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Deck Height Measurement

t8fanning

t8fanning

8v are still cool, right?
Joined
Oct 10, 2010
Location
Vancouver, WA
I know this is an incredibly noob question, but I've haven't done a head gasket job before, and haven't found a really good resource for how to measure deck height of dished pistons online. I want to measure the deck height to determine what thickness of Cometic gasket I should order and if any head decking is required to get to a squish of 0.0030-0.034" as I've seen recommended here. I also want to check to see if I bent any rods with all the coolant in my cylinders.

I understand there are a few methods to measure deck height including using a straight edge and feeler gauges, or the basic idea of using a dial indicator and zeroing it on the deck and then measuring the center of the piston relative to the deck. But how do you move the indicator such that the measurements are accurate? Do you fixture everything and then remove the base and reposition so the indicator is in the center of the piston? Are you really supposed to measure to the center of the piston when it's dished? I know if I measure to the edge of the piston it could introduce error in the form of piston rocking.

Additionally, what is the recommended way to remove carbon build up on piston tops? I know that will affect my measurement.

Again, sorry for the noob questions.

Here's a picture of my carnage, failure seems to have occurred on the fire ring of cylinder 2:

mzRV7oeh.jpg
 
Deck height is 231,7mm

The amount the piston is down the bore or sticking out is called in real engine builder lingo;

"The amount the piston is down the bore or sticking out"

Depth mike
Butt end of any old electronic "very-near"

What ever...It is not something that needs to be worried about that much like Oh dear one thou more...

You given any thought to checking deck fro straightness?

Last 23 or 24 inline 4s I've done (Redblocks, Limas and Cosworth YB) ALL want the decks surfaced...

And thats engine out and apart.
THEN checking bent rod is easy
 
t8fanning said:
That easy huh? I have a somewhat near vernier caliper that I could use.



I have not, but I probably should.
Click to expand...

Just did 2 more over xmas season..2.3 Ford Lima 2300 8v...both way wavier than sheeeeeut.. Machine to surface was going whaaaaaaaaaaaaaaaammmm uuuuuuhhhhhhmmmmmmm WHAAAAAAAAA uuuumhm..as it chopped and hit valley.
They're all crooked now.
 
John V said:
Just did 2 more over xmas season..2.3 Ford Lima 2300 8v...both way wavier than sheeeeeut.. Machine to surface was going whaaaaaaaaaaaaaaaammmm uuuuuuhhhhhhmmmmmmm WHAAAAAAAAA uuuumhm..as it chopped and hit valley.
They're all crooked now.
Click to expand...

Truth. On the last few I've done (not nearly as many as JVL), the heads have been fine-ish, but the blocks were not happy between cylinders 2 & 3.
 
Same as a head, straight edge and feelers. Get it really clean and check at different angles to try to find high/low spots.
 
t8fanning said:
So how do you check the block for straightness? A straight edge?
Click to expand...

These days i just say fawk it...surface the buggers...

Since every volvo i've done is getting bored as well and since that 231,7mm thing seems to be a rough guide line for whoever was surfacing the buggers back when they were born, I tell my happy customs to do things in right sequence:
Bore
test assemble the crank with a coupla main bearings into the block
slide pin thru new Sooooper Bitchin long rod and nice lightweight piston.
One upper bearing shell into rod
Slide piston in and carefully rock back and forth about 100 time to locate TDC
Measure where piston is.

If dead flush say to machine shop "Kiss it to clean" and you're groovy.
If down the bore say .004"/0,1mm say "surface it 006-008" aka 0,15-0,2mm

This will give you about .004/0,1mm stick out.

Now remember: we know that we improve detonation resistance and improve QUENCH getting the piston dead flush--"zero deck" to about 4 to 6 thou out.

We do not know with any kind of certainty if we get improved det resistence and/or quench bring the piston CLOSER...Only unverifiable claims and assertions..

So this number is KNOWN good and no problems.

More, we don't know.
Kiss to clean or surfacing to a number should cost the same...why not do some good for the same price and go 006-006 out and have a nice fresh flat surface?
 
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