Working out compression ratio

[neal1980]

Im trying to work out my compression ratio. Can anyone please do this for me its for a Rover V8 Engine I have the following information. Its probably simple to do but I dont want to come out with the wrong figures its important for my build.

4.6L
Bore 94mm

CC of heads 28cc (They have been refaced twice but can still get 28cc in each one)10 bolt late heads
CC Pistons in block at TDC 30cc

I will be running a composite gasket and according to the web the compressed thickness is:
3.9/4.0/4.2/4.6 Composite gaskets - 48thou (1.2mm)

Many thanks

[stevieturbo]

http://www.csgnetwork.com/compcalc.html

[fatjon]

I make it 9.6:1

[neal1980]

fatjon said:

I make it 9.6:1

Cheers Jon I got the same just got to be sure this time.

[rev-erend]

How did you measure the cc ..

How did you elimate surface tension of water in your measurement ?

[Poledriver]

rev-erend said:

How did you measure the cc ..

How did you elimate surface tension of water in your measurement ?

Couple of drops of washing-up liquid?

[stevieturbo]

Use vodka



Or teh correct way is to use a perspex plate to seal it up so the volume measured is accurate.

But even without the plate...I'm sure it wont make any odds worth worrying about this side of F1

[neal1980]

I put a smear of grease around the valves then put a perspex sheet across the head with some air holes in. Then filled with coloured anti freeze making sure no trapped air bubbles.

I hope this is about right

[rev-erend]

Can't get better..

The other way sounds like a waste of good Vodka !

[leorest]

rev-erend said:

Can't get better..

The other way sounds like a waste of good Vodka !

It's not a waste if you drink it
Absolute with a dash of engine oil a whiff of petrol, shaken and poured over ice. Served with a twist of rubber. We'll call it a Flaming Monster Eight. My cocktails have always been legendary!

[Ribol]

neal1980 said:

.........I dont want to come out with the wrong figures its important for my build.

4.6L
Bore 94mm

Not trying to nit pick here but are you sure it is 4.6L exactly?

[spend]

Ribol said:

neal1980 said:

.........I dont want to come out with the wrong figures its important for my build.

4.6L
Bore 94mm

Not trying to nit pick here but are you sure it is 4.6L exactly?

Why do you suspect he has a non standard crank?

[neal1980]

The crank size doesnt matter does it??

If I have set the pistons to TDC in each bore and have confirmed my bores are 94mm. I have taken measurments for piston area to top of block. Then cylinder head chamber.

Or am I missing something???

Cheers
Neal

Edited by neal1980 on Wednesday 25th November 09:21

[Ribol]

neal1980 said:

The crank size doesnt matter does it??

The stroke does, that together with the bore is what gets you the exact CC of the engine. That will obviously alter any compression ratio calcs. In reference to my comment above, as an eg. a 400 TVR engine is actually 3952cc, not 4000.

[macdeb]

I have the same, but only get 27.2 in heads. What will the copression ratio be on that? any ideas? I was told it was around 10.5;1.

[odyssey2200]

Swept volume + clearance volume / clearance volume :1

[neal1980]

Mac remember you have valve cut outs in your pistons and I dont...