Combustion chamber volume

[MerkXRTurbo]

Hey everybody, I just thought I'd post the info that I have learned to anyone else interested. I CC'd a head last night. The SHO combustion chamber volume is exactly 35cc.

 

[SHOZ123]

According to the Ford manual the 3.0L SHO motor CC volume is 47-48 cc and for the 3.2L it's 46.7-48.3 cc.

 

[Devin]

I must be confused then. If the engine is 3l, that's 3000 CCs which would be 500CCs per cylinder. That sounds about right because 3000CCs ≈ 183 cu in. What am I missing?

edit: Wait a sec... is the "combustion chamber volume" different from the cylinder volume in the way that the cylinder volume includes the entire range of the piston travel, and the combustion chamber volume only includes the volume of the cylinder and head at point of combustion? If so wouldn't that change if you use higher or lower octane gasolines?

 

[sho_sc]

Hey everybody, I just thought I'd post the info that I have learned to anyone else interested. I CC'd a head last night. The SHO combustion chamber volume is exactly 35cc.

Did you measure a compressed Head Gasket?

 

[rubydist]

Hey everybody, I just thought I'd post the info that I have learned to anyone else interested. I CC'd a head last night. The SHO combustion chamber volume is exactly 35cc.

The volume of the head is not the total cc volume - that would assume flat topped pistons and pistons that come up to exactly the top of the head gasket. To the measured 35cc you will need to add the volume that exists on the top of the piston.

 

[93rev2sev]

According to the Ford manual the 3.0L SHO motor CC volume is 47-48 cc and for the 3.2L it's 46.7-48.3 cc.

Factory numbers like those include piston to deck clearance, Head Gasket thickness, valve reliefs, and a plugged(flush with the chamber roof) spark plug hole.

Knowing that the actual size of the combustion chamber is 35cc helps when it's time to rebuild/mod the engine.

You can find out how things will be different of you deck the block or heads or if you want to figure a compression ratio based on different pistons.

 

[MerkXRTurbo]

According to the Ford manual the 3.0L SHO motor CC volume is 47-48 cc and for the 3.2L it's 46.7-48.3 cc.

Where exactly did you find this info? I wasn't able to find it anywhere, not even in the PDF SHO engine book.

Did you measure a compressed Head Gasket?

Nope, don't have one available.

 

[MerkXRTurbo]

I must be confused then. If the engine is 3l, that's 3000 CCs which would be 500CCs per cylinder. That sounds about right because 3000CCs ≈ 183 cu in. What am I missing?

edit: Wait a sec... is the "combustion chamber volume" different from the cylinder volume in the way that the cylinder volume includes the entire range of the piston travel, and the combustion chamber volume only includes the volume of the cylinder and head at point of combustion? If so wouldn't that change if you use higher or lower octane gasolines?

No cylinder volume involved what-so-ever - Just the volume of the combustion chamber in the heads with valves and spark plug in it. And no, this is not subject to change unless one were to mill the heads.

 

[Devin]

^ Newbie!

Got it. I was getting the cylinders mixed in there, but of course if the pistons clear the deck then obviously that doesn't matter.

 

[SHOZ123]

Where exactly did you find this info? I wasn't able to find it anywhere, not even in the PDF SHO engine book.

Ford Technical Service Information
Electronic Publications
«1995 Taurus/Sable Table of Contents»
«Group 03: ENGINE»
«Section 03-01B: Engine, 3.0L/3.2L SHO»

Hope you got the pics before the post was deleted.

 

[zak]

Paul's factory combustion chamber numbers are also published in the 1995 Helms factory service manual (and agree with what he posted). zak

 

[Pleky]

If the wikipedia page on compression ratio is to be believed, and their formula accurate, the combustion chamber volume should be 3.5857(roughly) cubic inches. Or 58.7591cc. That is assuming 3.6 stroke and 3.1 bore, neither of which I'm sure is right. Also, are we sure 9.8 is the stock compression? If 47-48.3 is the right volume, I get a ratio closer to 12.

 

[zak]

You need to account for the volume of the head gasket, valve reliefs, top piston ring to top of piston volume (I've calc'ed it, affects things by 0.0X), and dome volume. 80 mm is stock stroke, 89 and 92 mm are common bores with 93 mm being the largest common overbore. The pistons are not flat top . . .

zak

 

[Pleky]

I figured that I was missing the piston, but I would have thought the ford numbers would have accounted for at least the headgasket. What you say makes perfect sense though, and that seems like a lot of space missing from their numbers.