How To Measure Deck Height?
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
What it usually means is the distance from the top of a piston to the block deck where the head gasket sits. Generally with an unmachined block most piston manufactures use -.025 below the block deck as an industry standard.
This can't be measured until the rotating assembly is installed in the block
This can't be measured until the rotating assembly is installed in the block
Instructor
Joined: Jul 2004
Posts: 245
Likes: 0
Originally Posted by Edzred72
Please describe this procedure for a bare block...from where to where????
Eddie
Eddie
Very hard to get an accurate measurement...at least in my experiance. As gkull stated, most piston manufacturers give you an installed deck clearance based on rod length, piston pin height, and the piston size with an undecked/stock block.
I hope that I made it clear...if not, someone else is sure to let you know.
Good luck,
Jeff
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
U need the rotating assembly installed or a purpose built jig.
Originally Posted by Edzred72
Please describe this procedure for a bare block...from where to where????
Eddie
Eddie
cardo0
Race Director
Joined: Nov 2000
Posts: 11,872
Likes: 12
From: Waterloo ontario Canada
Originally Posted by comp
NO 
,,,,, The only way is as George said. You have to install the piston assembly and then measure from the block down to the piston dome. This also varies from side to side by a few thousands.
I have my block decked, install the crank and pistons, measure each one, take the average and have the block redecked a second time removing what it takes to put the average piston flush with the deck of the block. The .040 gasket then gives the needed clearance.
Racer
Joined: Apr 2004
Posts: 401
Likes: 0
From: IL
This is the way to measure the piston in relation to deck height. Though in this picture I'm actually measuring the center (for picture sake) of the piston, normally it would be measured at the center but at the sides of the piston. From front to rear, not top to bottom of the cylinder, this way your measuring along the wrist pin with less change in data. Otherwise the piston could be rocked top to bottom and give big number changes in data. Front to rear (side to side) along wrist pin centerline would be "averaged" already.
Another way to measure with digital caliper, this will get you close enough for rough measurements. Again not the correct position to measure but for picture sake, good enough.
Hope these help,
Later.
Another way to measure with digital caliper, this will get you close enough for rough measurements. Again not the correct position to measure but for picture sake, good enough.
Hope these help,
Later.
Race Director
Joined: Apr 2000
Posts: 17,676
Likes: 201
From: Who says "Nothing is impossible" ? I've been doing nothing for years.
I believe he is asking how to measure for deck heght of a bare block which as he already knows now is from crank center line to deck surface. He wants to know how to measure this, I would too as I don't know what special tools are involved here, it is one of the only measurements I was unable to do when building my 406ci 
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
Team Owner
Joined: Sep 2003
Posts: 88,393
Likes: 2
From: eville in
Originally Posted by norvalwilhelm
Comp instead of all the stupid comments why don't you just read and learn and forget the post count??
The only way is as George said. You have to install the piston assembly and then measure from the block down to the piston dome. This also varies from side to side by a few thousands.
I have my block decked, install the crank and pistons, measure each one, take the average and have the block redecked a second time removing what it takes to put the average piston flush with the deck of the block. The .040 gasket then gives the needed clearance.
The only way is as George said. You have to install the piston assembly and then measure from the block down to the piston dome. This also varies from side to side by a few thousands.
I have my block decked, install the crank and pistons, measure each one, take the average and have the block redecked a second time removing what it takes to put the average piston flush with the deck of the block. The .040 gasket then gives the needed clearance.
Burning Brakes
Joined: Sep 2004
Posts: 1,167
Likes: 2
From: Ft.Worth Texas
I'm not sure why you want this info but here is a way to check it....
With crank installed rotate it to the closest it comes to deck and measure with depth mike. Take another measurement with the journal at its fartherest point. The difference is the stroke. One half
the stroke plus the measurement at top of stroke plus one half the journal diameter is the height from crank centerline to deck.
Seems to me the important measurement is from deck to top of piston, the distance from open valves to mating surface of head and the gasket thickness.
(corrected goofy stroke statement)
With crank installed rotate it to the closest it comes to deck and measure with depth mike. Take another measurement with the journal at its fartherest point. The difference is the stroke. One half
the stroke plus the measurement at top of stroke plus one half the journal diameter is the height from crank centerline to deck.
Seems to me the important measurement is from deck to top of piston, the distance from open valves to mating surface of head and the gasket thickness.
(corrected goofy stroke statement)
Last edited by David Ey; Dec 11, 2005 at 08:44 AM.
Racer
Joined: Apr 2004
Posts: 401
Likes: 0
From: IL
Your right, was still a little foggy, try this.
On the cheap, I made a precision spacer machined to fit two crank bores (at each end) and is 2" in between. Using a large 0-12" digital caliper (mostly for rough measurements with .001") measure down from the deck to the spacer/crank stub and subtract 1". This is now the value from center of the crank to the deck surface. Used to use this in a head gasket testing fixture using solid steel slug, HD one piece rod, and a dummy crank slug/arbor to handle high PSI tests. We had engine blocks shipped right off the O.E. assembly lines, had to check them as some times they would send them from the defect pile (broken tap in a hole or cracked ear somewhere) so we would verify each block prior to testing.
Here's a similar arbor used in the machining process, just measure down from the deck surface to the arbor and subtract half of it's (arbor) diameter from your distance measurement.
Why are you asking, have a block done already or double checking the machineshop? Try Goodson Tool and Supply for other tools as well.
Later.
On the cheap, I made a precision spacer machined to fit two crank bores (at each end) and is 2" in between. Using a large 0-12" digital caliper (mostly for rough measurements with .001") measure down from the deck to the spacer/crank stub and subtract 1". This is now the value from center of the crank to the deck surface. Used to use this in a head gasket testing fixture using solid steel slug, HD one piece rod, and a dummy crank slug/arbor to handle high PSI tests. We had engine blocks shipped right off the O.E. assembly lines, had to check them as some times they would send them from the defect pile (broken tap in a hole or cracked ear somewhere) so we would verify each block prior to testing.
Here's a similar arbor used in the machining process, just measure down from the deck surface to the arbor and subtract half of it's (arbor) diameter from your distance measurement.
Why are you asking, have a block done already or double checking the machineshop? Try Goodson Tool and Supply for other tools as well.
Later.
Last edited by GasketDude; Dec 10, 2005 at 11:23 PM.
Thread Starter
Le Mans Master
Joined: Oct 2001
Posts: 5,943
Likes: 3
From: Wildwood IL
Thanks for all the replies & jokes.. 
guys. I'm not sure if my block has been decked and I am trying to play with compression ratios in my 406. Deck height is one of the values needed for an accurate comp ratio. With all the feedback you have provided, I have a pretty good idea how. Thanks again...
Eddie
P.S. Anybody know the standard deck height of a SB400??
guys. I'm not sure if my block has been decked and I am trying to play with compression ratios in my 406. Deck height is one of the values needed for an accurate comp ratio. With all the feedback you have provided, I have a pretty good idea how. Thanks again...Eddie
P.S. Anybody know the standard deck height of a SB400??
Last edited by Edzred72; Dec 11, 2005 at 12:42 AM.
Thread Starter
Le Mans Master
Joined: Oct 2001
Posts: 5,943
Likes: 3
From: Wildwood IL
Originally Posted by MotorHead
I believe he is asking how to measure for deck heght of a bare block which as he already knows now is from crank center line to deck surface. He wants to know how to measure this, I would too as I don't know what special tools are involved here, it is one of the only measurements I was unable to do when building my 406ci
Thanks Motorhead
Eddie
Race Director
Joined: Apr 2000
Posts: 17,676
Likes: 201
From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Eddie if you are getting short block done at a shop them tell them to 0 deck the block, the Felpro 1004 gasket has a compressed thickness of .041", so that will be your quench.
If you are doing it at home you need to do it like Norval states above. Find TDC using a degree wheel, measure how far the piston is in hole using a dial gauge and take the block to the machine shop and have them deck it to your specs. THis usually involves 2 or three trips to the machne shop. One to have it bored, line honed etc. Then you install the crank assembly to measure piston to deck. Then back to have it decked once or twice, have fun
If you are doing it at home you need to do it like Norval states above. Find TDC using a degree wheel, measure how far the piston is in hole using a dial gauge and take the block to the machine shop and have them deck it to your specs. THis usually involves 2 or three trips to the machne shop. One to have it bored, line honed etc. Then you install the crank assembly to measure piston to deck. Then back to have it decked once or twice, have fun
Race Director
Joined: Nov 2000
Posts: 11,872
Likes: 12
From: Waterloo ontario Canada
Originally Posted by GDaina
Dial gague with a magnetic base is easy..adjust the pointer to zero on the block surface then swing it into the hole...bring the piston up slowly.
Le Mans Master
Joined: Dec 2003
Posts: 5,727
Likes: 38
From: Fremont CA
Go tothe Harbor Freight store, buy a 12" electronic caliper, set it to zero in the inch scale, place one end into the main bearing saddle, th eother end on the deck surface, play around with the caliper location to make sure you get a accurate reading. Then measure the diameter of the main bearing bores and divide by 2, add the figure to the legth from step 1, you are DONE. This is the "shade tree" method, the coreecet method is to have a machine shop install a BHJ products "Deck True" fixture onto the block and check the entire surface area across the ENTIRE deck for straightness and being 90 degrees from the opposite cylinder head deck. I can use a "Block True" for "free" you will have to pay because they cost over $2000 to buy. Good Luck!
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
Awh, just let Bubba do it.
For $2000 i'll try the shade tree method. Heck thats more than half of what i paid for my shark.
Using a straight edge on block deck would be easy but to make a perpendicual with the crank c/l and measure within .001"-.002" is the real test.
Well maybe if i turn the block over and lay my tape measure along the main brg saddles then use a 12" dial calipers hmmmmm...... .
Or maybe how much modling clay would it take to fill the bottom end then dry/harden and remove to measure.
Ok, ok, ok. How 'bout fit the bore with'a piece of paper extending through past the crank saddles and mark it with a pen or pencil mounted to a straight edge in the saddle bores. Yea man draw a full circle on the paper with that straight edge then do the fancy math.
Alright hears the beast idea'r. Tip ove'r the block an' sshine a layzer beaam down that brg saddle an' read the hieght on a 12" machinist rule.
Just thought i'd share som' a mi science with the think tank here on the forum.
cardo0
Heck thats more than half of what i paid for my shark. Using a straight edge on block deck would be easy but to make a perpendicual with the crank c/l and measure within .001"-.002" is the real test.
Well maybe if i turn the block over and lay my tape measure along the main brg saddles then use a 12" dial calipers hmmmmm...... .
Or maybe how much modling clay would it take to fill the bottom end then dry/harden and remove to measure.
Ok, ok, ok. How 'bout fit the bore with'a piece of paper extending through past the crank saddles and mark it with a pen or pencil mounted to a straight edge in the saddle bores. Yea man draw a full circle on the paper with that straight edge then do the fancy math.
Alright hears the beast idea'r. Tip ove'r the block an' sshine a layzer beaam down that brg saddle an' read the hieght on a 12" machinist rule.
Just thought i'd share som' a mi science with the think tank here on the forum.
cardo0
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Originally Posted by Edzred72
Thanks for all the replies & jokes.. guys. I'm not sure if my block has been decked and I am trying to play with compression ratios in my 406. Deck height is one of the values needed for an accurate comp ratio. With all the feedback you have provided, I have a pretty good idea how. Thanks again...
Eddie
P.S. Anybody know the standard deck height of a SB400??
guys. I'm not sure if my block has been decked and I am trying to play with compression ratios in my 406. Deck height is one of the values needed for an accurate comp ratio. With all the feedback you have provided, I have a pretty good idea how. Thanks again...Eddie
P.S. Anybody know the standard deck height of a SB400??
When you planing a motor build just figure .040 - .045 Because if your pistons are -.025 then you always buy the .015 steel head gasket if you use iron heads. Aftermarket head gaskets also start at @.020 thickness for most aluminum heads.
When I build motors I always have a machine shop true the surface for the best sealing. This usually only takes a few thousands off. My present motor has piston to deck of about .020 and I'm using .021 head gaskets to get @.040 quench height.
