretty much stops helping after about .060". The smallest clearance is 1 molecule short of smacking the head when at full temp & RPM, perhaps as small as .032" with tight pistons but using .040" is easier on the nerves and 90% as effective.

how important is it to increase valve size?

i have called around for some prices and get any where from 400 to 1000+
and although i find it hard to believe the are all telling me it will not create more hp or be beneficial to the head
but i have done a lump port install on it and the paper that came from hotrod6 said bigger valves were of benefit

Tlowe spearheaded an extensive dyno test session with both a 250 and 292 engine a few years back, and absolutely, bigger valves help tremendously.

How much of a difference does it make to bore the cylinders with and without a torque plate?

Depending on the engine : +/- a couple/three/four thousandths of runout on a bore gage as measured at the top of the cylinder when the head is torqued down.

If you bore and hone a block without a torque plate, when you do torque the head in place it pulls the cylinders into an oval shape and the result is a round ring trying to seal an oval hole, and that won't work very good. You also get the same results if the main caps aren't torqued when the block is bore and honed. So to have a jam up rebuild, always bore and hone with a torque plate and make sure the main caps are torqued when all the machine work is being performed.

So make sure the main caps and torque plate are on for all machine work? Or mains for every thing and torque plate aswell for boreing?

Main caps for everything and torque plate for bore and honing.

Thanks cnc dude you're always much help its appreciated by all i'm sure!

Never caught your name mines josh

Hey Josh, im Scott.

How long you been into inlines?

Well, I got my start back in 1984 when I went to work for probably the most famous and winningest Chevy inline 6 cylinder engine builder. So, im kinda' continuing the tradition in a way.

Thats awesome man yiu have been into this a long time!

"84 is not so long ago, seems like yesterday.

Haha beater i was born in 91

I built the 270 GMC in my '53 Chevy pickup in '78(the first time). Runnin' and building these things since the early '60s and I'm not one of the old guys here. There is Inline History here and like Scott said he and others are dedicated to passing it along. We're just looking for the next generation. Tag,You're it!

Haha well i sure would appreciate all the info i can get i sold all my v style things fr inline power! got my fried who has a small block in a 54 3100 all nervous hen he comes and looks at my parts!

Have a build form of my truck on porterbuilt kinda new style feel free to check it out

http://www.porterbuiltfabrication.com/showthread.php?465-dirt-job-under-construction

Copy and paste

Man, That thing is low! You must be fearless to have even started that project. Good work.

Beater, i like that word fearless! Not sure what it means but my dad always tells me i'm stupid! Ha i just tell him its different!

Pluse he hasn't built a truck his project sets in the garage thats why mine is an iut side dog crappy but gives it potential

I would have to say that for a street chevy six build boring and honeing with or without torque plates would never show up on a dyno. It certainly wouldn't hurt but you would never see it. On a comp type engine with low drag rings and high rpm the extra money would be well spent.

Even under boost pressure that "oval shape" that scott was talkin about what be of any effect?

Just got my clifford back from the chrome shop got it unplated back to aluminuminuminums(bought it used and it was crappy chrome so i removed it even though thats like 15 hp i just lost haha spacer and powerjection 3 test fitted to a spare block and it fits but its very very close!

I torque plate honed my 292 that is built to be turbocharged. I prefer to with any 4 bolt per cylinder engine.

When you are rough boring a block with a Power Hone like a Sunnen CK-10 or CV-616, you finally get the ring ridge removed from the cylinders and the honing stones are making a nice smooth cutting sound, then you stop and torque the torque plate onto the block and restart the hone without making any changes to stone cutting pressure and the hone sounds like it is trying to hone a square cylinder. After you've seen and done this several hundred times to blocks of all types, you become a firm believer in the importance of a torque plate, for street or race.

Scott love the reference to boring a square cylinder i have heard that noise on a Cummings when i bored it for learning purposes

I have a honing deck plate that can be rented. PM for info. Or emaill tom@12bolt.com .

Tom let me talk to the shop i am at and check woth them if not i will mostlikely rent it from you

Thanks so much

P.s. can't wait to see all my parts from you in the mail!

Josh, went over and saw the pics.Very cool, looking forward to seeing it in person!

I like to animate my illustrations. But all kidding aside, it is money well spent regardless of how you intend to use your engine.

Thanks roch its been about a yar and a half so far i hope to have it driveable by te " cruise to the pines" i can't wait to finally meet the guys from az inliners ad see their builds!

And scott i am glad i can hear the square bore now!

Why not rhn a square bore over a round bore pick your brain on that!



And does anybody know where i can get one of those fancy bolt on oil filler caps that goes onthe side of the valve cover?

Dude, just wondering if you have ever quantified the distortion on #6 after the bell housing was torqued? I chased an oil consumption problem on an offshore built inline that was a result of overtorqueing the bell housing on installation; don't know if it would effect our domestic 6's as greatly because the bolt spread and proximity to the bore is different but it could have an impact.....fats

Absolutely, about 5 years ago I made a reference to a trick we used to prevent that. We torqued a bellhousing to the block after we discovered this was happening to Cotton's engines, much like a torque plate on the deck surface.

Now what if you torqued the bell housing then the torque plate for maching and upon assembly you torqued the head and then adapted your trans how much variation would that cause if any?

Well, if you used both a torque plate and a bellhousing bolted to the block for machining, you would be duplicating that process when you assembled for engine and bolted it into your vehicle, so you should be fine.

Was curious at to what direction the ring inside the trust plate faces hen installing a can gear and the clearances for te cam gear to thrust plate

If i remember right it was sonething like .001-.005?