Is this zero decked?
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Joined: Oct 2001
Posts: 3,155
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From: Louisville, Ky
Car: 1991 Z28
Engine: 383
Transmission: T-5
Axle/Gears: 3.08 10 Bolt
Is this zero decked?

Not the perfect pic but what are your opinions. I did not have the proper tool before installing the heads to check the deck but it looked like it to me.
If so, I'd be pushing 11.5:1


Joined: Mar 2000
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From: Littleton, CO USA
Car: 82 Berlinetta/57 Bel Air
Engine: L92/LQ4 (both w/4" stroke)
Transmission: 4L80E/4L80E
Axle/Gears: 12B-3.73/9"-3.89
Zero decked would have the piston crown even with the block surface, not even with the head gasket head side.
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From: Calgary, AB, Canada
Car: 1982 Trans-Am
Engine: 355 w/ ported 416s
Transmission: T10, hurst shifter
Axle/Gears: 10 bolt, true-trac, 3.73
Re: Is this zero decked?
It's hard to tell.
Remove the head gasket, and lay a steel straight edge across the center of the bore, in line with the wrist pin.
try and stick feeler gauges under it, at the center of the piston. Make damn sure you're at TDC on that hole.
Do it for a few cylinders, each corner, average the results. That's your deck height.
Remove the head gasket, and lay a steel straight edge across the center of the bore, in line with the wrist pin.
try and stick feeler gauges under it, at the center of the piston. Make damn sure you're at TDC on that hole.
Do it for a few cylinders, each corner, average the results. That's your deck height.
Thread Starter
Supreme Member
Joined: Oct 2001
Posts: 3,155
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From: Louisville, Ky
Car: 1991 Z28
Engine: 383
Transmission: T-5
Axle/Gears: 3.08 10 Bolt
Re: Is this zero decked?
five7...I am aware of that but this is the only pic I have. The heads are already installed, however, these were referenced from my valve to piston clearance.
Because of the huge 4.166" head gasket bore you can see the block deck and I was looking for second opinions on how close it is to zero.
Because of the huge 4.166" head gasket bore you can see the block deck and I was looking for second opinions on how close it is to zero.
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Joined: Jul 2004
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From: Calgary, AB, Canada
Car: 1982 Trans-Am
Engine: 355 w/ ported 416s
Transmission: T10, hurst shifter
Axle/Gears: 10 bolt, true-trac, 3.73
Re: Is this zero decked?
zero decked and non-zero decked is such a small amount of material, it's really hard to see.
They could have shaved .005" off to get it flat, now you have a pristine block surface, so you know it's been decked, but you don't know how much. You're talking about maybe a .020" difference, which is almost invisible across a 4" piston. Really hard to tell from a picture, let alone leaning over with good lighting and a magnifying glass! A dial indicator, straight edge, and feeler gauges are the only way to know for sure.
They could have shaved .005" off to get it flat, now you have a pristine block surface, so you know it's been decked, but you don't know how much. You're talking about maybe a .020" difference, which is almost invisible across a 4" piston. Really hard to tell from a picture, let alone leaning over with good lighting and a magnifying glass! A dial indicator, straight edge, and feeler gauges are the only way to know for sure.
Thread Starter
Supreme Member
Joined: Oct 2001
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From: Louisville, Ky
Car: 1991 Z28
Engine: 383
Transmission: T-5
Axle/Gears: 3.08 10 Bolt
Re: Is this zero decked?
Yea I forgot to add the block was decked .015" years ago from the previous owner (jtmiller92).
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From: Ontario, Canada
Car: 1988 Firebird S/E
Engine: 406Ci Vortec SBC
Transmission: TH-350/3500stall
Axle/Gears: 7.5" Auburn 4.10 Posi-Traction
Re: Is this zero decked?
based on your pictures and assuming the piston is at TDC, no it is not '0decked".
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Thread Starter
Supreme Member
Joined: Oct 2001
Posts: 3,155
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From: Louisville, Ky
Car: 1991 Z28
Engine: 383
Transmission: T-5
Axle/Gears: 3.08 10 Bolt
Re: Is this zero decked?
Well the heads are on it but it looks like they will be coming off since my pushrods are possibly interfering with my heads on 4 valves.
How is one to make a tool to securely mount a dial indicator and measure the deck height?
How is one to make a tool to securely mount a dial indicator and measure the deck height?
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From: Calgary, AB, Canada
Car: 1982 Trans-Am
Engine: 355 w/ ported 416s
Transmission: T10, hurst shifter
Axle/Gears: 10 bolt, true-trac, 3.73
Re: Is this zero decked?
Dial indicators usually come with a magnetic base.... you just mag it up on the deck surface, and set the dial indicator where the piston comes up, across the wrist pin.
Rotate the engine over to find the highest point for the piston.
That's TDC
Then you just use a ruler and feeler gauges for the deck height,.
Rotate the engine over to find the highest point for the piston.
That's TDC
Then you just use a ruler and feeler gauges for the deck height,.
Thread Starter
Supreme Member
Joined: Oct 2001
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From: Louisville, Ky
Car: 1991 Z28
Engine: 383
Transmission: T-5
Axle/Gears: 3.08 10 Bolt
Re: Is this zero decked?
I do have a magnetic base (purchased seperatly) and could find TDC but do not trust any ruler/yardstick/level I have to be straight. Every one I have checked on my glass door has been off at one end or another or in the middle. I do not have an actual machinest straightedge known to be perfectly flat and even bought an expensive metal yardstick to no avail.
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iTrader: (1)
Joined: Jul 2004
Posts: 10,763
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From: Calgary, AB, Canada
Car: 1982 Trans-Am
Engine: 355 w/ ported 416s
Transmission: T10, hurst shifter
Axle/Gears: 10 bolt, true-trac, 3.73
Re: Is this zero decked?
I just bought a 12" steel ruler.... hold it on it's straightest side, ie if will bow in the middle if you have the 1/8" thick part across the cylinder, but the 1" thick side will be fine.
Joined: Mar 2000
Posts: 43,187
Likes: 43
From: Littleton, CO USA
Car: 82 Berlinetta/57 Bel Air
Engine: L92/LQ4 (both w/4" stroke)
Transmission: 4L80E/4L80E
Axle/Gears: 12B-3.73/9"-3.89
A depth gage is simple enough to use. I just used the one on the end of my dial caliper. http://www.harborfreight.com/cpi/cta...temnumber=5658
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Joined: Sep 2001
Posts: 6,111
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From: Ontario, Canada
Car: 1988 Firebird S/E
Engine: 406Ci Vortec SBC
Transmission: TH-350/3500stall
Axle/Gears: 7.5" Auburn 4.10 Posi-Traction
Re: Is this zero decked?
A CD-ROM disc and a dial caliper depth gauge will work.
Subtract the thickness of the CD-ROM disc from the gauge reading.
Subtract the thickness of the CD-ROM disc from the gauge reading.
Last edited by F-BIRD'88; Nov 14, 2008 at 06:21 PM.
Thread Starter
Supreme Member
Joined: Oct 2001
Posts: 3,155
Likes: 2
From: Louisville, Ky
Car: 1991 Z28
Engine: 383
Transmission: T-5
Axle/Gears: 3.08 10 Bolt
Re: Is this zero decked?
Thanks all. I will play with my dial caliper a little after I get it at TDC with the Dial Indicator. F'BIRD nice idea and pic 
Heads are coming off again (one already is) and I am clearancing the pushrod slots...the Trickflow's stock pushrod slots on each corner are way off.

Heads are coming off again (one already is) and I am clearancing the pushrod slots...the Trickflow's stock pushrod slots on each corner are way off.
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From: MD
Car: '88 IROC-Z medium orange metallic
Engine: L98
Transmission: 700R4
Axle/Gears: 3.27
Re: Is this zero decked?
You're measuring +/-.001 so you want some accuracy. A feeler gauge or a pair of verneers (aka very nears) will get you close but not enough for precise measurements. What you want is to get what's called a bridge mic. There are a couple different types, some with a dial and some with an anvil (like an outside mic). I prefer the type with the dial. The base has two machined surfaces that bridge the bore. You zero the gauge on the deck, then move it over the crown of the piston. Bring the piston to TDC and note the measurement. This is your deck height. This tool is the easiest to use and requires the least amount of math. Here is a photo of each gauge;


Last edited by Dialed_In; Nov 17, 2008 at 08:17 AM.
Thread Starter
Supreme Member
Joined: Oct 2001
Posts: 3,155
Likes: 2
From: Louisville, Ky
Car: 1991 Z28
Engine: 383
Transmission: T-5
Axle/Gears: 3.08 10 Bolt
Re: Is this zero decked?
The dial bridge mic is what I'm interested in since I could use it with my dial indicator however buying one for this one time use is kind of silly I think since I don't need it, I guess.
Cheapest one is $30 from Summit.
Possible to make one I suppose but I need some square scrap steel, two bolts, and some washers. I might try that...how would one attach the dial indicator to a homemade stand?
Cheapest one is $30 from Summit.
Possible to make one I suppose but I need some square scrap steel, two bolts, and some washers. I might try that...how would one attach the dial indicator to a homemade stand?
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