200ci deck height

[tom_66]

Anyone knows the correct deck height or deck clearance (distance between the top of the piston to the top of the cylinder) on a 200ci stock engine?
The CI tech section says 0.019", but the falcon performance handbook says 0.030" (on page 16).



Tom

 

[cr_bobcat]

It's 0.019" when you run the numbers. If I were at my computer instead of my cell phone I could quote the right links and show the math...

 

[cr_bobcat]

Now, if you're running aftermarket pistons, beware that the compression height of the newer pistons is shallower than OEM. That's why it's always a good idea to triple check things

 

[tom_66]

Cr_bobcat,
This is for a 200 to 250 head swap.
I checked 3 online c/r calculators, using the following numbers (stock 200ci block):

Deck height: 0.019"
Bore: 3.68"
Stroke: 3.126"
Flat pistons
Gasket thickness: 0.044"
Gasket bore:3.81
Combustion chamber: 52cc

Using thise numbers, I get 9.59 c/r.
In order to get my goal c/r (9.2), I have to use 55cc for the combustion chamber.
The falcon handbook and CI website recomment 52cc, but I think 9.59 c/r is a little high for a stock engine.


Tom

 

[cr_bobcat]

Let me check tomorrow to see what my homebrew calculator says. 9.6:1 could still be fine depending on the cam. I think you would still be OK with pump gas as long as your DCR is south of 8.5:1. My goal SCR is 9.5:1 with a head I got off of a 250. Supposed to get it back from the machine shop on Wed.

What is the compression height of that piston?

 

[tom_66]

I don't know the compression height of the pistons. Those are the stock pistons that came on the 200ci.



Tom

 

[CZLN6]

Howdy Tom and All:

We use .025" for an estimate of deck height on a stock, OEM 200. That estimate comes from measuring many 200s. FYI- The deck height is from the top of the piston to the top of the block. Deck clearance includes deck height plus the thickness of the gasket. Gasket thickness varies with brand and type. We measured a bunch of them. (Page 17 in the Handbook). Chamber volume on pre-seventies 200s typically measure at about 52cc. Variances exist from head to head as well as from chamber to chamber.

So, when you ask for "the correct deck height", you might get a factory specification number or a real world number. The hard truth is that until you measure yours it is just a guess. For our planning purposes we use the .025" estimate. I hope that helps

Adios, David

 

[cr_bobcat]

David is spot on wrt measured vs theory. I just doublechecked and OEM pistons are quoted as having a 1.511" compression height. The aftermarket pistons are listed as 1.500". There's your difference in quoted values. You just never know what's in there or if someone already took 0.005" off to true the block....

So always check, doublecheck, and measure on separate days after taking the mag stand apart

 

[tom_66]

Excellent. Thank you guys.
I will do the measurement when the stock head comes off.



Tom

 

[drag-200stang]

Howdy Tom and All:

We use .025" for an estimate of deck height on a stock, OEM 200. That estimate comes from measuring many 200s. FYI- The deck height is from the top of the piston to the top of the block. Deck clearance includes deck height plus the thickness of the gasket. Gasket thickness varies with brand and type. We measured a bunch of them. (Page 17 in the Handbook). Chamber volume on pre-seventies 200s typically measure at about 52cc. Variances exist from head to head as well as from chamber to chamber.

So, when you ask for "the correct deck height", you might get a factory specification number or a real world number. The hard truth is that until you measure yours it is just a guess. For our planning purposes we use the .025" estimate. I hope that helps

Adios, David

x2