I have a 40 over 272 block and want to cut it to a 0 deck height. Is there a measurement available for this?

I know about the assembly and measure deal but the machinist I talked to seems to think there should be a dimension available (IE Scrub are 9" etc.). I'm not building this for big horsepower but just as a solid runner for my McCullouch set up. I have new pistons, a 10/10 crank and balanced prepped rods for it. I intend to have the assembly balanced while I'm at it.

Y's guys rule!
Looking for McCullouch VS57 brackets and parts. Also looking for 28 Chrysler series 72 parts. And early Hemi parts.

MoonShadow, 292 w/McCulloch, 28 Chrysler Roadster, 354 Hemi)
Manchester, New Hampshire

Chuck,
It may be better to go ahead and take the measurement with the crank, rods, and pistons installed.  This way you know where it's at and it could save time and money if you cut too much from the deck and then have to cut the pistons for 0 deck.

Several years ago, during the first build of my engine we cut the deck "blindly" to the 0 spec.  On this second build, with the stroker I had to cut the pistons.  Mummert thought it was odd that I had to cut the pistons.  They seemed to range from .010 to .020 out of the hole.  I think I set them to .005 out to get .040 for quench with the gaskets I used.  Of course I didn't check the piston height on the first build so I don't know where they were.

So I say go ahead and get your measurements and have them cut the deck based on that.  If you really want to make sure things are where you want them, measure all 8 pistons.  And have the deck cut to the clearance you want with the lowest piston and then have the other pistons cut to match.  You should go back and check everything after the deck is cut and before the pistons are cut.  It's tedious but it's worth it.  I've accelerated up hill in 3rd from 30mph with compression around 9.5:1 without a knock in the Hotlanta heat.

Lawrenceville, GA

Ditto on Charlie’s comments.  Here’s more on the subject.

 

I typically use 9.775” as a starting point but it’s simply a starting point.  Most Y’s end up around 9.755” when I’m through with them.  The deck spec for the scrub engine is 9.025” and most rotating assemblies for this engine are designed for a 9.000” deck so shops will arbitrarily just cut the decks to that.  If wanting to deck the block without actually dry assembling the crank, rods, and pistons into the block, then you can measure the crankshaft stroke, rod length, and piston pin compression height and, in theory, get there using these values. 

 

(Crankshaft stroke / 2) + rod length + compression height = top of piston or deck height if zero decking.  If you want the piston 0.005” in the hole, then you’d simply add 0.005” to the formula.

 

It’s then up to your machinist to accurately locate crankshaft centerline and put these numbers to use.

 

I still dry assemble every engine to check the actual deck height and then mill the decks accordingly.  I recommend this over doing a blind cut.  It’s not unusual for the decks to be lopp-jawed and require different amounts of cut from one end of the deck to the other.  Be cognizant that connecting rod lengths as well as crankshaft strokes throughout the various journals have been known to vary so this has to be checked and taken into account regardless of the method used to measure the deck height.

Lorena, Texas (South of Waco)

Great info. I found a shop that uses the main bearing bores and the cam bearing bores to locate the centerline of the block, and goes 45 in either direction. I tried to tell him that I used a rod and piston and found the piston to be about .020 in the hole except for the corner of the block where cylinder number 8 was. The piston was about .025 or more. But he told me he wanted the piston height, rod length and stroke. He recommended leaving the piston about .005 in the hole to allow for future cuts. He uses a CNC mill to deck and bore.

Best regards,



Paul Menten

Meridian, Idaho

Chuck ,

The guy who rebuilt my  292 motor in the Victoria did exactly as Ted said . After acid dipping and hot tanking the block ,he dry assembled the motor with 1,4,5 and 8 pistons ,rods and crank.One side was out .020 ,from front to rear .My engine was built with the pistons .005 out of the hole .Compression is around 10;1 . I use 98 octane gas all the time .It has great top end with 3.22 gears and loves to cruise at 90mph .

Lon

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